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Bermuda Petrel replies
- To: carolinabirds@duke.edu
- Subject: Bermuda Petrel replies
- From: "Will Cook" <cwcook@duke.edu>
- Date: Thu, 8 Jun 2000 09:29:07 -0400
- Priority: normal
- Sender: carolinabirds-owner@acpub.duke.edu
Here are some replies (from Birdchat) to the messages fowarded yesterday...
------------------------------
Date: Wed, 7 Jun 2000 11:43:02 -0400
From: Macklin Smith <macklins@UMICH.EDU>
Subject: Re: Trip Report: North Carolina Pelagics, 6/2/00 -- 6/4/00
All--
I'm not an expert on this, but I suspect that Martin Meyers probably did
see a Cahow (Bermuda Petrel), although he supplies few details! Perhaps
he was wishing-wishing, but I suspect that was not the case at all, that
he was simply summarizing a thoughtful experience.
As Ron Orenstein points out, Cahow and Black-capped can be confused, and
there are records of runt Black-cappeds with scant white on nape and/or
rump. I have not seen such birds, and to me BC's are typically
black-capped (cap, not cowl) with bright white nape and rump area. At a
distance BC's look like a blackish wing with two white areas fore and aft,
and the underwing of this creature has largely white-appearing underwings.
Cahow, in contrast, is 50% dark under the wing, with a different pattern
and a special "thumbnail" mark. Cahow never has a white nape, and half
the time shows little or no white in the "rump" area. It has a cowl, with
a very striking mask above the bill (cf. Murphy's Petrel, but brighter,
very conspicuous). The coloration is different. The smaller weight of
Cahow results in a very different flight pattern, more like Fea's than
Black-capped in my view, but not quite like Fea's either: confident yet
bouyant, light on the wing, no high arcs. If BC seems blackish, C seems
charcoal grayish to light gray, with some brown tones even.
I have seen about 5000 Black-cappeds and 2 Bermuda Petrels. Although I
have not seen the odd Black-capped that might look like Cahow, I am
content to report that these species are probably much more different than
some myths suggest, with respect to weight, flight, evident field marks.
For birders interested in confirming ID's, I would suggest ignoring
Harrison's book and looking at Brian Patteson's on-deck and published
photos.
But all of this is presumptuous. David Winfield, Ned Brinkley, Brian
Patteson, and others know a lot more about this than I do, that's for
sure. My only intent is to stem the myth that Cahow can't be told from
Black-capped. It can. Still, observers should be observant, not
assertive, yes? Cheers,
Macklin Smith
University of Michigan
Ann Arbor, MI 48104
macklins@umich.edu
------------------------------
Date: Wed, 7 Jun 2000 20:15:39 -0700
From: Joseph Morlan <jmorlan@CCSF.CC.CA.US>
Subject: Re: Trip Report: North Carolina Pelagics, 6/2/00 -- 6/4/00
Chatters,
I have posted some preliminary details on the Bermuda Petrel described
by Martin Meyers on 2 June at:
http://fog.ccsf.cc.ca.us/~jmorlan/bepe.htm
I haven't yet linked this page publicly because I'm still working on
it. Any comments would be much appreciated. Does anybody know when
Bermuda Petrel was added to the ABA Checklist?
Also, if you have time, you may wish to ponder this month's mystery
birds at:
http://fog.ccsf.cc.ca.us/~jmorlan/mysteries.htm
and there is an account of a singing Blue-headed Vireo in California
at:
http://fog.ccsf.cc.ca.us/~jmorlan/descriptions.htm
Enjoy!
--
Joseph Morlan, Pacifica, CA 94044: mailto:jmorlan@ccsf.cc.ca.us
Fall Birding Classes begin Sept 5: http://fog.ccsf.cc.ca.us/~jmorlan/
California Bird Records Committee: http://www.wfo-cbrc.org/cbrc/
------------------------------
Date: Wed, 7 Jun 2000 23:22:08 -0700
From: Todd McGrath <skua@EMAIL.MSN.COM>
Subject: Bermuda Petrel
Dear Birdchatters,
There have been a number of excellent posts about recent sightings of
bermuda petrels off North Carolina, but I wanted to weigh in on several
aspects that have not been previously mentioned in detail. I have seen 3
Bermuda Petrels off of North Carolina. One in May of 1996, two in May of
2000. As a particpant or trip leader on about 50 NC pelagics, I think I
have a reasonable experience level to comment on the separation of black-
capped and bermuda petrels.
