>> From: Andy Stepniewski <steppie at wolfenet.com>
>> To: TWEETERS <tweeters at u.washington.edu>
>> Subject: West Mexico waifs in the Pacific NW during 1997-1998
>> Date: Monday, January 26, 1998 1:34 PM
>>
>> Tweets,
>>
>> To date the following West Mexican residents have appeared in the Pacific
>> Northwest beginning in the fall of 1998, heralded as the "most intense El
>> Nino" on record. There are probably others; these are the species I know
>> about.
>>
>> Brown Booby-confirmed
>> Crested Caracara-confirmed
>> American Oystercatcher-possible sighting
>> Xantus' Hummingbird-confirmed
>>
>> The origin (wild, ship-assist, or escapee) of these birds is the subject
>>of debate.
>>
>> In my mind, we have the elements of a pattern here, particularly when we
>> note all four are truly vagrants to this region. Any thoughts?
>>
>> Andy Stepniewski

Thoughts? You bet.

I thought readily apparent El Nio effects were limited to oceanic
creatures such as fish and birds. They are affected by changes in oceanic
food resources brought about by temperature changes and are big enough to
be noticed. One might consider a Brown Booby a likely vagrant from these
changes, although I hadn't noticed an increase in booby records in
California recently. Has there been a booby incursion farther south? And
how far are birds likely to vagrate (to coin a new verb) under these
conditions? Brown Pelicans, Heermann's Gulls, and Elegant Terns have always
flown north during their nonbreeding season, and the terns are merely
following a normal pattern but flying farther when they come up our way,
perhaps because they don't find enough to eat in California.

We've had some pretty severe El Nio years in the past decades without any
apparent vagrancy, right?

Am. Oystercatchers might be affected by changes in intertidal food
resources, but I had not heard of El Nio causing this to occur, and this
species has remained rare in California even with the increase in birders
there over the years. Nevertheless, I see it as a real possibility. Some of
you may not know about the record from Idaho in April 1981, a really
shocking occurrence. It would be great if the Marysville bird could be
relocated and photographed to be sure of the subspecific (and even the
specific) identification. I don't suppose the observer thought of
distinguishing between American and Eurasian as this surprising bird flew
past.

Of course, caracaras and hummingbirds wouldn't be affected by marine food
resources.

El Nio, of courses, also changes weather on a broad scale. Is there
anything about weather patterns in, say, northern Mexico, that would
increase the likelihood of vagrancy? I don't know if I can buy the idea
that a hurricane crossing Baja would displace a Xantus' Hummingbird or
caracara all the way up here. I suppose either species could get blown onto
a boat offshore that was heading up this way, but what would they eat? I
can envision crew members putting out food for a caracara, but how about a
hummingbird? They need to eat constantly to survive, and I doubt if ships
routinely carry hummingbird feeders.

Parenthetically, with the abundance of Caribbean hurricanes, and the high
frequency of Caribbean and Atlantic seabirds being seen up and down the
Atlantic coast and even inland (see the last Field Notes), I don't recall
reading about a single West Indian *land bird* turning up north of Florida
on the Atlantic coast. The Bahamas are full of land birds that don't occur
in the U. S. Does anyone know of such records? Perhaps this should be our
clue?

The other alternative is just plain vagrancy, independent of global
perturbations, and 4 species in a year from the same region (presumably)
does seem to be more than usual. However, bear in mind that there are more
birders all the time and--maybe even more important--more communication
about birding, and it may be in part that there are always lots of unlikely
birds in any given area but that we're learning about more of them now. I
don't know the history of the booby discovery, but the caracara, the
hummingbird, the oystercatcher, and the Yellow-throated Warbler were all
reported by people who weren't part of the active birding community, I
think. A Summer Tanager--first for Washington--spent part of this winter at
the feeder of such a person on the Skagit Flats, another such example. I
feel strongly that improved communication is increasing the number of
rarities detected.

And think of how many there must be! We don't really think that everyone
who sees a bird at their feeder that they can't identify immediately calls
the local Audubon society, do we?

Finally, about captivity: we take for granted nowadays that many of the
exotic waterfowl we see must be escaped captives, because they're so far
from their normal range, although they scarcely ever have bands or
indications of captivity. I suspect that birds of more kinds than we think
are kept nowadays as pets/captives, both legally and illegally, and that
this is always at least a possible alternative to bonafide occurrences of
far-out (in the sense of the 60s) vagrancy.

Dennis Paulson, Director phone 253-756-3798
Slater Museum of Natural History fax 253-756-3352
University of Puget Sound e-mail dpaulson at ups.edu
Tacoma, WA 98416
http://www.ups.edu/biology/museum/museum.html