J. Zool., Lond. (2001) 254, 391±404 # 2001 The Zoological Society of London Printed in the United Kingdom Foraging destinations of three low-latitude albatross (Phoebastria) species Patricia FernaÂndez1, David J. Anderson1*, Paul R. Sievert2 and Kathryn P. Huyvaert1 1 Department of Biology, Wake Forest University, Winston-Salem, NC 27109-7325, U.S.A. 2 Department of Natural Resources Conservation, University of Massachusetts, Amherst, MA 01003-4210, U.S.A. (Accepted 6 September 2000) Abstract Satellite telemetry was used to identify the foraging distributions of three congeneric species of albatrosses that nest in the tropics/subtropics. Breeding waved albatrosses Phoebastria irrorata from the GalaÂpagos Islands travelled to the productive upwelling near the Peruvian coast and nearby areas during the rearing period in 1996. Black-footed albatrosses P. nigripes and Laysan albatrosses P. immutabilis nesting in the Hawaiian Islands and tracked during the 1997±98 and 1998±99 breeding seasons also performed long foraging trips, to continental shelf areas of North America. In both years, breeding black-footed albatrosses made long trips to the west coast of North America (British Columbia to California). In 1997±98, breeding Laysan albatrosses travelled primarily to the north of the Hawaiian Islands and reached the waters of the Aleutian Islands and the Gulf of Alaska. In 1998±99, Laysan albatrosses had a complete breeding failure, and no long trips by breeders were tracked as a result. These three species mixed short and long trips during the chick-rearing period, but not the brooding period nor incubation period. Waved albatrosses made only long trips during the incubation period. Analysis of movement patterns showed that the core feeding areas during long trips were located over the continental shelves of North and South America. The data on foraging biology of these species have implications for assessing bycatch risk in commercial ®sheries. Key words: albatross, Phoebastria, foraging, bycatch INTRODUCTION particularly distribution of albatrosses at sea in relation to bycatch risk in ®sheries operations (Croxall & Prince, Recent advances in satellite telemetry have opened a 1996; Brothers et al., 1998; Prince, Croxall et al., 1998). window on the previously obscure life of albatrosses at Most of the albatross species that have been tracked sea. They have shown, for example, that breeding by satellite nest on high-latitude islands in the Southern wandering albatrosses Diomedea exulans can cover Ocean. Little is known about the foraging characteris- between 3600 and 15 000 km between visits to their tics of the albatross species nesting in the tropics and chick, reaching speeds of up to 80 km/h over distances subtropics; these species comprise the genus Phoebas- of up to 900 km/day (Jouventin & Weimerskirch, 1990). tria, the `North Paci®c' albatross clade (see Robertson This technique has been applied to various studies of & Nunn, 1998). Of these species, the black-footed seabird foraging ecology, documenting resource parti- albatross P. nigripes and Laysan albatross P. immut- tioning between sympatric species (Waugh et al., 1999) abilis nest primarily in the Hawaiian Islands and are and between sexes (Prince, Wood et al., 1992), changes sympatric on most of their breeding islands. The short- in foraging behaviour through the breeding season tailed albatross P. albatrus, currently limited to a single (Weimerskirch, Salamolard et al., 1993; Arnould et al., breeding population on Torishima Island, Japan, and 1996; Weimerskirch, Wilson & Lys, 1997), biotic and the waved albatross P. irrorata of the GalaÂpagos Islands abiotic properties of the feeding site (Rodhouse & are the remaining members of the genus. The objective Prince, 1993; Weimerskirch, Doncaster et al., 1994; of this study was to use satellite telemetry to identify the Cherel & Weimerskirch, 1995; Weimerskirch, Wilson, foraging areas of three of these species: black-footed, Guinet et al., 1995; Hull, Hindell & Michael, 1997), and Laysan, and waved albatrosses. Ship-based sightings show that Laysan albatrosses *All correspondence to: D. J. Anderson. are observed and recovered in greatest numbers in the E-mail: [email protected] north-western part of the Paci®c during their breeding 392 P. FernA ndez ET AL. season, whereas the number of black-footed albatrosses Laysan albatrosses, also during brooding. One set of 16 increases to the south-east and east, to the North birds were tracked through their entire breeding effort, American coast, during the same period (Shuntov, but transmitters recovered from 3 birds whose chicks 1974). The distribution data used to reach these conclu- died was mounted on 3 other individuals (2 black- sions depended in part on the distribution of boats footed and 1 Laysan albatross). Therefore, in 1998±99, bearing observers, with the resulting potential for sam- a total of 10 black-footed albatrosses and 9 Laysan pling bias. Satellite tracking overcomes this bias