Site‐specific dynamics in remnant populations of Northern Wheatears Oenanthe oenanthe in the Netherlands

Abstract

Dynamics of populations may be synchronized at large spatial scales, indicating driving forces acting beyond local scales, but may also vary locally as a result of site‐specific conditions. Conservation measures for fragmented and declining populations may need to address such local effects to avoid local extinction before measures at large spatial scales become effective. To assess differences in local population dynamics, we aimed to determine the demographic drivers controlling population trends in three remaining populations of the Northern Wheatear Oenanthe oenanthe in the Netherlands, as a basis for conservation actions. An integrated population model (IPM) was fitted to field data collected in each site in 2007–2011 to estimate fecundity, survival and immigration. Sites were 40–120 km apart, yet first‐year recruits were observed to move between some of the sites, albeit rarely. All three populations were equally sensitive to changes in fecundity and first‐year survival. One population was less sensitive to adult survival but more sensitive to immigration. A life table response experiment suggested that differences in immigration were important determinants of differences in population growth between sites. Given the importance of immigration for local dynamics along with high philopatry, resulting in low exchange between sites, creating a metapopulation structure by improving connectivity and the protection of local populations are important for the conservation of these populations. Site‐specific conservation actions will therefore be efficient and, for the short term, we propose different site‐specific conservation actions.

Stage-dependent survival in relation to timing of fledging in a migratory passerine, the Northern Wheatear (Oenanthe oenanthe)

“…However, since previous analyses showed that juvenile and adult survival differ among sites (Van Oosten et al 2015) and fledging date also differed among the three sites (general linear model in SPSS 21.0, Table 2). Values (mean and SD) shown per year for all three sites combined J Ornithol (2017) 158:133-144 139 F = 46.30, df = 2, P B0.0001), we used a starting model that did include site when testing for effects of fledging period.…”

“…Between 2007 and 2011, we intensively studied three populations of Northern Wheatears in the Netherlands by colour-ringing nestlings and adults (Van Oosten et al 2015): the inland population at Aekingerzand (268 ha; 52°55 0 N, 6°18 0 E); the coastal population at Castricum (74 ha; 52°33 0 N, 4°36 0 E), and the nearby coastal population at Den Helder (160 ha; 52°52 0 N, 4°43 0 E). Sites are described in more detail in Van Oosten et al (2015).…”

“…Sites are described in more detail in Van Oosten et al (2015). Except for a few single pairs elsewhere the three populations are the remaining mainland breeding populations of Northern Wheatears in the Netherlands, i.e.…”

“…Capture-mark-recapture study Northern Wheatears are strongly philopatric and very conspicuous in their open habitat, a combination which allows for very high annual resighting probabilities between years (Van Oosten et al 2015). This provides an excellent setting to study survival in more detail.…”

“…The resulting best model including site was used in further analyses testing for effects of fledging period. We chose the best model with site, since we previously showed that juvenile and adult survival differs between the three sites (Van Oosten et al 2015), as does timing of fledging.…”