The population biology of 555 Laysan Albatrosses on Oahu gets studied by Pacific Rim Conservation

Eric Vanderwerf and Lindsay Young (Pacific Rim Conservation) write about aspects of the population biology of ACAP-listed Laysan Albatrosses Phoebastria immutabilis in the Kaena Point Natural Area Reserve and Kuaokala Game Management Area on the Hawaiian island of Oahu in the journal The Condor – Ornithological Applications.

The paper’s abstract follows:

“Understanding population dynamics and determining conservation priorities in long-lived species with delayed breeding often is hampered by lack of information about younger age classes.  Obtaining accurate estimates of juvenile survival and recruitment can be difficult because young individuals are infrequently observed.  We used mark– recapture models to estimate age-specific survival, recruitment, population size, and encounter probability of Laysan Albatrosses (Phoebastria immutabilis) using a 14-yr dataset from Oahu, Hawaii, USA.  We also measured the long-term effect of avian pox virus (Poxvirus avium) on the survival and recruitment of albatrosses infected as nestlings.  Survival of juvenile albatrosses during the first year after fledging was 0.757 6 0.042.  We were able to estimate juvenile survival, the first such estimate in any long-lived seabird, because our high search effort revealed that some birds began visiting the natal colony at the age of 1 yr.  The survival of prebreeders increased rapidly and reached a value in the second year (0.973 6 0.008) that was similar to the survival of breeding adults (0.973 6 0.017).  The average age of first return to the natal colony was 4.24 6 0.11 yr.  The average age at first breeding was 8.44 6 0.15 yr, with recruitment probability peaking at ages 9–10 yr and a single bird being recruited into the breeding population at the age of 4 yr.  Pox virus decreased survival in the first year by 4%–13% and decreased recruitment probability up to age 12 by 4%–26%, depending on the severity of infection.  The total size of the Laysan Albatross population on Oahu in 2015 was 555 birds, consisting of 270 active breeders, 231 prebreeders, and 54 birds that likely skipped breeding that year.  The number of prebreeders constituted an average of 44% of the total population.  These demographic estimates will be useful for population modeling exercises involving various threat and management scenarios, and for examining environmental factors that influence demography.”

A Laysan Albatross pair with their chick at Kaena Point, photograph by Lindsay Young 

Reference:

VanderWerf, E.A. & Young, L.C. 2016.  Juvenile survival, recruitment, population size, and effects of avian pox virus in Laysan Albatross (Phoebastria immutabilis) on Oahu, Hawaii, USA.  Condor 118: 804–814.

John Cooper, ACAP Information Officer, 02 November 2016