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Bermuda Petrel replies



Here are some replies (from Birdchat) to the messages fowarded yesterday...

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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

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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