thesis-final paper
TRANSCRIPT
Drew University: Undergraduate student;The Department of Biology
An Observational Study at the Raptor Trust to Determine the Ecological
Status of Wild BirdsAmanda Cox
Abstract
Analysis of qualitative data from a wild bird rehabilitation center, the Raptor Trust, was
statistically analyzed and converted to quantitative data. Statistical chi square analysis was
conducted to isolate trends and construct background for future research, while determining the
validity of researchers’ and rehabbers’ hypotheses. Ultimately aiming for the advancement in
knowledge about direct and indirect human causes to wild bird endangerment and population
risk factors in the state of New Jersey.
Introduction
Classification
By 1979, it was recorded that 9,672 species of birds existed in the world9. In order to
identify these numerous and various species, Carl Linnaeus’s taxonomical classification had
been utilized at the start of the 1700’s. This type of classification considered a generalized
similarity between many species, grouping them together into their own phenotypic cluster11.
Taxonomy also considered the phylogenetic, or cladistics, classification and further grouped
species by specific characteristics in common11.
Two major types of data are utilized to classify birds into their correct taxonomical
nomenclature. “Morphological data are those that arise from measurement of characteristics of a
bird’s form or appearance”9. Since the 1980’s, behavioral data has also been included to assist
with classifying birds by phylogeny; for example, bird calls have been included in
accompaniment with nesting and breeding behaviors9. The other major type of data collection is
biochemical data, which developed closer to the 20th century9. Biochemical data considers the
DNA and chemical similarities between individuals9.
Birds have since been grouped into three major categories: Precocial birds, Altricial
birds, and Raptors. Precocial birds incubate within their eggs for a long period of time, allowing
significant time for development13. As a result of this, when the birds hatch they are able to walk
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immediately and are covered in feathers13. This category includes waterfowl birds as a majority;
such as, geese, ducks, and other webbed foot birds. They remain with their parents for long
periods of time to allow for proper social interactions, protection, and to learn proper foraging
techniques13. On the other hand, altricial birds hatch in a state of underdevelopment, requiring
their parents to physically feed and house them while providing protection and social
interactions14. Altricial birds include passerines as a majority: robins, blue jays, grackles, etc.
Raptors, also called ‘birds of prey’ significantly vary in type. ‘Birds of prey’ encompasses those
with talons and hooked bills that are predatory; for example, owls, hawks, eagles, etc. However,
these are just major categories with varying scientific classification within each.
The History
Once the hype of classification had died down, birds were considered little more than
vermin. This was particularly true for raptors because of their predatory behavior. “Some raptors
eat lambs, poultry or game birds, and they have been slaughtered in millions”8. Between 1850
and 1900 bird hunting was officially encouraged, each kill rewarded with a bounty8.
Pennsylvania permitted the scalping of owls and hawks, paying fifty cents for each scalp8. This
resulted in the slaughter of 180,000 birds in a two year period8. Market hunting emerged in the
19th century as a result of the feather trade and destroyed the pigeon, waterfowl, and shorebird
populations11. Gradually the methods of killing birds increased and diversified.
Shooting was utilized whenever birds congregated at a known nest or nesting site, as well
as when they flew within range of a gunman due to migration or foraging8. Leg traps were
extremely common and contained a spring jaw that held the bird tethered to a perch, pole,
carcasses or nest causing it to die of starvation8. In some cases, hunters would even poison birds
with pesticides deliberately, but also accidentally. Raptors often fell victim to bioaccumulation
which occurred when rodents and other prey animals were poisoned due to nuisance, the raptors
then consumed these animals and fell victim to the poison they contained11,8. Illegal live bird
trade also occurred in this time period, creating a “multi-million-dollar industry”1. Although
parrots were particularly susceptible to this industry, hawks and falcon populations also suffered
due to their desirability in falconry11.
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Vast killing focused on populations at the immediate start of the breeding season. This
particular time period was the population’s seasonal low, and eliminated the breeding adults,
causing extreme population decline8. Many species suffered elimination in the 1900’s as a result
of killing breeding pairs at the start of the breeding season8. The past 190 years has resulted in
population thinning and threats8.
Populations and Habitat Influence
After years of overexploitation, scientists decided that it was time to prevent population
depletions. They began to assess populations on a global scale, determining “the density of a
species as a measure of the number of birds in a standard area, and the geographic range as the
area over which the species occurs”11. The size of a bird often impacts the population density,
meaning larger birds tend to have lower densities because of the necessity for larger ranges to
forage11. To clarify, “overall abundance of bird species depends on the extent of its geographical
range, amount of suitable habitat within that range, and a mean density achieved within that
habitat”9.
Available habitat for particular species influences population sizes11. A habitat that is
suitable and beneficial to a species permits high rates of reproduction and overall survival of the
population11. “Sites where population is able to produce an excess of young are called sources,
and other sites, called sinks, do not support self-sustaining populations and rely on immigration
of excess birds from source populations to replace those that succumb to disease, predators, and
the like”11.
Loss of these necessary habitats cause population declines in great significance11. Habitat
depletion is a direct or indirect result of humans11. Habitats can be lost because humans convert
land for agricultural and developmental purposes; destroying native grasslands11. Wetlands are
lost as a result of water diversion to increase water availability for cities11. “More than half of the
wetlands have disappeared in the last 200 years; in California less than 10 percent remain11.
Shrub habitats are especially concerning because the natural disturbances that cause these
habitats to form no longer occur, meaning the available shrub habitats that currently exist are the
last of their kind11.
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Habitat destruction can also occur in fragments, leaving patches of unusable land. This
fragmentation reduces the likelihood of immigration among a population, reducing the chance
for an individual to move away from its birthplace for reproduction11. It also causes edges on
each habitat, an edge is where two different habitats meet, increasing the likelihood of a
predatory attack11. Since the highest density of a population remains on the interior of a habitat,
most bird egg and nestling predators remain on the edge of habitats preying on population
stragglers11. In particular, brood parasites tend to occupy open areas; thus fragmentation allows
brood parasites to occupy spaces intermittently throughout a population habitat, this gives them
more access to nests within that habitat11.
Bird Counts
As a result of constantly changing habitats and population sizes, it is important to
document bird counts periodically. This assists with determining species success, specific
species themselves, and the overall environmental success. However, studying a numerical value
for a whole population on a global scale is impossible. This causes scientists to focus population
studies on a particular area9. This defined area must consist of a large enough range that could
logically influence the estimate of the species population as a whole9. Since not all bird species
migrate at the same time or distance, it is difficult to use migration for population counts.
Thus other aspects of count are utilized; for example, counting specific concentration
areas, breeding pairs, breeding display males, etc. Due to the variety of ways to count birds, it is
necessary to know their annual cycles which are common to the majority of birds. Most birds
undergo a summer breeding season where population counts increase because reproduction rates
are higher than mortality rates11,9. Non-breeding winter season is where population counts
decrease because mortality rates are higher than reproduction rates11,9.
