Evidence of Large-Scale Source–sink Dynamics and Long-Distance Dispersal Among Wood Thrush Populations

Abstract

Source-sink dynamics are commonly thought to occur among Wood Thrush (Hylocichla mustelina) and other songbird populations, allowing for the persistence of populations with negative growth rates ("sinks") through immigration from populations with positive growth rates ("sources"). Knowledge of source-sink dynamics is important for management and conservation because the removal of source habitat should result in the extinction of dependent sinks. However, since research has focused on identifying individual sources/sink populations, not source-sink pairs, we cannot predict these effects or the scale over which they occur. We posit that, when dispersal occurs from a source to a sink year after year, there will be a one-year time-lagged correlation in abundance between the two populations. This should occur for populations separated by distances over which juveniles disperse. Using the North American Breeding Bird Survey data, we tested for such time-lagged correlations between paired Wood Thrush populations from 10 to 200 km apart. Populations were linked with a one-year time lag over distances from 60 to 80 km, indicating that dispersal and source-sink dynamics may occur over these long distances. There was also a declining trend in forest cover from sources to sinks. Conservation and management strategies should therefore be designed at large scales, with consideration for source-sink dynamics and forest cover.

Survival of Adult Songbirds in Boreal Forest Landscapes Fragmented by Clearcuts and Natural Openings

“…3). Our results are consistent with recent observations that most boreal songbirds use home ranges far larger than their defended territories, that individuals respond to landscape-scale habitat, and that populations are synchronized on a scale of kilometers to tens of kilometers (Toms et al 2004, Betts et al 2006a, Taylor and Krawchuk 2006, Tittler et al 2006, Leonard 2007, Rempel 2007). …”

“…Recent research has made it clear that regular landscape-scale extra-territorial movements are typical behavior for most forest songbird species, that nonterritorial "floaters" are common in some situations, and that the expression of both of these behaviors is often influenced by landscape structure (Norris and Stutchbury 2001, Fraser and Stutchbury 2004, Woolfenden et al 2005). All of these forms of movement can be affected by a species' population status and likely play an important role in synchronizing the dynamics of forest songbird populations on a scale of kilometers to tens of kilometers (Toms et al 2004, Tittler et al 2006. Consequently, consideration of patterns of space use will enhance interpretation of information on the demographics and resilience of local songbird populations.…”

The first 50 years of the North American Breeding Bird Survey

“…For instance, because adult birds are typically considered highly philopatric (e.g., Greenwood andHarvey 1982, Holmes and, natal dispersal distances will often determine distances between interacting sites of population sources and population sinks. A few previous studies have found correlations in the abundance of passerine birds from one year to the next in areas 2-100 km apart, which is evidence of source-sink dynamics at this spatial scale (Winkler et al 2005, Tittler et al 2006, McKim-Louder et al 2013). However, the geographic scales at which source-sink dynamics operate in avian ecology remain poorly understood.…”

Towards modelling persistence of woodland birds: the role of genetics

“…These effects seem to be general. Evolution of dispersal strategies have major impacts on rate and mode of range-shifting (Dytham 2009), and variance in dispersal distance is critical in landscape-scale population connectivity and recolonisation (Trakhtenbrot et al 2005;Tittler et al 2006;van Houtan et al 2007).…”