Sandwich Tern, Sterna sandvicensis in New York

Despite foggy conditions we were enjoying scanning a large and very dynamic feeding flock of terns and gull a few hundred yards off Montauk Point, when Tony Lauro drew everyone's attention to a largish white tern leaving the flock and heading west along the beach. Tony was quick enough to see the bill which appeared to be dark, and this was confirmed by Andy Guthrie and Paul Buckley. All of us felt certain, based on the bill and the relative size compared to the Common (S. hirundo) and Forster's Terns (S. fosteri) (as well as the Royal Terns (S. maxima) that we had seen earlier in the morning), that we were looking at a Sandwich Tern (S. sandvicensis).

We relocated the Sandwich Tern further along the beach, roosting on some small partially submerged rocks along with a flock of 30-50 Common Terns and at least 2 Roseate Terns (S. dougallii). We were able to approach within 50 yards and photograph the bird (see enclosed figures), which appeared to be a subadult Sandwich Tern (S. sandvicensis) probably in its 2nd calander year (see below).


Figure 1. In flight. Notice the dark outer primaries, dark greater coverts and incomplete secondary bar. The newer inner primaries are white. The outertail feathers are relatively short. (Image Copyright © of Angus Wilson)


Figure 2. Close-up view showing long black bill with yellow tip. The feathering across the forehead and crown are white. (Image Copyright © of Angus Wilson)


Figure 3. Perched on the crest of a boulder with Common Terns. (Image Copyright © of Angus Wilson)


Figure 4. Perched on a boulder with Common Terns and a Double-crested Cormorant. (Image Copyright © of Angus Wilson)


Figure 5.Landing on a boulder amid Laughing Gulls and Common Terns. (Image Copyright © of Angus Wilson)


Figure 6.Falling asleep! (Image Copyright © of Angus Wilson)

Identification:

Given the prolonged close views and detailed photographs, the identification was straight forward. The key features included:

(1) Size - significantly larger than accompanying Common Terns, although not as large or as long-legged as Laughing Gulls (Larus atricilla).

(2) Bill shape and color - Long, slightly down-curved dark bill complete with yellow tip.

(3) Head pattern - Long and angular head with a flat crown. White forehead and central part of crown with dark remnants of cap restricted to the nape.

(4) Primary pattern - Dark outer primaries (due to wear?).

(5) Aging - The presence of a dark subterimal bar across the central secondaries, and the minimal tail fork both suggest the bird might be a subadult in its second summer (Olsen and Larsson, 1995).

Literature:

Olsen, K. M. and Larsson, H. (1995) Terns of Europe and North America. Princeton University Press.

Copyright © 1998 All rights reserved. Angus Wilson (e-mail: wilsoa02@endeavor.med.nyu.edu)
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