Date: 7/23/17 11:23 am
From: Nathaniel Wander <nw105...>
Subject: [obol] Yellowlegs' molt and migration
That yellowlegs molt during migration seems well-established and well-known.  Equally, that yellowlegs 'straggle' during migration.  Adults begin leaving their breeding grounds in late June, but often do not reach wintering grounds until October or later.  It has been suggested that the function of the 'straggle' is to facilitate the molt.
Bent quoting Nichols on why yellowlegs appear along the migration path in bunches writes:
"The fluctuation in numbers of the shorebirds on Long Island during the fall migration period may best be explained by supposing that the bulk of each species has a more or less definite late summer range to which it travels from the breeding grounds and where, if conditions are favorable, it remains until autumn.  Before the main flight, birds of each species are mostly adults, during it, mixed adults and young.  To explain double abundance of most species in southward migration by first the passage of adults, then that of young, is pretty surely erroneous."
Apparently the feathers grown out in the spring pre-migration molt are still good enough to get the adults to the autumn feeding grounds and the feeding grounds provide sufficient nutrition to grow out the new plumage which will carry the birds to their wintering grounds. Nathaniel WanderPortland, OR
"Don't work towards freedom.  Make the work the freedom."
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