Sterna nilotica
Though included in the genus Sterna by the 7th. edition of the A.Q.U. Checklist )Am. Ornithol. Union 1998) and the Birds of North America series (Parnell et al. 1995), the Gull-billed Tern might best be thought to represent the monotypic genus Gelochelidon. This was the opinion of Oberholser (1974) and is the current opinion of many other authorities (Olsen and Larsson 1995, Cramp 1985, Urban et al 1986). The issue is succinctly summed up by Cramp who states “Generic differences from Sterna obvious in prolonged observation,….”.
By any name the Gull-billed Tern is an attractive, medium-sized tern and a permanent resident of coastal Texas. Different from other terns closely tied to beaches, surf and salt water bays, this tern is usually seen coursing salt marsh ponds and canals away from the salt water’s edge, hawking the insects which make up the largest part of its diet. The older name of Marsh Tern reflects this habitat preference (Bent 1921). Though truly inland records are rare, it is often seen over flooded fields along the sub-coastal rice belt during the spring. It is easily identified by its gull-like all black bill, black feet and legs, medium size, overall paleness, and slightly chunky build.
DISTRIBUTION: Nowhere numerous, this bird occurs over much of the temperate and tropical areas of the world. Away from North America, especially in Europe and Asia, it is often found as an inland species. In North America, however, it is almost entirely coastal in its distribution, and this is especially true for Texas. The breeding range map demonstrates quite well that the Gull-billed Tern nests only along the coastal rip in this state. After the nesting season it still is found almost entirely along the coastal tier of counties.
SEASONAL OCCURRENCE. The presence of this tern is easy to document. It is conspicuous in its habitat and identification is straightforward, and, its status as a breeding bird is equally easy to document with confidence. As is true with most birds nesting on the open ground, if adult birds are present during the nesting season a bit of searching will usually turn up the nests. Note the big majority of confirmed nesting records on theaccompanying map. The tern is a permanent Texas resident. Apparently some birds leave the state in the winter for its numbers are fewer then than in the summer (Oberholser 1974). However, Texas still has a healthy winter population, and it is usually easy to find in the appropriate coastal habitat. Nesting occurs from late spring through the summer. Oberholser (1974) reported eggs from April 14 to July 17.
BREEDING HABITAT. Nineteenth century reports indicate this tern may have been a marsh nester then, at least in part.
However, all twentieth century accounts invariably mention nesting on sandy beaches, dry sand flats, sand spits, or other similar situations. At present in Texas dredged spoil banks lining the intracoastal canal probably represent the most commonly used nesting site. Of necessity the nests are placed above the ordinary high tide level, but unusually high spring tides can and do inundate these nests destroying eggs and chicks. Renesting can occur following such loss. The nests are simple affairs; usually a slight depression in the sand lined, at best, with a few bits of shell and some dune grass. Several pairs may nest together in a loose colony along with Black Skimmers (Rynchops niger) and Forster’s Terns (Sterna forsteri). The usual clutch size is two or three, rarely four (Harrison 1975, RJG).
STATUS: The twentieth century has not been kind to the Gull-billed Tern in the United States. East coast populations especially have declined. The Saltori Sea, California colony has declined 75% according to several studies Parnell et al. 1995). Texas, though, has remained something of a stronghold. A 1988 report indicated 59% of U. S. breeding pairs were in Texas, the majority of those being in south Texas (Spendelow and Patten 1988). My own opinion, based entirely on anecdotal evidence, is that the Texas population has definitely increased during the last thirty years.
Text by William J. Graber, III (posted wth updates 2007)
Literature cited.
American Ornithologists’ Union. 1998. Checklist of North American birds, 7th ed. Am, Ornithol. Union, Washington, DC.
Bent, A. C. 1921. Life histories of North American gulls and terns. U. S. Nat. Mus. Bull. 113.
Cramp, S., ed. 1985. Handbook of the birds of Europe, the Middle East and North Africa, Vol. 4. Oxford University Press, Oxford,UK.
Harrison, H. H. 1975. A field guide to birds nests. Houghton Mifflin, Boston, MA.
Oberholser,Harry C. 1974. The bird life of Texas. University of Texas Press, Austin .
Olsen, K. M. and H. Larsson. 1995. Terns of Europe and North America. Princeton University Press, Princeton, NJ.
Parnell, J. F., R. M. Erwin and K. C. Molina. 1995. Gull-billed Tern (Sterna nilotica). In The birds of North America, No. 140 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Spendelow, J. A., and S. R. Patton. 1988. National atlas of coastal waterbird colonies in the contiguous United States: 1976-1982. U. S. Fish Wildl. Serv. Biol., Rep. 88. Washington, DC.
Urban, E. K., C. H. Fry and S. Keith, eds. 1986. The birds of Africa. Vol.2. Academic Press. London, UK.