** Reply to note from tweeters at u.washington.edu Tue, 7 Apr 1998 00:09:36 PDT


> Apparently a hundred or so Western Sandpipers Calidris mauri came in to the
> tip of the Iona S Jetty, some in fresh Alternate about four days ago. Now
> whether these were northerly-wintering birds moving up with Dunlin C. alpina
> from a wintering site not far south of here, perhaps even as close as
> Roberts Bank, or an actual first-arrival long-distance flock from S America
> is, I think, a point worthy of discussion. Some of the Dunlin were showing
> some russet scapulars and black mottling on their bellies.
>
> The difficulty of assigning arrival status to these birds is that we know
> next to nothing of their molt-cycle when they winter in the vicinity. Do
> Dunlin, wintering Western Sandpipers, wintering Black-bellied Plover
> Pluvialis squatarola begin to show their pre-Alternate molt plumages here,
> or do they begin molt only after leaving the wintering ground? How much
> moving around--if any--do they do during the later stages of the winter but
> before the arrival of the actual northbond migration?

My feeling is that molt is tied in with all the other hormonal changes brought
about by seasonality. So I vote for molt schedule to be similar within a
shorebird species (within limits of individual variation) regardless of its
wintering latitude. Of course, one could argue that those Western Sandpipers
wintering along the northern S. American coast do not experience an increasing
daylight trigger given their proximity to the equator. Perhaps we humans are
just too insensitive to notice the subtle changes.

- Jack


--------------
Jack Bowling
Prince George, BC
jbowling at direct.ca