Bird Anatomy

Circulatory SystemSeparate systemic, pulmonary circulations4-chambered heartSame in mammals - homeotherms

Hearts1.5-2 X larger than in comparable mammalsMaintain higher metabolismSmaller birds have relatively larger hearts than larger birdsHeart size increases with latitude, altitude for same species

Heart BeatHeart beat slower than in mammalsSmaller birds have faster heartbeats than larger birds

Blood PressureSlightly higher than mammalsBordering on safetyHeart, aortic ruptures can occur

Respiratory SystemMost efficient among vertebratesUnique designComplex flow-through system of sacs & interconnecting tubes

Respiratory SystemSmall lungs (2% of body volume) connected to large air sacs (~10X larger)4 pairs of sacs plus 1 unpaired sac (some variation)

Respiratory SystemTiny, inelastic lungs filled with tubular air capillaries - parabronchiUnidirectional movement of air through parabronchi compared to dead-end structure of mammalian alveoli

Respiratory System

Respiratory SystemProcess - 2-cycle pump2 inhalation/exhalation cycles required to move each breath totally through respiratory systemPosterior air sacs to lungs to anterior air sacs

Respiratory System

Respiratory SystemUnidirectional air flow through lungsOxygenated air during both inhalation and exhalationBlood flows in opposite direction

Air SacsMay also aid in:CoolingBuoyancyDefecation/egg-laying muscle assistanceCourtship

Accessory ThingsSyrinx - voiceboxWhere trachea splits into bronchiVarious types, but generally are complex arrangements of muscles, membranes

Accessory ThingsSounds (songs) produced in several waysVibrating membranesChanging size of openingsChanging air movement patterns

ExcretionKidneys and salt glandsKidneys similar to mammal kidneys2X as large (relative)More rapid metabolismNot as efficient at removing saltNeed for salt glands

ExcretionKidneys produce primarily uric acid rather than urea Requires less water (not as toxic as urea)Holdover from embryo (egg)

ExcretionUric acid works well in dry climates, conserves weightWater not needed in large quantitiesWastes dumped into cloaca (no urinary bladder), mixed with feces, forms white paste with dark lumps

ExcretionSalt glands in headConcentrate salt 3-5X that in bloodDischarge through nostrilsEspecially active in marine birds

Reproductive Anatomy - MalePaired testesGrow during breeding season, shrink otherwiseUp to 200-300X difference in size between seasons

Reproductive Anatomy - Male

Reproductive Anatomy - MaleLeft testis slightly larger than rightRelated to female - left side only?

Reproductive Anatomy - MaleVas deferens - wavy tubesMature sperm collect until transferredEnd nearest cloaca may swell to serve as storage sac

Reproductive Anatomy - MaleCopulatory organ - present in more primitive birdsE.g., flightless ratites, Galliformes, ducks & geeseErectile, grooved structure used to guide sperm into females cloaca during copulationBirds lacking feature just press cloacal openings together

Sperm DevelopmentHigh body temperature causes problemsSperm cells cant develop at normal body temperatures

Sperm DevelopmentAlternatives:Develop at night when body temperature may dropDelay final development until storage in cooler sac or pouch near cloaca

Sperm OutputMillions to billions per copulation

Sperm in FemaleSperm may be stored in female temporarily in lower oviduct pouchStored sperm may remain viable for up to several months before eggs are laidHighly variable among species

FertilizationOne to many copulations may be required for fertilizationParthenogenesis possible in some species (e.g., turkeys)

Reproductive Anatomy - FemaleLeft side onlyOvary, oviductRight ovary, oviduct whither awayWeight reduction?But paired systems (abnormal) have been observed in dozens of species

Reproductive Anatomy - FemaleEnlarge during breeding season, shrink after

Reproductive Anatomy - FemaleOvary may contain thousands of ovarian folliclesOnly few per year mature into ovaRapid growth through addition of fat, protein food (yolk) probably from liver

Reproductive Anatomy - FemaleOviduct responsible for adding albumen, shell membranes, shell, pigment to ovaFive regions

Reproductive Anatomy - FemaleInfundibulum - funnels, captures released ova2 ova released simultaneously produce double-yolked eggOvum spends ~18 minutes here in chicken

Reproductive Anatomy - FemaleMagnum - largest regionSecretes layers of albumen (egg-white)Moisture and cushioningOvum spends ~4 hrs here in chicken

Reproductive Anatomy - FemaleIsthmusProduces shell membranesFlexible keratinOvum spends ~1.25 hrs here in chicken

Reproductive Anatomy - FemaleUterusShell gland produces the calcium carbonate shellPigment glands apply color(s)Ovum spends ~18-20 hrs here in chicken

Reproductive Anatomy - FemaleVagina Lined with mucous glands and muscular to aid egg-layingOvum spends very brief time here in chicken - just passing through!

