000			02781nab a22002777u 4500
003			EC-PaCDF
005			20171113113549.0
008			060603t19681968||||||||||||||||||||eng||
040			_aEC-PaCDF
041			_aeng
082	0	4	_a598.338 _222
100	1		_aSnow, Barbara K.
245	1	0	_aBehavior of the swallow-tailed gull of the Galápagos.
520			_aA breeding colony of Swallow-tailed Gulls, Creagrus furcatus, was studied on South Plaza Island in the Galapagos Archipelago from February 1963 to April 1964, and supplementary observations were made on Tower Island in May 1964. Pair formation takes place at the nest site, which is acquired by the male. This is in contrast to pair formation at “clubs,” which occurs in typical gulls, and probably results from the shortage of suitable sites. All marked males returned to the sites that they had used previously, but some females changed their site. Calls and displays are described, and are classified as follows: The Rattle and Whistle, an unusual and unique call, used only in response to alarm from potential predators; the Departure Call, used only when birds are leaving the colony in the evening; Downward Piping, uttered by paired birds on their territory, in both agonistic and courtship situations; the Upward Jerk, one of the main advertisement displays used by unpaired males, but also used by paired birds; the Head-up Tailup posture, Facing Away, and the Landing Gape, characteristic of the early stages of courtship; the Breast-lowered posture, which tends to replace the Head-up Tail-up posture later in courtship; the Regurgitation Bow, a ritualized preliminary to courtship feeding; Courtship Feeding, which is most frequent in the three weeks before egg-laying; and Head-tossing, which is the usual preliminary to copulation. Purely aggressive displays, connected with the acquisition and defense of territories, include a silent Threat-gape and the Head-forward Rattle. Foot-watching occurs both as a display and autochthonously, as in other gulls. Nest-building, parental care, and the devel-opment of the chick are briefly described. It is suggested that pelagic feeding, colonial cliff-nesting, and nocturnal habits resulted from a combination of poor inshore feeding conditions with the presence of frigatebirds. These in turn have led to a complex of subsidiary adaptations, and courtship and associated behavior have been profoundly affected in various ways.
546			_aEnglish
550			_a86
653		0	_aBirds
653		0	_aAves
653		0	_aBreeding
653		0	_aApariamiento
653		0	_aSwallow tailed gull
653		0	_aGaviota de cola bifurcada
653		0	_aGalápagos
773	0		_tThe Condor _gVol. 70, no. 3 (July 1968), p. 252-264
942			_2ddc _cARTICLE
999			_c6730 _d6730