Demographic response of a neotropical migrant songbird to forest management and climate change scenarios

Abstract Demographic models for species sensitive to human activities that are still relatively common are of particular interest to compare the relative influence of human land use and climate on population trends. Yet, data limitations often restrict our ability to interpret the numerical response of species to habitat alteration and climatic change adds to this challenge. In this study, we used habitat-specific demographic information from an individually-marked population of Ovenbird ( Seiurus aurocapilla ) and a forest timber supply model to project population trends over an 80-year horizon. We modelled changes in Ovenbird abundance, productivity, and population growth rate as a function of harvesting scenarios (no harvest, forestry-as-usual, and increased [10% or 20%] harvesting intensity) and projected impacts of climate change (0%, 10%, and 50% reductions in population size over the 80-year period), as well as contrasting assumptions about population dynamics (i.e. open vs. closed population). Among the many effects of climate change, it has been hypothesized that reductions in annual snow cover will occur, causing deeper and more frequent frost penetration into the soil and, in turn, a reduction in invertebrate (food) abundance during the following breeding season. Our models suggest that the study area currently is a demographic sink ( λ  = 0.920) for Ovenbirds, although some habitat types still act as demographic sources. Over the first 7 years, a large decline in abundance of territorial males (∼25%) is projected, unless population levels are maintained through immigration. Interestingly, when we allowed for immigration from outside the study area, population growth rate remained