Ornithology Exam 2 (Reading Notes)

Medullary tissue

generated by the primordial germ cells; becomes the primary tissue of the testes and secondary tissue of the ovary

Cortex

principle tissue of the ovary

Oocytes

cells that give rise to ova; already present in the cortex of a hatchling bird

Follicular maturation

period of yolk formation; lasts 4-5 days in passerines, 6-8in larger birds, 16 in some penguins

Central latebra

center of the yolk

Vitellin

white, fluid substance found in the central latebra

Parthenogenesis

development of unfertilized eggs

Primary sex ratio

differences in the survival of the embryos favor one sex or the other and thus the relative numbers of males and females that hatch

Seminiferous tubules

a dense mass of tiny, convoluted tubes that the thick, outer fibrous sheath of the testis encases

Avian penis

special modification of the ventral wall of the cloaca, which is the cavity at the end of the digestive tract that releases both excretory and genital products; not very common in birds

sperm-storage tubules

structures within the female reproductive tract of birds that store sperm after mating, allowing for delayed fertilization; sperm can remind viable for a few days or even between 30-72 in chickens and turkeys

Cleidoic egg

closed egg that allowed reptiles to move away from bodies of water to lay eggs like their amphibian ancestors

Freshly laid egg consists of:

1. ovum if unfertilized; embryo if fertilized

2. a full supply of food to nourish the embryo

3. protective layers to safeguard the internal environment

Magnum

the anterior section of the oviduct; adds four layers of albumen

Chalazae

twisted strands of albumen; form as the yolk rotates

Cuticle

a thin, proteinaceous froth of air bubbles that blocks invasion by microorganisms; covers the outer surface of the eggshell

Oviparity

when a shelled egg is laid for external incubation

Capital breeders

species that draw heavily on stored energy and nutrient reserves to produce their large, expensive eggs

Income breeders

species that ingest, on a daily basis, the resources that they need for egg production

Direct benefits hypothesis

proposes that sexual ornaments communicate a potential mate’s ability to provide resources or protections that enhance the female’s survivorship or her fecundity

Arbitrary choice and runaway selection

sexual ornamentation evolves through arbitrary choice and runaway selection for aesthetically pleasing ornaments; sexy males will produce sexy sons that have higher chances of breeding

“Hot spot” model

males gather at sites where they are most likely to encounter roaming females

“Hotshot” model

males gather around experienced, attractive, or dominant males to increase their chances of being noticed within large aggregations

Female preference model

females prefer to visit large clusters of males over small clusters or solitary males; females can make safer and more efficient comparisons

Black hole model

females are highly mobile, moving within the habitat and mating with the male in whose territory they finally happen to be present

Extra-pair copulations

copulations by females with additional males

Social monogamy

pair bond formed for social and parental reasons, but not sexually exclusive; male mate may take care of another’s offspring

Cooperative polyandry

when several males cooperate to assist one or several females

Intraspecific brood parasitism

species sometimes lay extra eggs in the nests of other females of the same species as a supplement to those tended in their own nest; occasional occurrence/facultative

Obligate brood parasites

species that never build their own nests or raise their young, instead relying entirely on other species for parental care

Cooperative breeding

any breeding system in which more than three individuals participate in raising offspring that cannot all be their own

Kin selection

when helpers obtain benefits by enhancing their inclusive fitness through the production of genetic relatives

Reciprocal altruism

when helpers obtain help in return for their care; many helpers stick around despite being capable of reproduction themselves

Family structures

social groups in which offspring continue to interact beneficially with their parents into adulthood

Inbreeding depression

reduced survival and fertility of offspring of related individuals; a potential cost of cooperative breeding with relatives

Causes of nest FAILURE

• Predation; causes the most nest failures

• Starvation

• Desertion

• Hatching failure

• Adverse weather

Extended phenotype

the total of the individual’s effect on its environment

Cavity nesting is safer than open nesting

True, half of the avian orders nest in holes or cavities

Some birds build nests near large animals or stinging insects to inadvertently protect their nests

True

Other birds will draw predators away by pretending to be injured or by acting like rodents; Killdeer do this

True

Prolactin

hormone that mediates the incubation behavior of birds

Incubation period

the time required by embryos to develop in freshly laid eggs that receive normal attention by incubating parents

Egg tooth

a special, calcified end of the bill that helps the chick break the shell

Megapodes

aka mound builders, are fowl-like galliform birds from Australia, New Guinea, and eastern Indonesia that use heat from decomposing vegetation, geothermal springs, or the sun to incubate their eggs

nidicolous

referring to bird species that remain in the nest for an extended period after hatching, relying on parents for food and protection

nidifugous

referring to bird species that leave the nest shortly after hatching and are able to forage for food independently

Tissue-allocation hypothesis

suggests that the growth of tissue mass and the maturation of tissue functions are mutually exclusive

Homeothermy

the ability to generate metabolic heat (endothermy) and to maintain a high, constant body temp

Sigmoid curve

the S-shaped curve of growth of body mass a baby bird follows during development

Siblicide

when one young kills another to improve chances of being fed and surviving

Head start hypothesis

idea that males develop faster and leave the nest earlier than their sisters in order to spend more time honing their flight and hunting skills

Nestling period

interval between hatching and departure from the nest

Fledging period

interval between hatching and flight

Age-specific survivorship

the probability of living to a particular age

Annual fecundity

the number of young successfully fledged in a year; increases directly with annual adult mortality

Life tables

integrate the vital measures of age-specific survivorship and also age-specific fecundity

Actuarial senescence

death rate that increases with age

Senescence

age-related declines in immune function

Increased investment into annual reproduction may take its toll on a parent’s physical condition, reproductive potential in the following year, and annual survival rate

True

Food-limitation hypothesis

created by David Lack; posits that food availability affects clutch size and often relates to latitude

Seasonality hypothesis

clutch sizes vary with the surplus of resources during breeding season relative to the number of adults

Nest predation favors smaller clutches for several reasons:

1. Shorter time to complete (i.e. fledgling times are typically shorter and they can become independent faster)

2. Fewer nestlings = less noise (and smell)

3. Smaller broods require less parental visitation