Bird Anatomy

Circulatory System

• Separate systemic, pulmonary circulations

• 4-chambered heart• Same in mammals -

homeotherms

Hearts

• 1.5-2 X larger than in comparable mammals

• Maintain higher metabolism

• Smaller birds have relatively larger hearts than larger birds

• Heart size increases with latitude, altitude for same species

Heart Beat

• Heart beat slower than in mammals

• Smaller birds have faster heartbeats than larger birds

Blood Pressure

• Slightly higher than mammals

• Bordering on safety• Heart, aortic ruptures

can occur

Respiratory System

• Most efficient among vertebrates

• Unique design• Complex flow-through

system of sacs & interconnecting tubes

Respiratory System

• Small lungs (2% of body volume) connected to large air sacs (~10X larger)

• 4 pairs of sacs plus 1 unpaired sac (some variation)

Respiratory System

• Tiny, inelastic lungs filled with tubular air capillaries - parabronchi

• Unidirectional movement of air through parabronchi compared to dead-end structure of mammalian alveoli

Respiratory System

Respiratory System

• Process - 2-cycle pump

• 2 inhalation/exhalation cycles required to move each breath totally through respiratory system

• Posterior air sacs to lungs to anterior air sacs

Respiratory System

Respiratory System

• Unidirectional air flow through lungs

• Oxygenated air during both inhalation and exhalation

• Blood flows in opposite direction

Air Sacs

• May also aid in:• Cooling• Buoyancy• Defecation/egg-laying

muscle assistance• Courtship

Accessory Things

• Syrinx - voicebox• Where trachea splits

into bronchi• Various types, but

generally are complex arrangements of muscles, membranes

Accessory Things

• Sounds (songs) produced in several ways

• Vibrating membranes• Changing size of

openings• Changing are

movement patterns

Excretion

• Kidneys and salt glands

• Kidneys similar to mammal kidneys

• 2X as large (relative)– More rapid metabolism

• Not as efficient at removing salt– Need for salt glands

Excretion

• Kidneys produce primarily uric acid rather than urea

• Requires less water (not as toxic as urea)

• Holdover from embryo (egg)

Excretion

• Uric acid works well in dry climates, conserves weight

• Water not needed in large quantities

• Wastes dumped into cloaca (no urinary bladder), mixed with feces, forms white paste with dark lumps

Excretion

• Salt glands in head• Concentrate salt 3-

5X that in blood• Discharge through

nostrils• Especially active in

marine birds

Reproductive Anatomy - Male

• Paired testes• Grow during

breeding season, shrink otherwise

• Up to 200-300X difference in size between seasons

Reproductive Anatomy - Male

Reproductive Anatomy - Male

• Left testis slightly larger than right

• Related to female - left side only?

Reproductive Anatomy - Male

• Vas deferens - wavy tubes

• Mature sperm collect until transferred

• End nearest cloaca may swell to serve as storage sac

Reproductive Anatomy - Male

• Copulatory organ - present in more primitive birds

• E.g., flightless ratites, Galliformes, ducks & geese

• Erectile, grooved structure used to guide sperm into female’s cloaca during copulation

• Birds lacking feature just press cloacal openings together

Sperm Development

• High body temperature causes problems

• Sperm cells can’t develop at normal body temperatures

Sperm Development

• Alternatives:• Develop at night when

body temperature may drop

• Delay final development until storage in cooler sac or pouch near cloaca

Sperm Output

• Millions to billions per copulation

Sperm in Female

• Sperm may be stored in female temporarily in lower oviduct pouch

• Stored sperm may remain viable for up to several months before eggs are laid– Highly variable

among species

Fertilization

• One to many copulations may be required for fertilization

• Parthenogenesis possible in some species (e.g., turkeys)

Reproductive Anatomy - Female

• Left side only• Ovary, oviduct• Right ovary, oviduct

whither away• Weight reduction?• But paired systems

(abnormal) have been observed in dozens of species

Reproductive Anatomy - Female

• Enlarge during breeding season, shrink after

Reproductive Anatomy - Female

• Ovary may contain thousands of ovarian follicles

• Only few per year mature into ova

• Rapid growth through addition of fat, protein food (yolk) probably from liver

Reproductive Anatomy - Female

• Oviduct responsible for adding albumen, shell membranes, shell, pigment to ova

• Five regions

Reproductive Anatomy - Female

• Infundibulum - funnels, captures released ova

• 2 ova released simultaneously produce “double-yolked” egg

• Ovum spends ~18 minutes here in chicken

Reproductive Anatomy - Female

• Magnum - largest region

• Secretes layers of albumen (egg-white)

• Moisture and cushioning

• Ovum spends ~4 hrs here in chicken

Reproductive Anatomy - Female

• Isthmus• Produces shell

membranes• Flexible keratin• Ovum spends ~1.25

hrs here in chicken

Reproductive Anatomy - Female

• Uterus• Shell gland produces

the calcium carbonate shell

• Pigment glands apply color(s)

• Ovum spends ~18-20 hrs here in chicken

Reproductive Anatomy - Female

• Vagina • Lined with mucous

glands and muscular to aid egg-laying

• Ovum spends very brief time here in chicken - just passing through!