The desire to monitor populations caused the creation of the National Audubon Society
and the American Society for the Prevention of Cruelty to Animals11. Currently, there are “three
nationally coordinated efforts to gather data on bird populations: The Christmas Counts and
Breeding Bird Census sponsored by the National Audubon Society, and the Breeding Bird
Survey sponsored by the US Fish and Wildlife Services”15. The Christmas Count was the first
record of bird populations, originating in 1900 at Central Park in New York4. This count focuses
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on birds present in the non-breeding winter season, and remains the longest continuous record in
existence15. The Breeding Bird Census is to determine breeding pairs within a defined area and
requires repeated recordings15. This particular study enlists the help of bird watchers, and often is
not entirely accurate due to “imbalanced coverage, inadequate plot sizes, and poor record
continuation”15.
The Christmas Bird Count enlists the manpower of volunteers who follow an assigned
recording route15. Along this route of rural roads, the volunteers stop every half mile to record
the birds heard and saw in a three minute interval15. Each route occurs for about three hours
every May and June each year, to accompany each population peak and lull15.
Present Threats
Population and bird counts fluctuate throughout the year naturally, however; both are
significantly affected by existing threats that are mostly human based. As mentioned, habitat loss
and fragmentation is of great concern due to urbanization, but other threats also exist9. Pollution
from agricultural runoff, pesticides, or oil can cause significant damage to bird survivability.
Rainwater passing over streets can cause contaminants, including oil, to run into sewage which
eventually joins natural waterways11. Pesticides accumulate up the food chain by
bioaccumulation, poisoning predatory animals11. “Sewage treatment plants, livestock barns,
paper mills, mines, garbage dumps, factories, and traffic” all add to the pollution accumulating to
negatively affect birds11. There are other forms of pollution as well, but one might not consider
them to fall under this category; such as, light pollution disrupting night-migration pathways or
nocturnal birds11.
Climate change and global warming also plays a part in population changes9.
Temperature change as a result of fossil fuels, as well as, rainfall fluctuations contribute to
habitat distribution and food availability changes11. This forces species into undesirable habitats
by default and limiting reproductive success. It has already been documented that climate has
caused breeding seasons to shift in particular species, ultimately affecting migration which uses
breeding season as a signal factor11. Not only that but “the distributions of predators and disease
are also likely to change if weather patterns are altered”11. Even resources can undergo shortages
as a result of climate change9.
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Populations are also affected by naturally occurring factors. A factor to consider is inter-
specific competition where an “overlap in food and other resources provides the potential for
competition, because some of the resources removed by one species might otherwise have been
available for a second9. But competition is not limited to food resources. Thus, nests can also
undergo shortages as a result of another species overtaking them prior to the opportunity for a
second to obtain them9. Simply put, competition creates advantages for one species but
completely reduces the potential success of another; this can even cause aggressive disputes
between those individuals9.
Indirect human disturbances also prohibit natural behaviors of birds, thus negatively
affecting their survivability. Such disturbances could be vehicles utilizing back-roads, which
disturbs species nesting in isolated areas11. Overhunting still occurs in some areas and limits bird
populations9. Even netting from fishing gear or wires from telephone poles cause population
declines9.
Conservancy
George Fenwick founded the American Bird Conservancy in 1994 because “12 percent of
4,230 species in North and South America were threatened with extinction”4. Thirty-seven
percent of United States native species are currently declining in population4. The goal of the
conservancy was to collaborate the interests of many and create a uniform society that values the
protection of birds throughout the world, ultimately considering the wellbeing and effect of birds
with every use of land and environmental policy4.
This conservancy built its visionary statement knowing that birds have always been
admired, even if only by a small few. In fact, images of birds appear in “Neolithic caves,
Egyptian pyramids, Mayan temples, American homes”, and many other places4. Specific birds
have been used as symbolism for stories and life events: owls, crows, and ravens representing
death, even using storks as representation for human birth4.
Various state governments throughout the United States track wild bird populations to
determine the health of an environmental area. As stated previously, birds are extremely
sensitive to habitat changes; therefore, the health of birds in a particular area help measure the
overall health of a habitat4. Thus counting birds help measure ecosystem success, which predicts
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agricultural production, overall wildlife success, water cleanliness, and the success tourism might
bring as a result4. And of course, high tourism turnout results in increased profit for an area.
Birds also contribute to rodent and insect control, eliminating the high necessity for pesticides
that are harmful to animals and the environment4. Birds, such as hummingbirds, assist with plant
pollination and seed dispersal4.
Beyond the Conservancy’s vision statement, it has a plan of action set up to aid in its
cause. Halting extinctions to promote endangered bird population revival; targeting a network of
70 wildlife reserves aimed to protect rare species, funding support through policies, and
promoting sustainability of fisheries for seabird revival4. Conservation habitats to provide
sustainable conditions for resident and migratory birds by helping landowners manage their
properties, preserving resting sites of migration, and increasing migratory bird conservation
through funding4. Eliminating threats by addressing human-caused populations decline factors:
feral and outdoor cats, window strikes, collisions with turbines, pesticide use, and depleted
fisheries4. Finally, empowering people through communication and unification4.
Wildlife Rehabilitation and Licensing
Willowbrook Wildlife Haven founded the National Wildlife Rehabilitators Association in
1982 at the first Wildlife Rehabilitation Symposium, an event that encompassed 262 guests and
22 states7. Those attended represented various facilities working to promote wildlife
survivability: zoos, universities, and nature centers to name just a few7. The goal of the
association aimed to improve the profession of rehabilitation, develop a code of ethics and
standards, encourage unification and cooperation, and serving as a voice of respect and
professionalism7.
When a sick, injured, or orphaned wildlife animal is found, it is required by law to
immediately contact a wildlife rehabilitator or facility. Ultimately the goal of these facilities is to
release wildlife back to the wild and ensure the public’s health and safety; whether that be by
feeding babies hourly, preventing hypothermia, providing emergency stitches, or euthanasia to
prevent inhumane suffering5. However, rehabilitation facilities are required to undergo
inspection to obtain licensing. The beginning step is to obtain a rehabilitator permit, which
covers only certain species and requires only temporary holding of the animal.
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Obtaining this permit requires an apprenticeship, a letter of recommendation from that
mentor, a letter of loyalty and commitment from a willing veterinarian, an on-site inspection, and
annual reports and renewals5. Volunteers may be utilized to assist a rehabilitator at a facility, but
they must be trained with adequate knowledge5.
Funding is rarely provided by the state, unless specific studies are proposed (ie. studying
an eagle for a particular reason), and it is illegal for the rehabilitator to charge for the care of
admitted wildlife. Facilities are permitted to acquire donations, if the public citizens choose to do
so themselves5. Various general requirements must also be maintained: posting the permit,
permit renewal, maintaining a telephone and answering system, facility inspections, and accurate
record maintenance5.
