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Mating Systems in Birds Monogamy (> 90% of all birds) Polygamy (~2% of birds) Promiscuity (~6% of birds) Although most birds are ‘monogamous’, DNA fingerprinting and other methods show surprising results. EPCs: extra-pair Copulations Advantage of EPCs obvious for males
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Mating Systems in Birds Monogamy (> 90% of all birds) Polygamy (~2% of birds) Promiscuity (~6% of birds) Although most birds are ‘monogamous’, DNA fingerprinting and other methods show surprising results
EPCs: extra-pair Copulations Advantage of EPCs obvious for males For females, may hedge against infertile mates or help maximize genetic diversity of offspring Result is a parent or parents raising offspring not their own
Some species have intraspecific brood parasitism… buffalodreaming.com Cliff Swallow colony
latimesblogs.latimes.com Females carry eggs to other nests Males guard nests to prevent egg dumping, but also visit other nests to destroy eggs Results in up to 43% of nests in a colony with chicks not related to adult pair at nest
For cliff swallows, this behavior exists because nest parasites will fledge more chicks than non-parasites, thus have greater reproductive success This is true for EPCs as well. Although birds are mostly monogamous, it is not strict monogamy and there are selective reasons for these behaviors Molecular studies in 1990s to recent have shown how prevalent this behavior is among birds as well
Polygamy -- polygyny, or one male and many females -- polyandry, or one female and many males -- can occur only if both parents not needed to successfully raise offspring -- polygyny most common in marsh habitats -- of 14 polygynous spp. in North America, 11 are in marsh habitats
Red-winged Blackbird -- marshes are relatively safe from predators -- lots of food, but patchy -- males with territories in high-quality patches can support more females and offspring
Polygyny begins with female choice: Choose poor patch with one male, or share good patch with one male and another female? Polygyny Threshold Model RS
Polyandry much rarer in birds (< 1% of species) -- Spotted Sandpiper and other shorebirds -- Female maximizes reproductive success -- Lays one clutch with one male, he incubates and raises young while she lays another clutch with a new male -- may do this up to four times and she takes care of last clutch
Promiscuity in ~6% of birds Sage Grouse and Leks -- male uses cervical air sacs in neck during display -- females choose males, then leaves to raise young on her own