[Tweeters] Re: Question About Site Fidelity in Tropical Kingbirds

Wayne Weber contopus at telus.net
Tue Nov 17 13:22:30 PST 2015


Tweeters,



I'd like to respond to recent messages from Bob Boekelheide and Dennis
Paulson about the Tropical Kingbird thread.



First of all, concerning Bob's comment that "not all records have made it to
eBird yet"- of course he is correct, because most birders are still not
using eBird, although the percentage who do is increasing every year. As an
eBird regional editor myself, I am very much aware of that. For any given
migratory species in the state of Washington (or any other area), there are
probably earlier and later records on file than eBird shows. Bob, thanks for
mentioning the mid-December record from Three Crabs. However, it is also
true that for any species in a well-birded area like Washington, the general
seasonal pattern of occurrence shown by eBird bar graphs is quite accurate.
For Tropical Kingbirds, as I indicated, nearly all records in WA are between
mid-September and early December, with most of them in October and November.



I don't think my conclusion that most or all Tropical Kingbirds that show up
in Washington, Oregon, and BC are doomed was "glib", although it is
admittedly without proof. I reached the same conclusion long ago about
Cattle Egrets, which used to occur in significant numbers in the Pacific
Northwest every fall, although that movement seems to be much smaller in
recent years. In the case of Cattle Egrets (which, like Tropical Kingbirds,
are also largely insectivorous), we have proof that many individuals were
starving or otherwise stressed. Quite a few Cattle Egrets have been found
dead in late fall and early winter, and others which were captured and taken
to rehab centers have proved to be severely underweight and apparently
starving. However, with Cattle Egrets, I think there is a much better chance
that some of them make it back south.



As for Tropical Kingbirds surviving the winter- some of them may do so even
in northern California, where winter weather is much milder than in
Washington. I've seen Tropical Kingbirds in January near Eureka, but even
there I'm not sure if they routinely survive the winter. (There are no
January, February, or March records at all for this species in eBird for OR,
WA, or BC, and I don't think there are any non-eBird records either.)



Dennis opened another question about Tropical Kingbirds-- the question of
why the number of fall records in the Pacific Northwest has increased so
dramatically in the last 10 or 20 years. I'm certain that any objective
analysis would show that the number of kingbird sightings has increased much
faster than the number of birders.

The answer, I'm sure, is that the world population of Tropical Kingbirds has
increased-- not that the percentage of them that migrate the wrong way has
increased.

Tropical Kingbirds are one of the most common and characteristic bird
species of open areas at low altitudes in the Neotropics, all the way from
southernmost Arizona and Texas south to central Argentina. Every year, more
and more lowland tropical forest is cleared, and open-country birds like
Tropical Kingbirds take the place of forest birds, many of which are now
threatened or endangered. So while the occurrence of Tropical Kingbirds in
the Northwest may add a bit of spice to birding for local birders, I believe
that it's one of the signs of a serious environmental crisis in Mexico,
Central America, and much of South America. We should probably be alarmed,
not pleased, that Tropical Kingbirds are showing up more and more often in
Washington and nearby areas.



Wayne C. Weber

Delta, BC

contopus at telus.net





From: tweeters-bounces at mailman1.u.washington.edu
[mailto:tweeters-bounces at mailman1.u.washington.edu] On Behalf Of Dennis
Paulson
Sent: November-17-15 10:46 AM
To: B B
Cc: Mike Patterson; TWEETERS
Subject: Re: [Tweeters] Re: Question About Site Fidelity in Tropical
Kingbirds



Blair, you raised good questions.



One thing seems clear from TRKI movements is that individuals, perhaps from
populations in the northwestern part of the range of the species but perhaps
from elsewhere, routinely move in a northwesterly direction in the fall. Are
they programmed to move all the way up here, or are they not programmed to
stop somewhere farther south? We know a lot of birds go the wrong way in the
fall in the mirror-image migration that Dave DeSante described so long ago
in California, but this is another phenomenon, reversed-direction migration,
assuming those kingbirds would normally have migrated south-southeast, along
the axis of Mexico and Central America. That seems to be less common, but I
wonder if the kingbirds aren't the poster child for it just because they are
conspicuous. Perhaps a lot of other sw US/nw Mexico birds are also coming up
here but remain undetected. Well, we know this happens in Lucy's Warblers as
well, probably Vermilion Flycatchers, surely other examples.



Farther south, the coasts of CA and OR are saturated with TRKI records.
There are also a lot of them in the interior of CA and AZ. But an
interesting thing about many of the southern and interior records is that
they can be at any time of year, so they probably aren't part of the
movement, which really seems to end up along the coast. As you go north
along the coast from southern California, all of a sudden pretty much all
the records are in the fall, and there are a huge number of them (plus, as
Bob Boekelheide wrote, not all bird records are on eBird, and I hope
everyone always keeps that in mind).



So there is a major movement up the Pacific coast in fall. If you set the
eBird date range to Dec-Feb, the number of records diminishes greatly, with
only a single record from WA and five from OR, all in December, at the early
part of the winter. But there are quite a few from about Eureka south, some
of them in Jan/Feb, although nothing like the number in fall. Do these
winter records all represent birds that migrated to that point and were
still present in winter, or could some of them represent birds moving back
to the south? Obviously we have no idea, without marked birds. I didn't
pursue the records enough to see whether some of those in the Eureka area
were the same birds reported in Oct/Nov. That would indicate survival, but
that's a lot farther south than WA, and other flycatchers survive winters at
that latitude.



Set the date range to Mar-May, and there are still a few birds from northern
CA south, but again a lot fewer. The majority from around Eureka were in
March and then presumably left. That seems more likely than that they died
in March. Lots of birds in AZ at this time, perhaps overshoots of birds
already in northbound migration from the tropics.



It's a lot of work sifting through these records, and I often wish that
eBird would post just one record for one bird rather than all the records
from everyone who saw the bird. You open a record and see a long list, and
your impression is of lots of occurrences, and then you realize that this
long list was from one bird seen by many, many observers. I don't know what
the solution is to this, but it will presumably only get worse in the
future.



I can't conclude as glibly as Wayne did that all the birds are doomed when
they come up this far. I don't strongly disagree with him, as I've had the
same thoughts myself, but we still don't have any evidence that they don't
turn around and head back south. Even if they disappeared with the first bad
weather, either alternative could have occurred. Tree Swallows move south en
masse along the Atlantic Coast when bad weather comes in, and kingbirds seem
to be strong fliers. The lack of records of them in southbound movement
could be because they are moving pretty fast, not hanging around in one
place where birders come upon them. Too bad it's not easy to capture
kingbirds for banding!



I agree that selection should be working against individuals that fly so far
northward if in fact they are dying, and that should reduce the tendency to
do that in populations. But as has been asked, then why are there more and
more such records? I think we need to consider the fact that there are more,
and more savvy, observers all the time, so are there really more birds? If
there are, I don't know if climate change can explain it, as western
Washington in winter is still not kingbird-friendly. An increase in the
populations of the species could explain it, and we should look at that
perhaps to determine if it is the case.



One interesting thing is how they pile up at Neah Bay, as if they would be
going still farther north if it weren't for the water barrier. There is at
least one record from the southern Alaskan islands in fall.



I'd say we really don't what is going on-sorry it took me that long to say
it.



Dennis Paulson

Seattle





Dennis Paulson

1724 NE 98 St.

Seattle, WA 98115

206-528-1382

dennispaulson at comcast.net











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