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Birds of the Pacific
Swallow-tailed Gull
Creagus furcatus
The
Swallow-tailed gull (Creagus furcatus) is a nocturnal
foraging seabird that breeds mostly in the Galapagos Islands;
a few pairs nest on Malpelo Island off Colombia (Harrison
1983). Nesting pairs feed nearby their nesting islands but
when it is not breeding, the swallow-tailed gull travels
widely in Humboldt Current region including as far north as
Panama, and south to Peru.
Its habit of
nocturnal foraging is unique among gulls. Its diet is squid
and fish (Harris 1970). Nocturnal foraging might be an
adaptation to avoid kleptoparasitism (piracy) by frigatebirds.
Also unusual among gulls is the swallow-tailed gulls single
egg clutch. Most gulls and relatives lay 2-3 eggs in a clutch.
Eggs are laid through the year in cliff nests around the
Galapagos Islands. Eggs are incubated on average for 32.7 days
(Harris 1970). The young take their first flight at about 60
days of age. Adult male swallow-tailed gulls are slightly
larger than females (mean of 713 g vs 673 g). About 10,000
pairs of gulls nested in the Galapagos in the last census
(Harris 1970).
References
Agreda, ANA
and DJ Anerson. 2003. Evolution of single chick broods in the
swallow-tailed gull Creagus furcatus. Ibis 145: 53-58.
Hailman, J.
1964. The Galapagos Swallow-tailed Gull is nocturnal. Wilson
Bulletin 76: 347-354.
Harris, MP
1970. Breeding ecology of the Swallow-tailed Gull. Auk
87:215-243.
Harrison, P.
1983. Seabirds. Houghton Mifflin, Boston.
November 2009
Swallow-tailed Gull Photos
Photos:
Rob Butler
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