Research Papers, part of a Special Feature on Bird Conservation in the Boreal Forest: Is there a Case for Resilience? Survival of Adult Songbirds in Boreal Forest Landscapes Fragmented by Clearcuts and Natural Openings Taux de survie d'oiseaux adultes dans des paysages forestiers boréaux fragmentés par la coupe à blanc et les ouvertures naturelles

There exists little information on demographic responses of boreal songbirds to logging. We conducted a 4-yr (2003-2006) songbird mark-recapture study in western Newfoundland, where land cover is a naturally heterogeneous mosaic of productive spruce-fir forest, stunted taiga, and openings such as bogs, fens, and riparian zones. We compared apparent survival and rate of transience for adults of 14 species between areas having forests fragmented primarily by either natural openings or 3-7 yr-old clearcuts. Data were collected on three landscape pairs, with birds being marked on three 4-6 ha netting sites on each landscape (total = 18 netting sites). Survival rates were estimated using multi-strata mark-recapture models with landscape types specified as model strata. Landscape type was retained in the best model for only two species, Ruby-crowned Kinglet and Yellow-rumped Warbler, in both cases indicating lower apparent survival in landscapes having clearcuts. Though parameter estimates suggested lower survival in clearcut landscapes for several species, meta-analysis across all species detected no general difference between landscape types. Further, we did not detect any relation between landscape differences in survival and a species' habitat affinity, migratory strategy, or the proportion of transients in its population. Although sensitivity to logging was limited, we observed high interspecific variation in rates of breeding season apparent survival (48% (Dark-eyed Junco) to 100% (several species)), overwinter apparent survival (0.3% (Ruby-crowned Kinglet) to 86.5% (Gray Jay)), and transience ( ≈0% (several species) to 61% (Ruby- crowned Kinglet in clearcut landscapes)). For Lincoln's and White-throated Sparrows, over-winter apparent survival was >2× higher for males than females, and rate of transience was > 8× higher for White-throated Sparrow males than females. Moderately male-biased sex ratios suggested that both lower mortality and higher site fidelity contributed to higher apparent survival of males. Overall, variability in our estimates of survival was too great to be explained by mortality alone, suggesting a large influence of landscape- scale movement by adults, e.g., breeding dispersal, extra-territorial forays, and transience, on the dynamics of boreal songbird populations. These movement patterns may also confer resilience to localized disturbance in boreal landscapes. RESUME. Peu d'informations nous permettent de mesurer la reponse demographique des oiseaux boreaux a l'exploitation forestiere. Afin de pallier a cette situation, nous avons effectue une etude par capture- recapture d'une duree de 4 ans (2003-2006) dans l'ouest de Terre-Neuve, ou l'on retrouve une mosaique naturellement heterogene de peuplements forestiers productifs d'epinettes-sapins, de taiga rabougrie et d'ouvertures telles que des tourbieres, fens et zones riveraines. Nous avons compare le taux de survie apparent et la proportion d'individus en transit pour des adultes de 14 especes entre des zones de forets principalement fragmentees par des ouvertures naturelles versus des coupes a blanc de 3 a 7 ans. Les donnees ont ete recoltees dans trois paires de paysages, les oiseaux etant marques dans trois sites de capture

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