Calcium Sources for EggsDiet most important source for most birdsBones serve as a secondary source

Bird Songs & CallsCalls are brief sounds with simple acoustic structureUsually 1 or 2 notes, rarely 4 or 5Used for behavior coordinationNon-sexualFlocking, feeding, migration, predator reactionSome innate, others learned

Bird Songs & CallsSongs are complex soundsGroups of notes separated from one another by relatively long pauses

Bird Songs & CallsSongs often serve as substitute for physical combat (territory defense)Maintaining pair bondStimulate, synchronize reproductionMore commonly modified by learning than are calls

Bird Songs & CallsOverall functions:Reproductive Social Individual

Calls as VocabulariesMany different birds have different callsEnable members of a species to talk to one anotherDifferent calls have different meanings:AssemblyAlarmDistressFeedingIndividual name calls

Cluck-Cluck-CluckChicken has at least 10 different calls for communicating with othersSpecies generally have calls numbering in the teens or twentiesSongbirds average ~15Como estan ustedes?Some calls also may be interspecificSpecies that often flock together have relatively common calls that all species can understand

Chink-Chink-ChinkUsed by many species to indicate stationary threatLow frequencyRepeatedEasy to locate caller

SeeetUsed to indicate moving threatHigh frequencySingularDifficult to locate caller

Source of SoundSyrinx - found only in birdsSounds produced by vibrations of vocal membranes in syrinx, or vibration of air columns

Source of SoundAir in trachea or air sacs may also resonate and either dampen or enhance vibrations caused by vocal membranes

Source of SoundSome birds capable of producing two unrelated (harmonically) sounds simultaneouslyDuplicate membranes controlled by separate muscles in each bronchus

Trachea and PitchLength, diameter of trachea determines pitchLong & wide - deep voiceShort & narrow - high voice

Trachea and PitchGeese, swans, etc. have strange method for lengthening trachea, deepening voiceSome birds compress trachea to increase pitchAlso inflate air sacs to add resonance, volume

Primary SongsLoudCourtship and territory defenseAdult males mostly

Secondary SongsSubsongs or whisper songsWeak, quiet - practice?Young males, males outside of breeding season, females

Song CyclesSeasonal variation correlated with breeding activity, hormone productionRichest, fullest song in springTerritory establishment, courtship

Song CyclesDecreases after mating, during family rearingRarely sing on or near nestSilent during molt, cold weatherTestosterone can induce song out of season

Song Cycles - DailyMost vigorous at dawn, tapers to midday, increases into evening, ceases at duskNocturnal species oppositeChief stimulus - light intensity - minimum to initiateInverse in nocturnal species

Innate vs. LearnedSome species have entirely inherited songsComplete song develops in absence of exposure to adults - innateOther species songs have both innate, learned components

Innate SongInnate pattern is rather simpleServes as a template

Learned SongLearning enhances the templateCritical period learners - learning can only be done before a certain ageOpen-ended learners - learning can occur at any time

Open-ended LearningSong may be changed from year to yearMay learn a more complex songMay show experience and more successfully attract a mate

Song MimicryMany species capable of mimicking calls, songs of other speciesMimidae (catbird, mockingbird, thrasher), starling, crowMay also imitate other animals, sounds

Song MimicryWhy?Ulterior motives?Imitated sounds apparently not used to keep away those speciesBetter mimic may be more likely to attract its own mate

Song DialectsGeographic variation in songs - dialectsSpecies members in one area sing similar songs, but different from same species elsewhere

Song DialectsWidely separated birds may sing such dissimilar songs that they may not recognize each other as members of same speciesYoung learn dialects from parents and/or neighbors

Song DialectsFamiliar neighbors song may elicit less of a response than song of non-neighborIntruder?