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CHAPTER CHAPTER CHAPTER CHAPTER
BirdsBirds BirdsBirds
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DiversityDiversity
ProfileProfile Over 9,700 species have been Over 9,700 species have been
described worldwidedescribed worldwide Birds live in all biomesBirds live in all biomes Some live in dark caves, and some dive Some live in dark caves, and some dive
to 45 meters depthto 45 meters depth The “bee” hummingbird is one of the The “bee” hummingbird is one of the
smallest vertebrate endothermssmallest vertebrate endotherms
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The The featherfeather is the unique and essential is the unique and essential feature or hallmark of birdsfeature or hallmark of birds Some feathers were also present in some Some feathers were also present in some
dinosaursdinosaurs These feathers were not capable of supporting These feathers were not capable of supporting
flight flight Obviously served in other capacities such as Obviously served in other capacities such as
thermoregulation or mating behaviorthermoregulation or mating behavior
DiversityDiversity
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Uniformity in StructureUniformity in Structure Forelimbs are modified as wings, although not all Forelimbs are modified as wings, although not all
are capable of flightare capable of flight Hindlimbs are adapted for walking, swimming or Hindlimbs are adapted for walking, swimming or
perchingperching All birds have horny, keratinized beaksAll birds have horny, keratinized beaks All birds lay eggsAll birds lay eggs
DiversityDiversity
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Origin and RelationshipsOrigin and Relationships
HistoryHistory Discovery of the fossil of Discovery of the fossil of Archaeopteryx Archaeopteryx
lithographicalithographica in 1861 linked birds and in 1861 linked birds and dinosaursdinosaurs Skull resembled modern birds but had teeth rather Skull resembled modern birds but had teeth rather
than a beakthan a beak Skeleton was reptilian with clawed fingers, Skeleton was reptilian with clawed fingers,
abdominal ribs, and a long bony tailabdominal ribs, and a long bony tail FeathersFeathers were unmistakably imprinted along wings were unmistakably imprinted along wings
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Archaeopteryx - 147 million year old ancestor of bids
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RelationshipsRelationships Modern birds include:Modern birds include:
PaleognathaePaleognathae (Ratite) (Ratite) Large flightless birdsLarge flightless birds with a flat sternum (no keel extension)with a flat sternum (no keel extension)
NeognathaeNeognathae with a keeled sternum (keel is an extension of sternum for high with a keeled sternum (keel is an extension of sternum for high
muscle attachment)muscle attachment) All flying birds…but some non-flyersAll flying birds…but some non-flyers
Original theories were based on ability to flyOriginal theories were based on ability to fly Smaller birds can revert to flightlessness on islands Smaller birds can revert to flightlessness on islands
that lack terrestrial predatorsthat lack terrestrial predators
Origin and RelationshipsOrigin and Relationships
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Cormorant: FlightlessNeognathae Bird -
(keeled sternum)Lives in GalapagosExcellent Swimmer
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Larger flightless birds such Larger flightless birds such as the ostrich and emu can as the ostrich and emu can outrun predatorsoutrun predators
Flightless birds are free Flightless birds are free from weight restrictions of from weight restrictions of flight and some evolved to flight and some evolved to very large sizesvery large sizes
Origin and RelationshipsOrigin and Relationships
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Paleognathae Bird
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Structural and Functional Adaptations for FlightStructural and Functional Adaptations for Flight
Feathers Feathers StructureStructure
Hollow quillHollow quill emerges from skin follicle and emerges from skin follicle and continues as a continues as a shaft or rachisshaft or rachis
Rachis bears numerous Rachis bears numerous barbsbarbs Up to several hundred barbs are arranged to form Up to several hundred barbs are arranged to form
a flat, webbed surface, thea flat, webbed surface, the vane vane Each barb resembles a Each barb resembles a miniature featherminiature feather
Numerous Numerous barbulesbarbules spread laterally spread laterally
