Waterfowl rely on continent-wide wetland networks supporting migratory pathways that connect important breeding and wintering grounds. Globally, 30 to 90% of these networks are threatened or have been heavily modified or destroyed by human development. Locally, wetland habitat availability is affected by water policy and regional environmental characteristics that result in substantial annual variation in the quantity and quality of habitats available to waterfowl and other waterbirds. Throughout much of western North America, fall migration coincides with the lowest availability of wetland habitats on the landscape. This timing suggests that species which migrate through arid and semi-arid regions of western North America may be at risk from habitat limitations during fall migration. Given that persistent drought conditions are resulting in changes in water policy and patterns of use, it is important that patterns of habitat selection by migrating waterfowl are understood so the provisioning of suitable habitats can be continued in the face of climate and policy changes.
Using high spatiotemporal resolution GSM-GPS transmitters, USGS scientists analyzed 61 fall migration tracks of Cinnamon Teal (Spatula cyanoptera) across western North America during a three-year study (2017–2019), resulting in the identification of 186 stopover sites used during fall migrations. Landsat-derived imagery was analyzed for flooding regimes and surface water extent using Google Earth Engine, and wetland types were manually digitized.
Cinnamon Teal selected a variety of flooded habitats including natural, riparian, tidal and managed wetlands, flooded agriculture, wastewater sites, and golf and urban ponds. Wetlands associated with agriculture were the most used habitat type (29.8%), though several other anthropogenic habitat types (chiefly golf and wastewater ponds) were highly selected within some stopover sites. Over 72% of stopover locations were on private land. Resources used by Cinnamon Teal reflect wetland availability across the West and further emphasize adaptability to dynamic resource conditions in arid and semi-arid landscapes. Such adaptability may be limited by large-scale reductions in wetland extent that result from extended drought or changes in agroeconomic patterns.
Habitat selection by migrating Cinnamon Teal through arid and semi-arid landscapes was highly variable, reflecting both plasticity in the selection of habitats and local limitations in higher quality habitats within regions of western North America. Dry habitats, whether agriculture or matrix non-habitats, were avoided in all regions. The importance of anthropogenically provided water, such as managed wetlands, urbanized water sources, and wet agriculture, was reflected in high selection ratios for these land cover types.
Stopover locations selected by Cinnamon Teal during migration through arid and semi-arid landscapes show the preference of the species for both natural and managed wetlands.