These photos from Florida trip in February, Fred Howard Park, Tarpon Springs. I think they show a male Skimmer, because of the gap in the bill. The deep black suggests alternate plumage. The frontal shot show the laterally compressed bill, which enables it to slice through the water with minimal resistance.
Side view shows the long wings (span 44") and short red-orange legs, and of course that amazing underbite:
Last shot gives us a closer look at the bill. Skimmers fly very close to the water, dipping the lower mandible into the water's surface and snapping it shut when they contact a fish. Fun to watch.
Skimmers are seen on both coasts. In California their northern range limit is the SF Bay Area. Once year we had one loafing at Shorebird Marsh in Corte Madera, Marin County. They are seen regularly at preserves in the south bay, and are known to breed there.
The Black Skimmer, Rhynchops niger, displays great size differences between male and female, with the larger male fully 10% bigger or more in all measurements, and fully 30% heavier (365 gm. vs 265 gm., or 12.9 oz. vs 9.3 oz.). The male has a bowed or "open" bill (BNA account).
Skimmer taxonomy tends to vary with the source, and remains unresolved. What follows is the mostly widely accepted understanding, and to me the most sensible.
Order: Charadriiformes - Huge and diverse order, including shorebirds, gulls, auks, etc.
Family: Laridae - Gulls, Terns, and Skimmers. (Skuas and Jaegers now have their own family)
Subfamily: Rhynchopinae - The Skimmers. Only one genus here. The other sub-families in Laridae are Larinae (Gulls and Kittiwakes) and Sterninae (Terns and Noddies). Skimmers thought to be closer to the terns, but really not very close.
Genus: Rhynchops - Skimmers. 3 species world-wide. Other two are the African Skimmer (yellow tip on bill, and not dimorphic) and the Indian Skimmer (always with white collar, and orange-yellow on bill).
Species: Rhyncops niger - Black Skimmer. 3 subspecies, all in the New World. Ours in North America is the nominate subspecies, R. n. niger, which is mostly coastal, but seen inland in Florida and California (especially at the Salton Sea). Subspecies further south are more riverine in their nesting and foraging.
Skimmer population in NA is fairly stable, but nesting success in not high (less than 50%), with disruption by flooding, predation and human disturbance. Caution advised in banding or observing nesting colonies (duh).
