Conifer plantations consistently act as barriers to movement in a deciduous forest songbird: A translocation experiment

Many authors have concluded that habitat loss has a greater influence on biodiversity than habitat fragmentation per se. Yet, several animal species have been shown to be reluctant to move across inhospitable landscape matrices, a phenomenon that would be expected to exacerbate fragmentation effects. In this study, we tested the ability of a forest songbird (Ovenbird, Seiurus aurocapilla) to move across two contrasting landscapes whose matrix (intensively managed forest) would be expected to be relatively permeable compared to agricultural or urban matrices. We hypothesized that males would be less likely to return to their territory in a landscape dominated by forest generally unsuitable for breeding (spruce plantations) than in another dominated by potential breeding habitat (deciduous forest). The probability of resighting translocated males (n = 48) on their territory was significantly lower in the plantation landscape and this relationship was consistent over two successive years. Neither translocation time nor body mass, time of capture, or structural size were significant predictors of probability of resighting. Although this species is sufficiently vagile to return quickly to its territory (e.g. one male returning in less than 2 h), these results indicate that even a forested matrix may impose a resistance to the movements of a forest bird species when its structure or composition differs from that of breeding habitat. Matrix resistance to movements potentially restricts the ability of individuals to detect and colonize suitable habitat fragments. Less vagile species would be even more affected and, therefore, we submit that a more inclusive perspective on effects of landscape change is warranted.