Fregata Magnificens Research Articles

Postbreeding Movements of Frigatebirds Tracked with Satellite Telemetry

Abstract Using satellite telemetry, we studied the postbreeding movements of Great (Fregata minor) and Magnificent Frigatebirds (F. magnificens) at two breeding colonies in the Indian and Atlantic Oceans. After breeding failure, 67% of the birds with satellite transmitters remained on the breeding colonies and continued to perform foraging trips similar to those undertaken while breeding. Two Magnificent Frigatebirds that bred at a colony off the coast of French Guiana moved west along the coast of South America, and one of the two reached Trinidad 1400 km away. One Great Frigatebird moved 4400 km from Europa Island in the Mozambique Channel to the Maldive Islands. It roosted there for at least four months, making foraging trips of up to 240 km, mainly to an area known for its high concentration of tuna. These results show that frigatebirds are able to make rapid and directed long-distance dispersal movements to other colonies or roosting sites, although the majority of birds remain based on breeding colo...

CHICK GROWTH VARIABILITY AND PARENTAL PROVISIONING IN THE MAGNIFICENT FRIGATEBIRD

Abstract In two contrasting breeding seasons, we investigated the effects of provisioning on chick growth and survival of the Magnificent Frigatebird (Fregata magnificens), a socially monogamous, dimorphic seabird that rears a single chick for more than a year, shows specialized feeding techniques, and depends on unpredictable food sources. We hypothesized that chicks of this seabird would increase their chances of survival by varying their growth in relation to food availability. We estimated the amount of food ingested by a chick using electronic scales placed at the nest and recorded feeding rates, growth rate, fledging size, and fledging age. Body mass and bill and ulna lengths were also measured. Not surprisingly, provisioning and growth were higher in the year with apparently higher food availability; however, developmental variables did not show the same pattern. This work shows a clear relationship between provisioning and growth and that growth variability occurs in this species. Understanding th...

Breeding seabirds in the British Virgin Islands

Caribbean seabirds are subject to numerous threats, and population levels are thought to be at a fraction of historical levels. Despite being a well-known taxonomic group there is still a paucity of data for most seabird species on many of the Caribbean islands. We carried out detailed surveys of the seabird breeding populations in the British Virgin Islands (BVI) during the breeding seasons of 2004 and 2005. We surveyed 42 different islands and cays over the 2 yr with 60 and 63% of these having at least one breeding seabird species in 2004 and 2005, respectively. A total of 15 spe- cies of breeding seabird was recorded, one of which, the gull-billed tern Sterna nilotica, was pre- viously thought to have been extirpated. Two species, roseate tern Sterna dougallii and magnificent frigatebird Fregata magnificens, had globally significant colonies in the BVI and a further 8 species had a regionally significant population in the BVI. We discuss our findings within a global and regional conservation context and provide recommendations for ensuring the continued existence of BVI seabird populations.

High levels of LH and testosterone in a tropical seabird with an elaborate courtship display

For birds breeding in temperate areas, territoriality and courtship co-occur during spring and are mirrored by elevated plasma levels of luteinizing hormone (LH) and testosterone. By contrast, several tropical species show no major changes in LH and testosterone throughout the year and plasma levels are often low. This study describes changes in body condition, LH and testosterone levels throughout breeding in a tropical seabird, the magnificent frigatebird ( Fregata magnificens). Although bi-parental care is the rule in frigatebirds, these seabirds are unique among seabirds in having a lek-like mating system where males perform an elaborate courtship display during which an extravagant sexual ornament (gular pouch) is inflated. Body condition peaked during the displaying stage in males and declined gradually in both sexes, being the lowest during chick-rearing. LH and testosterone titers were the highest in displaying males with a fully inflated gular pouch (means: 23.6 ng/ml for LH and 6.2 ng/ml for testosterone) and remained low (means: 3.8 ng/ml for LH and 0.3 ng/ml for testosterone) during incubation and chick-rearing in both sexes. Body condition was positively related to testosterone levels in displaying males. In male frigatebirds, high levels of testosterone are not associated with aggression but are probably required to display the inflated gular pouch and to perform an elaborate courtship display. Because males invest in incubation and chick-rearing, testosterone has to return to low levels, to permit parental care. This hormonal pattern differs greatly with that of the few tropical seabirds studied so far and is probably related to the unique reproductive strategy of frigatebirds.

