Subject: Re: immature Bonaparte's Gul;l plumage
Date: Jun 19 14:26:09 1995
From: Dennis Paulson - dpaulson at ups.edu


>Tweets,
>
>I saw about a half dozen Bonaparte's Gulls off South Whidbey Island state
>park yesterday. Or, at least I *think* I saw immatures. These birds had a
>black terminal band on the tails, no hood (but a dark spot behind the eyes),
>somewhat mottled wings, with at least one having a blackish band on the tips
>of the trailing wing feathers (apologies for lack of the correct terms here -
>would "tips of the primaries and secondaries" be more accurate?).
>
>Question: are these likely immatures from this year's breeding, are they
>immatures from last year? The range map in the National Geographic guide
>indicates they are in their wintering grounds; does this imply that immatures
>migrate this early, or is this an atypical observation?
>--
>Michael Patrick

Michael, these are presumably one-year-old birds, still in a plumage fairly
similar to that in which they spent the winter, although they replace a lot
of their body feathers in the spring. Their wings should be in molt at
this time of year. Non-breeding yearlings often spend their first year on
their wintering grounds, but perhaps just as many others make a partial
migration toward the breeding grounds. Very few show up on the breeding
grounds.

We still know very close to nothing about the details of this, as so few of
these birds have been banded or tagged. I imagine one could examine the
Bird Banding Laboratory's records and get at least some records of
individual birds, but you'd have to examine a lot of species; an individual
species may have very little in the way of information-rich returns. Where
your birds came from, where they are going - ????

We don't seem to have enough birders at enough localities on enough
occasions (and keeping and submitting enough records) to get at some of
these questions. You can see why some of us get frustrated that there is
such a small percentage of birders who transfer information from field
observation to notes to recordkeepers. Some of these types of questions
*could* be answered.

Juvenile Bonaparte's, which are heavily suffused with brown above, ought to
appear in our waters by early August, not too long after the first
returning adults show up.

Dennis Paulson, Director phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416