Wildlife rehabilitation facilities must incorporate indoor and outdoor enclosures, strongly
encouraging enclosures that allow public viewing in some aspects, but requiring some which
prevent viewing in others5. Noise and odor levels must be limited to simulate natural wild habitat
conditions5. These facilities are also strongly encouraged to host educational programs yearly to
promote knowledge and unification for those with common goals5. And birds they release back
to the wild must meet minimum standards constructed by the state: “recognize, obtain and
process naturally found food, evade and defend against predators, acquire shelter and defend
territories, and perform normal socialization with conspecifics (though there are variations
among species)5. Any bird unable to meet these conditions must be euthanized humanely or
made a residential ambassador bird; depending on suitability determined by the individual’s
condition5.
The Raptor Trust
In 1968 Leonard J. Soucy was a naturalist, photographer, lecturer, author, and raptor
researcher that founded the Raptor Trust Avian Rehabilitation Center. However, this was not the
facility’s name originally, because the facility began in Soucy’s 14-acre backyard in Millington,
New Jersey. His 45 years of Raptor experience made him extremely capable, and the logical
option, to undertake injured raptors and nurse them back to health. It was well-known that he
kindled an intense thirst for knowledge, admirable networking skills, extensive libraries, and
strong management skills.
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This facility now encompasses a medical infirmary, an educational center, a gift shop,
and 70 exterior aviaries12. There are both indoor and outdoor aviaries, as well as, rehabilitation
and residential aviaries. By the 1970s, hundreds of birds were admitted annually at the Raptor
Trust. “From 1982 to 2015 over 90,000 hawks, owls, and other wild birds have been cared for at
the facility and nearly half have been released to the wild”12.
Currently 50 un-releasable raptors live permanently at the Raptor Trust, the majority of
which are females. These birds are kept for various reasons: inability to survive in the wild,
captive breeding, foster parenting, and public education12. It was in 1982 that the facility received
its name and became a non-profit corporation. The facility has since obtained awards and
recognition from US Fish and Wildlife Services, Us Environmental Protection Agency, NJ
Veterinary Foundation, and the Humane Society of the US12. The facility was awarded the
National Wildlife Rehabilitators Association Lifetime Achievement Award in 198612.
The mission of the Raptor Trust is to care for injured, sick, and orphaned wild birds. With
the medical facility, they are capable of doing “diagnostics, intensive care, x-rays, orthopedic
repair, and specialized diets”12. As well as educate people about wild birds, in particular about
Birds of Prey, through educational programs run by two full-time teachers and naturalists12.
These educational programs are hosted on the premises of the facility, but also are held at
schools or nature organizations12. The programs include live birds to help increase admiration
and interest, pamphlets of facts handed out, and a website with free informational resources12.
The Study
Rehabilitation facilities send annual reports to the state based on intakes and releases, but
after their submission these reports are rarely analyzed extensively. Not only that, but all birds
are initially admitted for reasons determined by the finders of the birds. These admit reasons are
rarely examined, except for the times some statistical trends are used for educational programs.
Thus these admit reasons were researched to determine commonly admitted species and
admit reasons to which they are susceptible. Analyzing the data over the past five years will lead
to an advancement in knowledge about indirect and direct human causes to wild bird
endangerment and population risk factors. As well as shifts in natural behaviors like breeding
seasons, migration patterns, or incubation periods.
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This knowledge will assist in determining preventatives that can be implemented to
revise protection plans. The hope is that this research can be incorporated into existing
educational programs and protection policies, currently in place, to further protect wild bird
populations and educate the public about the benefit of rehabilitation centers; such as the Raptor
Trust.
Methods
TRT Data Collection
Wild birds brought to The Raptor Trust are catalogued in an online database created by
one of the facility’s staff members. This database records basic information provided by the
finder of the bird. Initial questions are recorded at the time of admittance; for example: the date
of admittance, the number of birds being admitted by that finder, the state, town, and county
where the bird was found. The finder’s name, address, and phone number are also recorded. This
enables the facility to obtain further details about the initial condition a bird was found in, obtain
specific locations and spots for reintroduction after full recovery, or even to obtain records of
populations seen in a particular area for state and federal protected species. The finders also
inform the staff members of why they brought the bird to the facility by checking off a box of
common admit reasons.
Following admittance, all birds undergo an exam by a staff member. These exams
determine the bird’s species, age, and whether the bird has external parasites. Another
examination occurs after the bird has destressed in an enclosure located in the intensive care unit
or the raptor holding area. This follow up examination determines overall health of the animal,
which often includes dehydration or malnutrition, fractured bones, neurological disorders, or the
presence and degree of imprint. At this point, the admit reasons provided by the finders are
updated to reflect the true nature of the bird’s condition to provide insight as to why it required
the assistance of humans. Throughout the bird’s time at The Raptor Trust, all medical treatments
and changes are recorded in the digital database. The final outcome of the bird is the last thing to
be updated into the system, whether that means the bird was humanely euthanized, released,
transferred, or died on the premises.
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Over 11,500 data entries were obtained from the digital database and organized into an
excel file by admit date. These data entries span from April 8, 2010 to September 5, 2015.
Admit Reasons: Originals and Condensed
As previously stated, initial admit reasons are recorded by the finder of the admitted bird.
This is done by checking off a reason from a provided, staff written, list of common admit
reasons. Such admit reasons include: Caught by cat, caught by dog/other, found on side of
road/sidewalk, found on ground in yard, flew into window, hit by car, impact/other, caught in
netting/fishing line, fell from nest/orphaned, or shot. Staff members then update these admit
reasons after examinations based on injuries and the information provided by the finder,
ultimately to record a more realistic and correct reason for the bird’s presence at the Raptor
Trust.
In order to run understandable statistical tests and to ensure clarity of the research, the
admit reasons were condensed by similar categories. “Caught by cat” and “caught by dog/other”
were combined into one admit reason of “caught by animal”. “Found on side of road/sidewalk”
and “found on ground in yard” were combined to “found on ground”. “Flew into window”, “hit
by car”, and “impact/other” were combined to “impact”. “Fell from nest/orphaned”, “caught in
netting/fishing line”, and “shot” were all kept the same because they did not relate significantly
with another admit reason category.
Omitted Data
There were some admit reasons that were omitted, completely, for various reasons. For
example, despite the attempts of the Raptor Trust staff members some admit reasons are
unknown by the finder and records. This could be a result of the finder not seeing any incident
occur, delivering the bird to the facility for a friend, or any number of other reasons. As a result,
there are two admit reasons in the digital database called “Blank” and “reason not given” where
an admit reason is simply not provided. As a result, data falling into this category were omitted
because the category does not fit into a study where research focuses on admit reasons of wild
birds in rehabilitation centers.