Macklin Smith's post does a good job of summarizing the key differences,
and please review the excellent article in Birding referenced in Joe
Morlan's post.
Since those posts and the Birding article accurately describe the
separation of the species, I will instead comment on the range of variation
I have seen in black-capped petrel. Just this May I, and several
participants on a Brian Patteson pelagic saw a black-capped petrel that
represented the dark extreme of the species. This bird had an almost hooded
appearance, and an incomplete breastband. There was no collar on the back,
although if the bird had approached very closely, I suspect a trace of the
collar would been present.Often black-cappeds will lack a strong collar,
and several times I have seen birds that lacked this collar completely, at
least at a distance, but I have seen only this one black-capped that
exhibited a hooded look approaching bermuda petrel. Since the bird was
flying toward the boat, my first look at it was of the head and breast, so
for a second, I thought I might have a bermuda, but almost immediately
other clues allowed me to correctly identify the bird as a black-capped.
Size was the first clue. While there is some overlap between bermuda and
black-capped as far a measurements, black-capped is a heavier bird. The
first impression of bermuda is more like that of Fea's petrel (or
Fea's/Zino's petrel, but that's another post). Macklin's description of the
differences in flight style are pretty much on the mark. Obviously, the use
of size, shape and flight style can be done only with a fair bit of
experience with black-capped, so is probably of limited use for
inexperienced gulfstream birders. I have never seen a black-capped petrel
that looked as small and as slight as any of the three bermudas I have
seen.
This odd black-capped exhibited several other distinctive black-capped
marks. First, the amount of black on the underwing, as well as the pattern
of that black were more typical of black-capped. The black on the underwing
of black-capped petrel is narrow, and the leading edge of the underwing is
white from the body almost to the bend in the wing. Near the bend in the
wing the black angles in towards the center of the wing. On Bermuda Petrel,
that leading edge is much darker, and does not separate from the leading
edge of the underwing until much closer to the body. Even in black-capped
petrels that are a little darker than usual on the underwing, the pattern
seems to remain constant based on my observations. I have never seen a
black-capped petrel with an underwing as dark as bermuda, but they do vary
somewhat. Brian Patteson has several good pictures of black-caps with
darker underwings than is typical. Again, look also at the pattern of the
dark
The coloration on the back can also be useful. black-capped petrels are
also black-backed, as was this unusual bird. At close range, bermuda petrel
sometimes exhibits a gray, or sooty coloration on the back. This was
particulary noticeable on the 1st Bermuda Petrel this May.
Finally, tail pattern is also an excellent mark. Although often bermuda
petrels seen in May are in heavy moult, and exhibit a bit more white in the
tail than one might expect. This white will be confined to the upper tail
coverts, and in fresh plumage grayish rather than white. On my odd
black-capped, there was extensive white on the tail, not limited to the
uppertail.
I would also like to comment on the variation in plumage I have noticed in
bermuda petrel. The first bird I saw in 1996 did not appear to be in moult,
in fact the plumage seemed relatively fresh. This bird is the one
photographed in the Birding Article. The first bird seen in 2000 was in
heavy moult. I have also seen photgraphs of a bird from May of 1998 that
was in heavy moult. The second bird I saw this year looked more like the 96
bird. I don't know enough about bermuda petrel to explain this variation in
moult among birds seen at the same time of year, but it is worth mentioning
that most of the birds from a small but growing sample of sighting do not
appear to look exactly like the bird photographed in Birding.
Next, I would like to comment on the use of Harrison's Seabirds Guide to
deal with very difficult species groups. I personally believe that this
book is one of the greatest field identification guides ever published. It
is absolutely a pioneering work, and served to stimulate interest in
pelagic birds all over the world. It is dated however, and it should not be
relied upon as the only reference, as our understanding of seabird taxonomy
and identification has advanced substantially since its publication.
Finally, It would be inappropriate for me to post any discussion about
seabirds in the gulf stream without acknowledging Brian Patteson and Ned
Brinkley for the many hours of thoughtful conversation. I would
particularly like to thank Brian for providing me with numerous
opportunities to get offshore.
Todd McGrath
Marina Del Rey CA
SKUA@MSN.com
------------------------------
--
Charles W. "Will" Cook w 919-660-7423
cwcook@duke.edu h 919-967-5446
Duke University Botany Dept., Durham, North Carolina
http://www.duke.edu/~cwcook