Lecture 11: Incubation nests & nesting

How to test for Sexual selection for sensory exploitation

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Incubation

birds have eggs, with a period of embryonic development outside the parent’s body

Embryos in Incubation

normally require constant warmth for development, close to adults body temperature 37-38 degrees

Hormones involved in incubation behavior

Prolactin: hormone that stimulates incubation behavior

Testosterone: inhibits incubation behavior

Brood Patches

Highly vascular and callused bare patches of skin that is brought in contact with eggs

____ Species lacks brood patches

Sulidae

Egg Neglect in Ancient Murrelet

An adaptive trade off that occurs in early incubation, adults leave the nest to feed at sea and restore energy. The eggs can tolerate some cooling during absences. Increased risk of predation during this period.,

Purpose of egg rolling

During incubation, prevents internal membranes from sticking

Solutions to egg chilling

insulated nests and constant incubation so both sides of egg are in contact with warm surface

Solutions to egg overheating

shading and wetting eggs

Species with females only incubation behavior

Boreal Owl, Red Crossbill, Hornbills

→fed entirely by male

Species wit Male only Incubation Behavior

in classic polyandry: Red Phalarope and Emperor Penguin

Coloniality

Highly clumped nesting aggregations →bird colonies exist for breeding and nesting ONLY

Communial Roosts

Used for nesting, sleeping, and shelter

→is NOT a colony

Examples of Colonial Birds

Virtually all seabirds: Leach’s Storm Petrel, Cormorants, Gulls and terns, ect

Philopatry

tendency to return to place of birth or fist settlement to breed

→ ex: Murres

Explanation for Coloniality

• a shortage of nesting sites that are safe

• Dependence on abundant/unpredictable food that is located distantly from nesting habitat

Food related hypothesis to the evolution of coloniality

centrally located colony minimizes travel time to feeding areas

Information Centre Hypothesis

a hypothesis to the evolution of coloniality based on cooperation, two function corollary experienced dominant members shielded from predators, subordinate inexperienced birds get information about location of food

→terns, Murres, Osprey

Cost of Information center coloniality

increased competition

Predator related hypothesis to the evolution of coloniality

many eyes are more suited to spot predators, as well as cooperative defense and predator swamping. However it does attract more predaors, competition, and transmission of disease

Factor of Nest Inevitability

• eggs must be incubated and insulated

• young of most birds are helpless and require brooding and feeding for many days before they become independant

mud nests

cups or cavities constructed of hardened mud

→cliff swallows, oven birds

Nests made of plant material

cup-like of bag-like nests made of plants, usually contains a lining of fine insulating material, and an outer shell of coarse damage-resistant material

→typical of Passeriformes

Floating nests

on mats of vegitation

→common in marsh birds like Red-Necked Grebe

Communal Grass Nests

giant thatched nests

→common in Monk Parakeets, and Sociable Weaver

Saliva Nests

in Swifts, egg is glued to a leaf

→Edible-nest Swiftlet

Mounds of rotting vegitation

a self incubating nest via decomposition.

→Megapodes

Nest Engineering Considerations

• Warmth

• Cooling

• Ventilation

• Resistance to invasion by parasitic insects, brood parasitic birds

Predator Swamping

an anti-predator strategy where prey reduce the risk of being eaten by appearing in a large group or at a synchronized time, overwhelming the predator's ability to consume them all