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A - E: DevelopmentOf Contour FeatherProtective Sheath splits open
when growth is complete.Contour Feathers = Flight Feathers
G: Filoplumes Hairlike, connected to
nervous system (barbs only at top)
H: Down Feather (no hooks, rachis reduced)
Function -Conserve HeatLocated under contour feathers
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Up to Up to 600 barbules in each side600 barbules in each side of a barb of a barb May be May be over one millionover one million in the whole feather in the whole feather
Barbules from two neighboring barbs overlapBarbules from two neighboring barbs overlap ““Zip” together with tinyZip” together with tiny hooks hooks
When separated, they are “zipped” back together When separated, they are “zipped” back together by by preeningpreening
Preening gland (uropygial gland)- secretes oil Preening gland (uropygial gland)- secretes oil (waterproof)(waterproof)
Structural and Functional Adaptations for FlightStructural and Functional Adaptations for Flight
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Structural and Functional Adaptations for FlightStructural and Functional Adaptations for Flight
Molting Molting Fully-grown feather is a dead structureFully-grown feather is a dead structure
Shedding or molting is an orderly processShedding or molting is an orderly process Except in penguins, molting is a gradual process Except in penguins, molting is a gradual process
that avoids leaving bare spotsthat avoids leaving bare spots Flight and tail feathers are lost in pairs,Flight and tail feathers are lost in pairs, one on one on
each side, to maintain balanceeach side, to maintain balance In some species, In some species, replacement is continuousreplacement is continuous
Flight is unimpairedFlight is unimpaired In many water birds,In many water birds, primary feathers are molted primary feathers are molted
all at once all at once Birds are temporarily groundedBirds are temporarily grounded
Most birds Most birds molt once a year,molt once a year, usually in late usually in late summer after the nesting seasonsummer after the nesting season
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Osprey feathers molt in sequence with exact pairs to maintain balance during flight.
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SkeletonSkeleton Bone WeightBone Weight
Modern birds have light, delicate bones laced with Modern birds have light, delicate bones laced with air cavitiesair cavities
Termed pneumatized bonesTermed pneumatized bones Very strongVery strong Total weight of a bird’s feathers may outweigh Total weight of a bird’s feathers may outweigh
skeletonskeleton
Structural and Functional Adaptations for FlightStructural and Functional Adaptations for Flight
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Hollow Wing Bone:(Pneumatized)
Shows Struts andAir Spaces
Strut
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Muscular SystemMuscular System Pectoralis musclesPectoralis muscles
Depress the wing in flight and attached to the Depress the wing in flight and attached to the keelkeel Supracoracoideus muscleSupracoracoideus muscle
Raises the wing, is also attached to the Raises the wing, is also attached to the keelkeel Lays under the pectoralis musclesLays under the pectoralis muscles Pulls the wing up from below by way of a “rope-Pulls the wing up from below by way of a “rope-
and-pulley” type of arrangementand-pulley” type of arrangement
Structural and Functional Adaptations for FlightStructural and Functional Adaptations for Flight
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Flight Muscles:
Contraction of pectoralispulls wing down.
Contraction of Supracoracoideus pulls
wing upward.
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Main leg muscle mass is in thigh with connections by Main leg muscle mass is in thigh with connections by long tendons to feet and toeslong tendons to feet and toes
Toe-locking mechanismToe-locking mechanism prevents a perching bird prevents a perching bird from falling off a branch while asleepfrom falling off a branch while asleep
Structural and Functional Adaptations for FlightStructural and Functional Adaptations for Flight
Tendons automatically
tighten, closingtoes around the
perch
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Food, Feeding and DigestionFood, Feeding and Digestion
Beaks of birdsBeaks of birds often reveal their food often reveal their food habits and vary between seed-eaters, habits and vary between seed-eaters, insect-eaters, etc.insect-eaters, etc.
