The Wilson Journal of Ornithology 123(1): 121-125, 2011 
GEOLOCATION TRACKING OF THE ANNUAL MIGRATION OF 
ADULT AUSTRALASIAN GANNETS (MORUS SERRATOR) BREEDING 
IN NEW ZEALAND 
STEFANIE M. H. ISMAR, 1 ' 5 RICHARD A. PHILLIPS, 2 
MATT J. RAYNER, 1 ’ 3 AND MARK E. HAUBER 14 
ABSTRACT.—The long breeding period and high reproductive investment of seabirds make use of resource-rich foraging 
areas pivotal both during and between breeding seasons. We tracked adult Australasian Gannets {Morus senator) from their 
New Zealand breeding colony at Cape Kidnappers to Australia during the non-breeding period to assess wintering behavior 
and migratory routes for this species. Data from three recovered geolocation sensor (GLS) tags showed that both a mai e an a 
female M. senator , and a hybrid M. capensis X M. senator migrated across the Tasman Sea to winter in Australian and 
Tasmanian coastal waters. Tracked birds covered distances of up to 13,000 km on their migration. These movements were 
consistent with historical records of band recoveries. Received 28 April 2010. Accepted 29 September 2010. 
Adults of many seabird species, in systems with 
obligate biparental care, invest heavily during 
breeding (Brooke 2004). Life history theory 
predicts that parents must balance the costs of 
current reproduction with future attempts, and the 
availability of good foraging conditions is criti¬ 
cally important (Quillfeldt et al. 2005, Rayner et 
al. 2008). This is especially true as the inter¬ 
breeding period may be a time of peak mortality 
in the breeding cycle (Barbraud and Weimers- 
kirch 2003). Increasing attention has focused on 
assessing migration strategies and foraging areas 
°f seabirds during the non-breeding period 
(Phillips et al. 2006, Bost et al. 2009, Catry et 
al- 2009), since emergence of economical archival 
low-impact geolocator sensor (GLS) loggers 
fRayner 2007) with long battery lives (Afanasyev 
2 °04, Shaffer et al. 2006). 
The Australasian Gannet (Morus senator) is a 
predominantly monogamous seabird with an obli- 
Sately biparental system, endemic to Australia and 
^ ew Zealand (Nelson 1978, Ismar et al. 2010a). 
Migration strategies, particularly of the New 
Zealand population, are poorly known. Large 
numbers of recoveries in Australia from banded 
School of Biological Sciences, University of Auckland, 
vate Bag 92019, Auckland, New Zealand. 
British Antarctic Survey, Natural Environment Re- 
!? rc h Council, High Cross, Madingley Road, Cambridge 
CB3 0ET, UK. 
National Institute of Water and Atmospheric Research 
ld - (NIWA), P. O. Box 99940, Newmarket 1149, New 
Zealand. 
Department of Psychology, Hunter College of the City 
diversity of New York, 695 Park Avenue, New York, NY 
1 q 065, USA. 
Corresponding author; e-mail: sism 007 @aucklanduni.ac.nz 
New Zealand breeding gannets include only one 
record of a bird known to be of sufficient age to 
breed (5 years; Hitchcock and Carrick 1958). This 
suggests a westward migration during the non¬ 
breeding season from New Zealand. Single band 
recoveries from dead adult Australasian Gannets 
have been reported between 2007 and 2010 from 
several New Zealand locations: Opotiki, Bay of 
Plenty; Wellington, Shelley Bay; Fiordland, South 
Coast; as well as two band recoveries from the 
Cape Kidnappers breeding site, and two observa¬ 
tions of marked live birds from a gannetry at 
Farewell Spit (Mala Nesaratnam, Department of 
Conservation, Wellington, NZ, pers. comm.). One 
recovery has been reported from Wollongong in 
New South Wales, Australia; the gannet had last 
been recorded in New Zealand as a fledgling. 
Migration to warmer, more productive waters 
has been recorded for gannet fledglings from New 
Zealand (Ismar et al. 2010b) and for adults of the 
congeneric Northern Gannet (M. bassanus) and 
Cape Gannet (M. capensis) that breed at temper¬ 
ate latitudes (Nelson 1978, Kubetzki et al. 2009). 
Thus, we hypothesized that breeding adult 
Australasian Gannets from New Zealand migrate 
to similar wintering areas as conspecific fledg¬ 
lings. Our objectives were to: (1) test the 
hypothesis that adult New Zealand breeding 
Australasian Gannets migrate to Australia be¬ 
tween breeding seasons and to provide the first 
detailed information on migration routes and 
timing, and (2) test the use of GLS devices to 
monitor wintering behavior of the species. 
METHODS 
Five breeding adult Australasian Gannets 
(which raised chicks in the 2007-2008 breed- 
121 
