Saturday, August 13, 2011

Chipping Sparrow

Because juvenal-plumaged Chipping Sparrows are not included in some field guides, these birds can be difficult to identify. As you can see in theses photographs, juvenals are streaky below and lack the adults' rufous caps. This plumage is acquired quickly by nestlings--by eight days hatchlings are recognizably in juvenal plumage and, after a month, they are fully molted. The time young birds spend in juvenal plumage varies greatly. They begin molting into their winter (basic) plumage as soon as two weeks or as late as a month after hatching. Early broods stay in juvenal plumage longer than later hatched birds. Birds in eastern North America tend to molt out of juvenal plumage in their summer range. Western birds suspend their molt, completing it after they migrate to their wintering grounds (Middleton 1998).

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