Strandings and feeding records of Bryde's whales (Balaenoptera edeni) in south-eastern Brazil

Information on Balaenoptera edeni strandings along the Brazilian south-east coast and feeding associations with other marine vertebrates are reported. A total of 19 strandings were observed from 1972 to 2003 along ≈1200 km of coast. Strandings were evenly distributed among seasons with no distinguishable peaks. Besides the stranding data, opportunistic observations on Bryde's whales engaged in feeding activities were reported from nine cruises along São Paulo and Rio de Janeiro State coasts (22–24°S). Bryde's whales were observed preying on Brazilian sardines (Sardinella brasiliensis) in at least three events, and possibly two others. Associations with other marine vertebrates were observed, and included dolphin fish (Coryphaena hippurus), little tunny (Euthynnus alletteratus), unidentified sharks, terns (Sterna hirundinacea, Sterna spp.), brown boobies (Sula leucogaster), frigate birds (Fregata magnificens), parasitic jaeger (Stercorarius cf. parasiticus), albatrosses (Thalassarche spp.), and bottlenose dolphins (Tursiops truncatus). Stranding data and on-board observations support the hypothesis that Bryde's whales are common in coastal waters of south-eastern Brazil.

Sexual conflict and parental care in magnificent frigatebirds: full compensation by deserted females

Parental care is a cooperative venture between a male and a female in many socially monogamous birds. Care is costly, and thus, sexual conflict arises between the parents about how much effort they should invest into rearing their young. The sexual conflict over care is most apparent when one parent abandons the brood before the offspring are independent. The deserted parent has three options: (1) desert the brood because a single parent is unable to raise the young on its own; (2) continue care provision at the same level as during biparental care, and thus do not compensate for the absence of mate; or (3) increase care and compensate partially or totally. We investigated these options in the magnificent frigatebird, Fregata magnificens, a species in which the male deserts his mate and brood before the chick is independent. During biparental care, females fed the chick more often than the males. After their mate deserted, the females nearly doubled their feeding rate and thus, fully compensated for the lost care. Consistent with these observations, growth rates of chicks provided with biparental and female-only care did not differ. These results support recent theoretical models of parental care, and suggest that females may withhold care during biparental care to manoeuvre their mates into prolonged care provision. A female only provides at her full capacity once her mate has deserted.

Bimodal Signaling of a Sexually Selected Trait: Gular Pouch Drumming in the Magnificent Frigatebird

AbstractFemale Magnificent Frigatebirds (Fregata magnificens) search for mates while flying and by visiting males at their display sites. Males respond with an intense courtship display that includes making a characteristic drumming sound and presenting the inflated gular pouch, a likely sexually selected trait. Viewing angle, male posturing, and proximity might, however, limit females' ability to appraise pouch size exactly. We investigated whether drumming provides the same information about pouch size and indeed found fundamental frequencies to be negatively correlated with estimated pouch sizes. Probably, the gular pouch functions as a resonance chamber. Females' assessment of gular pouch size could therefore be enhanced by the combination of visual and auditory signals.La Señalización Bimodal de un Atributo Seleccionado Sexualmente: El Sonido de la Bolsa Gular en Fregata magnificensResumen. La búsqueda de pareja en las hembras de Fregata magnificens incluye la inspección durante el vuelo y visitas a los machos en sus sitios de despliegue. Los machos responden con despliegues de cortejo intensos que incluyen un sonido característico de tamborileo y la presentación de la bolsa gular inflable, un atributo probablemente seleccionado sexualmente. El ángulo de visión, la postura del macho y la proximidad podría obscurecer la evaluación visual del tamaño de la bolsa por las hembras. Investigamos si el tamborileo provee la misma información sobre el tamaño de la bolsa y encontramos que las frecuencias fundamentales del tamborileo estuvieron negativamente correlacionadas con los tamaños estimados de las bolsas gulares. Probablemente la bolsa gular funciona como una cámara de resonancia. Las hembras podrían hacer una mejor evaluación del tamaño de la bolsa gracias a la combinación entre las señales visuales y auditivas.

