| Common name: |
Least Tern |
| Scientific name: | Sterna antillarum |
| Date: | 12 June 1993 |
| Time: | 11:50 - 12:00, 12:19 - 12:20 |
| Length of time observed: | 10 minutes |
| Number: | 1 |
| Age: | adult |
| Sex: | |
| Location: | Lat. 39° 52' 30" N, Long. 113° 22' 30" W., Fish Springs N.W.R., Curlew & Shoveler unites |
| County: | Juab |
| Latilong: | |
| Elevation: | ? |
| Distance to bird: | Less than 50 feet |
| Optical equipment: | 10 x 40 Bausch & Lomb Custom binoculars |
| Weather: | |
| Light Conditions: | Very good, clear sunlight. |
| Detailed description of bird: |
-- Tiny tern (very noticeable even before forster's terns showed up for size
comparisons) --Light ashy gray above, all the way to tail, though outer tail retrices white (a subtle but notable contrast). No black on body except on wings (see below) and cap --Yellow bill (I did not notice black tip, but nor did I look for it) --Black cap coming down far down face (as other terns) --Tail very slightly forked for a tern. When spread, as it usually was during hovering flight, the outer retrices only barely extended beyond rest of tail. This gave the tern a very "short" appearance. --White forehead turning into white streak/wedge above eye (as in book) --Wings strongly marked as follows: Long, dark wedge on the outermost primaries on upper surface; from below the outer edges of the wings were outlined with a thinner black line near the tip, extending 1/3 of the way up to the wrist (and symmetrically along the tips of the primaries). See my sketch, as drawn in the field:  |
| Song or call & method of delivery: | Silent |
| Behavior: | Hovering about 15-20' off the water, and plunging repeatedly (though never deep) into the water after prey. While hovering the tern was arched over very strongly, perhaps into an acute angle, so that tail was about vertical. The wingbeats were noticeably faster than other terns. For the first ten minutes it was alone. Later, I briefly saw it amid a flock of Forster's terns swooping upon a raptor on their nesting island. |
| Habitat: | Open fresh water with grassy edges (flooded in part). Some times it dove into very shallow water near the bank. |
| Similar
species and how were they eliminated: |
--Black tern: Yellow bill, small size, no dark on flanks of the
torso in front of the wings, dark pattern on wings, white forehead & eyebrow
stripe, flight, incessant diving behavior. Besides, all the black terns I
have seen this time of year are in their black breeding plumage. --Forster's & common tern: Small size (there were Forster's tern's about for direct comparison), yellow bill, white wedge in the black cap, shortness of outer retrices, rapid & unlanguid wingbeats, slightly darker above than nearby Forster's terns, silent compared to raucous Forster's terns (obviously not a decisive "field mark", but something I noticed). -- Sooty, bridled, and Aleutian terns: small size, pale color of back. -- Small gull: Shape of dark cap, eyebrow stripe, tip of bill pointed rather than rounded as in gull. |
| Previous experience with this & similar species: | I have seen the white-winged black terns and black terns in Europe and Africa (plus black terns here often) in all plumages. Also I once saw the (formerly conspecific) little tern in Africa, during which sighting the rapid wingbeats were also noted. |
| References consulted: |
Peterson's A field Guide to Western Birds, 3rd ed. -- in the field after
I had made my field notes & opinion. Seabirds: An Identification Guide -- A couple of days later, to check alternate plumages and species options, and to check the conspecificity to the little tern of Africa and Europe. This did not affect this description at all, only confirming what I had already decided about the tern. |
| Significance of record in this area or the state: | This puppy is not on the list! |
| Description from: | Notes taken at time of sighting |
| Observer: | David Salas Wheeler |
| Observer's address: | 2196 So. 1000 Ea., Salt Lake City, UT 84106 Phone: (801) 484-7319 |
| Observer's e-mail address: | |
| Other
observers who independently identified this bird: |
-- |
| Date prepared: | 15 June 1993 |
| Additional material: | -- |
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