BIOL 1902 Lecture Notes - Lecture 23: Gray Jay, Altricial, Precocial
22 Apr 2016
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Document Summary
Shells require lots of calcium & yolk. Ducks, grouse, sandpipers = large eggs, 40% yolk: little effort in nest building. Songbirds = small eggs, 25% yolk: elaborate nests. Why the difference: after hatch, altricial nestlings stay in nest, precocial chicks leave nest after hatching, longer development in egg allows chicks to hatch & mobile & largely self- sufficient. Birds sit on eggs to keep them warm: brood patches = featherless heating pads that keep eggs at 37oc (99of) Phalaropes males only incubate, only develop brood patches. Female ducks & grouse do all of the incubation: after mating, males desert females, e. g. In species where pair bond remains intact, sometimes females do all incubation: many songbirds, female only incubates, but male feeds female and/or guards nest, e. g. Gray jay: female only incubation, male feeds female on nest (& off nest: e. g. House finch: female incubates, male feeds female on nest. In other species, both sexes incubate: e. g.