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Some birds are admitted by the Raptor Trust staff members as a result of coming upon
injured and orphaned birds when not at the facility. Although these birds often have a particular
reason for admit, like impact, they are generally categorized as “TRT-Off site”. Due to the
uninformative nature of this particular admit reason, it has been omitted to prevent inaccuracies
in the data. The same is also true for the admit reason “Transferred”, which encompasses birds
that have been admitted from other rehabilitation centers and rescue facilities; such as the
ASPCA.
Finally, the admit reason “other” was omitted to prevent confusion and inaccuracies. This
admit reason is often checked off by the finder themselves and should be updated upon further
examination of the bird; however, this does not always happen due to immediate euthanasia,
death, or release. As a result, this admit reason is a bit misleading, indicating unknown injuries or
reason for admittance when there may truly be a more specific admit reason that explains the
bird’s condition.
Statistics
A Chi Square goodness of fit test was utilized to compare the distribution of admit
reasons overall, as well as, pairwise among all of them. For clarity the top five species, those
with the highest admit counts, were focused on for a chi square test of independence. This test
compared the distribution of the five specific species among themselves to determine the most
and least likely admit reason for each species. Another Chi Square test was utilized to determine
if population sizes in the state of New Jersey contributed to the intake counts of particular
species. All Chi Square tests were processed by the Drew University SPSS statistical program,
and all testing was overseen by a Drew University Statistics professor.
Population Data
Species population data was collected through the Audubon Society’s Christmas bird
count. All population data was tabulated and organized in a marked line graph by the Audubon
Society’s website. The population data obtained were constricted to the five-year period of
interest (2010-2015).
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Comparison Data
To determine if the statistical analyses and trends determined from the data collected
from The Raptor Trust were specific to that facility, data were also collected from other wild bird
rehabilitation center in New Jersey. By using data that was analyzed by the same statistical tests
as the Raptor Trust data, it can be determined if the admit reason trends are specific to this
particular facility or common throughout the many wild bird rehabilitation centers located in the
state of New Jersey. All data from other facilities were emailed by the facility directors or other
staff members with permission to be utilized in this research study.
Results
Admittance vs. PopulationA chi square goodness of fit test confirmed that the thirteen species of interest were not
admitted in equal numbers to the Raptor Trust facility. The same was true for all admit reasons;
the chi square goodness of fit test confirmed that admit reasons were not equal in number to each
bird admit at the Raptor Trust facility (they were not uniform). Utilizing a chi square test of
independence, it was found that all data were statistically significant. Birds were admitted to the
Raptor Trust in different proportions than expected based on their NJ populations. Admit reasons
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varied in likelihood for each species of interest at the Raptor Trust.
Figure 1: The 5 most admitted species to TRT based on admit counts were admitted in different proportions than their state population totals between 2010-2015 (A). The 5 most admitted raptor species to TRT based on admit counts were admitted in different proportions than their state population totals (B). TRT has species admitted that are considered threatened, endangered, or a special concern as determined by NJ US Fish and Wildlife Services; these species were admitted in different proportions than their state population totals (C).
According to the chi square test of independence, all thirteen species of interest at the
Raptor Trust are admitted in proportions different than their NJ populations (N= 1,050,445,
df=12) = 37,653.84, p < 0.0005. It can be seen that the five most admitted species, highest admit
count, entered the Raptor Trust in counts different than expected based on their NJ populations
(Figure 1A-C). For example, based on NJ populations, the Common Grackle was expected to
have 2,872 individuals enter the facility (as determined by the chi square test of independence).
However, only 629 individuals were actually observed at the facility (Figure 1A). In contrast,
the Mourning Dove was expected to have 341 individuals based on NJ populations; however, the
Raptor Trust admitted 1,068 individuals (Figure 1A). The Red-Tailed Hawk was also admitted in
higher numbers than expected based on the NJ populations (Figure 1A).
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The five most admitted raptor species, highest admit counts, at the Raptor Trust all had
higher admit counts then expected based on their NJ populations (Figure 1B). It can be seen that
Red-Tailed Hawks were the most admitted species of the five species focused on specifically
(Figure 1B). Based on population data, Red-Tailed Hawks were expected to be admitted most
often with an admit count of 47 individuals, but were actually admitted with 633 individuals
(Figure 1B).
Furthermore, the Raptor Trust has admitted five species that are classified as threatened,
endangered, or of special concern by the US Fish and Wildlife Services. Of these five special
interest species, all are admitted to the facility in higher counts than expected by their
populations (Figure 1C). For example, the American Kestrel was expected to have 4 individuals
admitted to the Raptor Trust, but 175 individuals were actually observed at the facility (Figure
1C). The Peregrine Falcon was expected to have 2 individuals admitted, but 63 individuals were
admitted in actuality (Figure 1C).
Admittance vs. Proximity
Figure 2: National Audubon Society has many Christmas Bird Count routes throughout the world (A). NJ has a total of 8 licensed rehabilitation centers that take in wild birds (B).
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TRT receives admit birds in counties around NJ, but the majority tend to come from counties near the facility that lack other rehabilitation centers (C).
It can be seen that the National Audubon Society has recorded an extremely large number
of Christmas Bird Count routes to account for vast numbers of bird populations (Figure 2A).
New Jersey has a total of eight rehabilitation centers that accept wild birds (Figure 2A). The
Raptor Trust, specifically a wild bird rehabilitation center, is located in Morris County. It can be
seen that the thirteen species of interest are admitted in counties relatively close to the Raptor
Trust (Figure 2C). Furthermore, it can be seen that birds from counties with other rehabilitation
centers get admitted in far less numbers; thus, proximity plays a role in admittance (Figure 2C).
Species Entering TRT for Various Admit Reasons
Figure 3: Admit totals of the top 5 most admitted birds to TRT by count. Mourning Doves admitted to TRT enter in different proportions than expected for each admit reason (A). Mallard Ducks admitted to TRT enter in different proportions than expected for each admit reason (B). Common Grackles admitted to TRT enter in different proportions than expected for each admit reason (C). American Robins admitted to TRT enter in different proportions than expected for each admit reason (D). Red-Tailed Hawks admitted to TRT enter in different proportions than expected for each admit reason (E).