BIMODAL SIGNALING OF A SEXUALLY SELECTED TRAIT: GULAR POUCH DRUMMING IN THE MAGNIFICENT FRIGATEBIRD

Abstract Female Magnificent Frigatebirds (Fregata magnificens) search for mates while flying and by visiting males at their display sites. Males respond with an intense courtship display that includes making a characteristic drumming sound and presenting the inflated gular pouch, a likely sexually selected trait. Viewing angle, male posturing, and proximity might, however, limit females' ability to appraise pouch size exactly. We investigated whether drumming provides the same information about pouch size and indeed found fundamental frequencies to be negatively correlated with estimated pouch sizes. Probably, the gular pouch functions as a resonance chamber. Females' assessment of gular pouch size could therefore be enhanced by the combination of visual and auditory signals. La Senalizacion Bimodal de un Atributo Seleccionado Sexualmente: El Sonido de la Bolsa Gular en Fregata magnificens Resumen. La busqueda de pareja en las hembras de Fregata magnificens incluye la inspeccion durante el vuelo y visitas...

British Ornithologists’ Union Records Committee: 30th Report (October 2003)

British Ornithologists’ Union Records Committee: 30th Report (October 2003)

Reprodução das aves marinhas nas ilhas costeiras de Santa Catarina, Brasil

Studies involving the reproduction of seabirds in the Santa Catarina coast are scarce. From 1996 to 2002 a sampling program was implanted with the objectives of identifying the ranches, the species and to study some aspects of their reproductive cycle. Five species: Sula leucogaster Boddaert, 1783; Fregata magnificens Matheus, 1914; Larus dominicanus Lichtenstein, 1823; Sterna hirundinacea Lesson, 1831; S. eurygnatha Sauders, 1876, breed in the islands of Santa Catarina, with the largest intensity in the period of May to December. The size of the colonies varied in function of the species and of the reproduction area.

THE CHANGING STATUS OF MARINE BIRDS BREEDING AT SAN BENEDICTO ISLAND, MEXICO

We reviewed the status of the breeding marine birds on San Benedicto Island, Mexico, based on >100 years of published observations and seven of our own surveys conducted between 1978 and 2000. We found that there have been marked changes in the island avifauna with two main trends evident. First, a volcanic eruption destroyed much of the island in 1952. The Wedge-tailed Shearwater (Puffinus pacificus; estimated breeding population 1,000 pairs), Townsend's Shearwater (Puffinus auricularis; probable breeder, small numbers), and Red-footed Booby (Sula sula; 60 pairs) historically had much larger populations, but they apparently never fully recovered from the eruption. The Masked Booby (Sula dactylatra; 2,185 pairs), however, has become much more abundant perhaps due to changes in the vegetation. The second trend is that within the last three decades at least two, and possibly four, species from the central Pacific have colonized the island. The Laysan Albatross (Phoebastria immutabilis; 12 pairs) started breeding in the late 1980s; Black-footed Albatross (Phoebastria nigripes; 1 pair) in 2000. Red-tailed Tropicbirds (Phaethon rubricauda; probable breeder, 10 pairs) may have started breeding in the 1980s, and at least some of the breeding Brown Boobies (Sula leucogaster; 300 pairs) are from central Pacific populations. The reason(s) for this influx of central Pacific species is unknown, but likely involves changes in the marine environment. Other breeding species include the Red-billed Tropicbird (Phaethon aethereus; 200 pairs), Nazca Booby (Sula granti; 50 pairs), Great Frigatebird (Fregata minor; 165 pairs), and Magnificent Frigatebird (Fregata magnificens; 5 pairs).

A condition dependent link between testosterone and disease resistance in the house finch.

Testosterone has recently been proposed as a link between male quality and health and the expression of sexual traits. We investigated the relationship between testosterone and measures of the individual condition and health of males in a natural population of house finches (Carpodacus mexicanus). We also conducted a captive experiment in order to test for the effects of testosterone on resistance to coccidia, which is a common parasite of house finches. Free-living males in better condition had higher testosterone levels and lower corticosterone levels than free-living males in poor condition. In our captive experiment, increased testosterone accelerated the rate of coccidial infection as compared with sham-implanted or gonadectomized males. Although the differences were not significant, free-living males infected with coccidia had lower levels of testosterone and higher levels of corticosterone than males that were not infected. Thus, experimentally elevating testosterone levels in captive males resulted in a higher percentage of infected males, while free-living males with coccidial infection had low testosterone levels. This apparent discrepancy between captive and free-living males in the association of testosterone and disease may be explained by the condition dependence of testosterone. These results suggest that the testosterone-dependent sexual traits reliably indicate male overall condition and health and, thus, females could benefit from assessing potential mates based on these traits.