Calcium Sources for Eggs

• Diet most important source for most birds

• Bones serve as a secondary source

Bird Songs & Calls

• Calls are brief sounds with simple acoustic structure

• Usually 1 or 2 notes, rarely 4 or 5

• Used for behavior coordination– Non-sexual– Flocking, feeding,

migration, predator reaction

• Some innate, others learned

Bird Songs & Calls

• Songs are complex sounds

• Groups of notes separated from one another by relatively long pauses

Bird Songs & Calls

• Songs often serve as substitute for physical combat (territory defense)

• Maintaining pair bond• Stimulate, synchronize

reproduction• More commonly

modified by learning than are calls

Bird Songs & Calls

• Overall functions:• Reproductive • Social • Individual

Calls as Vocabularies

• Many different birds have different calls

• Enable members of a species to “talk” to one another

• Different calls have different meanings:

• Assembly• Alarm• Distress• Feeding• Individual “name”

calls

Cluck-Cluck-Cluck

• Chicken has at least 10 different calls for communicating with others

• Species generally have calls numbering in the teens or twenties

• Songbirds average ~15

• ¿Como estan ustedes?• Some calls also may

be interspecific• Species that often

flock together have relatively common calls that all species can understand

Chink-Chink-Chink

• Used by many species to indicate stationary threat

• Low frequency

• Repeated

• Easy to locate caller

Seeet

• Used to indicate moving threat

• High frequency

• Singular

• Difficult to locate caller

Source of Sound

• Syrinx - found only in birds

• Sounds produced by vibrations of vocal membranes in syrinx, or vibration of air columns

Source of Sound

• Air in trachea or air sacs may also resonate and either dampen or enhance vibrations caused by vocal membranes

Source of Sound

• Some birds capable of producing two unrelated (harmonically) sounds simultaneously

• Duplicate membranes controlled by separate muscles in each bronchus

Trachea and Pitch

• Length, diameter of trachea determines pitch

• Long & wide - deep voice

• Short & narrow - high voice

Trachea and Pitch

• Geese, swans, etc. have strange method for lengthening trachea, deepening voice

• Some birds compress trachea to increase pitch

• Also inflate air sacs to add resonance, volume

Primary Songs

• Loud• Courtship and

territory defense• Adult males mostly

Secondary Songs

• “Subsongs” or “whisper songs”

• Weak, quiet - practice?

• Young males, males outside of breeding season, females

Song Cycles

• Seasonal variation correlated with breeding activity, hormone production

• Richest, fullest song in spring– Territory

establishment, courtship

Song Cycles

• Decreases after mating, during family rearing

• Rarely sing on or near nest

• Silent during molt, cold weather

• Testosterone can induce song out of season

Song Cycles - Daily

• Most vigorous at dawn, tapers to midday, increases into evening, ceases at dusk

• Nocturnal species opposite

• Chief stimulus - light intensity - minimum to initiate– Inverse in nocturnal

species

Innate vs. Learned

• Some species have entirely inherited songs

• Complete song develops in absence of exposure to adults - innate

• Other species’ songs have both innate, learned components

Innate Song

• Innate pattern is rather simple

• Serves as a “template”

Learned Song

• Learning enhances the template

• Critical period learners - learning can only be done before a certain age

• Open-ended learners - learning can occur at any time

Open-ended Learning

• Song may be changed from year to year

• May learn a more complex song

• May show “experience” and more successfully attract a mate

Song Mimicry

• Many species capable of mimicking calls, songs of other species

• Mimidae (catbird, mockingbird, thrasher), starling, crow

• May also imitate other animals, sounds

Song Mimicry

• Why?• Ulterior motives?• Imitated sounds

apparently not used to keep away those species

• Better mimic may be more likely to attract its own mate

Song Dialects

• Geographic variation in songs - dialects

• Species members in one area sing similar songs, but different from same species elsewhere

Song Dialects

• Widely separated birds may sing such dissimilar songs that they may not recognize each other as members of same species

• Young learn dialects from parents and/or neighbors

Song Dialects

• Familiar neighbor’s song may elicit less of a response than song of non-neighbor

• Intruder?