Woodpecker has a straight, hard, chisel-like Woodpecker has a straight, hard, chisel-like beak to expose insect burrowsbeak to expose insect burrows
Long, flexible, barbed tongue seeks out insects Long, flexible, barbed tongue seeks out insects in wood galleriesin wood galleries
Characteristics of BirdsCharacteristics of Birds
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Different bills of birds
showing adaptationsto different
environments
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Food QuantityFood Quantity Birds are Birds are BIG feeders BIG feeders Have a Have a high metabolic ratehigh metabolic rate
Small birds need even more food per body massSmall birds need even more food per body mass Hummingbirds use oxygen 12 times faster than a Hummingbirds use oxygen 12 times faster than a
pigeon and 25 times that of a chickenpigeon and 25 times that of a chicken Eats 100% of body weight each dayEats 100% of body weight each day Canary about 30% Canary about 30% Chicken about 3.4%Chicken about 3.4%
Have rapid and efficient digestive systems Have rapid and efficient digestive systems A shrike can digest a mouse in 3 hoursA shrike can digest a mouse in 3 hours A thrush will pass berries through the tract in just 30 A thrush will pass berries through the tract in just 30
minutesminutes
Characteristics of BirdsCharacteristics of Birds
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Loggerhead Shrike
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Blue-Whistling Thrush
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Because birds Because birds lack teethlack teeth Foods that require grinding are cut apart in the Foods that require grinding are cut apart in the
gizzardgizzard Few taste buds Few taste buds Many have a Many have a crop crop that serves to store food that serves to store food
at lower end of esophagusat lower end of esophagus
Characteristics of BirdsCharacteristics of Birds
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Stomach: 1st Chamber
Stomach’s 2nd chamber: Gizzard
Crop will store food and also regurgitate during nesting time for young.1st chamber of stomach secretes enzymes and acid to help break down food.
Muscular walls of Gizzard move around contents and stones help break down food
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Stomach consists of 2 chambers:Stomach consists of 2 chambers: 1st: Proventriculus1st: Proventriculus
Secretes gastric juice Secretes gastric juice 2nd: Gizzard2nd: Gizzard
Grinds foodGrinds food Birds may Birds may swallow pebbles or gritswallow pebbles or grit to assist to assist
grinding in gizzardgrinding in gizzard Birds of preyBirds of prey such as owls such as owls
Form a Form a pellet pellet of indigestible material in the of indigestible material in the proventriculus and eject itproventriculus and eject it
End of the digestive system is the End of the digestive system is the cloacacloaca Also receives products from genital ducts and uretersAlso receives products from genital ducts and ureters
Characteristics of BirdsCharacteristics of Birds
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Circulatory SystemCirculatory System 4-chambered heart4-chambered heart is large, with strong is large, with strong
ventricular wallsventricular walls Share with mammals:Share with mammals:
complete separation complete separation (oxygenated/deoxygenated)(oxygenated/deoxygenated)
Characteristics of BirdsCharacteristics of Birds
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Characteristics of BirdsCharacteristics of Birds
Larger birds have slower heart rate (Turkey =93 beats/minute)Hummingbird heart rate is over 500 beats/minute
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Respiratory System Respiratory System Differs radically from lungs of reptiles and Differs radically from lungs of reptiles and
mammalsmammals Bird LungsBird Lungs
Air sacs Air sacs Extend into thorax, abdomen, and long bonesExtend into thorax, abdomen, and long bones
Large portion of air bypasses lungs and flows Large portion of air bypasses lungs and flows directly to air sacs on inspirationdirectly to air sacs on inspiration
On expiration, oxygenated air flows through lungsOn expiration, oxygenated air flows through lungs Continuous air flow to anterior air sacs, then exitsContinuous air flow to anterior air sacs, then exits
Takes 2 respiratory Takes 2 respiratory cyclescycles for a single breath of air for a single breath of air to pass through systemto pass through system
Most efficient respiratory system of any vertebrateMost efficient respiratory system of any vertebrate
Characteristics of BirdsCharacteristics of Birds
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One side of lungs and air sacs Showing 2 cycle process of respiratory system
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An air sac system helps An air sac system helps cool bird during cool bird during vigorous exercisevigorous exercise when up to 27 times more when up to 27 times more heat is producedheat is produced
Air sacs extend into bones, legs and wings, Air sacs extend into bones, legs and wings, providing considerable buoyancy providing considerable buoyancy
Characteristics of BirdsCharacteristics of Birds
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Excretory System Excretory System Pair of large Pair of large kidneyskidneys is composed of many is composed of many
thousands of thousands of nephronsnephrons Urine flows through Urine flows through uretersureters to the to the cloacacloaca
Characteristics of BirdsCharacteristics of Birds
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Marine birdsMarine birds excrete larger salt loads due excrete larger salt loads due diet and seawater they drinkdiet and seawater they drink Salt glandsSalt glands located above each eye excrete highly located above each eye excrete highly
