Female red-winged blackbird
Agelaius phoeniceus
Different populations and subspecies of Red-winged Blackbirds vary markedly in size and proportions. An experiment was conducted that moved nestlings between populations and found that the chicks grew up to resemble their foster parents. This study indicated that much of the difference seen between populations is the result of different environments rather than different genetic makeups.
Source -Cornell Lab of Ornithology- All About Birds
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