Descartes da pesca do camarão sete-barbas como fonte de alimento para aves marinhas

From July 1996 to June 1997, in Armacao do Itapocoroy, Penha, Santa Catarina State, Brazil, monthly census were done in three areas of traditional fishery and Itacolomis islands. A total of 10021 seabirds were registered, belonging to eight species, five genus and four families. The average number of seabirds per dragging varied between 80,2 and 113,6. Sterna spp, appeared at first in 43,3% of the released by-catch, followed by Larus dominicanus Lichtenstein, 1823, Fregata magnificens Matheus, 1914, Phalacrocorax brasilianus (Humboldt, 1805) and Sula leucogaster Boddaert, 1783. The average size of the fish consumed by the seabirds oscillated from 8,3 cm (Sterna spp.) to 18,5 cm (F. magnificens), with an average time from 6,12 to 7,55 minutes per by-catch released. In general, seabirds use 84,0% of the by-catch fish as a feeding source.

Bird Behavior During a Total Solar Eclipse

I report avian behavioral responses to a total solar eclipse on the north coast of Venezuela during the afternoon of 26 February 1998. Magnificent Frigate-birds (Fregata magnificens), Brown Pelicans (Pelecanus occidentalis), and Royal Terns (Sterna maxima), which had been foraging over the water before the eclipse, left the bay 39 (terns) or 13 (frigate-birds and pelicans) min before the eclipse became total. The frigate-birds flew inland and the pelicans went to roosts on cliffs bordering the bay. Residents of the local village, who knew the birds' behavior well, remarked that the frigate-birds and pelicans were behaving as they normally did at sunset. Laughing Gulls (Larus atricilla) ceased foraging and flew rapidly back and forth over the water in a tight flock during the 3 min 40 s of totality. Twelve minutes after the solar disc emerged, the frigate-birds and pelicans began to return to the bay, and they and the gulls resumed foraging. The terns still had not reappeared more than 1 hr after totality. Solar eclipses, although of brief duration, apparently reduce light levels sufficiently to temporarily interrupt normal avian diurnal behavior.

The Diet of the Magnificent Frigatebird During Chick Rearing

Abstract We describe the diet of the Magnificent Frigatebird Fregata magnificens at Isla Isabel off the Pacific coast of Mexico based on 158 regurgitates (555 prey items) from males, females, chicks, and juveniles. The diet included 50 species of fishes (21 identified to genus only), 1 species of squid, and 2 species of crustaceans. Diplectum pacificum and Anchoa lucida were the most frequent species of fish in the frigatebird's diet. No differences in prey composition or prey size were found between males and females, but females disgorged 62% more food. This difference mirrors the bigger size (15% larger than males) and larger contribution of females to chick feeding. Flying juveniles consumed prey in different proportions than the adults and disgorged marginally more food. Juveniles may obtain food in different patches than adults and complement this source with maternal feedings, or they may be more likely to regurgitate. Diet composition of males, females, and flying juveniles changed during the 4-month period of this study, but the mass of regurgitates did not change as the breeding season progressed, suggesting that availability of prey species changes over time. Most of the diet of this population probably comes from opportunistic feeding on fisheries, because the variety of fishes disgorged is remarkably similar to the published list of fishes discarded by prawn-fishing boats in the area. If our assumption is true, kleptoparasitism and direct fishing are only marginally represented in the diet of this population.

The Diet of the Magnificent Frigatebird during Chick Rearing

The Diet of the Magnificent Frigatebird during Chick Rearing

THE DIET OF THE MAGNIFICENT FRIGATEBIRD DURING CHICK REARING

Abstract We describe the diet of the Magnificent Frigatebird Fregata magnificens at Isla Isabel off the Pacific coast of Mexico based on 158 regurgitates (555 prey items) from males, females, chicks, and juveniles. The diet included 50 species of fishes (21 identified to genus only), 1 species of squid, and 2 species of crustaceans. Diplectum pacificum and Anchoa lucida were the most frequent species of fish in the frigatebird's diet. No differences in prey composition or prey size were found between males and females, but females disgorged 62% more food. This difference mirrors the bigger size (15% larger than males) and larger contribution of females to chick feeding. Flying juveniles consumed prey in different proportions than the adults and disgorged marginally more food. Juveniles may obtain food in different patches than adults and complement this source with maternal feedings, or they may be more likely to regurgitate. Diet composition of males, females, and flying juveniles changed during the 4-mo...

