Conserving Stopover Sites for Forest-Dwelling Migratory Landbirds

Abstract

This framework reflects our experiences in eastern North America. In other parts of North America or the Neotropics, important stopover sites may have other distinctive attributes. For example, many migrants in western North America use riparian corridors in both spring and fall (Finch and Yong 2000). During fall migration, high-elevation sites are also important (Hutto 1985a). In southwestern deserts, the density of migrants at even small oases rivals that in riparian corridors along the San Pedro River (Skagen et al. 1998). We intend to modify this framework in the future and encourage others to do so by expanding its geographic scope and making more explicit recommendations. The strength of the framework is that it is based on the function of sites from the migrants’ perspective. This foundation allows for the flexibility necessary to easily refine the framework as research on migration ecology advances. We strongly suggest that stopover sites be included in any comprehensive biodiversity planning effort. Preliminary investigations of some of these plans (e.g. Foreman et al. 2000, Groves et al. 2000, Noss 2003) suggest that current or proposed conservation areas selected to protect other components of biodiversity also capture a significant percentage of known and predicted stopover sites (Duncan et al. 2002). However, this may not be true in all geographic areas. In North America, areas that especially need further assessment are the Atlantic Coast, central Midwest, Great Lakes region, Great Plains, western deserts, and the West Coast. Stopover sites most likely to be missed are relatively small sites that are important because of their proximity to ecological or physical barriers (fire escapes) or their position within a matrix of agricultural and urban land use (convenience stores). An excellent example of a strategy that has the potential to enhance fi re escapes and convenience stores within large metropolitan areas is the Urban Conservation Treaty for Migratory Birds developed by the U.S. Fish and Wildlife Service (see Acknowledgments). Although the relative numbers of sites to be conserved in each functional category will likely vary among geographic regions, we suggest that fire escapes and convenience stores should receive the most attention, for three reasons. First, these sites are least likely to be identified and managed with conservation objectives in mind. Second, there are few remaining opportunities to protect these types of sites, especially fire escapes. Third, these small remnants of suitable habitat are being rapidly destroyed and degraded (e.g. by invasive species and changes in hydrology). These three characteristics of fi re escapes and convenience stores combine to leave them vulnerable to the influences of unpredictable external forces. The landscape-scale nature of full-service hotel sites means that they are likely already either under conservation ownership or have been targeted for conservation action, even if not with migratory birds in mind. Bird conservation planning efforts have repeatedly identified the imperative need to understand migratory stopover sites from both the research and conservation perspectives (Bonney et al. 2000, Carter et al. 2000, Moore 2000, Donovan et al. 2002, Ruth et al. 2003). Efforts are underway by the conservation and academic research communities to fill these gaps, typically on a regional basis. One of the goals of this paper is to encourage attention and research on the ecology and protection of stopover habitat, including development of appropriate funding sources. We anticipate that government or private agencies will soon develop the capacity to collate data from diverse geographic areas that will allow us to achieve the systematic hemispheric synthesis we so urgently need. Ideally, a complete network of migration stopover sites would be identifi ed systematically as part of broad-scale planning efforts. This is difficult, however, given the limited knowledge about migration in many areas and our current inability to estimate how many sites are needed and their spatial distribution. This obliges planners to begin working at smaller spatial scales, using local expertise and readily available, but often anecdotal, information. We recommend including migration stopover needs in site or regional conservation planning efforts that are conducted to design networks or portfolios of conservation areas (see The Nature Conservancy 1999). As our understanding of migration ecology advances, local and regional plans could then be merged into an intercontinental network of protected stopover habitats. In light of the growing evidence that stopover habitat may be limiting to populations of at least some migratory landbirds (Sille and Holmes 2002, Berthold et al. 2003; but see Faaborg 2002 for an alternative view) and the certainty of rapid anthropogenic landscape changes in eastern North America (National Oceanic and Atmospheric Administration 1998, Jones et al. 2001), it is critically important that stopover habitat be protected and that this protection occur sooner rather than later. Particular attention needs to be paid to geographic areas where stopover habitat is scarce (i.e. holes in the stopover safety net), where fire escapes are inadequate or lacking, and where sites that receive heavy and consistent use may be lost. Protecting stopover habitat is a proactive conservation strategy that will yield enormous biological and economic benefits well into the future. At the same time, research needs to be directed to understanding the stopover ecology, habitat requirements, and demography of migratory landbirds to ensure that conservation action is based on sound science and is as cost effective as possible.