Download - Birds & Conservation
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Birds & Conservation
A Global & Local Perspective
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Major Conservation Issues• Humans• Habitat• Toxic compounds• Exotic species• Island Effect• Nest Parasites
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General Effects of Humans:we take up space & demand resources
• Human population & associated effects– Huge size (~ 6 billion)– Future increases in population - some
models suggest peaks @ between 12-20 billion
• Development (all ↓ available habitat)– Housing– Industry– Agricultural
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Human Presence
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Other Associated Human Effects
• Excessive Hunting – when going beyond sustainable levels– turn of century feather collectors– poaching of endangered species
• Examples:– Passenger Pigeon– Great Auk– Eskimo Curlew & other shorebirds
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Once the most abundantbird in North America, thePassenger Pigeon is nowextinct. Overhunting for markets is though to beone contributing factor.
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Eskimo Curlew
Texas 1962
Formerly a common spring migrant inin eastern SD; now probably extinct
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Upcoming Schedule• Final Field Trip – Sat., May 1
– Newton Hills State Park– 0730-1400
• Final Exam– Thursday, May 6– 1230 to 1430– Will cover material since second exam
(Social Systems through Conservation)
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Other Associated Human Effects……
• Road Kills• Cats• Collisions
– buildings, windows, communications towers• Human activities directly kill an
estimated 1 billion birds each year in the U.S.
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Avian Collision Study (Erickson et al.2005)
Annual estimates of U.S. Mortality• Vehicles (80 million)• Buildings/Windows (100 million-1 billion)• Powerlines (130 million)• Communication Towers (4-5 million)• Wind Turbines (20-40 thousand)• For comparison: house cats = about 100
million annually in N. America• Total anthropogenic mortality = > 1 billion
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Habitat Destruction• Loss
– destroyed altogether– removal and replacement with human-
altered habitat• Fragmentation
– partial destruction as well as separation of once-connected areas into isolated fragments
– leads to lower total area & possible separation of populations in fragments
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Habitat Destruction……• Degradation
– lower quality due to a variety of factors such as exotic species, increased edge, toxins, etc.• cheatgrass or other weeds• agricultural runoff in a stream
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Many habitats are threatened
• Tropical Rainforests• Temperate Forests• Wetlands/Riparian Areas• Grasslands
• With loss of habitat, there is less area to sustain populations
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New World Rainforest
Gray: extant forestBlack: destroyed
p. 642
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Gray: extant forestBlack: destroyed
SE Asian Rainforest
p. 642
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Examples• Golden-cheeked Warbler
– breeds central Texas– winters S Mexico– housing developments, recreation, etc.– cowbirds
• Riparian birds in South Dakota– many woodland habitats now gone due to
dams and conversion to agriculture– limited habitat area for populations
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Note dramatic decreases in forest and grassland habitats
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Migratory Birds• Need suitable habitat for all phases
of life cycle:– breeding, wintering, migration
• Habitats migrants use often differs among seasons
• Conservation plans must be complex to safeguard all important habitats
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Habitat Conservation Efforts
• Preserves:– National Parks, National Wildlife Refuges,
National Forests & Grasslands, state & local parks, private
• Conservation easements:– private land set aside, CRP
• Endangered Species Act:– mandates protection for species threatened by
human activities• Need ecosystem-based approaches
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Environmental toxins
• Pesticides– DDT– PCB’s
• Fertilizers• Fossil Fuels• Household Chemicals
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Pesticides• Widespread use:
– household & lawns– agricultural– pest control
• Many effects– reduce prey populations– non-target mortalities
• For example, Birds of Prey– bio-accumulation and bio-magnification
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Example of Pesticide Effects: DDT
• DDT: 1,1,1-trichloro-2,2-bis-(p-chlorophenyl) ethane– widespread use mid-1900s– population declines noticed in many
birds, especially predators– Osprey, Bald Eagle, Peregrine Falcon– Peregrine almost extinct in eastern US
• DDT banned in US in 1972• subsequent rebound of all raptor
species affected
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Bald Eagles before & after DDT ban: Reproduction & amounts of DDE
p. 565
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Local Toxin Example: Selenium & colonial waterbirds
• Selenium (Se):– trace mineral– important in small amounts– key component of enzymes
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Selenium & colonial waterbirds
• The problem:– high concentrations of Se found in
some soil types: (e.g., marine shale)– Se leaches from soil in high amounts– agricultural run-off leads to high [ ] in
bodies of water– Se will bioaccumulate (increasing
levels as you move up food chain)
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Selenium & colonial waterbirds
• Effects on birds:– deformities– reduced reproductive success
• Rookery @ Stratford Slough (Brown Co., SD)– ~ 1000 birds ‘destroyed’ due to
selenium
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Exotic Species
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Exotic Species• Exotic Introduced Non-native
– any species living outside of its natural range
• Sources:– human colonists (“acclimatization societies”)
– agriculture– accidental transport– biological control– ‘just for fun’
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Examples of Exotic Species
• southern US: Fire Ants • Guam: Brown Tree Snake • US: European Starling
– House Sparrow– Rock Pigeon– Ring-necked Pheasants
• Hawaii: > 50 introduced bird species
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Why are exotics a problem?
