Temporal variation in apparent annual survival rates of Ovenbird males from control and treated plots, based on the second best model (φ_t+y p.).

<p>The treatment (selection harvesting; 30–40% basal area removal) was applied during the winter of 2006–2007.</p

ENSO, Nest Predation Risk, Food Abundance, and Male Status Fail to Explain Annual Variations in the Apparent Survival Rate of a Migratory Songbird

<div><p>Adult mortality can be a major driver of population decline in species whose productivity is relatively low. Yet, little is known about the factors influencing adult survival rates in migratory bird species, nor do we know much about the longer-term effects of habitat disturbance on the fitness of individuals. The Ovenbird (<i>Seiurus aurocapilla</i>) is one of the vertebrate species most sensitive to forest management, yet it is still common and widespread. We monitored the fate of 330 colour-banded Ovenbird males in four pairs of 25-ha plots during 9 successive breeding seasons. One plot of each pair was treated through selection harvesting (30–40% basal area removed) during the first winter. We tested the following hypotheses: (1) higher physiological costs in harvested plots as a result of lower food abundance will reduce apparent survival rate (ASR) relative to controls; (2) lower ASR following years with low nest survival and higher probability of renesting; (3) fluctuations in ASR reflecting El Niño Southern Oscillation (ENSO); and (4) higher ASR in returning males than in recruits (unbanded immigrants) owing to greater site familiarity in the former. We tested the relative importance of these hypotheses, or combinations thereof, by generating 23 models explaining variation in ASR. The year-dependent model received the most support, showing a 41% decrease in ASR from 2007 to 2014. The important year-to-year variation we observed in ASR (Σ<i>w_i</i> = 0.99) was not explained by variation in nest predation risk nor by ENSO. There was also little evidence for an effect of selection harvesting on ASR of Ovenbird males, despite a slight reduction in lifespan relative to males from control plots (2.7 vs 2.9 years). An avenue worth exploring to explain this intriguing pattern would be to determine whether conditions at migratory stopover sites or in the wintering area of our focal population have gradually worsened over the past decade.</p></div

Evaluation of mark-resighting models for male Ovenbirds monitored from 2006 to 2014 to assess variation in apparent annual survival (φ) and resighting probabilities (p).

<p>Symbols: φ = survival, p = resighting probability, (.) parameter constant, + = additive effect between two variables (e.g. T+Y), × = interaction effect between two variables (e.g. T×Y), * = full interaction between two parameters (e.g. T*Y = T+Y+T×Y).</p><p>Models were tested as functions of status, treatment, and annual variations (ENSO, daily nest survival, and nesting success). Bold type indicates the best-fit model. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113844#pone-0113844-t001" target="_blank">Table 1</a> for meaning of codes.</p><p>Evaluation of mark-resighting models for male Ovenbirds monitored from 2006 to 2014 to assess variation in apparent annual survival (φ) and resighting probabilities (p).</p

Survival curves of the seven cohorts of banded Ovenbird males pooled from the four pairs of plots, from capture (year 0) until 2014.

<p>Each curve corresponds to a separate cohort (i.e. group of newly-marked males during a breeding season, irrespective of their age) whose year of marking is indicated in the legend. Sample sizes per cohort were 98 (2006 cohort), 32 (2007), 29 (2008), 43 (2009), 46 (2010), 37 (2011), and 45 (2012).</p

Appendix B. Results from the multiple comparison analyses testing for year-specific treatment effects and figures presenting mean abundance and biomass of Coleoptera and Gastropoda for each year and habitat type and abundance between skid trails and inter-trail forest within treated plots.

Results from the multiple comparison analyses testing for year-specific treatment effects and figures presenting mean abundance and biomass of Coleoptera and Gastropoda for each year and habitat type and abundance between skid trails and inter-trail forest within treated plots

Model parameters fitted in Cormack-Jolly-Seber models to assess their influence on apparent survival rate (ASR) of male Ovenbirds monitored from 2006–2014.

<p>Model parameters fitted in Cormack-Jolly-Seber models to assess their influence on apparent survival rate (ASR) of male Ovenbirds monitored from 2006–2014.</p

Appendix A. Additional details on methods used to determine breeding status of territorial Ovenbirds, invertebrate sampling design, and statistical analyses.

Additional details on methods used to determine breeding status of territorial Ovenbirds, invertebrate sampling design, and statistical analyses

δ²H_f (A) and δ³⁴S_f (B) Ovenbird isoscapes based on samples from ASY males collected in 2010 and calibrated 2011 and 2012 data.

<p>Isoscapes were based on ordinary Gaussian and ordinary spherical semivariogram models, respectively. Blue points are the 26 sampling locations and in black is the Black Brook district.</p

Histograms of δ²H_f (A) and δ³⁴S_f (B) from returning ASY (n = 23) and SY (n = 35) males breeding in the Black Brook district, New Brunswick, in 2010.

<p>Histograms of δ²H_f (A) and δ³⁴S_f (B) from returning ASY (n = 23) and SY (n = 35) males breeding in the Black Brook district, New Brunswick, in 2010.</p

Tracking Natal Dispersal in a Coastal Population of a Migratory Songbird Using Feather Stable Isotope (δ²H, δ³⁴S) Tracers

<div><p>Adult birds tend to show high fidelity to their breeding territory or disperse over relatively short distances. Gene flow among avian populations is thus expected to occur primarily through natal dispersal. Although natal dispersal is a critical demographic process reflecting the area over which population dynamics take place, low recapture rates of birds breeding for the first time have limited our ability to reliably estimate dispersal rates and distances. Stable isotope approaches can elucidate origins of unmarked birds and so we generated year- and age-specific δ²H and δ³⁴S feather isoscapes (ca. 180 000 km²) of coastal-breeding Ovenbirds (<i>Seiurus aurocapilla</i>) and used bivariate probability density functions to assign the likely natal areas of 35 males recruited as first-year breeders into a population located in northwestern New Brunswick, Canada. Most individuals (80–94% depending on the magnitude of an age correction factor used; i.e. 28–33 out of 35) were classified as residents (i.e. fledged within our study area) and estimated minimum dispersal distances of immigrants were between 40 and 240 km. Even when considering maximum dispersal distances, the likely origin of most first-year breeders was<200 km from our study area. Our method identified recruitment into our population from large geographic areas with relatively few samples whereas previous mark-recapture based methods have required orders of magnitude more individuals to describe dispersal at such geographic scales. Natal dispersal movements revealed here suggest the spatial scale over which many population processes are taking place and we suggest that conservation plans aiming to maintain populations of Ovenbirds and ecologically-similar species should consider management units within 100 or at most 200 km of target breeding populations.</p></div