Fwd: [TEXBIRDS] Kelp and Black-tailed Gulls (long)
Phil Davis (pdavis@ix.netcom.com)
Wed, 10 Mar 1999 20:52:38 -0500
Ospreyers -
Thought you might be interested in this Texbirds cross-post from John O'Brien.
Phil
>X-Sender: johnobrien@eye.med.uth.tmc.edu
>X-Mailer: QUALCOMM Windows Eudora Pro Version 4.1
>Date: Wed, 10 Mar 1999 15:49:59 -0600
>Reply-To: "John O'Brien" <johnobrien@EYE.MED.UTH.TMC.EDU>
>Sender: Audubon birding discussion list for Texas
><TEXBIRDS@LIST.AUDUBON.ORG>
>From: "John O'Brien" <johnobrien@EYE.MED.UTH.TMC.EDU>
>Subject: [TEXBIRDS] Kelp and Black-tailed Gulls (long)
>To: TEXBIRDS@LIST.AUDUBON.ORG
>
>Texbirders,
>
>I came back from a very enjoyable Rio Grande Valley trip
>Monday night, and now have my slides of the Kelp-type
>and Black-tailed Gulls at the Brownsville dump. I thought
>you would like to read some details about these birds.
>I was down in the valley with my father (Paul O'Brien),
>Paul Pisano, and Dick Wright. This was the first valley
>trip for Dick and the first time in the lower valley for Paul P.
>We were quite lucky that the Tamaulipas Crows at the
>Brownsville Dump were recalcitrant, because after about
>45 minutes of unsuccesful searching for them, we found the
>large dark-backed gull that captured our attention for the
>next 2 hours. I spent a long time photographing this bird
>when I noticed through the camera viewfinder a smaller
>dark-backed gull with bright yellow legs next to it. I assumed
>the other bird was an adult Lesser Black-backed Gull, but
>when I looked at it with binoculars, and when Paul got on it
>with the scope, we both exclaimed that it was the BLACK-
>TAILED GULL!! This just about caused heart attacks all
>around. There, standing two feet apart, were a Black-tailed
>Gull and a Kelp Gull (or Kelp/Herring hybrid; see below).
>In fact many of my slides of the pair have 5 species of gulls
>in them: Black-tailed, Kelp-type, Herring, Ring-billed, and
>Laughing. The only one not in the picture was the second
>winter Lesser Black-back that was about 25 feet away on
>the ridge top. Hopefully I'll get these pictures up on the web
>for everyone to look at soon.
>
>The Kelp-type gull deserves some discussion (previous
>posts on the Black-tailed covered that bird well). From our
>observations of the gull, features visible in the slides, and
>from my reading of the article by Donna Dittman and Steve
>Cardiff about Kelp/Herring hybrids in the LOS newsletter
>(see http://losbird.org/los_news_181_98july.htm), I'm
>reasonably convinced that this bird is a Kelp/Herring
>hybrid, or more likely (based on back color) a back-cross
>with a Kelp parent. Paul O'Brien and Paul Pisano, who
>had seen the Maryland Kelp Gull just two weeks earlier,
>had a great handle on many of the features of this bird that
>seemed different in comparison to the Maryland bird and
>suggested hybrid origin.
>
>Here's a description. I'll try to be brief. When the pictures
>are posted, you can study them in more detail. If you're not
>into gulls, bail out now.
>
>Age and molt: Adult; possibly 4th winter (there was a thin
>black bar on the bill near the tip). There was no obvious
>molt in progress and wingtips were slightly worn.
>
>Size: About in the middle of the range of Herring Gull sizes.
>Several Herring gulls present were a bit larger, but most
>were about the same size.
>
>Back color: The back and wings were dark slate gray; nearly
>as dark as a Great Black-backed Gull's but with a detectable
>contrast between the black wingtips and the dark gray back.
>This is probably about the same back color as intermedius
>Lesser Black-backed Gull, but I have no first-hand experience
>with this form.