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According to the chi square test of independence, all thirteen species of interest at the
Raptor Trust are admitted for various reasons (N= 4946, df=60) = 1,678.89, p < 0.0005. Thus, it
can be seen that each of the five most admitted species at the Raptor Trust were likely to be
admitted for certain admit reasons over others (Figure 3A-E). The Mourning Dove was more
likely to be admitted to the Raptor Trust because they were found on the ground (39.08%), and
least likely to be admitted due to a shooting injury (0%) (Figure 3A). The Mallard Duck was
more likely to be admitted to the Raptor Trust as a result of falling from their nest (80.88%), and
least likely to be admitted due to a shooting injury (0%) (Figure 3B). The Common Grackle was
more likely to be admitted to the Raptor Trust because they fell from their nest (56.3%), and
least likely to be admitted to the facility due to being caught in netting/fishing line (0%) or a
shooting injury (0%) (Figure 3C). The American Robin was admitted to the facility more often
due to falling from their nest (62.45%), and was less likely to be admitted due to a shooting
injury (0.06%) (Figure 3D). Red-Tailed Hawks were more likely to be admitted to the facility
because they were found on the ground (66.19%), and least likely to be admitted because they
were caught in netting/fishing line (0.21%) (Figure 3E). In all cases, the most likely admit reason
(between 2010-2015) for the top five species of interest was falling from their nest or being
found on the ground (Figure 3A-E).
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Figure 4: Admit totals of the top 5 most admitted raptor species to TRT by count. American Kestrels admitted to TRT enter in different proportions than expected for each admit reason (A). Cooper’s Hawks admitted to TRT enter in different proportions than expected for each admit reason (B). Eastern Screech Owls admitted to TRT enter in different proportions than expected for each admit reason (C). Great Horned Owls admitted to TRT enter in different proportions than expected for each admit reason (D). Red-Tailed Hawks admitted to TRT enter in different proportions than expected for each admit reason (E).
It can be seen that each of the five raptor species of interest were likely to be admitted for
certain admit reasons over others (Figure 4A-E). The American Kestrel was more likely to be
admitted to the Raptor Trust because they fell from their nest (65.75%), and least likely to be
admitted due to being caught in netting/fishing line (0%) or a shooting injury (0%) (Figure 4A).
The Cooper’s Hawk was more likely to be admitted to the Raptor Trust as a result of being found
on the ground (59.62%), and least likely to be admitted due to being caught in netting/fishing
line (0%) (Figure 4B). The Eastern Screech Owl was more likely to be admitted to the Raptor
Trust because they were found on the ground (44.8%), and least likely to be admitted to the
facility due to a shooting injury (0%) (Figure 4C). The Great Horned Owl was admitted to the
facility more often due to being found on the ground (55.84%), and were less likely to be
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admitted due to a shooting injury (0%) (Figure 4D). Red-Tailed Hawks were more likely to be
admitted to the facility because they were found on the ground (66.19%), and least likely to be
admitted because they were caught in netting/fishing line (0.21%) (Figure 4E). In all cases, the
most likely admit reason for the top five raptor species of interest was falling from their nest or
being found on the ground (Figure 4A-E).
Figure 5: Admit totals of Threatened, Endangered, and Special Concern birds to TRT. American Kestrels admitted to TRT enter in different proportions than expected for each admit reason (A). Barred Owls admitted to TRT enter in different proportions than expected for each admit reason (B). Bald Eagles admitted to TRT enter in different proportions than expected for each admit reason (C). Peregrine Falcons admitted to TRT enter in different proportions than expected for each admit reason (D). Red-Shouldered Hawks admitted to TRT enter in different proportions than expected for each admit reason (E).
It can be seen that each of the threatened, endangered, or special concern species at the
Raptor Trust were likely to be admitted for certain admit reasons over others (Figure 5A-E). The
American Kestrel was more likely to be admitted to the Raptor Trust because they fell from their
nest (65.75%), and least likely to be admitted due to being caught in netting/fishing line (0%) or
a shooting injury (0%) (Figure 5A). The Barred Owl was more likely to be admitted to the
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Raptor Trust as a result of being found on the ground (72.22%), and least likely to be admitted
for any other admit reason (Figure 5B). The Bald Eagle was more likely to be admitted to the
Raptor Trust because they were found on the ground (61.54%), and least likely to be admitted to
the facility due to being caught by an animal (0%) or being caught in netting/fishing line (0%)
(Figure 5C). The Peregrine Falcon was admitted to the facility more often due to being found on
the ground (51.43%), and were less likely to be admitted for any other admit reason (Figure 5D).
The Red-Shouldered Hawk was more likely to be admitted to the facility because they were
found on the ground (60.0%), and least likely to be admitted because they were caught in
netting/fishing line (0%) (Figure 5E). In all cases, the most likely admit reason for the top five
species of interest was falling from their nest or being found on the ground (Figure 5A-E).
Analysis of Admit Reasons
Figure 6: Over a 5-year period Admit Reason totals vary in count (A). In 2010, most birds admitted to TRT enter because they were Found on the Ground (B). In 2015, most birds admitted to TRT enter because they Fell from their Nest or were Found on the Ground (C).
Over a 5-year period (2010-2015), all admit reasons have increased in total counts
(Figure 6A). Both fallen from nest and found on ground are admit reasons that increased the
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most (Figure 6A). It can be seen that in 2010, the majority of birds admitted to the Raptor Trust
entered because they were found on the ground (Figure 6B). In 2015, fewer birds were admitted
to the Raptor Trust due to being found on the ground, but an extremely high number were
admitted to the facility because they fell from their nest (Figure 6C). Overall, admit reasons at
the Raptor Trust increased in admit counts by 2015 (Figure 1A, C).
Similarities between Rehabilitation Centers within New Jersey
Figure 7: The Avian Wildlife Center admits birds for similar Admit Reasons to TRT. In Sussex County, at the Avian Wildlife Center, the majority of its birds were admitted due to Impact Injuries in 2014 (A). In Morris County, at TRT, the majority of its birds were admitted due to falling from their nest (B).
It can be seen that the Avian Wildlife Center in Sussex County admits birds to the facility
for similar reason to the Raptor Trust. Of these admitted birds, the majority were admitted due to
impact in 2014 (Figure 8A). Morris County’s Raptor Trust admitted more birds over all in a 1-
year period; for example, TRT admitted 489 American Robins in 2014 but the Avian Wildlife
Center admitted 45 American Robins in the same year. The Raptor Trust admitted the majority
of its birds because they fell from their nest in 2014 (Figure 8B). However, both facilities
admitted the thirteen species of interest; all were admitted for similar reasons despite the two
facilities being in different counties (Figure 8A, B).
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Raptor Trust Success
Figure 8: Over a 5-year period most birds admitted to TRT enter because they Fell from their Nest or because they were Found on the Ground (A). Following their recovery at TRT, the majority of birds are released back to the wild to live a healthy life (B).
To reiterate, the admit reasons found on ground and fell from nest had the two highest
admit counts at the Raptor Trust (Figure 7A). The least likely admit reason at the Raptor Trust
was caught in netting/fishing line in the 5-year period (Figure 7A). It can be seen that the Raptor
Trust records all final dispositions for individual birds admitted to the facility. Of the thirteen
species admitted to the Raptor Trust, the majority are released back to the wild after
rehabilitation (Figure 7B). Very few individuals of the species of interest are kept as residential
ambassador birds (Figure 7B).
