magnificent frigatebird diet

Financial support came from a grant provided by The National Geographic Society to H. Drummond. Size. This is consistent with the fact that the differences in diet composition between age classes were largely due to the disproportionately high abundance of Clupeiform fish (surface-dwelling) in juvenile crops. The frequency of occurrence method was determined by counting the number of regurgitations including a particular type (species or order) of prey. 0000001070 00000 n Finally, typically demersal and demerso-bentonic prey were attributed to opportunist feeding near prawn-fishing boats pulling nets in an extensive zone around the island. We used t-test or two-way ANOVA to analyze prey size and food amount or their normalized equivalent (logarithm or square root) of males and females. 70-275, México, D.F. This result is not surprising, because the variety of available prey is expected to change during the breeding season, and adults may also change their foraging tactics in response to the presumably increasing demand of food from growing chicks. Consequently, total sample sizes were 13 males, 72 females, 21 flying juveniles, and 52 chicks. Not surprisingly, prey belonging to particular orders or species were consumed more often than prey from different taxa (orders: χ26 = 443, P < 0.001; species: χ25 = 471, P < 0.001). The mass (wet weight) of regurgitations did not change as the reproductive season progressed (April: 81.9 ± 19.2; May: 89.3 ± 5.5; June: 105.5 ± 10.0; July: 103.0 ± 11.7; Kruskal-Wallis H = 4.5, P = 0.2). The male inflates his bright red throat pouch to attract females. In spite of the reversed, sexual size dimorphism in the Magnificent Frigatebird, females did not capture larger prey than males, although sample sizes were small. Taxonomía, biología y evaluación de la ictiofauna demersal del Golfo de California. 0000017599 00000 n This is the largest frigatebird, with a body length of 41–44 in (103–112 cm), a wing span of 91 in (230 cm), and weight of 3.1–3.3 lb (1.4–1.5 kg). physical characteristics. Serv. forage by surface dipping, kleptoparasitism, and opportunistic feeding such as scavenging from fisheries. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. M. P.Seki. According to the IUCN Red List, the total population size of Magnificent frigatebird is approximately 100,000-499,999 individuals. Mostly fish. Leticia Durand helped during the fieldwork. Age differences in foraging efficiency have been reported for this species (Gochfeld and Burger 1983) and for the Great Frigatebird (Gilardi 1994). Diplectum pacificum and Anchoa lucida were the most frequent species of fish in the frigatebird's diet. The rocky-shore fishes of the Gulf of California. Minister of Supply and Service Canada. Notes on the behavioural ecology of the Magnificent Frigatebird. Oxford University Press is a department of the University of Oxford. Because flying juveniles are still fed by females for more than 9 months after fledging, the expected foraging inefficiency of juveniles may not necessarily translate in their diet composition. 04510, México. The diet included 50 species of fishes (21 identified to genus only), 1 species of squid, and 2 species of crustaceans. Feeds mainly on small fish, also squid, jellyfish, crustaceans. D. A., The amount disgorged by females (96.2 ± 5.9 g, n = 72) was 63% more than the amount of food disgorged by males (58.8 ± 10.5 g, n = 13; t-test, t83 = −3.1, P = 0.003 on a log transformed variable). C.MacÍas-Garcia. Programa, Universitario de Alimentos, Inst. Dictionary of evolutionary fish osteology. C. S., We propose that kleptoparasitism and direct fishing can represent at best, a small fraction of the total diet of the Magnificent Frigatebird on Isla Isabel. However, opportunism on fisheries may be the most profitable feeding tactic in this population. Seabird ecology and the marine environment. Climate threats facing the Magnificent Frigatebird. Seabirds: feeding ecology and role in marine ecosystems. The power of an equivalent t-test was only 0.06, indicating we need to take this result with caution. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. �D Ѡ�f. No differences in prey composition or prey size were found between males and females, but females disgorged 62% more food. J. D.Ferraris. 0000001091 00000 n We measured the total length of the head and the ratio of the total length/maximal height of 93 complete prey of the three more frequent species. 3. Trivelpiece, We compared (a) prey composition, (b) food amount (wet weight), and (c) prey size by date (month), sex and age of the bird disgorging any of the six most frequent orders (when sample sizes were appropriate) and at the level of the seven most frequent species in the sample of 158 stomach contents. Mean ± SE and percentages are reported when appropriate. Diet studies of seabirds: review of methods. Thomson, 1992), suggest that kleptoparasitism is probably only an opportunistic feeding strategy for frigatebirds at Isla Isabel. The average wet mass of 155 regurgitations regardless of the species and age class (3 items were not weighed) was 104.6 ± 4.3 g. Of all the recovered items (n = 555), 96.8% were fish, 2.3% were cephalopods, and 0.9% were crustaceans (0.5% decapods and 0.4% stomatopods). Marine birds: their feeding ecology and commercial fisheries relationships. The diet included 50 species of fishes (21 identified to genus only), 1 species of squid, and 2 species of crustaceans. The 20 weighed juvenile regurgitations (103.2 ± 7.4 g) had on average 15% more mass than adult regurgitations (90.5 ± 5.4 g, n = 85) but the difference was not significant (Mann-Whitney U-test, Z = 1.7, P = 0.07). The resulting number expressed as a percentage of the total number of regurgitations (n = 158) indicates the number of birds regurgitating a particular prey type, but it does not indicate its absolute abundance. Seven species were present in at least 5% of the regurgitations and were deemed the most frequent species (Table 1). 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. 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). Although stomach contents are likely to be a more accurate method of analyzing diet, that method necessitates sacrificing the birds.