Birds Flashcards
Q: Key developments in the ancestors of birds leading to modern birds
> 200 MYA, after major extinction event, dinosaurs began rapidly diversifying in body size to fill new ecological niches
Over 50 M year period, theropod ancestors of birds continuously shrank
Small size, light weight allowed escape from predators by climbing trees, gliding, flying
66 MYA, K-T mass extinction, end of Cretaceous– their small size, efficient insulation (feathers), and ability to fly may have helped birds survive the dinosaur extinction event.
Underwent explosive adaptive radiation, forming the diverse group of birds that we see today.
Q: How are birds related to dinosaurs?
Birds are closest living relatives to all extinct dinosaurs
Birds evolved from theropods, a group of meat-eating dinosaurs
Archaeopteryx may be the evolutionary link between dinosaurs and birds
Q: Physical/behavioral similarities between birds and theropods?
Walking on two legs, scales on legs, pneumatized (air-filled) bones, having feathers, laying eggs, nesting and brooding.
Q: Primary function of early dinosaur feathers
Insulation
Q: What species is commonly considered the first bird?
Archaeopteryx
Discovery of this feathered fossil provided evidence that birds are flying dinosaurs and diverged from small, bipedal theropods.
Q: Theropods
Two-legged, carnivorous dinosaurs
Include Tyrannosaurus rex, velociraptors
Ancestors of birds
Q: Bipedal
Form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs.
Q: Where are birds classified taxonomically?
Birds are one of the five (actually >5 because multiple fish classes) classes in the Vertebrata subphylum.
Kingdom: Animalia; Phylum: Chordata; Subphylum: Vertebrata; Class: Aves.
Q: What has driven many of the major characteristics of birds?
Adaptation to flight
Q: Bird adaptations to flight
Reduced weight (pneumatized bones, lack of teeth)
Strengthened skeleton with several specific adaptations (details on separate card)
Strong flight muscles, attached to keeled sternum
Fast metabolism (can’t store heavy foods for long periods of time; also need energy for flight)
Large eyes (avoiding collisions in flight, spotting prey from a distance)
Efficient, one-way respiration system (details on separate card)
Missing/reduced organs decrease weight (e.g., no bladder, urethra, only one ovary in some birds; reproductive organs reduce in size outside of breeding season)
Q: Bird skeleton adaptations to flight
-reduced in weight and strengthened (pneumatized bones)
-bones are reduced in number
-some bones are fused to increase skeletal strength
-keeled sternum (breastbone); attachment point for powerful flight muscles
-The “wishbone” (furcula)
–found only in birds
–strengthens thoracic skeleton to withstand the rigors of flight
–provides flexible attachment site for the breast muscles
-ribs have boney extensions that go from rib to rib
–serve as attachment sites for scapula muscles
–strengthen the rib cage overlapping with the rib behind them
–increase effectiveness of muscles involved in inspiration (yes, birds are inspiring, but this refers to intake of breath)
Q: Name some examples of birds that cannot fly
Penguins
Ratites (ostrich, cassowary, emu, rhea, kiwi).
Q: Bird characteristics
Feathers (defining characteristic)
Hard-shelled, amniotic eggs
Scales on legs
Beaks or bills
Tails
Wings (though not all can fly)
Relatively large eyes
Bipedal
Endothermic
Vertebrates
Pneumatized bones (except penguins, loons, and puffins)
Q: Endothermic
Dependent on or capable of the internal generation of heat. The animal is able to maintain a relatively constant internal temperature, irrespective of the temperature of the surroundings.
Q: Do any living animals have feathers besides birds?
No
Q: Functions of feathers
Thermoregulation (more efficient than fur), flight, waterproofing, protection from the elements, camouflage, mating displays, aid in egg incubation
Q: Common ancestor of modern reptiles, birds, and mammals
A scaled reptile
Over 300 MYA
Q: Benefits of birds having relatively large eyes?
avoiding collisions in flight
spotting/capturing fast-moving or camouflaged prey
Q: Two general differences between birds that tend to be predators vs. prey
Predators: maintain a more vertical stance (egrets, hawks); eyes more forward-facing
Prey: more horizontal posture (eat seeds, plants, and insects off the ground) (jays and finches); eyes more side-facing
Q: Key difference between bird eggs and reptile eggs
Bird eggs have a hard shell. Stronger and can support the embryo inside through harsher conditions (i.e. like rolling out of a nest).
Q: Endothermic vs. ectothermic animal food consumption
To sustain their higher metabolism, endothermic animals typically require several times as much food as ectothermic animals.
Q: Pneumatized bones
Air pockets within the bones
Reduced weight
Have criss-crossing struts or trusses for structural strength
Q: Compare bones of flighted and flightless birds
Birds that have lost their ability to fly have heavier bones than flighted birds but they are still comparatively lighter than a similar sized mammal bone.
