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|Title: ||Foraging strategies of Southern Royal Albatrosses, Diomedea epomophora, Campbell Island during incubation|
|Author: ||Troup, Christina|
|Degree: ||Master of Applied Science|
|Institution: ||Lincoln University|
|Item Type: ||Thesis|
|Abstract: ||Among the species of Diomedea albatrosses, diverse foraging strategies during
breeding have been described, indicating species differences in foraging ecology and
behaviour. Foraging strategies of Southern Royal Albatrosses, Diomedea epomophora
(SRA) breeding on Campbell Island were studied in January – early February 1999
during the latter half of incubation. Movements and activity of ten birds were
monitored using satellite transmitters and wet-dry activity recorders. Three birds from
a pilot tracking study in February 1997 were also included in some analyses. Foraging
strategies, zones used, factors influencing the duration of foraging trips, and the
influence of wind conditions were investigated.
Foraging activity took place at sites with bathymetric characteristics associated with
high productivity: outer shelf and shelf-break zones, with a concentration of activity
on a shelf contour south of the Snares Islands. This is in contrast to Wandering (D.
exulans) and Gibson’s (D. gibsoni) albatrosses, typically deep oceanic foragers, but is
similar to Northern Royal Albatross (D. sanfordi). The maximum distance of foraging
trips from the colony was 1250 kilometres (mean 584 +351(SD)). This was closer
than for incubating Wandering and Gibson’s Albatrosses but more distant than for
Northern Royal Albatross from the Otago Peninsula.
The mean duration of 77 foraging trips from 52 nests was 10.11 days for females and
8.76 for males (ns). Foraging trips became shorter as incubation progressed. Foraging
trips were shorter, but not significantly so, when the median wind speed throughout
the foraging trip was higher. No significant relationship was found between bird mass and duration of foraging trips. The mean cumulative distance flown by the ten birds
tracked in 1999 was 4262 km + 1318 (SD).
Eight of the ten SRA employed a ‘commute, forage, commute’ foraging strategy, and
the other two alternated short bouts of commuting and foraging. Commuting phases
were characterised by rapid directional flight with a straight-line distance (range) of
180 km to 800 km between positions 24 hours apart. Foraging phases were
characterised by a range of less than 180 km per 24 hour interval and frequent tight
turns. Displacement rate between successive uplinks was significantly higher during
commuting phases (28.6 kph + 1.93 SE) than foraging phases (15.1 kph + 1.4 SE).
Wind strength and direction influenced the timing of the return commute to the
colony. SRA covered greater distances at more favourable wind angles relative to
flight track (broad reach and close reach) than in head, tail or direct side winds. Birds
of low mass (< 8kg) made fewer landings in winds above 40 kph than in lighter
winds, whereas heavier birds had a similar level of landing activity across all wind
speed bands. One bird was delayed for several days by light winds, and another flew
off course during strong winds. Two birds exploited the same window of wind
conditions to return to the colony, each flying a similar course in both timing and
These results define the foraging strategies of SRA during incubation, and
demonstrate the influence of wind conditions and other factors on the overall duration
of foraging trips and on the timing of commuting and foraging phases.|
|Supervisor: ||Paterson, Adrian|
|Persistent URL (URI): ||http://hdl.handle.net/10182/1273|
|Appears in Collections:||Masters Theses|
Department of Ecology
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