Exam 3 Flashcards
What are some examples of pair-bond formation in birds, and how long do they last?
Ducks form pairs just in the winter. Hawks, like Red-tails, form them in early spring. Migrant passerines tend to form bonds quickly after arriving to breeding grounds. Birds like Sandhill Cranes have them year round until one dies!
What are the benefits of a territory?
It secures food at a uniform, low density, and also helps to reduce interference from other birds, such as the theft of nest material and the destruction of eggs.
How long is a territory typically established and defended?
For small passerines, its a few days before nesting. For bigger birds like Sandhill Cranes, it can be weeks.
What can cause territory size to fluctuate?
It can fluctuate in relation to diet (like hoatzins), body size, and food density (like jaegars and lemmings).
What are the benefits and costs of a rookery/colony?
They are very dense, and each individual needs to defend only a small space. They can also detect predators faster and information sharing is great. However, food cannot be defended, and the number of sites protected from predators is very limited. Risk of disease and interference from conspecifics (like parasitizing and fucking with eggs) is higher.
What is the trend with nest location and capability of young?
Ground nesters tend to have the least capable flyers but less helpless young, with the opposite being true for complex, elevated nests.
What are sex roles in nest building like for different mating strategies?
In polygynous, the females build the nest. In polyandrous species, the males do. In socially monagamous species, they have nearly equal roles - with sometimes males gathering materials while the female builds, or the male building the structure and the female adding lining (like raptors). Swifts have very predator prood adherent nests. Pendulous nests are typical of orioles.
What are some examples of nests?
Killdeer have a slight scratch in the ground, owls use existing cavities or burrows, herons and doves have simple elevated platform nests, coots and grebes have floating nests, swallows nest in vertical bands, seabirds on mammal-free islands use ground burrows.
When did open cup nests evolve?
They evolved from roofed nests somewhere in early passerines.
What is the proximate and ultimate factor of the timing of breeding?
Day length is proximate, whereas food supply is the ultimate factor. The goal is to match the need of young birds with food availability!
How long does egg laying take?
Can take up to a minute for small passerines, but an hour or more for larger birds like geese. Intervals for eggs can range from 24 hours (most small birds) to up to 6 days (penguins).
What does it cost to lay an egg?
50% (songbirds) to 200% (waterfowl) of the basal metabolic rate. During this time, females are heavier and slower, and have less aerobic capacity because estradiol inhibits the production of RBCs. It also reduces survival rate, vs. adult females who are not breeding.
What is calcium’s role in the egg laying process?
A laying female needs 10-15x more Ca than a similar sized mammal. They can get this Ca from food or from their skeletons. Lack of Ca causes thing and brittle eggs that will break before hatching and/or porous eggs that can cause the embryo to rot.
What are sex chromosomes like in birds?
Eggs have 2 different chromosomes (Z and W) and sperm has two identical (Z and Z). Females therefore determine gender.
How does copulation work in birds?
97% of species perform a “cloacal kiss” which transfers sperm and takes a few seconds. Females can store the sperm, so they can produce eggs long after copulation happens.
Which birds have phalluses?
About 3% of birds do, with ratites (where they tend to be smaller in monagamous species) and waterfowl (where it helps with underwater copulation) having one. In waterfowl, phalluses and vaginas have co-evolved along each oter as a result of sexual conflict.
Why do some bird embryos develop a phallus that later falls off?
Two theories: male survival is greater without one, or females started preferring males with smaller phalluses so they could exert more choice on the fathers of their chicks.
What is the role of sperm in birds?
Sperm development occurs at night when it is cooler, and is stored in the seminal vesicles in the cloacal protuberance, which is a cooler part of the body. Size of the CP and the testes are larger in promiscuous species and are directly related to sperm competition. One testis is larger than the other, too.
What is a bird ova?
A follicle that creates the embryo. Yolk gets added to create mature ovum, which can take 4-15 days.
What is the germinal disk and pronucleus?
The pronucleus is a gamete that contains half the number of chromosomes as the parent cell, and it floats on the surface of the germinal disk, which is on the surface of the yolk in a mature ovum.
What is polyspermy?
When multiple sperm penetrates the ovum. It’s normal in birds, with 4-6 sperm being required to successfully develop an embryo, but will kill in mammals. Only one sperm ends up fusing with the female pronucleus.
What happens in the oviduct?
As it moves down the oviduct, several coatings of albumin are added, and the the shell gland adds shell membranes - which are fibrous, calcite-promoting proteins. Pigments are added by the shell gland too.
How does egg color work in birds?
Ground colors are added first, with spots and streaks added later. Egg color is a pretty constant factor for a species, and in some, egg color can vary greatly. White is an ancestral color, with most cavity nesters having white eggs. Egg color also helps with camouflage, signals female quality to the mate, and can help with egg recognition.
How do females regulate sperm?
They can regulate which sperm reaches the ova - they can eject it, or give the last sperm in an advantage for moving up the oviduct. They also regulate the number of sperm - when the number of sperm is low, they can help a large proportion reach infindibulum to minimize the risk of infertility.