concentrated solutionsconcentrated solutions Salt solution runs out the nostrilsSalt solution runs out the nostrils Gulls and other sea birds have a perpetual “runny Gulls and other sea birds have a perpetual “runny
nose”nose”
Characteristics of BirdsCharacteristics of Birds
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Salt Gland of Marine Birds:Salt is secreted into many
radial tubules, then flows intocentral canal that leads to nose,
causing “Runny Nose”
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Nervous and Sensory SystemsNervous and Sensory Systems Have Have good hearing and superb visiongood hearing and superb vision
Best in the animal kingdomBest in the animal kingdom Although Although sense of smell and taste is poorsense of smell and taste is poor in most in most
EarEar is similar to that of mammals is similar to that of mammals External ear canal leads to an eardrumExternal ear canal leads to an eardrum
Eye Eye is similar to mammal eye, but it is larger is similar to mammal eye, but it is larger for a relative to body sizefor a relative to body size Less spherical and almost immobileLess spherical and almost immobile
Bird turns its head rather than eyesBird turns its head rather than eyes Has both rods and conesHas both rods and cones
Characteristics of BirdsCharacteristics of Birds
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Hawk Eye: Pecten nourishes retinaCone cells on Foveae- 1.5 million for hawk, 0.2 million for human
Allows for better vision
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Birds of preyBirds of prey have eyes directed forward have eyes directed forward Provides Provides better depth perceptionbetter depth perception
A hawk has eight times the visual acuity of a A hawk has eight times the visual acuity of a human and can see a rabbit over a kilometer human and can see a rabbit over a kilometer awayaway
An owl’s ability to see in dim light is more An owl’s ability to see in dim light is more than ten times that of a humanthan ten times that of a human
Characteristics of BirdsCharacteristics of Birds
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FlightFlight
Characteristics of BirdsCharacteristics of Birds
Normal Flapping Flight of Strong Flappers: the wings sweep downward and forwardfully extended. To begin upbeat the wing is bent, bringing it upward and backward.
Hummingbirds can change direction instantly or hang motionless.Its hinged at the shoulder by a swivel joint, and powered by flight muscles.
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4 Basic Forms of Bird Wings
A. Slotted wing tipPrevents stalling, and quick maneuvering
B. Long Migration birds High Speeds
C. Soaring, poor Maneuvering,
Strong to handle ocean winds and currents
D. High lift, slow speed, Land Soarers
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Migration and NavigationMigration and Navigation
MigrationMigration About half of all bird species migrateAbout half of all bird species migrate Can exploit seasonal changes in abundance Can exploit seasonal changes in abundance
of insects and avoid predatorsof insects and avoid predators Appearing one time a year Appearing one time a year prevents buildup prevents buildup
of specialized predatorsof specialized predators Migration also expands living spaceMigration also expands living space Migration Migration favors homeostasis,favors homeostasis, allowing birds to allowing birds to
avoid climatic extremes and food shortagesavoid climatic extremes and food shortages
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Migration RoutesMigration Routes Most migratory birds follow Most migratory birds follow established established
north-south routesnorth-south routes Some use different routes in Some use different routes in the fall and the fall and
springspring
Migration and NavigationMigration and Navigation
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Migration: 14,000 miles
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Stimulus for MigrationStimulus for Migration Long days of late winter and early spring Long days of late winter and early spring
stimulatestimulate Gonadal growth, fat deposition, migration, Gonadal growth, fat deposition, migration,
courtship, mating behavior, and care of youngcourtship, mating behavior, and care of young Gonadotropic hormoneGonadotropic hormone
Migration and NavigationMigration and Navigation
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Direction Finding in Migration Direction Finding in Migration Experiments suggest birds Experiments suggest birds navigate navigate
chiefly by sightchiefly by sight Birds recognize topographical Birds recognize topographical
landmarks and follow familiar migratory landmarks and follow familiar migratory routesroutes
Research indicates they can navigate by Research indicates they can navigate by the the earth’s magnetic fieldearth’s magnetic field
Migration and NavigationMigration and Navigation
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Sun OrientationSun Orientation Birds navigate by Birds navigate by sun at daysun at day Use the Use the North StarNorth Star as an axis at night as an axis at night
Natural selection culls individuals that Natural selection culls individuals that make errorsmake errors Only the best navigators leave offspringOnly the best navigators leave offspring
Migration and NavigationMigration and Navigation
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Bird maintains same relative position to sun when placed in
experimental situation.Birds use sun as a compass.
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Pelicans Feeding:Work together form a
horseshoe to drive fish together. Then
they plunge at same time to scoop-out fish.