Discussion Qualitative data from the Raptor Trust, an avian wildlife rehabilitation center, was
statistically analyzed for trend observation. Manipulating the data into quantitative information
was useful to provide validity to impressions provided by local rehabilitators and
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conservationists. Speculated reasoning for rehabilitation necessity was supported by the data in
various ways.
Admittance vs. PopulationFive years of data from the Raptor Trust was initially analyzed to determine if some
species were admitted to the facility in higher numbers simply because that particular species has
a higher population in New Jersey. However, statistical analysis confirmed that population
densities throughout New Jersey do not impact the rate of admits at the Raptor Trust; instead,
each species is admitted in different proportions than would be expected based on their
populations.
Furthermore, when considering the five most admitted species to the facility, it is noted
that Common Grackles should be admitted in much larger quantities based on their population in
the state (Figure 1). Thus, it can be stated that Common Grackles are able to protect themselves
against potential threats that would result in their admittance to rehabilitation centers; more so
than any other species analyzed. One might believe that habitat behavior would attribute to
increased safety, or at least limited exposure to human interference, but Common Grackles are
present in various habitat types. These birds can be found in parks, residential areas, meadows,
or even agricultural fields; to name a few4. It is possible that the flocking behavior of the
Common Grackle provides increased protection per individual, especially since these flocks are
known to be extremely vocal4. After all, there has been evidence of passerine species, considered
cooperative breeders, that defend territory and young in flocks by offensive attacks against
predators11,4.
The success of Common Grackles raises the question of whether self-sustainability is a
common trend among other passerine birds admitted to the Raptor trust. However, it is noted that
the American Robin is admitted in close relation to the expectation created by population
densities in New Jersey. Surprisingly, American Robins are extremely similar to Common
Grackles: encompassing the same habitats, foraging the ground, nesting in trees, and maintaining
year round residence in New Jersey4. Perhaps Robins enter the facility in higher number because
they are simply more appealing to human finders (Common Grackles resemble Blackbirds and
Crows); however, survey and observational studies are necessary to confirm this hypothesis.
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In contrast, Mourning Doves are admitted to the facility in extremely high quantities,
much more than population density suggests (Figure 1). Thus, it can be concluded that Mourning
Doves are more susceptible to potential threats. This could be a result of habitat preference,
because these birds are often found in open areas lacking foliage4. Thus, it is important to
analyze where each species was found in terms of the facility, as well as, why each species of
interest was admitted to the Raptor Trust. Further analysis to determine which admit reasons the
species were more susceptible to in New Jersey was important for all raptor species analyzed.
This is because all five of the most admitted raptor species to the facility, including those
categorized as “threatened, endangered, and special concern” by the US Fish and Wildlife
Services, enter in extremely high amounts relative to their population densities (Figure 1).
Admittance vs. Proximity Upon analysis of proximity, it is apparent that a higher density of admitted birds occurs in
counties closer to the Raptor Trust’s location in Morris County (Figure 2). Furthermore, fewer
admits are observed in counties encompassing their own wild bird rehabilitation center. This in
itself is reasoning enough for why counties closer to Morris County result in higher admit
numbers. However, further research should be invested in comparing the admit densities per
county with the residential density of each county. It is hypothesized that there is a correlation
between county development and the amount of individual birds found in the area; a testament to
habitat loss and fragmentation.
Species Entering TRT for Various Admit ReasonsStatistical analysis of admitted counts indicated each of the five most admitted species
are categorized as “fallen from their nest” or “found on ground”. Since the categorization of the
birds at initial admit are based on the knowledge of the finder, they are not always one hundred
percent accurate. In cases of “impact” or “caught by animal”, the staff members of the facility
have the ability to adjust the admit reason to reflect a more accurate portrayal of an individual
case. However, in the case of “fallen from nest” or “fallen on ground”, it can be a bit more
difficult to determine accuracy: the bird’s age should be considered and medical assessments
utilized to determine potential pathogens or injuries, both of which can be difficult and
subjective.
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In the case of the five most admitted birds to the Raptor Trust, “found on ground” is the
most likely admit reason for Mourning Doves and Red-tailed Hawks (Figure 3). As mentioned
previously, Mourning Doves are extremely susceptible to potential threats causing high admit
numbers of this species; thus, it can be rationalized that Mourning Doves are most susceptible to
being found on the ground. This could be a result of their habitat preference, because they are
known to prefer scarce or barren lands (ie. Deserts or open grounds)4. In fact, this species is
known for scavenging the ground for extended periods of time before retreating to a higher
altitude11. Furthermore, Mourning Doves have little bias when it comes to nest construction; in
fact, they are willing to nest in dense foliage or even on the ground in the presence of humans7.
This could account for the high volume of individuals of this species entering rehabilitation
because they were found on the ground. To clarify, it is possible that humans simply misinterpret
the condition of the mourning doves, admitting healthy or normal behaving birds out of concern
for their location; such as the ground, which is actually normal with this species. Although, it is
possible that some individual birds found on the ground have fallen from their nest but were
incorrectly categorized upon admittance (ie. Fledglings). This is rational because Mourning
Doves tend to weave nests with weak materials (ie. Pine needles) lacking liners, potentially
contributing to fallen or lost young4.
“Fallen from nest” is the most likely admit reason for Mallard Ducks, Common Grackles,
and American Robins (Figure 3). It is possible that Mallard Ducks are admitted because of their
common interactions with humans, especially during migration where food resources become
scarce4. However, it is more likely that young Mallards are admitted because they have wandered
from their nests or lost their parents. This species commonly nests in depressions made in the
soil close to water, although the female attempts to conceal the nest with vegetation, it is possible
humans will still come across the young4. Female Mallard ducks are the sole incubators of the
eggs because the males tend to stray from their monogamy to partake in “extra-pair copulations”,
where many males mate with one female11,4. Despite an attentive parent, young Mallard Ducks
can be abandoned if there is a disturbance during various stages of brooding; whether it be
predators, conspecific individuals, or human visitation/disturbance11. Abandonment and loss of
young is more likely to occur in waterfowl, such as the Mallard Duck, since typically only one
parent provides the care. Single parent care is typical for waterfowl because the young hatch in a
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“precocial” state, thus they are more developed and require less care (ie. they feed themselves
and walk immediately)11. Sadly, the females are often completely abandoned by males during
incubation (unless there is opportunity for re-mating) and females can be killed off by predators
or external fluctuations (ie. drastic habitat changes); inevitably the young are abandoned and
many die without human intervention11,4. Human intervention is also common in cases where the
young inadequately feed themselves, a survival skill not performed by parents in this species;
without human intervention, the young would become malnourished and die11.
