Adult and pre-breeding survival estimates of the Whiskered Tern Chlidonias hybrida breeding in southern Poland

Mateusz Ledwoń,Grzegorz Neubauer,Jacek Betleja

doi:10.1007/s10336-012-0926-z

Abstract

We present the first-ever survival estimates of the Whiskered Tern Chlidonias hybrida, based on the analysis of capture–recapture data (403 adults and 1,484 chicks ringed) collected between 1993 and 2011 in an increasing breeding population in southern Poland. Data were modelled using multistate models with an unobservable state, accounting for the period during which young terns remain at their winter quarters. Model-averaged pre-breeding and breeding survival were estimated to be 0.54 [standard error (SE) 0.28] and 0.80 (SE = 0.05), respectively. All models were in agreement that the relative proportion of breeders was nearly zero in the second calendar year, increasing to reach values close to 0.8 in the fifth calendar year, which confirms the observation of a much delayed maturation of the Whiskered Tern. Our data indicate that most Whiskered Tern start to breed about 1 year earlier than members of genera Sterna and Onychoprion. However, the precision of the estimates for the parameter describing the transition probability from the unobservable pre-breeding to the observable breeding state was extremely poor; therefore, these estimates should be treated as tentative until more data are collected. The three best-supported models indicated significant annual variation in recapture probability. The results also suggested that forced exchange of breeding colonies is frequent in the study area; consequently, a large proportion of birds ringed as chicks are breeding in colonies other than their respective natal colony. This exchange is best explained not by the trapping and ringing activity but by human management of the environment, such as water level changes in dam reservoirs and carp Cyprinus carpio farming at fish ponds, both of which result in breeding habitats becoming unstable and periodically unavailable, possibly forcing birds to change breeding sites.

Highlights

The survival rate in any animal population is a joint product of variations in the rates of birth, death and movements of individuals (Lebreton et al 1992)
We present the first-ever survival estimates of the Whiskered Tern Chlidonias hybrida, based on the analysis of capture–recapture data (403 adults and 1,484 chicks ringed) collected between 1993 and 2011 in an increasing breeding population in southern Poland
In study reported here we focused on the survival of the Whiskered Tern Ch. hybrida—a marsh tern species whose population has declined in Europe since the 1970s, but which has recovered beginning in 1990, with clear increases in central and eastern parts of the continent (BirdLife International 2004)

Summary

Introduction

The survival rate in any animal population is a joint product of variations in the rates of birth, death and movements of individuals (Lebreton et al 1992). The lower survival rate of prebreeding birds relative to adult birds is a consequence of the higher mortality of inexperienced young birds (Spendelow 1991; Lebreton et al 2003). Adult and prebreeding survival are among the key parameters affecting population dynamics (Lebreton et al 1992). Estimation of these parameters is of particular importance for assessing population dynamics, understanding life-history parameters and, for managing populations (Perrins et al 1993; Williams et al 2002)

Methods

Results

Conclusion