Final Flashcards
What are the changes that occur during a bird’s annual cycle?
Colors (molt), reproductive structures atrophy
Typical cycle of a migratory bird
As day length increases, molt into breeding plumage, gonadal enlargement, pair formation.
As day length decreases migration, nesting, egg-laying and incubation
Typical cycle of a non-migratory bird
in the presence of good food and mate: initiate breeding plumage, gonadal enlargement
If good food or mate are absent: non-breeding molt
Light deprivation studies
in the absence of daylight cues, individuals typically follow a regular, near - 24 hr. cycle, but it gets off slightly
Atypical examples of annual cycles of birds
the kingfisher delays having offpsring until late summer, when the fishing is better bc winter runoff has passed
Origin of migration
increases fitness by making more food available to individuals
Why migrate?
food availability
How do migrating birds navigate?
They navigate using the magnetic fields of the earth, and also by sight, sun and moon and star position, and landmarks
Differences between spring and fall migration
In spring, there are less birds, and the migration takes place much more rapidly. Males especially come back quickly to establish territories
In fall there are more birds, and the migration is much lazier
How do migrating birds navigate?
They navigate using the magnetic fields of the earth, and also by sight, sun and moon and stars position, and landmarks
Different migration strategies
Osprey have long, slow migrations
Eared grebes get really fat before migrating (store energy)
Arctic tern migrate only over the ocean, long distances
What is the bottom line of breeding?
pass your genes onto the next generation. Includes direct offspring and related individuals’ offspring
Differential investment in offspring (male vs female)
Sperm are cheap and eggs are expensive. Explains breeding patterns and the parental differences between the sexes
Two hypotheses for elaborate plumage
Good genes - handicap and male health
arbitrary choice or runaway selection - female selection is no longer governed by fitness. They simply like bright colors
What is the bottom line of breeding?
pass your genes onto the next generation.
How can breeding be accomplished (two ways)?
Either by having your own offspring, or by helping raise related individuals’ offspring
What is the typical size of a clutch?
Most have 3-6 eggs
Why are bird eggs bright blue?
They signal the good genes of the female, incentivize male to provide for offspring
Niche vs neutral theory
niche theory - distribution of species is explained by a set of conditions needed to thrive, each species thriving in its own niche
neutral theory - competing theory that says the pattern of distribution of species is totally random
Island biogeography theory
You can know (estimate) about the number of species that an island (or other isolated chunk of habitat) can support by knowing its size and shape
Purpose of nests
protection against predators and protects the eggs and incubator against the elements
nest parasitism (species, reasons, implications, etc.)
conspecific brood parasitism common in ducks, common cuckoo parasitizes wrens
nest parasitism (species, reasons, implications, etc.)
conspecific brood parasitism common in ducks, common cuckoo parasitizes wrens
Reasons: either the parents cannot tell the difference between the eggs / offspring (recognition error), or mafia hypothesis
Implication: areas with high parasitism have egg speckles which closely resemble each other, making it easier to detect the mimic
Definition of a population
A group of individuals of the same species interbreeding and found in the same space at the same time