>
>Head: The head was largely white, but there was a small
>mask of thin brown streaks around the eye, extending back
>from the eye partway around the back of the head. The nape
>was mottled with brown blotches. I don't have good references
>for Kelp Gull plumages, but I think that they don't really acquire
>brown blotching in the winter; this is more of a Herring Gull
>feature.
>
>Eye: The eye was clear greenish-yellow. All the Herrings had
>much yellower eyes, or yellow eyes with brown (plum?) tones.
>The orbital ring was orange. This color should be red in a Kelp
>Gull, yellow in Herring.
>
>Bill: A little thicker than a Herring's and about the same length.
>There was a very prominent gonydeal angle and steeply curved
>culmen tip, giving the bill a fairly thick-tipped and bulbous look.
>The color was yellow with a red gonydeal spot and a blackish
>bar in front of the gonydeal spot. The bill seems to be like a
>Kelp Gull's.
>
>Underparts and legs: The underparts were all white, as was the
>tail. The legs and feet were gray with a slight greenish cast. In
>some slides the legs appear to have a pinksh cast, though far
>less pink than any Herring Gulls (even first winter). Other photos
>show the greenish look. Dittman and Cardiff point out that all of
>the presumed pure Kelps in Louisiana had greenish or even
>yellowish legs (in breeding season), while the hybrids had
>gray legs.
>
>Wings: The wing pattern gives the key clues suggesting that
>this may be a hybrid. There was a broad white tertial crescent
>and a small white scapular crescent. The size of these white
>markings was probably within the range for Kelp, but perhaps
>a bit narrow in both cases. In flight, the broad white tertial and
>secondary tips give the wings a very wide white trailing edge.
> There was a single white mirror on P10 (the outermost
>primary) that covered both webs of the primary. No other
>primaries had white mirrors but all had small, worn, white tips.
> The primary projection was very short; in absolute length
>about half that of the Herrings. The tail tip is even with or just
>beyond the third white primary tip (I think P10 is visible on the
>folded wing, so I think this is P8), and comes to the middle of
>the white mirror on P10. On Herrings, the inner edge of the
>white mirror on P10 just meets the tail tip (the mirror is entirely
>beyond the tail tip in Lesser Black-backs). I'm not sure what the
>pattern should be for Kelp, but pictures on the web of the
>Maryland bird (http://www.bway.net/~lewis/birds/mkelp.html)
>show the same primary projection and mirror position as
>the Brownsville bird.
> From below, only the outer two primaries are
>extensively black, P8 is about half black and P7-P5 have
>smallish black bands at the tips. The black wingtips are
>only slightly more extensive than in typical Herrings, and
>less so than in Kelp. Furthermore, there are pale tongues
>separating the black bands from the gray feather bases on
>P7-P5. On the Maryland bird, only P6 and P5 had pale
>tongues, and they were smaller than in the Brownsville bird.
>As I mentioned earlier, the bases of the inner primaries and
>all secondaries look gray from below, substantially darker
>than in Herring gulls, but apparently paler than in typical
>Kelp gulls. This primary pattern looks very much like the
>illustration in Dittman and Cardiff of an f1 Kelp-Herring
>hybrid, although the back color of the Brownsville bird is
>much darker than the illustration of that hybrid.
>
>While this bird looks superficially very much like a Kelp
>Gull, I think several features suggest it is a Kelp-Herring
>hybrid of some type. These are, in particular, the orange
>orbital ring and the restricted black on the primaries. The
>gray rather than greenish legs may or may not support this
>assessment. The back color, almost as dark as a Kelp,
>suggest that it may be a backcross between a Kelp-Herring
>hybrid and a Kelp.
>
>I hope this bird shows up again for others to look at. It is
>certainly an interesting study. I'll work on scanning some
>slides tonight and hope to get photos up on the web soon.
>
>John O'Brien
>
>
>--
>For other Audubon lists, visit <http://www.audubon.org/listserv/>.
================================================
Phil Davis
home: PDavis@ix.netcom.com Davidsonville, Maryland USA
work: PDavis@OAO.com Greenbelt, Maryland USA
================================================