In passerines, like the American Robin and the Common Grackle, the “fell from nest”
susceptibility is shocking! American Robins enter the facility more often than Common
Grackles, but both are most likely to be admitted because they fell from their nest. Both species
tend to congregate during nesting and fledging. In fact, American Robins would be expected to
have the least amount of young admits because both parents cooperatively care for the young;
the mother care for the young at the nest, while the males care for the young independent enough
to leave the nest (ie. Fledglings and older)4. In contrast, the Common Grackles commonly group
with large numbers of similar species in the winter season but it is more common to see smaller
groupings during nesting season4. Passerine birds hatch in a state of “altricial” development,
where the young are naked and blind, thus they require intensive parental care. As a result, one
would hypothesize the American Robin, with co-parenting techniques, would result in lower
admittance of young; however, this is not the case. Perhaps this can be rationalized as a result of
nesting location: American Robins nest primarily in the mid-levels of trees but can be found to
nest on the ground or on human made structures (ie. Gutters or Garden fixtures), whereas
Common Grackles primarily nest in the high-levels of trees away from human made structures4.
As a result, it is possible that human intervention of the American Robin occurs more often
because they are in locations near human residential areas. Future observational studies are
necessary to compare nest-building and brooding behaviors of the Common Grackle and
American Robin.
Finally, through observation at the Raptor Trust, there is evidence that the public lacks
education in Passerine developmental stages of life; this results in a misunderstanding of a
healthy young bird (cared for by parents above in the treetops) versus an abandoned
malnourished counterpart. For example, American Robin fledglings (a developmental phase
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where young begin to gain independence) venture out of the nest for increasing increments and
distances each day attempting to forage on their own, while their parents keep a watchful but
distant eye from the treetops. Thus, human intervention occurs unnecessarily.
The five most admitted raptor species to the Raptor Trust are most likely to be admitted
because they were “found on the ground”, with the exception of the American Kestrel; which is
most likely to be admitted to the facility because they “fell from their nest” (Figure 4). Most owl
and hawk species have some sort of monogamous relationship with a variation of co-parenting;
this is particularly true for the raptor species of interest in this study. Female Hawks are
responsible for the feeding of young, while males hunt for food resources, bringing them back to
the nest1. Young Hawks tend to venture out of the nest, remaining in the immediate area, about
one month after hatching11. Although parents continue to feed their young, as young become
more independent, the female ventures away from the nest to assist the male with hunting11,4.
Until the young can make their own kills, the parents attentively care for their young; it is
common for human intervention to occur during the fledgling stage because the young appear
vulnerable and abandoned (due to parents being gone for increasingly longer intervals).
Similarly, Owls tend to form monogamous pair bonds that can last until the death of an
individual11,4! Like hawks, female owls perform incubation while the male provides food to the
nest; when the chicks get larger and increasingly demanding, the female leaves the nest to assist
with hunting11,4. Despite the occasional venture for food, hawks and owls are attentive parents
that care for their young up until sustainable flight is possible; thus, it is reasonable that these
types of birds are less susceptible to falling from their nest.
Much like owls and hawks, falcon species (ie. American Kestrels) have attentive co-
parenting monogamous pair bonds coming together during breeding seasons after solitary
lifestyles11,4,10. However, American Kestrels are susceptible to predation due to their continuous
vocalizations around nesting sites, and abandonment is possible if disturbance is incessant11,10.
Thus it can be rationalized that falling from their nest is a concern for young American Kestrels
who lose their parents to abandonment or predation. In addition, fledgling Kestrels tend to leave
the nest after only weeks of hatching to learn to hunt and become independent11. Furthermore,
nesting behavior of the American Kestrel potentially increases the susceptibility towards falling
from their nest. Unlike the hawk and owl species discussed in this study (Cooper’s Hawk, Red-
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tailed Hawk, and Great Horned Owl), American Kestrels and Eastern Screech Owls are cavity-
nesters; requiring hollowed out tree holes or nest boxes for breeding11,4,10. Despite this, Eastern
Screech Owls prefer denser foliage, an attribution to why they are less susceptible to falling from
their nest; whereas, American Kestrels are extremely attracted toward human made fixtures and
structures. In fact, many Kestrels have been seen hiding food or nesting on signs, fences, or even
buildings4. This occurs because of the lost habitat and nest cavities due to human encroachment
by urbanization and agricultural expansion4,15. As a result, it is hypothesized that American
Kestrels are more susceptible to falling from their nest because they have been forced to shift
their nesting sites to more densely populated human locations and structures; however, more
research in Kestrel specific behavior compared to other falcon and raptor species is necessary.
The Raptor trust admits five species considered “threatened”, “endangered”, or “special
concern”: American Kestrel, Barred Owl, Bald Eagle, Peregrine Falcon, and the Red-Shouldered
Hawk. The American Kestrel and Barred Owl species are termed threatened; the Bald Eagle,
Peregrine Falcon, and Red-Shouldered Hawk are termed endangered by the US Fish and Wildlife
Services5. Threatened species are those with the potential to become endangered if current
conditions persist; endangered species are those suffering survivability danger due to various
environmental and human threats5. Special concern species, Red-shouldered Hawk and Peregrine
Falcon, are categorized as such because they suffer survivability danger due to environmental
factors; such as, habitat loss or change and resource limitation5. All species of New Jersey state
concern are admitted more often because they were found on the ground, with the exception of
American Kestrels that are more susceptible to falling from their nest (Figure 5). It is
hypothesized that these birds are found on the ground more often as a result of habitat preference
or habitat change forced by human encroachment. In many cases, this is supported by nesting
behaviors; for example, the Red-shouldered Hawks and Barred Owls return to the same nest each
breeding season. Habitat changes and encroachments can alter breeding lands or destroy nests,
thus these species face decreasing brooding success and population declines11,4,10. Bald Eagles
and Peregrine Falcons tend to nest on cliff sides, but travel the world in younger years; therefore,
habitat shifts can disorientate these species and make them susceptible to population declines4,10.
These habitat changes and threats are potential causes that make these species susceptible to
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being found on the ground; in addition, the young of these species tend to venture out of the
nests at younger ages or wander various territories11,4,10.
Analysis of Admit Reasons and Similarities to Other FacilitiesThe Raptor trust has remained constant with overall admit likelihood in the past five
years (Figure 6). “Fell from nest” and “found on ground” have consistently remained the most
likely admit reason for all species analyzed at the Raptor Trust in a five-year period. There are
many reasons why this is the case, as was explained on a species specific level, but overall
threats have been consistent throughout the five years of analysis: habitat loss, climate change,
resource limitation, pollution and human interference11,9.
Habitat loss is an increasing problem as urbanization and development has increased.
Habitat changes cause alterations in bird population distributions and population success11,9.
