LOUISIANA BIRD RECORDS COMMITTEE

REPORT FORM

1. English and Scientific names: Great Black-backed Gull, Larus marinus

2. Number of individuals, sexes, ages, general plumage (e.g., 2 in alternate plumage): 1 first winter bird

3. Locality: Parish: Vermilion

Specific Locality: mouth of Freshwater Bayou at Gulf of Mexico, at approx. 29.5336, -92.3087.

4. Date(s) when observed: February 10, 2014

5. Time(s) of day when observed:

6. Reporting observer and address: Paul Conover, Lafayette LA 70506

7. Other observers accompanying reporter who also identified the bird(s): Judge Edwards, Dave Patton

8. Other observers who independently identified the bird(s):

9. Light conditions (position of bird in relation to shade and to direction and amount of light): Good light. Overcast, but bright

10. Optical equipment (type, power, condition): eyes, good condition; Nikon d50 w/300 mm lens in decent condition but didn’t get on the bird until it was passing out of sight

11. Distance to bird(s): passed within 20 yards at closest

12. Duration of observation: perhaps 15-20 seconds

13. Habitat: Freshwater Bayou is a shipping channel running into the Gulf of Mexico. It empties into the Gulf in the middle of uninhabited marsh. There is a small shell spoil bank at the mouth, and a lock just upstream that provide resting places for gulls and other birds. The gulf beach to the east and west of the bayou is actually short mud walls, the result of marsh cutaway from wave erosion and provides little resting space for flocks. The gulf is very shallow in the nearshore, but deepens enough offshore to allow shrimp boats to work, which probably accounts for the number of gulls in the area.

14. Behavior of bird / circumstances of observation (flying, feeding, resting; include and stress habits used in identification; relate events surrounding observation): We were drifting down the channel of Freshwater Bayou where it empties into the Gulf, and throwing popcorn to attract gulls. We had attracted quite a swarm of gulls, mainly Laughing and Ring-billed, but also a small group of Herring Gulls and Bonaparte’s, so we had a lot of gulls to sift through. A large gull came in from the east, probably 30 feet above the water It had a white head and black bill and from what I could see a white rump and dark tail band. I didn’t know if Dave had spotted it, so I alerted him and Judge that a black-backed gull was joining the swarm. The bird made an arc around the rear edge of the flock behind a screen of gulls and its path swung it quickly to the side of the boat. I was crossed up and couldn’t get my camera in play, but Dave got some photos as it flew by the side of the boat on its closest pass. Instead of returning and entering the fray, the bird continued on its path back into the gulf and off to the east. I managed to snap some photos as the bird was moving away. I mostly got naked eye looks at the bird, but in general terms the looks were good. I couldn’t be sure given the quick pass and the angle, but I felt the bird more likely a Great Black-backed because I felt I had seen more contrast in the wings and mantle than a Lesser Black-backed would show.

15. Description: A large, stocky first winter gull with a white head and a dark bill on one end, a whitish rump and tail with a black subterminal band on the other, and in between, dark flight feathers but patches of paler color on the upperwings and mantle. Relative size was impossible to judge as it wasn’t directly comparable to other similar gulls. That was about all I saw of the bird with naked eye. If not for Dave’s photos, this gull would have been relegated to “probable” GBBG status and no report submitted.

Looking at Dave’s photos, I can fill in the written description in the event that his record loses its images at some point:

Bill black and large, with an abrupt downcurve at the tip, giving the bill a meat cleaver look. Small pale tip of maxilla. White head in string contrast to dark bill, small dusky patch around eye, narrow before eye then broadening behind eye. Light dusky streaking on crown, collar of light streaking.

Underparts white on chin, throat, and breast, marked with thick, dusky, smudgy and wavy lines on belly. Undertail coverts with clean white ground color, marked with a few discrete transverse bars.

Upperparts marbled with dusky feather centers and internal markings with broad grayish fringes. Scapulars not solidly colored, but light with irregular dark markings based on shafts.

Upperwings with moderate contrast, median and greater secondary coverts mostly dark, but appear to be barred, probably with dark centers but white cutaways from margin. These coverts tipped conspicuously in white. This barring produced an impression of a series of parallel white lines running through otherwise dark coverts. The series of lines on the greater secondary coverts were most distinct proximally, and petered out about halfway out toward the junction with the primaries. Secondaries dark, contrasting well with remainder of inner upperwing.

A weak but noticeable inner primary window, the result of an interesting pattern. Outer 4 primaries mostly dark, inner web of rest of primaries with paler areas, dark tips, and small paler areas (“lozenges”) just proximal to dark tips on outer webs on primaries 1-4. Primary coverts dark, greater primary coverts with paler inner webs shading darker distally. Pale patch in lesser primary covert area.

Underwings largely brown, axillaries evenly and narrowly barred brown and pale brown, flight feathers with paler echo of upperwing pattern.

Rump and tail white, with sparse irregular wavy bars. Black subterminal band on distal ¼ or so of tail, with white fringe on rear edge. Black band thickest in middle, narrowing on ends. Outer rectrix mainly white, with what appears to be a wavy thin black subterminal bar and one narrower wavy black bar proximal to this.

Eye dark brown. Legs pink.

16. Voice: Not noted. The bird didn’t come in to fight other gulls for food, which is when we usually hear them screaming.

17. Similar species: Tail band, degree of contrast between secondaries and greater secondary coverts eliminate Lesser Black-backed Gull, with bill size and shape, stockiness of bird also good indicators. Herring Gull removed by tail pattern. Hybrid GBBG X Herring Gull seemingly eliminated by suite of features falling well within range of GBBG, with no readily discernible intermediate features.

18. Photographs or tape recordings obtained?

I took poor, non-illustrative photos. Dave Patton took a nice series of shots that show most of the landscape of this bird.

19. Previous experience with this species: Decent amount of experience, but mostly in summer on breeding grounds, thus not in this plumage.

20. Identification aids: (list books, illustrations, other birders, etc. used in identification):

a. at time of observation:

b. after observation: Olsen and Larsson, Howell and Dunn.

21. This description is written from: memory, but mostly study of photos.

22. Are you positive of your identification if not, explain: Yes

23. Date: 2/10/2014