Ostriches and emus need the heavier bones to meet the demands of running.
Penguins need heavier bones to dive for food otherwise they would bob like corks near the surface.
Many flightless birds lack keeled sternum.
Q: Bird foot vs dinosaur foot
Classic bird foot that separated birds from the dinosaurs was three toes in front and a hallux in back (homologous to human big toe)
Dinosaurs had three toes. [In theropods, hallux was non-opposable and too short to touch ground.]
Q: Name some parts of a bird that can tell us about their lifestyle
Beak, feet, wings (details on separate cards)
Q: Modern bird feet, and reasons for the different adaptations
Foot type can indicate lifestyle
Two to four toes on each foot
Most perching birds and raptors have anisodactyl foot- three forward toes and hallux in back (homologous to human big toe). “Anisos” means unequal.
Some perching birds have zygodactyl foot- two toes forward and two rear facing. Good for clinging to and climbing through trees. “Zygo” prefix originates from “yoke,” and as a prefix, means “paired” or “union”.
Runners like the ostrich have a reduction in the number of toes and all their toes facing forward. Ostrich is only bird w/2 toes. Cassowary, rhea, and emu all have 3.
Webbed feet (useful for swimming and sure footing on wet ground):
-palmate: front 3 digits are webbed. Most common type of webbed foot. Ducks, geese, swans, gulls, and other aquatic birds.
-totipalmate: all four toes united by web. Pelican, cormorant, boobies, gannets.
Birds’ legs and feet are covered in scales, a holdover from their reptile ancestors.
Raptors (birds of prey) have long, strong digits w/ heavy claws for catching, holding, and killing prey. Owls, hawks, eagles, and falcons.
Q: Two most common types of feet in perching birds
Anisodactyl- having the hallux behind and the other three toes are in front as in a thrush. “Anisos” means unequal.
Zygodactyl- having the toes of each foot arranged in pairs, with two toes in front and two behind as in a woodpecker, parrot, osprey. “Zygo” prefix originates from “yoke,” and as a prefix, means “paired” or “union”.
Q: Words for two of the types of webbed feet
Palmate- front toes are united as in ducks and gulls.
Totipalmate- fully webbed; all four toes are united by ample webs, as in a pelican or cormorant.
Q: Raptorial toes
Bird toes that are deeply cleft, with large, strong, sharply curved nails (talons), as in hawks & owls.
Q: What is sexual dimorphism?
When two sexes of the same species exhibit different characteristics aside from differences in sexual organs.
Q: What is sexual dichromatism?
Sexual dimorphism involving a difference in coloring or marking patterns between male and female members of the same species.
Q: Example of sexually dimorphic birds at the zoo
Eclectus parrot is unusual in that both the male and the female display bright colors
Extreme sexual dimorphism
Male is mostly green whereas the female is red
Both the male and female have multiple mating partners; they are both trying to attract the opposite sex.
Q: Why are birds so much more colorful in the tropics than in the temperate areas?
Outside of the tropics, bright colors would often make a bird too vulnerable to predators.
Birds in trees in tropical areas are actually well-hidden because of their bright colors. Green feathers blend into the trees which are green all year-round in tropical climates. As the birds dart through the flashes of light in the forest, their colors actually make them harder to see.
Q: General features of flight feathers
Flighted birds have asymmetrical feathers.
Wings curved convexly over the top edge, which creates a greater pressure underneath the wing and produces lift, just like an airplane.
Q: What can we learn about a bird from its wing shape?
Indicates lifestyle.
Fast flyers, like swifts and falcons, have long pointed wings.
Soaring birds have broad, large wings to gain lift from thermal air pockets.
Long wings could be problematic in a forested area.
Q: What’s special about owl feathers?
Specialized feathers reduce noise of air rushing over the wing.
Silence helps them both to hear prey, and to remain undetected.
Owls are night predators with a keen sense of hearing.
More details from National Audubon Society: Comb-like serrations on the leading edge of wing feathers break up the turbulent air that typically creates a swooshing sound. Those smaller streams of air are further dampened by a velvety texture unique to owl feathers and by a soft fringe on a wing’s trailing edge.
Q: Bird feather anatomy
Made of keratin.
Light-reflecting pigments
Not living tissue.
When growing, have blood supply that enters through the calamus, or quill end.
Rachis: Main shaft.
Barbs: Branches coming off rachis that form a flat surface.
Barbules: Tiny parts on each barb that lock together to give feather its stiffness.
Hooklets: Tiny parts that lock the barbules [of adjacent barbs?] together.
Vane/blade: Smooth surface formed by interlocked barbs that come off the rachis.
