Geography of Spring Landbird Migration Through Riparian Habitats in Southwestern North America

Abstract

Migration stopover resources, particularly riparian habitats, are critically important to landbirds migrating across the arid southwestern region of North America. To explore the effects of species biogeography and habitat affinity on spring migration patterns, we synthesized existing bird abundance and capture data collected in riparian habitats of the borderlands region of the U.S. and Mexico. We determined the importance of geographic factors (longitude and latitude) in explaining variation in abundances and capture rates of 32 longdistance and three short-distance migrant species. Abundances and capture rates of 13 and 11 species, respectively, increased with increasing longitude, and four species' abundance and capture rates decreased with increasing longitude. Riparian associates, but not nonriparian species, were more abundant in western sites. Their abundance patterns were only weakly influenced by species biogeography. In contrast, biogeography did influence abundance patterns of nonriparian birds, suggesting that they choose the shortest, most direct route between wintering and breeding areas. We hypothesize that riparian obligate birds may, to some degree, adjust their migration routes to maximize time spent in high-quality riparian zones, but they are able to find suitable habitat opportunistically when crossing more hostile landscapes. In contrast, nonriparian birds adhere more closely to a hierarchical model in which the migratory route is determined by biogeographic constraints. Conservation of riparian habitats is necessary to meet future habitat stopover requirements of many western Neotropical migrant birds. We advocate a coordinated research effort to further elucidate patterns of distribution and habitat use so that conservation activities can be focused effectively.

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

“…Although use of stopover sites in the Caribbean and Latin America is relatively unknown (but see Latta andBrown 1999, Deppe andRotenberry 2008), in eastern North America deciduous forest is widely available, and it is hard to believe that stop-over habitat is typically limiting in this region. In the American West, where much of the habitat is arid grasslands or alpine habitats, riparian vegetation is likely critical to the movements of many migrants and is potentially limiting; recent studies have identified adaptations associated with movements in this relatively harsh environment (Griffis-Kyle and Beier 2005, Skagen et al 2005, van Riper III et al 2008. Many species in this region make molt-migrations in midsummer, when they leave their breeding area and fly to parts of Arizona, New Mexico, and Mexico affected by monsoonal rains.…”

Vulnerability of riparian ecosystems to elevated CO2 and climate change in arid and semiarid western North America

“…L.) and Russian olive (Elaeagnus angustifolia L.) (Table 1) Scott et al, 2009). Riparian ecosystems support a large proportion of SAWNA invertebrate, amphibian, reptile, mammal, and breeding bird species (Warner & Hendrix, 1984;Knopf & Samson, 1994;Naiman et al, 2005), are critical habitat for Neotropical migrant birds (Skagen et al, 2005), and supply the allochthonous stream inputs that support aquatic communities (Naiman et al, 2005).…”

LiDAR derived ecological integrity indicators for riparian zones: Application to the Houille river in Southern Belgium/Northern France

“…As ecotones located at the intersection of land and water, riparian zones are exceptionally rich in biodiversity (Naiman and Décamps, 1990;Naiman et al, 1993). They represent ecological corridors (Rodriguez-Iturbe et al, 2009) and provide a crucial habitat for terrestrial animals and for migrating birds (Hilty and Merenlender, 2004;Machtans et al, 1996;Skagen et al, 1998Skagen et al, , 2005. The width of a zone can range from a few metres to several kilometres.…”