Tracking Ocean Wanders (PDF, 5 MB) - BirdLife International

Tracking ocean wanderers: the global distribution of albatrosses and petrels – Results
undertaken. It is worth noting, for example, that the most
recent GPS data indicates that during incubation, females
also travel through the Drake Passage as far as 78°W (c.f.
Figure 3.10). This emphasises that conclusions concerning
sexual segregation based on small samples sizes must be
viewed with considerable caution.
During brood-guard, differences are more clear-cut.
Occasionally, both males and females (cf. Prince et al. 1998)
have been recorded travelling to Falkland Islands
(Malvinas)/Burdwood Bank waters (Croxall et al. 1999).
Otherwise, males feed predominantly on the local South
Georgia shelf and shelf-slope. By comparison, females
utilise these habitats to a lesser extent, instead feeding
routinely in oceanic waters from 51°–56°S. This is
corroborated by dietary analyses: during brooding, males
consume large amounts of Patagonian Toothfish
Dissostichus eleginoides presumably obtained as discards
from long-line fishing vessels, whereas females feed on a
much greater diversity of fish and squid
Richard Phillips and John Croxall
Buller’s Albatross Thalassarche bulleri – Snares
Among breeders from the Snares Islands, foraging distributions
of males and females tended to be largely segregated during
most of the breeding cycle as a result of differences in foraging
time allocation between long and short trips, in foraging
destinations and range during long trips, and in habitat
utilisation with respect to water depth (Stahl and Sagar 2000b).
During the pre-egg stage (Figure 3.11A, B), foraging
trips of both males and females were either to the Tasman
Sea (long trips) or within 180 km of the Snares (short trips).
Males then spend much more time at the nest than females,
and allocated 69% of foraging time to short trips, with sites
of most intensive foraging located over the shelf and slope
south and east of the Snares. Females overlapped with
males in that area, but in contrast to males, allocated 99%
of foraging time to long trips, with sites of most intensive
utilisation located over oceanic waters in the southern and
central part of the Tasman Sea.
During the incubation period (Figure 3.11C, D), long
trips accounted for over 98% of foraging time in both sexes,
and sexual segregation at that time stemmed primarily from
Figure 3.11. Utilisation
distribution maps for
breeding male and female
Buller’s Albatrosses tracked
from the Snares Islands.
A. pre-egg females
(n=1,497 hrs, 2 indivs);
B. pre-egg males (n=1,128 hrs,
2 indivs); C. incubating
females (n=4,622 hrs, 15
indivs); D. incubating males
(n=3,750 hrs, 12 indivs);
E. guard stage females
(n=1,803 hrs, 7 indivs);
F. guard stage males
(n=1,229 hrs, 6 indivs);
G. post guard females
(n=2,902 hrs, 6 indivs);
H. post guard males
(n=5,684 hrs, 7 indivs).
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