• Freedom from usual population limitation– no natural predators– no usual diseases
• Competition with or predation of native species:– native species may have not evolved
defenses or necessary behaviors to ‘deal with’ exotics
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Effects of Fire Ants:predationcompetition
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Brown Tree Snake in Guam
Bird
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Exotic Birds• European Starling:
– introduced to Central Park in NYC ~ 1890– now most common bird in US– competes for food & nest cavities
• House Sparrow & Rock Pigeon– more confined to human areas– still compete w/ natives– House Sparrow vs. Purple Martin
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More Exotic Birds• Ring-necked Pheasant & other
game birds (Chukar, Gray Partridge, etc.)– favored for hunting– may compete w/ native grouse (???)
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Birds and Islands
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Island Biogeography• ‘The small island effect’• Small islands support small
populations• Island populations often not exposed
to full range of ecological factors– predators– pathogens
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Island Biogeography……• Evolve unique adaptations, which
often lead to speciation– flightlessness– ground-nesting
• More sensitive to changes in environment– Hawaii– Guam– fragmented habitats
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Hawaii
• Isolated volcanic islands• populated by founder species that
colonized• adaptive radiation• many unique, locally adapted species
– flightless Ibis & honeycreepers• few predators
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Hawaii…… Human effects over last 2 millenia:
• introduced pigs & other ungulates– over-grazing/browsing
• introduced rats (nocturnal)– predators of many unsuspecting birds
• introduced mongoose (diurnal)– preys on many birds (not rats!)
• introduced mosquitoes• avian malaria w/ introduced birds
– spread by mosquitoes
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Hawaii……• ~ 1/2 of original species remain• many remaining are threatened by
habitat loss, diseases, & vagaries of small population size
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Guam
• Brown Tree Snake• elimination of all wild populations
of Guam’s endemic birds:– rail, kingfisher, songbirds, etc.
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Island Biogeography & Mainland Ecosystems
• Naturally occurring ‘islands of habitat’:– Black Hills– ‘Sky Islands’ of desert southwest
• Human-caused fragmentation:– once extensive areas now only patches– forest– grassland– etc.
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Cowbirds and Conservation• Brood parasitism has negative
impacts on host reproductive success• Cowbirds feed in open areas but
parasitize many forest-dwelling songbirds
• Human activities have allowed cowbirds to expand their range– Forest fragmentation more open areas– Cattle ranching associate with
bison/cattle
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Cowbirds and Conservation• Brown-headed Cowbirds have
parasitized over 220 species• Of these < 25 eject cowbird eggs, 37
desert nest to renest, only a few build a new floor over clutch. Most are susceptible.
• Parasitism probably not responsible for continent-wide population declines, but do impact some endangered species.– Least Bell’s Vireo, Kirtland’s Warbler, Black-
capped Vireo, SW Willow Flycatcher)
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Cowbirds and Conservation• Control Issues:
– Some view killing cowbirds as inhumane– Cowbird removal is only a short-term
solution to the problem– Cowbird removal is expensive
• Bell’s Vireo: over $665K/year (225 traps/yr, each trap gets about 3,000 cowbirds/yr)
• Kirtland’s Warbler: $90K/yr• Black-capped Vireo: $45K/yr
– Removal doesn’t increase population size for all species
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Cowbird Removal: Successes
• Golden-cheeked Warbler: rate of parasitized nests down from 90% in 1987 to 22% in 1996.
• Black-capped Vireo: rate of parasitized nests down from 90% in 1987 to <10% in 2000-2002; nest success increased from 3% to >40%.
• SW Willow Flycatcher: rate of parasitized nests down from 63% in 1989-1991 to 15% in 2003, nest success increased from 20 to 61%.
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Cowbird Removal: Mixed Results
• Least Bell’s Vireo: populations increased following cowbird control and efforts to improve habitat
• Kirtland’s Warbler: cowbird control and habitat restoration increased population from 200 breeding pairs in 1972 to 1800 breeding pairs in 2007.
• SW Willow Flycatcher: After 12 years of cowbird control CA pop. still decreased. Suggests that habitat, not cowbirds, is limiting factor.
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Cowbirds and Conservation• What to do about it?• Habitat issues are primary
concerns– Increase nesting habitat for songbirds– Decrease habitat fragmentation that favors
cowbirds• Cowbird Control = not a long-term
solution– May help very small populations increase
to reestablish a stable breeding population, but don’t promote long-term recovery