Birds are ususally in SOCIAL GROUPS!
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Reproductive SystemReproductive System TestesTestes are very small until the approach of are very small until the approach of
the breeding seasonthe breeding season May then enlarge 300 times May then enlarge 300 times
Before discharge, sperm are stored in a Before discharge, sperm are stored in a greatly enlarged greatly enlarged seminal vesicleseminal vesicle
Males of most species Males of most species lack a penislack a penis Mating involves bringing Mating involves bringing cloacal surfaces cloacal surfaces
in contact in contact In most birds, left ovary and oviduct develop In most birds, left ovary and oviduct develop
and and right ovary and oviduct degenerateright ovary and oviduct degenerate
Social Behavior and ReproductionSocial Behavior and Reproduction
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Albatrosses Mating: Press Cloaca together
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Right Side of reproductive tractdegenerates, leaving only
left side. Fertilization occur in upper oviduct and albumin
and shell membrane are addedseveral hours later in lower
oviduct and uterus
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Mating SystemsMating Systems Over 90% of bird species are Over 90% of bird species are monogamous monogamous
Only mate with one partner each breeding seasonOnly mate with one partner each breeding season In a few species, such as swans and geese, In a few species, such as swans and geese,
partners are partners are chosen for lifechosen for life Recent DNA analysesRecent DNA analyses have shown many have shown many
passerine species frequently are “unfaithful,” passerine species frequently are “unfaithful,” engaging in extra-pair copulationsengaging in extra-pair copulations Nests of many of these species may contain Nests of many of these species may contain 30% 30%
of youngof young with fathers other than attendant male with fathers other than attendant male In monogamous birds, both male and In monogamous birds, both male and
females are females are equally share most aspects of equally share most aspects of parental careparental care
Social Behavior and ReproductionSocial Behavior and Reproduction
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Some birds areSome birds are polygamous polygamous Individuals mate with two or more partners Individuals mate with two or more partners
each breeding seasoneach breeding season PolygynyPolygyny
Most common form of polygamy Most common form of polygamy One male mates with many femalesOne male mates with many females
Polyandry Polyandry in which a female mates with in which a female mates with several males and the male incubates the several males and the male incubates the eggs, is eggs, is relatively rare in birdsrelatively rare in birds
Spotted sandpiper (on right)Spotted sandpiper (on right)
Social Behavior and ReproductionSocial Behavior and Reproduction
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Male Grouse: Mates with many females
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Nesting and Care of YoungNesting and Care of Young Nearly all birds lay eggs that must be Nearly all birds lay eggs that must be
incubated incubated by one or both parentsby one or both parents Often the female performs most of the duties Often the female performs most of the duties
of incubationof incubation Rarely the male has equal or sole dutiesRarely the male has equal or sole duties
Cuckoos and cowbirds are Cuckoos and cowbirds are nest parasitenest parasite Lay eggs in other bird’s nestsLay eggs in other bird’s nests
Social Behavior and ReproductionSocial Behavior and Reproduction
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Anna’s Hummingbird: Mother cares for young aloneHummingbird eggs are size of peas.
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Precocial birdsPrecocial birds are able to feed and run or are able to feed and run or swim as soon as they are hatchedswim as soon as they are hatched
Altricial birdsAltricial birds are naked and helpless at birth are naked and helpless at birth and must be fed in the nest for a week or and must be fed in the nest for a week or moremore Nesting successNesting success in altricial birds is very low in altricial birds is very low
Sometimes barely 20% of nests produce young Sometimes barely 20% of nests produce young Causes of nesting failure include predators, nest Causes of nesting failure include predators, nest
parasites and other factorsparasites and other factors
Social Behavior and ReproductionSocial Behavior and Reproduction
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Since the dodo went extinct in Since the dodo went extinct in 1695 (flightless bird)1695 (flightless bird) More than More than 80 bird species80 bird species have have
also become extinct due to also become extinct due to human influencehuman influence
Causes of bird extinction Causes of bird extinction include include habitat destruction habitat destruction and huntingand hunting
Songbirds have declined: Songbirds have declined: Habitat destruction, house cats Habitat destruction, house cats
increased, etc.increased, etc.
Bird PopulationsBird Populations
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Dodo Bird
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Largest of All Living BirdsAfrican Ostrich
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