Field metabolic rates (FMR) and activity patterns of black-browed albatrosses Thalassarche melanophrys were measured while at sea and on nest during the incubation stage at Kerguelen Island, southwestern Indian Ocean. Activity-specific metabolic rates of five albatrosses at sea (FMRat-sea) were measured using doubly labeled water (DLW), and by equipping birds with wet-dry activity data loggers that determined when birds were in flight or on the water. The metabolic rates of four birds incubating their eggs (FMRon-nest) were also measured using DLW. The mean+/-SD FMRat-sea of albatrosses was 611+/-96 kJ kg(-1) d(-1) compared to FMRon-nest of 196+/-52 0 kg(-1) d(-1). While at sea, albatrosses spent 52.9+/-8.2% (N = 3) of their time in flight and they landed on the water 41.2+/-13.9 times per day. The FMR of black-browed albatrosses appear to be intermediate to that of three other albatross species. Based on at-sea activity, the power requirement of flight was estimated to be 8.7 W kg(-1) (or 4.0 x predicted BMR), which is high compared to other albatross species, but may be explained by the high activity levels of the birds when at sea. The FMRat-sea of albatrosses, when scaled with body mass, are lower than other seabirds of similar body size, which probably reflects the economical nature of their soaring flight.

1. Theoretical models predict that animals will vary their effort to maximize different currencies such as time and energy when the constraints of reproduction change during breeding, but this has been poorly studied in free-ranging animals. 2. Foraging effort (energy per unit time) was examined by comparing mass changes, foraging costs and activity-specific behaviours of Wandering Albatrosses (Diomedea exulans Linnaeus) during the incubation and chick-brooding stages. In 1998, 38 albatrosses (20 during incubation and 18 during brooding) were injected with doubly labelled water and equipped with satellite transmitters and activity data loggers. 3. During incubation, albatrosses travelled 3.7 times farther and were at sea 3.2 times longer, yet foraging costs were significantly lower than trips made during brooding (incubation 4.52 +/- 0.50 SD W kg(-1) vs brooding 4.98 +/- 0.55 SD W kg(-1)). 4. The rate of daily mass gain decreased significantly with time at sea during incubation whereas the rate of daily mass gain increased significantly with time at sea during brooding. 5. Foraging effort was higher during brooding, suggesting that birds were minimizing time at sea to maximize the rate of food delivery to chicks. In contrast, foraging effort was lower during incubation, suggesting that birds were maximizing time at sea and minimizing the energy costs of foraging. 6. Foraging costs were also different between sexes. However, this was related to body size differences and not to differences in foraging effort as suggested in previous studies.

Although several studies have described age-specific pattern of breeding performance, physiological and endocrine mechanisms underlying the variation in reproductive success in relation to age are poorly understood. We described baseline levels of. (1) corticosterone, which can trigger nest desertion when secreted at high levels, and (2) prolactin, a hormone known to trigger parental behaviour in incubating known-aged (7-39 years old) wandering albatrosses (Diomedea exulans). In this long-lived species, reproductive performance increases with age and breeding experience before it stabilizes in middle-aged individuals and declines in senescent individuals. We found that breeding experience was a much better statistical predictor of hormone levels than age. Baseline corticosterone levels slightly increased with advancing experience and reached maximal levels about the sixth breeding attempt. Similarly, prolactin levels were positively correlated with breeding experience in males. No such relationship was found in females, but first-time breeding females had lower prolactin levels than experienced females. This parallel increases in hormonal levels with advancing experience could result from improvements of skills, development of an endocrine system adapted to energetic constraints of reproduction or may mirror a higher investment in reproduction. Corticosterone levels decreased in senescent birds, but such a decline was not observed for prolactin. Low corticosterone levels in senescent birds could be associated with a lower ability to secrete/sustain elevated corticosterone levels or with a decreased parental expenditure. (c) 2006 Elsevier Inc. All rights reserved.

Electronic tracking tags have revolutionized our understanding of broad-scale movements and habitat use of highly mobile marine animals, but a large gap in our knowledge still remains for a wide range of small species. Here, we report the extraordinary transequatorial postbreeding migrations of a small seabird, the sooty shearwater, obtained with miniature archival tags that log data for estimating. position, dive depth, and ambient temperature. Tracks (262 +/- 23 days) reveal that shearwaters fly across the entire Pacific Ocean in a figure-eight pattern while traveling 64,037 +/- 9,779 km roundtrip, the longest animal migration ever recorded electronically. Each shearwater made a prolonged stopover in one of three discrete regions off Japan, Alaska, or California before returning to New Zealand through a relatively narrow corridor in the central Pacific Ocean. Transit rates as high as 910 +/- 186 km(.)day(-1) were recorded, and shearwaters accessed prey resources in both the Northern and Southern Hemisphere's most productive waters from the surface to 68.2 m depth. Our results indicate that sooty shearwaters integrate oceanic resources throughout the Pacific Basin on a yearly scale. Sooty shearwater populations today are declining, and because they operate on a global scale, they may serve as an important indicator of climate change and ocean health.