Conserving migratory land birds in the New World: Do we know enough?

Abstract

Abstract. Migratory bird needs must be met during four phases of the year: breeding season, fall migration, wintering, and spring migration; thus, management may be needed during all four phases. The bulk of research and management has focused on the breeding season, although several issues remain unsettled, including the spatial extent of habitat influences on fitness and the importance of habitat on the breeding grounds used after breeding. Although detailed investigations have shed light on the ecology and population dynamics of a few avian species, knowledge is sketchy for most species. Replication of comprehensive studies is needed for multiple species across a range of areas.Information deficiencies are even greater during the wintering season, when birds require sites that provide security and food resources needed for survival and developing nutrient reserves for spring migration and, possibly, reproduction. Research is needed on many species simply to identify geographic distributions, wintering sites, habitat use, and basic ecology. Studies are complicated, however, by the mobility of birds and by sexual segregation during winter. Stable-isotope methodology has offered an opportunity to identify linkages between breeding and wintering sites, which facilitates understanding the complete annual cycle of birds.The twice-annual migrations are the poorest-understood events in a bird's life. Migration has always been a risky undertaking, with such anthropogenic features as tall buildings, towers, and wind generators adding to the risk. Species such as woodland specialists migrating through eastern North America have numerous options for pausing during migration to replenish nutrients, but some species depend on limited stopover locations. Research needs for migration include identifying pathways and timetables of migration, quality and distribution of habitats, threats posed by towers and other tall structures, and any bottlenecks for migration. Issues such as human population growth, acid deposition, climate change, and exotic diseases are global concerns with uncertain consequences to migratory birds and even lesscertain remedies. Despite enormous gaps in our understanding of these birds, research, much of it occurring in the past 30 years, has provided sufficient information to make intelligent conservation efforts but needs to expand to handle future challenges.

A phantom road experiment reveals traffic noise is an invisible source of habitat degradation

“…Stopover habitat loss and degradation have been identified as major contributing factors to migratory songbird declines worldwide (37,38). Migrants are exposed to an unknown risk landscape at stopover sites and must therefore rely heavily on increased vigilance to compensate (39)(40)(41). Unlike resident species, successful conservation of migratory species requires protection of habitats in breeding, wintering, and stopover locations (41).…”

“…Migrants are exposed to an unknown risk landscape at stopover sites and must therefore rely heavily on increased vigilance to compensate (39)(40)(41). Unlike resident species, successful conservation of migratory species requires protection of habitats in breeding, wintering, and stopover locations (41). In addition, reduction in condition or delay in migration could have carry-over effects into the overwintering or breeding seasons (42).…”

Dramatic intraspecific differences in migratory routes, stopover sites and wintering areas, revealed using light-level geolocators

“…Research has also focused on the relevance of migratory divides to our understanding of the ecology and conservation of migrants; populations in divides encounter different sets of ecological conditions during migration and on the wintering grounds [16]. These differences could affect their reproduction on the breeding grounds [17,18] and suggest that these populations should be considered independent management units when establishing conservation strategies [13,19].…”

What are the roles of species distribution models in conservation planning?

“…The next difficult step is linking forest communities, which can be mapped remotely at broad scales, with animal communities, which are often loosely correlated to forest distributions and are often incompletely mapped at a much smaller scale. There are few animal communities understood to the degree that the distribution and extent of forest communities can serve as a surrogate for SDM purposes (Faaborg et al 2010).…”

“…Explicitly creating SDMs for policy development is more likely to produce applications that are useable and used by practitioners, and make better use of visualization tools (McIntyre & Strauss 2013). The development of joint ventures based around ecosystems (Bonnott et al 2011) or species (Lynch & Taylor 2010), or multi-agency partnerships for migratory bird conservation (Faaborg et al 2010), is a promising avenue for merging the science and management communities. (5) The conservation community is not the final user of any SDM.…”