Ornithology Lec 19: Nest and Eggs

What are the functions of nests?

1. structures that hold and protect eggs

2. protect developing young

3. safe place to roost even when not breeding

4. way to attract mates

5. courtship location

6. object built during pair formation and solidification

What are the nest types?

1. cavity nests

2. burrow nests

3. scrape nests

4. platform nests

5. cup nests

   a) statant cups, have hard support below

   b) pensile cups, hanging cup

   c) pendulous cups, entrance at top

   d) adherent cups, made of mud or saliva

   e) domed nests

   f) globular nests

   g) mound nests

Example of species with cavity nests

Northern flicker,

woodpeckers, owls, parrots, many passerines

Example species with burrow nests

Horned puffin,

swallows, kingfishers, petrels, other seabirds

Example species with scrape nests

Least tern,

shorebirds, gulls, terns, nighthawks

Example species with platform nests

Western grebe,

grebes, raptors, doves

Example species with statant cup nests

Anna’s hummingbird, American robin

Example species with pensile cup nests

Gold crowned kinglet, Hutton’s vireo

Example species with pendulous cup nests

Bullock’s oriole

Example species with adherent cup nests

barn swallow

Example species with domed nest

Western meadowlark

Example species with globular nests

Cactus wren

Example species with mound nests

African social weavers, Brush Turkey

What is the special nesting adaptation that Red Billed Quelas have?

Use a lot of different knot types between the different species, use different knots to weave nests vs to tie to the tree. Females decide if they do or do not like the nest a male is building, if they like it they will copulate and use the nest, if they do not they will untie the know and leave

What are the cost and benefit trade offs of breeding?

Costs: risk of death, reduced health, reduced future breeding potential

Benefit: fitness—> genes will carry on to the nest generation

What is an example of a strategy to reduce nest predation?

Manx shearwater breeding colonies are heavily predated on by gulls, the gulls chase away other potential predators (eagles, ravens, falcons, mammals). This reduces overall predation levels, increasing survival to adulthood.

How does the selective pressure of risk of nest predation affect nest building?

adaptations for:

• nest architecture

• nest placement

• clutch size

• nest defense

• nest parasitism

What are some adaptations for nest placement?

• high up—> hard for anything but aerial predators to reach

• cactuses—> reduced access due to spines

• cliffs—> dangerous to reach, also dangerous for eggs falling

• platform nests out in the water

What is a recent example of evolution of nest placement?

Tooth billed pigeons on the island of Samoa originally built ground nests but over 50 years shifted to nesting in trees after whalers introduced cats to the island

What are some adaptations for nest defense?

• build on an island

• build fake nests or a nest with multiple entrances

• nest colonially to mob predators

• nest near a larger predator

Example of adaptation for nest defense

The songbirds nesting under the Great Horned Owl

How do birds know how to build their nest?

Some learning involved especially with regard to nesting site, strong genetic component

What is and adaptation for nest sanitation?

Young excrete into fecal sacs that parents can remove

Characteristics of bird eggs

1. cleidoic, but not truely closed

2. ridgid shells

3. vapour permeable

What are the components of egg structure?

yolk: food supply for 11-80 days

albumen: source of water, cushions against shock, protects against temperature changes

eggshell

What is altricial?

Young are hatched helpless, require significant parental care. Often nidicolous, meaning they stay in the nest for a longer time after hatching

What is precocial?

Young are hatched well developed, require less parental care. Often nidifugous, leave nest soon after hatching

How is yolk percentage dependent on developmental extent of the hatchling?

The more extensively the developed (precocial) the chick is at hatching, the higher percentage of yolk there is.

ex: 70% in kiwis

What are the tradeoffs for eggshell thickness?

Thicker means more strong but also reduces gas exchange

What are the different egg shapes and examples?

• spheroid, ex: owls

• biconical, ex: grebes

• pyridiform, ex: murres and shorebirds

What are the advantages of pyridiform eggs for shorebirds?

pack together eggs in nests for insulation and preventing eggs form rolling away

What are egg pigments made of?

Porphyrins derived from hematin of old red blood cells

What are egg pigments used for?

camouflage

prevent water loss

protect from solar radiation

signal female quality

sometimes prevent brood parasitism

egg identification

lubricants

strengthen weak points of the eggshell

What is the precess of eggshell formation?

Eggs are formed in the uterus by the shell gland, the crystalline structure of calcium carbonate is created and then ground color is layed on the pallisade layer, the cuticle layer is layed down last along with intermixed layers of spot pigments