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

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 prebreeding 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.Keywords Whiskered Tern Á Chlidonias hybrida Á Capture-mark-recapture modelling Á Apparent survival Á Age at first breeding Á Fidelity Á Bird trapping

The Whiskered Tern Chlidonias hybrida expansion in Poland: the role of immigration

“…1,400 km 2 ); over 40 % of the national population breeds on 0.4 % of the country area. This is owing to its unique characteristics-the presence of carp ponds and high food availability (see Ledwoń et al 2013). This area was treated separately, because complete censuses were performed there since 1993 (the early phase of expansion) up to and including 2012, and therefore, the data obtained for Upper Vistula River Valley are reliable and reflect the true number of nesting pairs.…”

“…Apparent survival analysis was previously reported in detail (Ledwoń et al 2013), so we present only the main points of this analysis here. Estimation was based on the capturerecapture data (403 adults and 1,484 chicks ringed) collected between 1993 and 2011 in the breeding population of the Upper Vistula River Valley.…”

“…The matrix structure reflects juveniles, 1-year-old non-breeders, 2-year-old non-breeders, 1-year-old breeders, 2-year-old and older breeders. It has two survival probability parameters, taken from previous work (pre-breeding survival, U P = 0.54, adult survival, U B = 0.80, Ledwoń et al 2013). To address delayed maturity and the presence of non-breeders in the population (Ledwoń et al 2013), age-dependent recruitment term W was included (see Fig.…”

“…Therefore, the probability that a pre-breeder enters the breeding population at a given age is a product of U P and W specific for a given age. For simplicity, we assumed that recruitment is completed after age 2 and that age-specific recruitment probabilities are 0.045 at age 1 (W 1, second cy) and 0.508 at age 2 (W 2 , third cy) [calculated from Ledwoń et al (2013), following Pradel and Lebreton (1999)]. The mean number of female fledglings per pair (f) was also a known parameter (f = 0.95, SE = 0.09), estimated by molecular sexing of 47 chicks that were 10-21 days old from 25 nests in 2006 and 2007 from the Upper Vistula River Valley [for molecular methods, see Ledwoń (2011)].…”

“…Larids (gulls and terns) are frequently used species in various population-demographic studies (e.g., Nisbet and Cam 2002;Lebreton et al 2003;Cam et al 2004;Coulson and Coulson 2008;Szostek and Becker 2012;Doxa et al 2013), but the marsh terns (the genus Chlidonias) remain poorly studied so far (Shealer 2007;Van der Winden and van Horssen 2008;Ledwoń et al 2013). To fill this gap, in this paper we focus on the pattern of expansion of the Whiskered Tern Chlidonias hybrida, the marsh tern species that has been colonising Polish inland for the last four decades (Tomiałojć and Stawarczyk 2003;Betleja and Stawarczyk 2007).…”