The male inflates his bright red throat pouch to attract females. Well adapted to an aerial existence, the magnificent frigatebird is a marauder of the tropical coasts of North and South America. W. Z., and 0000001483 00000 n Males and females captured same-sized prey considering the specimens of the three most common families in the sample (Carangidae, Serranidae, and Triglidae) (females: 13.3 ± 0.7 cm, n = 26; males: 12.5 ± 1.1 cm, n = 6; two-way ANOVA, effects: sex F1,28 = 0.3, P = 0.57; fish family F2,28 = 4.5, P = 0.01; interaction F2,33 = 3.5, P = 0.04). Greater foraging success or greater efficiency at catching prey, although expected in adults (and confirmed in some studies) under challenging conditions, may not be apparent when food is abundant. Harrison, D. A., �H��6�C'a�W��p�+�k 0�x�'�Bp�?g�����jRb��pl�N�䚲N�c5��f� �2��:#h�7�~x�γ��r��'*w*�2>. Population number. (1983), and Duffy and Jackson (1986). H�c```g``.b`a`��� �� 6+s\ �ϊ\�f`�/�rz�; ���G��j$Z䀂�v������� �ձx'$?� ��j endstream endobj 77 0 obj 104 endobj 56 0 obj << /Type /Page /MediaBox [ 0 0 483 712 ] /Parent 51 0 R /Resources << /Font << /F0 57 0 R >> /XObject << /im1 75 0 R >> /ProcSet 73 0 R >> /Contents [ 59 0 R 61 0 R 63 0 R 65 0 R 67 0 R 69 0 R 71 0 R 74 0 R ] /CropBox [ 0 0 483 712 ] /Rotate 0 >> endobj 57 0 obj << /Type /Font /Subtype /Type1 /Name /F0 /BaseFont /Helvetica-Bold /Encoding /WinAnsiEncoding >> endobj 58 0 obj 2064 endobj 59 0 obj << /Filter /LZWDecode /Length 58 0 R >> stream We applied Generalized Linear Models (GLM; Crawley 1993) to analyze prey item composition of males, females, adults, and juveniles. The analysis included only those families represented in at least two regurgitates. Trivelpiece, Morphological differences between sexes, and different feeding skills associated with age and experience are known to influence the diet of individuals in marine birds (Orians 1969, Gilardi 1994). This species consumed 23 fish families and a single squid. Some chick regurgitations were obtained immediately after the chicks were fed by the father (n = 6) or the mother (n = 44); these items were assumed to represent the diet of the parent. Flying fishes and squid, commonly reported as the diet of frigatebirds (Diamond 1975), were relatively uncommon prey items of the frigatebirds at Isla Isabel. Dimorfismo sexual en la conducta de reproducción y la deserción del macho en. The diet included 50 species of fishes (21 identified to genus only), 1 species of squid, and 2 species of crustaceans. The relative abundance of most prey species was less than 2%. Seventy percent of prey items were identified to species, 88% to genus, and 99% to family level. data), which is the preferred kleptoparasitized bird at Isla Isabel (Osorno et al. Cienc. 0000013647 00000 n Meristic data were: (1) total length (the distance between the mouth and the tip of the tail), (2) standard length (the distance between the mouth and the tip of the caudal peduncle), (3) head length (the distance between the mouth and the end of the operculum), (4) maximal height (measured from the base of the dorsal fin to the base of the pelvic fin), and (5) the diameter of the eye (Rojo 1991). We used biometrics in fish identification to determine: (1) number of branquispines in the first brachial arch (prominent expansions of variable size also known as rakers; Rojo 1991), (2) the number of scales in the lateral line, (3) the form and position of the fins (ventral, thoracic or jugular), (4) the dorsal, pectoral, and anal fins formula (number of spines and radii), and (5) the presence of adipose fins, photophores, and barbells. They may also have greater fishing ability than males, or they may fish for longer periods of time to fill their larger crops. A comparison of seabird diets and foraging distribution around the Pribilof Islands, Alaska. The diet included 50 species of fishes (21 identified to genus only), 1 species of squid, and 2 species of crustaceans. 0000001505 00000 n The diet of the Magnificent Frigatebird at Isla Isabel is the broadest diet reported to date for this genus. We compared the diet of males and females, and of adults and flying juveniles, and assessed whether this diet varies during the breeding season. The magnificent frigatebird has several nicknames. Great Frigatebird kleptoparasitism: sex-specific host choice and age-related proficiency. Evolution of breeding behavior in the Magnificent Frigatebird: copulatory pattern and parental investment. The average total length of these 135 prey items was 12.5 ± 0.4 cm. The four most abundant fish families were Serranidae (31.0%), Triglidae (14.2%), Engraulidae (10.6%), and Bothidae (8.3%). We did not compare the longest prey because this may be meaningless, as it is uncertain whether the longest prey in a given sample is the longest prey a bird can capture.