Sh. Schweitzer et Dm. Leslie, FORAGING PATTERNS OF THE LEAST TERN (STERNA-ANTILLARUM) IN NORTH-CENTRAL OKLAHOMA, The Southwestern naturalist, 41(3), 1996, pp. 307-314
Because the interior least tern (Sterna antillarum) is piscivorous, lo
cations of colony sites and reproductive success are strongly influenc
ed by distance to bodies of water with available forage. We examined f
oraging patterns and success of the least tern nesting on a salt flat
in north-central Oklahoma during the 1992 and 1993 breeding seasons. O
ur objectives were to 1) estimate whether there were limited quantitie
s of forage available to breeding least terns, 2) examine least tern u
se of bodies of water adjacent to the salt flat, and 3) identify fish
species brought to colony sites and in bodies of water adjacent to the
salt flat. Chicks were fed smaller fish than were brooding adults and
chicks were offered more fish than they consumed. Adults did not fora
ge away from the salt flat during incubation and brooding (peak hatchi
ng). Foraging success of terns observed fishing away fr om the salt fl
at from May to June was increased by fingerlings available at a fish h
atchery approximately 12 km from the salt flat. During incubation, bro
oding, and fledging (July), the only location away from the salt flat
where terns were observed feeding was the eastern shoreline of the Gre
at Salt Plains Reservoir. Collections of fish dropped and left uneaten
by least terns in colony sites contained six species. These collectio
ns served as an index of species selected by the least tern. The six s
pecies of dropped fish were present in all samples seined from adjacen
t waterways. Sizes of fish in seine samples and of fish brought to nes
ts were smaller than those of fish found dropped and uneaten in colony
sites. These uneaten fish ma) have been too big to consume. Quantity
and quality of fish available to least terns during our study were ade
quate and did not appear to limit reproductive success. Forage availab
ility may only be a limiting factor to reproductive success during dro
ught years.