Photo Gallery of Rare Birds from the East End
Arctic Tern at Cupsogue County Park, Westhampton Dunes on 29 May 2006
Figure 1: Adult Arctic Tern (left) with adult Common Tern. Note the rounded head, short legs, lack of long neck, and entirely blood red bill. Also compare the position of the black cap relative to the eye and the gape; on Arctic Tern the slightly more extensive cap completely contains the eye and is separated from the gape by a very narrow white stripe, whereas on Common Tern the eye forms a small bulge along the lower edge of the cap and a broader white stripe separates the cap from the gape.
On 29 May 2006, on the mudflats at Cupsogue County Park, Shai Mitra found an adult Arctic Tern and an enigmatic immature tern that showed many features of Arctic Tern. The birds were not together when found and remained in different parts of the marsh for over an hour as Shai went back and forth between them, obtaining some nice photos of both birds. Eventually, the immature flew over and landed next to the adult. Patricia Lindsay joined Shai on the flats after the tide dropped and was able to study the adult, but not the immature, bird.
Arctic Tern is not only very rare on Long Island, but very difficult to distinguish confidently from Common Tern. Here I have posted several of Shai’s photos and his comments on each bird. All questions and comments are welcome.
“The adult Arctic was not particularly small-billed, but otherwise it showed the full suite of characters:
- bill blood red to tip
- rounded crown with steep forehead
- neckless appearance
- black cap completely enclosed eye and almost reached gape; compare with Common Terns in which eye often bulges down into white cheek and gape is separated from cap by broader white stripe
- extensively deep gray underparts set off from black cap by a narrow white cheek patch, recalling Whiskered Tern
- very short, blood red legs; in a couple of shots here the bird is relatively alert and standing up, but note the extremely short tarso-metatarsi (the lower portion of the leg, below the joint)
- uniformly medium gray primaries without molt limits (difference in feather age between inner and outer primaries)
thin, distinct, black trailing edge to underhand - underside of outermost primary extensively pale on both webs except for restricted black tip
- the primaries were all translucent from below, though this doesn’t show in the shot I included.
The immature bird was odd in that it did not look very short-legged (nor particularly short-billed), and it seemed a bit more advanced in soft parts coloration compared to most first-summer Arctics. On the plus side for Arctic:
- neckless appearance
- uniformly medium gray primaries without molt limits
- thin, distinct, black trailing edge to underhand
- translucent primaries
- relatively weak and diffuse carpal bar (immature/winter-plumaged Common Tern shows broader, blacker carpal bar)
- no dark secondary bar, as shown by immature/winter-plumaged Common Tern
- very long tail for an immature/winter-plumaged tern
- graceful flight action with thrusting downstrokes, different from the even, rowing action of Common Tern (I was better able to study this bird in flight than the adult)
- triangular black mask includes the eyes; compare the first summer Common Tern which shows the typical Common Tern pattern where the black blob enclosing the eye is somewhat distinct from the black nape; people talk about a flecked forehead and a white area immediately below the eye as features favoring Common Tern over Arctic Tern, but I think this refers to juveniles and first winter birds; this bird shows a suggestion of dark on the lower cheek, but it is more advanced than a first winter—it may be a second summer bird, or even an adult in retarded plumage.”
Figure 2: Adult Arctic Tern (right) flying with an adult Common Tern. Note the lack of black wedge, which is highly visible on the Common Tern, on the inner primaries, and also the thin black trailing edge on the underside of the primaries.
Figure 3: Immature Arctic Tern. Note the neckless appearance, rounded top of head and even gray on the upper surface of the primaries.
Figure 4: Immature Arctic Tern in flight. Note upper surface of primaries without dark wedge, rounded head, neckless appearance and lack of secondary bar.
Figure 5: Quiz photo. Can you pick out the Arctic Tern? How about the Roseate Tern?