Changes to habitats cause breeding declines because species are forced to choose unfavorable
nesting locations or materials. Young birds in various developmental stages face hardships they
are not evolutionarily suited to overcome when habitat loss occurs; for example, increased
predation or lack of foliage for concealment. Habitat change also alters migration patterns, which
indirectly impacts population success and breeding success11,15,3,2,6. Many researchers have
confirmed that migration, reliant on orientation and navigation during flight, is accomplished by
environmental factors11. In fact, it has been debated whether or not birds utilize odor cues or
landmarks to ensure correct navigation to seasonal stopover locations; thus, as habitats change,
various species of birds can become dioriented11. This disorientation can cause inappropriate stop
overs, ultimately affecting population success (specifically due to resource limitations/scarcity
and climate issues).
Climate change can affect more than population success during migration. It also
influences resources available in certain habitat locations; for example, rainfall alterations can
determine plant success and indirectly affect nesting for birds utilizing foliage for protection
against predation11. Perhaps more well-known are the affects temperature change has on hatching
behavior of various bird species; such as the proven correlation of higher temperatures triggering
egg laying and hatching earlier than optimally favorable3. According to Moller et. Al, 79% of
bird species show a significant negative relationship between egg laying dates and air
temperature3. It was also confirmed that migration distance, direction, timing and speed are
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altered in a significantly negative manner with temperature changes3. As a result, weather
changes can affect population distributions and densities; proving survivability success is
dependent on favorable weather tempeartures3.
However, the largest influence on bird populations and success rates of species, is that of
human interference and disturbance. Human presence is noted to affect migration patterns and
success; for example, artificial light created by urbanization can trigger inappropriate orientation
cues and cause migration issues11. Habitat loss is also associated with human presence, being lost
as a result of urbanization and residential encroachment11. As an example, natural habitats have
been lost to human development for agricultural land, residential development, or resource
attainment (ie. Mining)11. Even human visitation (ie. Bird watchers or trail hikers) can negatively
impact bird populations; such as, parent abandonment as a result of nest disturbance11.
Furthermore, urbanization has produced toxins poisonous to various species. Fertilizers and
sedimentation causes polluted runoff water into avian drinking reservoirs and habitat locations;
specifically affecting waterfowl11.
In clarification, the present threats existing today directly and indirectly affect bird
populations and success rates. These effects cause various individuals to be brought to
rehabilitation centers. Furthermore, each of the present threats provides rational for why birds
may be found on the ground or falling from their nests! An example would be habitat loss
pushing birds to display behavioral displacement, or behaviors unaccustomed to a species (ie.
nesting on the ground versus a more favorable location; like Mallards in agricultural fields when
wetlands are not readily available). Or, perhaps, individuals suffering pesticide toxicity due to
rainwater runoff resting on the ground because they are too weak to fly away. Each threat can
rationalize and provide an example of why “found on ground” and “fallen from nest” are the two
most likely reasons an individual bird species might enter a rehabilitation center! This is further
supported by the similar data obtained by the Avian Wildlife Center, located in a different county
than the Raptor Trust (Figure 7). The same types of admit reasons can be seen at this facility;
however, further research is necessary to determine rationality for the extremely high impact
admits at the Avian Wildlife Center. Perhaps additional research focusing solely on urbanization,
specifically, developmental densities would be beneficial on a county wide basis.
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Raptor Trust Success The sheer number of admitted birds to the raptor trust in the past five years is evidence
enough for the necessity of a wild bird rehabilitation center! These admits have been categorized
based on admit reason and rationalized with issues presently threatening wild bird populations,
providing strong evidence that wild bird populations need human intervention to counteract the
negative impact humans have inadvertently caused throughout our existence. Evidence has been
provided to prove that the threats causing species to require human intervention are not occurring
solely in one county, but rather occurring on a state wide level; proven by comparing another
facility’s admitted birds.
Furthermore, it can be seen that this particular rehabilitation center (The Raptor Trust) is
successful in its endeavors (Figure 8); in fact, the majority of admitted birds are released after
examination and treatment at the facility. This analysis has also determined that birds in New
Jersey are particularly susceptible to falling from their nests and requiring human intervention
due to being found on the ground; both were confirmed by various threats presented by other
researchers.
However, it is extremely evident that all facilities should increase their educational
outreach. This is because many of the direct and indirect negative effects on wild bird
populations are a result of human presence and development; increasing education about natural
bird behaviors, nesting, and developmental stages will limit the admittance of birds in healthy
condition (ie. Fledglings). Furthermore, education will provide understanding of our impact on
natural wild bird populations; ultimately allowing preventatives to be presented and
implemented. Of course, future research of various types would be extremely useful to the
populations of New Jersey; a few have been presented within the text of this study, but the
possibilities are infinite.
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References1. Baldassarre GA and Bolen EG. Waterfowl Ecology and Mangement. New York (NY);
1994. P. 29-30
2. Bildstein KL. Migrating Raptors of the World: Their Ecology and Conservation. Ithaca
(NY); 2006. P. 89-173.
3. Caswell H. Birds and Climate Change. Vol. 35. San Diego (CA); 2004. P. 23-193.
4. Cooke WF. American bird conservancy [Internet]. Plains (VA): American bird
conservancy; 2013 [cited 2015 Jun 10]. Available from http://www.abcbirds.org
5. Department of Environmental Protection. NJ licensed wildlife rehabilitator information
[Internet]. Trenton (NJ): Division of fish and wildlife; 1996 [cited 2015 Jun 10].
Available from http://www.njfishandwildlife.com/rehab_info.htm
6. Ligon DL. The Evolution of Avian Breeding Systems. Oxford (NY); 1999. P. 139-328.
7. Miller EA. Quick reference: national wildlife rehabilitators association. Third Edition. St.
Cloud (MN); 2006. p. 73-85 115 136.
8. Newton I. Population Ecology of Raptors. Vermillion (SD); 1979. p. 213-215, 224-227.
9. Newton I and Brockie K. Popoulation Limitation. San Diego (CA); 1998. p. 2-6, 9-13
10. Scouten T. Wildscreen Arkive [Internet]. Washington (DC): Wildscreen USA; 2003
[cited 2016 May 1]. Available from http://www.arkive.org
11. Sibley DA. National Audubon Society: The Sibley Guide to Bird Life and Behavior. A
Chantiecleer Press Edition. New York (NY); 2001. p. 44-48, 105-109, 113-118, 213-215,
224-227.
12. Soucy LJ. The raptor trust [Internet]. Millington (NJ): The raptor trust; 2013 [cited 2015
Jun 10]. Available from http://theraptortrust.org
13. Stern S. Summer internship binder. Millington (NJ): The raptor trust; 2015.
14. Stern S. Volunteer training manual. Millington (NJ): The raptor trust; 2015.
15. Terborgh J. Where Have All the Birds Gone? Princeton (NJ); 1989. p. 11-17.
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