suspected Slaty-backed Gull
22 January 2000
Harlan County Reservoir, Harlan County
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The HCR Dark-mantled (suspected Slaty-backed) Gull Description
TIME: 3:15-3:55 p.m. cst
LOCATION: West end of Harlan County Reservoir, Harlan County in south-central Nebraska
LIGHTING CONDITIONS: Skies were partly to mostly cloudy.
OPTICS USED: Kowa TSN-4, 20-60 eyepiece; photos taken with 1200mm photo attatchment
CIRCUMSTANCES: I observed the gull from my vehicle for about 20 minutes at a distance of approximately 700 ft. I then approached closer on foot and observed and subsequently photographed the bird at approximately 300 ft. I took three photographs, two of which turned out and are the ones above. As I was re-positioning to take more photos, the bird apparently independently flew away from the roost. I searched the rest of the day, and all day the next with no luck relocating the gull.
Description
GENERAL SIZE AND STRUCTUREThe Gull was large and heavy-bodied. Much larger than the nearby Ring-billed Gulls, and slightly larger and slightly heavier bodied than the few Herring Gulls present.
GENERAL PLUMAGE
The gull appeared to in adult plumage, with no signs of immaturity. It was a dark-mantled gull with a moderate to heavy hood.
BILL
The bill was fairly straight and thick, somewhat like a Herring Gull bill, but perhaps slightly thicker. Also, the distal end of the culmen appeared more rounded than a Herring Gull's bill, or in other words the upper mandible was straight until the very end, thus the curvature of the distal end of upper mandible was greater in a shorter distance. The resulting appearance was minor and subtle, but the bill appeared blunter at the end or even droopy looking at the end (although it wasn't) when compared with a Herring Gull's bill.
LEGS
The leg color was a very rich pink, even at the initial viewing distance this was obvious. Obviously the legs were a deeper pink than the nearby Herring Gulls.
EYE COLOR
The iris color was clear pale yellow, this too was obvious from the initial viewing distance. The iris appeared a "clearer" yellow than the nearby adult Herring Gulls, however this may have been due to the dark feather smudging adjacent to the eye, thus perhaps a "mascara affect".
HEAD SHAPE
Structurally, the head was gently rounded, sloping upwards and peaking behind the eye. The forecrown had a minor peak, but the high peak of the head was behind eye. The hindcrown was squared off, similar to the shape of the hindcrown often seen on Glaucous Gulls.
MANTLE
The mantle was a very dark gray. I consider the mantle moderately darker than a Lesser Black-backed Gull's (Larus fuscus graellsii) mantle, a species which I observed earlier in the day. The mantle was, however, obviously not as dark as the black primaries and there was an obvious contrast between the dark mantle and the black primaries. Whether this can be seen in the photos is probably best left to the individual reviewer. One note about the photos, they are rather dark, notice how dark the Mallard appears in the one photo.
HEAD COLORATION
The base color of the head (and the rest of the underparts for that matter) was white. The bird did possess moderate to moderately heavy gray-brown streaking or flecking on the head, thus giving the bird a hooded appearance. The hood was complete, and what I mean is that it extended down the hindneck and upper breast, and it completely enveloped the the head and neck. The hood appeared slightly darker at the base, especially from certain angles. The feather smudging around the eye was especially dark, appearing black adjacent to the eye. This set-off the clear pale yellow iris.
SCAPULAR CRESCENT
The bird possessed an obvious white scapular crescent.
TERTIALS
The tertials possessed a very large white tertial crescent. The tertial crescent appeared to approach, in length, the size of the bill.
FOLDED PRIMARIES
The folded primaries were black with white apical spots on the end of each primary. The apical spots on the outer three primaries were obvious, but the fourth one from the end was much larger. The white area of the tip of the feather appeared to be supplemented with white by a feather from behind, thus making the apical spot appear larger. This larger apical spot is visible in the slides, but isn't really visible in the scanned photo above.
EXTENDED WING
Unfortunately I was not able to see the outer primaries on the spread wing. I did get some views of the wing while the bird was preening. The bird possessed a exceptionally large white trailing edge on the secondaries.
SEPERATION FROM OTHER SPECIES
Common and lighter-mantled gull (specifically Herring, Ring-billed, Iceland, California, Thayer's, Glaucous Gulls) species can be easily eliminated from consideration as possible confusion species. This bird was obviously a very dark-mantled large gull. It should be noted that no dark-mantled gulls occurs in numbers in Nebraska. Perhaps the most regular dark-mantled gull is the Lesser Black-backed Gull. This species can probably be eliminated as a possible confusion species due leg color. I realize that some Lesser Black-backed Gulls can possess pinkish leg color, but as far as I know it is not a deep pink. Also, other characters such as mantle shade, tertial crescent size, and perhaps most importantly of all, size and structure, also eliminate Lesser Black-backed Gull.
That leaves the large, dark-mantled gulls, specifically Great Black-backed, Western, Yellow-footed, and Kelp Gulls. Yellow-footed and Kelp Gulls are remote possibilities, and leg color and the hooded appearance of this gull doesn't fit either species, so perhaps they can be eliminated. Western Gull is also unlikely, but it has occurred as far east as Illinois, and so it should be seriously considered. The hooded appearance and deep pink legs don't fit Western Gull. Also, the darker mantle shade of this bird, as well as the very clear yellow iris aren't particularly trademarks of Western Gulls. Structurally, the bill was not as thick or distally bulbous as most Western Gulls appear. This bird did not appear "flat-headed" like a typical Western Gull also.
That leaves Great Black-backed Gull, and perhaps it is the most likely confusion species since it occurs regularly on the Great Lakes and Plains states. First, I do not believe the mantle shade was dark enough. There was clearly contrast between dark gray mantle and the black primaries. Also, perhaps the overall size and structure was not massive enough for Great Black-backed Gull. Other factors, such as leg color (usual pale pink or flesh color in GBBGU), eye color (usually appearing dark from distance in GBBGU), and hooded appearance (white-headed in winter in GBBGU) are all strikes against Great Black-backed Gull.
A hybrid gull should also be considered. However, I'm not sure of any reasonable hybrid combination that would produce a gull with such an appearance. Perhaps Glaucous-winged X Western Gull and Great Black-backed X Herring Gull are two hybrids that should be considered. However, the same characteristics (leg color, hooded appearance, eye color, mantle color) all seem to reasonably eliminate these hybrids from consideration.
Any comments on this gull would be appreciated.
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Last Updated 2/18/00