No effect of habitat fragmentation on post‐fledging, first‐year and adult survival in the middle spotted woodpecker

Abstract

Despite its relevance for the dynamics of populations, the ecological mechanisms underlying juvenile and adult survival are poorly known in most bird species. This study focuses on the effect of habitat fragmentation on early post-fledging, first-year and adult survival of the middle spotted woodpecker Dendrocopus medius by combining data of radio-tagged and ringed birds. Among juveniles, most deaths occurred during the first three weeks after fledging (survival rate: 0.35990.077) and were mainly caused by predation. After independence, birds faced another critical period during their first autumn-winter that lowered first-year survival further (0.25590.044), whereas adult mortality was considerably lower (annual survival rate: 0.78690.074). We did not find any significant effect of habitat fragmentation (measured as patch size and connectivity) on juvenile or adult survival. Sex ratio at fledging did not differ significantly from parity (proportion of females: 0.513) and was not correlated to patch size. Regardless of age, survival did not differ between the sexes, suggesting that a femalebiased mortality was not the mechanism behind the presence of unpaired territorial males in this population. Lighter nestlings underwent significantly higher post-fledging mortality, indicating that conditions in the nest may substantially affect survival later in life.

Floaters may buffer the extinction risk of small populations: an empirical assessment

“…Under severe fragmentation conditions, small local populations of woodpeckers are subjected to a high extinction risk associated with demographic and environmental stochasticity [5]. Previous research shows the existence of floaters that may replace the lost breeders in the Cantabrian Mountains [25,26], further indicating the suitability of our study system for testing floater-related hypotheses of population persistence and turnover.…”

“…The study area covered approximately 770 km 2 on the Cantabrian Mountains (northwest Spain, 428 N, 58 W) [5,26]. The Cantabrian population of middle spotted woodpeckers is placed at the southwestern edge of the species' geographic range and the southern edge of its distribution in Spain [33][34][35].…”

“…Habitat patches (i.e. old-growth deciduous oak forests) covered approximately 4% of the study area [5,26].…”

Postfledging habitat selection of juvenile middle spotted woodpeckers: a multi‐scale approach

“…Transmitters BD-2 (Holohil Systems, Canada) that weigh either 1.6 g or 1.8 g (Â3% of average nestling mass) were attached with a leg-loop elastic harness to the young (Robles et al 2007a). Juveniles were sexed by molecular methods (Robles et al 2007a). Juveniles were sexed by molecular methods (Robles et al 2007a).…”

“…We examined habitat selection of radio-tracked juvenile middle spotted woodpeckers Dendrocopos medius at multiple hierarchically-nested spatial scales in Cantabrian Mountains (NW Spain). The first weeks after fledging are critical for juvenile survival, with fledglings in poor body condition experiencing higher mortality rates (Robles et al 2007a). Its habitat specialisation is based on the preference for large diameter rough-bark deciduous trees for foraging (Pasinelli and Hegelbach 1997, Hertel 2003, Robles et al 2007b).…”