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Biennially-breeding albatrosses skip breeding years which violates assumptions of the usually-used methods of mark-recapture modelling, leading to incorrect annual survival figures.

In a paper published in 2009 in the ornithological journal Auk, the problem is addressed by Sarah Converse of the Wildlife Research Center in Patuxent, Maryland, USA and three colleagues.  Data collected at a Grey-headed Albatross Thalassarche chrysostoma study colony at South Africa's Marion Island over the period 1996 to 2006 is used to test new types of multistate models. 

The study found that annual survival probability for Marion's Grey-heads was 0.951 ± 0.0006 and recommends use of multistate modelling for species that skip breeding ("exhibit temporary emigration").

 Reference:

 Converse, S.J., Kendall, W.L., Doherty Jr, P.F. & Ryan, P.G. 2009.  Multistate models for estimation of survival and reproduction in the Grey-headed Albatross (Thalassarche chrysostoma).  The Auk 126: 77-88.  http://caliber.ucpress.net/doi/abs/10.1525/auk.2009.07189

 John Cooper, ACAP Information Officer, 14 January 2009