Offspring Desertion in the Magnificent Frigatebird: Are Males Facing a Trade-Off between Current and Future Reproduction?

Timing of offspring desertion is expected to be the outcome of the trade-off between current and future reproductive benefits for deserters. I investigated this idea by analysing the timing of male desertion in the Magnificent Frigatebird Fregata magnificens. I recorded parental attendance, male desertion and chick survival from an average of 39 days old (+ 2.7 S.E. days) to fledging (181.2 + 3.4 days old, n = 24) at 42 nests, and checked the presence and breeding state of marked males (red gular pouch) at the colony the following breeding season. All male parents deserted their nest when their only chick was between 19 and 160 days old (77.1 + 5.0 days). Male desertion was influenced by settling and deserting dates: settling date correlated negatively with the age of the chick at the time of male desertion. Late-settling males deserted later during the year than males settling early, the condition of their chick (at the time of male desertion) was lower and their chick fledged late during the year. In spite of the obligate and apparently date-constrained desertion, chicks deserted when very young died more frequently than those deserted when older, and successful males deserting late during the year (after the average desertion date) were marginally less likely to be seen in reproductive state the following breeding season than those deserting early. The inter-individual variation is consistent with the idea that male frigatebirds may face a trade-off between current and future reproductive expectations: early-settled individuals began breeding before 16 October, deserted before the average deserting date, stayed with the chick for 92 days, their chicks survived well (84%) and 75% of these males were seen in reproductive state the following breeding season. Late-settled individuals began to breed around 19 December, deserted when their chick was 55 days old, chicks survived well (64%) but still only 50% of males were seen in breeding state the following breeding season. Some early-settled individuals who remained longer attending the chick (120 days) and whose chick survived, deserted after the average desertion date (20 April), but only 50% of them were seen in breeding state the following season.

On the evolutionary pathway of parental care in mouth–brooding cichlid fishes

Evolutionary theory predicts that differences in parental care patterns among species arose from interspecific differences in the costs and benefits of care for each sex. In Galilee St Peter9s fish, Sarotherodon galilaeus (Cichlidae), male care, female care and biparental care all occur in the same population. We exploit this unusual variability to isolate conditions favouring biparental versus uniparental mouth–brooding by males or females. We first review a game–theoretic model of parental care evolution, predictions of which we test experimentally in this paper. Manipulations of the operational sex ratio show that males and females desert their offspring more frequently when the costs of care are high (in terms of lost mating opportunities). Breeding trials with males of different sizes show that small fathers desert more frequently than large fathers. We attribute this to the associated difference in the fitness benefit of biparental care relative to female–only care. Our experimental results confirm that in St Peter9s fish the probability of caring is determined facultatively according to current conditions at each spawn. The experiments and model together suggest that interspecific variation in remating opportunities and clutch size may be responsible for differences in care patterns within the sub–family Tilapiini. Our results support the hypothesis that biparental mouth–brooding was the ancestral state of both male and female uniparental mouth–brooding in cichlid fishes.

Multispecies Seabird Feeding Flocks in the Galápagos Islands

I examined the species composition, frequency, distance offshore, and duration of multispecies seabird feeding flocks in the Galapagos Islands, Ecuador. Flocks were comprised of Galapagos Penguins (Spheniscus mendiculus), Flightless Cormorants (Campsohaelius [Nannopterum] harrisi), Brown Pelicans (Pelecanus occidentalis), Brown Noddies (Anous stolidus), Blue-footed (Sula nebouxii) and Masked Boobies (Sula dactylatra), Magnificent Frigatebirds (Fregata magnificens), and Audubon Shearwaters (Puffinus lherminieri). Pursuit-divers, such as Galapagos Penguins and Flightless Cormorants, increase the longevity of flocks. Species such as boobies may tend to dissipate flocks. This study provides field evidence that the presence of pursuit-diving seabirds has a positive effect on the duration of feeding flocks and that the mechanisms that keep prey close to the surface near shore may differ from those in the open ocean.