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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 1, March 2011 
the Tasman Sea to Australian coastal waters and 
back to the New Zealand gannetry was completed 
in 21 days, covering a minimum distance of 
6,900 km. 
The female Australasian Gannet All (Fig. IB) 
appeared to use Cook Strait (173.72° E, 40.70° S; 
1 Apr 2008) to cross the Tasman Sea towards 
Bass Strait (150.11° E, 39.41° S; 7 Apr 2008). Its 
wintering areas extended from Bass Strait both 
south of Tasmania (146.55° E, 44.95° S) and north 
along the Australian East Coast (150.88° E, 
34.82° S), from where it crossed the Tasman 
Sea again after 119 days, and reached the Cape 
Kidnappers Gannetry via Stewart Island and West 
Cape, and the East Coast of the South and the 
North islands New Zealand (167.87° E, 46.97° S; 
16 Aug 2008). It subsequently left Cape Kidnap¬ 
pers again for 23 days for the regions further north 
along the New Zealand East Coast, off the Bay of 
Plenty and the Bay of Islands. This female 
returned via the East Cape (178.79° E, 36.85° S; 
22 Oct 2008) to its Cape Kidnappers breeding 
areas. 
The hybrid male B60 (Fig. 1C) started its 
migration from the region of the Bay of Plenty 
(179.03 E, 37.40 S) on 8 April 2008, circum¬ 
vented the North Cape (176.35° E, 34.58° S) on 
11 April 2008, and appeared to follow the New 
Zealand west coast southward before starting its 
cross-Tasman flight from West Cape (167.43° E, 
48.54 S) on 15 April 2008. B60 stayed 59 days 
(21 Apr 2008—19 Jun 2008) in and around its 
wintering areas as defined by the highest 80% 
kernel density, which resembled that of All. B60 
spent 9 days in the region of the Lord Howe 
Islands (160.39° E, 34.90° S; 25 Jun 2008) on its 
flight across the Tasman Sea back to New 
Zealand, before it was tracked to waters north of 
North Cape (172.29° E, 33.12° S) on 7 July 2008. 
B60 consequently returned for 11 days to mid 
Tasman Sea waters (164.89° E, 36.25° S), before 
reaching the Cape Kidnappers breeding area again 
via the North Cape (176.42° E, 35.76° S; 25 Aug 
2009) and the Bay of Plenty (179.12° E 33 14° S- 
27 Aug 2008). 
Longitudinal movements of the three birds 
varied (Fig. 2). These birds spent 180, 208, and 
142 days, respectively, away from the colony 
before their final return to the breeding site. 
DISCUSSION 
We provide the first direct evidence that both 
male and female adult Australasian Gannets 
migrate from New Zealand breeding areas to 
winter in Australian waters. A hybrid (Cape X 
Australasian Gannet, Robertson and Stephenson 
2005) also displayed the same general pattern. 
Our study is suggestive of a high level of 
individual variability in routes, timing of arrival 
and departure, and duration and destination, 
suggesting considerable plasticity in migration 
behavior. Our findings indicate the importance of 
the Bay of Plenty and Bay of Islands north of the 
gannetry on the east New Zealand coast, which 
were frequented by all three tracked birds before 
departure on their trans-Tasman flights, or upon 
return to New Zealand prior to breeding. All three 
potential migration routes around New Zealand 
landmasses between Cape Kidnappers and the 
Tasman Sea (i.e.. North Cape, Cook Strait, and 
Stewart Island) were used. One bird (B60) 
appeared to forage extensively in the open waters 
of the Tasman Sea. However, sample sizes were 
small and further studies are required. Our results 
suggest adult migration behavior is more variable 
than that of fledglings, which appear to minimize 
time spent in flight and distance traveled over the 
open ocean (Ismar et al. 2010b). There may be 
less pressure on adults to travel directly because 
of their higher foraging efficiency (Nelson 1978). 
The female Australasian Gannet covered the 
shortest distance during migration, and spent the 
longest time away from the gannetry. This fits 
with a male accnied task of territorial establish¬ 
ment in the early breeding season, as found in the 
congeneric Northern Gannet (Nelson 2002). Thus, 
males should be more constrained in foraging 
ranges than females at this time of year. 
Asynchronous arrival at the breeding site by 
males and females is also suggested for M. 
serrator (Ismar et al. 2010a). Further research is 
needed to gain sufficient sample sizes to fully 
investigate differences in migration between male 
and female Australasian Gannets, and to compare 
migratory pathways and dynamics with birds from 
other New Zealand and Australian breeding 
locations. 
ACKNOWLEDGMENTS 
This research was funded by Education New Zealand 
through an International Doctoral Research Scholarship and 
by the Faculty of Science, University of Auckland (to 
SMHI), the University of Auckland’s Faculty of Science 
Research Committee (to MEH), and the British Antarctic 
Survey Ecosystem Programme (RAP). All research was 
conducted under Animal Ethics and Department of 
Conservation (DoC) research permits. The DoC, Napier 