by albatrosses were tracked. Overall, a total of 48 alba- having no geographical limits on observers. Satellite trosses (25 black-footed and 23 Laysan) were tracked tracking also allows the study of movements of speci®c for 4±182 days (x = 57 days). No bird was tracked in individuals of known status throughout their entire trip, both seasons. Transmitters in both seasons used 8 h on : which is not possible using non-telemetric methods. For 24 h off duty cycles. example, in a preliminary study satellite tracking was Previous satellite tracking studies of albatrosses have used to study movements of waved albatrosses during concluded that the PTT does not affect the perfor- the incubation period in 1995 (Anderson, Schwandt & mance of the bird measurably during the breeding Douglas, 1998). All tracked birds `commuted' c. 1200 km season (Jouventin & Weimerskirch, 1990; Prince, Wood from the breeding site on Isla EspanÄola, GalaÂpagos to et al., 1992; Wiemerskirch & Robertson, 1994; Arnould the cold upwelling area over the western South Amer- et al., 1996; Anderson et al., 1998). Moreover, innova- ican continental shelf, off the coasts of Peru and tions in the design of the transmitters have reduced Ecuador. While movement between GalaÂpagos and the their size; the mass of our transmitters (32 g) was c.1% continental shelf was direct and rapid, movement within of the bird's own mass, and was unlikely to impose a the upwelling zone was slow with frequent turning. signi®cant energetic cost on tagged birds (Anderson Simple distribution data would indicate that waved et al., 1998). Nevertheless, to identify any effect of albatrosses occupy the entire area between GalaÂpagos transmitters on the birds' reproductive success, we and the continent, while the satellite tracking data monitored nest histories of 20 time-matched nests, revealed the area-speci®c behaviour of the birds. located near the nests of tagged birds, that served as controls. We demonstrated that beak length accurately indicates gender by associating cloacal distension, at MATERIALS AND METHODS the time of egg laying, with beak length. Within Laysan albatross breeding pairs, 20/21 (95.2%) of males had Seven waved albatrosses breeding on Isla EspanÄola, longer beaks than their mates did. Similarly, 33/33 GalaÂpagos (1822'S, 89839'W) were tracked between (100%) of black-footed albatross males had longer 4 June and 13 October 1996, during the brooding beaks than their mates did. Beak length of both (hatching to chick age 18 days) and rearing (chick age members of a pair was used to determine the gender of > 18 days; Harris, 1973; Whittow, 1993a,b) periods as a the birds tracked in this study. In both the GalaÂpagos complement to work in the previous breeding season and Hawaii studies birds were chosen for tracking and during the incubation period, using the methods of for controls using only 2 criteria: they had a nest in the Anderson et al. (1998). PTT100 (Platform Transmitter area designated for the study and they had hatched Terminals; Microwave Telemetry, Columbia, MD) their egg. We are not aware of any other bias in our transmitters were attached to dorsal contour feathers choice of study animals or assignment to tracked or using epoxy glue. The signals from these transmitters control groups. were received by orbiting TIROS-N satellites, passed to Argos System performance on Tern Island was Argos System ground stations (Service Argos, Largo ground-truthed by comparing the reported locations of MD), and forwarded to us by electronic mail. all transmitters during 5 days with a known, stationary The two Hawaiian albatross species breeding on Tern location (by GPS). Anderson et al. (1998) conducted a Island (23852'N, 166817'W), French Frigate Shoals, similar exercise at the GalaÂpagos nesting site. To north-west Hawaiian Islands were also studied. Tape analyse the performance of the transmitters at different attachment, rather than glue, was used to ®x the trans- locations and years, we calculated the mean number of mitters to the mid-dorsal feathers of the mantle signals received per transmitter per day during each year (FernaÂndez, 1999). In January 1998, 12 PTT100 units of the study. These means were pooled and their were mounted on 6 Laysan and 6 black-footed alba- average calculated; the variation in reception frequency trosses during the brooding part (hatching to chick age is expressed with the standard error (se), as is commonly 18 days) of the nesting cycle. The transmitters were used to present the standard deviation of statistics removed from the ®rst set of birds after 10±16 days and (Sokal & Rohlf, 1995). re-mounted on a second set of 12 breeding adults. Five Descriptions of the movement parameters (distance, of these transmitters were recovered for deployment on maximum range, and days spent at sea) during the a third set of breeders, as a result of which, we were able breeding season were based on complete round-trips to track a total of 15 black-footed and 14 Laysan only.