Bird Reproduction and Behavior

Timing of Reproduction

  • Increasing day length in late winter

    • hormonal changes » nuptial plumage, courtship behavior, breeding, migration


Breeding Systems

  • Monogamy—one male, one female, shared parental care, most birds

  • Polygamy—multiples mates of opposite sex—only 3% of birds

    • Polygyny: one male, multiple females—2% of birds

      • red-winged blackbirds, indigo buntings

    • Polyandry: one female, multiple males <1% of birds

      • some sandpipers, some rails

    • Polygynangry: several males and several females form breeding unit—ostriches, rheas, emus


Lekking

  • Area for male courtship display and mating

  • Females pass through the Leks and choose a mate

  • Why?

    • Leks are a “hot spot” where females will gather

    • Males gather around the more experiences and attractive males to increase chance of being noticed

    • Females get to see all their choices in one place

    • Males of a lek show high kinship → inclusive fitness


Copulation and Fertilization

  • Most birds lack external genitalia—flight

  • “Cloacal kiss”

    • just a few seconds, sometimes in midair

  • Females of many bird species can store sperm in tubules—sometimes even during migration

  • When female has mated with multiple males—usually the case—sperm compete

    • usually the last deposited wins


Brood Parasitism

  • Addition of eggs to another female’s nest

    • increase number of eggs laid without increasing parental care

  • Intraspecific—same species

    • waterfowl—coots

    • pigeons

    • doves

    • starlings

  • Interspecific—obligate brood parasites lay eggs in nests of other species

    • cowbirds—can lay more eggs each season and not spend energy on taking care of young


Clutch Size

  • Wide range: 1-18 eggs per clutch

    • vultures = 1-2

    • shorebirds = 3-4

    • Hawks and songbirds = 2-5

    • Ducks = 7-12

    • Wild turkey = 8-15

  • Varies within and among species with locality, habitat, body size, etc


Incubation

  • Keep temperature stable to increase hatching success

  • Incubation period—time required for embryo to develop, laying—hatching

  • 10 days—some woodpeckers, small songbirds

  • Up to 90 days—albatrosses and kiwis

  • Brood patch/incubation patch—bare patch of skin for heat transfer


Hatchings

  • Precocial—Hatchlings leave the nest immediately, follow parents, pick up own food

    • ducks, shorebirds, grouse, quail

  • Altricial—naked, blind, and helpless at hatching

    • songbirds, woodpeckers, hummingbirds, swifts, pigeons, kingfishers


Global Change Fellowship, Science to Action Fellowship (graduate school fellowships)