New Zealand Journal of Zoology abstracts

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Variation in the size of Buller’s albatross (Thalassarche bulleri) eggs

P. M. Sagar
M. J. Unwin

National Institute of Water and Atmospheric Research Limited
P.O. Box 8602
Christchurch, New Zealand
p.sagar@niwa.co.nz

J. C. Stahl

Museum of New Zealand, Te Papa Tongarewa
P.O. Box 467
Wellington, New Zealand

John Warham

School of Biological Sciences
University of Canterbury
Private Bag
Christchurch, New Zealand

Abstract  The effect of minimum maternal experience, individual and year on egg size variation, breeding success and sex of the surviving chick were investigated in Buller’s albatrosses (Thalassarche bulleri) breeding at the Snares Islands. Minimum maternal experience and individual effects were studied over the 9 years 1996–2004, while a second set of data allowed inter-annual variation in egg size to be investigated over 4 additional years (1961, 1969, 1970, and 1993). Egg length, breadth, volume and eccentricity did not vary between years, but all four variables varied significantly between individuals. The size of eggs laid by one individual varied less than the variation across the population as a whole. Egg volume increased with minimum maternal breeding experience, mainly because eggs became broader but not longer, up to the fourth breeding attempt. There was a weak positive relationship between egg size and breeding success, but this correlation was confounded by maternal breeding experience. Breeding success decreased markedly among birds with >20 years breeding experience. There was no relationship between egg size and the sex of the resulting chick. The significant effects of minimum breeding experience and individual on egg size appear to be typical of seabirds. However, unlike other studies of egg size in albatrosses, we did not detect any between-year effects, perhaps because the experience of the breeding population changed little during the study period.

Keywords  Procellariiformes; minimum breeding experience; breeding success; sex of chick; individual variation; inter-annual variation

Z04044; Received 22 December 2004; accepted 31 March 2005; Online publication date 4 August 2005
New Zealand Journal of Zoology, 2005, Vol. 32: 171–180
0301–4223/05/3203–0171 © The Royal Society of New Zealand 2005

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