L’impact des routes, au-delà des collisions : le cas des oiseaux forestiers et des amphibiens

Bien que plus difficiles à quantifier, les effets indirects des routes sur la faune devraient être considérés au même titre que la mortalité routière, car certaines espèces évitent les abords des routes au moins durant une partie de l’année, ce qui peut mener à une fragmentation plus ou moins permanente de leurs populations. D’autre part, on observe chez plusieurs espèces un effet de bordure suivant lequel les abords des routes constituent un habitat de qualité marginale en raison du bruit, des substances et particules projetées par le passage des véhicules, des substances utilisées pour l’entretien routier (p. ex. sels de déglaçage) ou d’autres facteurs. Les oiseaux forestiers étudiés s’avèrent sensibles à la présence de routes à circulation intense, probablement en raison de la pollution sonore, alors qu’une espèce étudiée s’est avérée relativement tolérante à la construction d’une route de gravier. Quant aux amphibiens, les juvéniles en dispersion de 3 des 5 espèces étudiées semblaient éviter la traversée de routes pavées. Les gestionnaires de l’environnement devraient planifier l’aménagement des réseaux routiers dans la perspective du paysage afin d’éviter de dégrader ou de fragmenter les habitats critiques et de créer des barrières pour les mouvements saisonniers des espèces sensibles

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

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

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

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

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