Stopover habitats of spring migrating surf scoters in southeast Alaska

Abstract

Habitat conditions and nutrient reserve levels during spring migration have been suggested as important factors affecting population declines in waterfowl, emphasizing the need to identify key sites used during spring and understand habitat features and resource availability at stopover sites. We used satellite telemetry to identify stopover sites used by surf scoters migrating through southeast Alaska during spring. We then contrasted habitat features of these sites to those of random sites to determine habitat attributes corresponding to use by migrating scoters. We identified 14 stopover sites based on use by satellite tagged surf scoters from several wintering sites. We identified Lynn Canal as a particularly important stopover site for surf scoters originating throughout the Pacific winter range; approximately half of tagged coastally migrating surf scoters used this site, many for extended periods. Stopover sites were farther from the mainland coast and closer to herring spawn sites than random sites, whereas physical shoreline habitat attributes were generally poor predictors of site use. The geography and resource availability within southeast Alaska provides unique and potentially critical stopover habitat for spring migrating surf scoters. Our work identifies specific sites and habitat resources that deserve conservation and management consideration. Aggregations of birds are vulnerable to human activity impacts such as contaminant spills and resource management decisions. This information is of value to agencies and organizations responsible for emergency response planning, herring fisheries management, and bird and ecosystem conservation. © 2010 The Wildlife Society

Mercury in birds of San Francisco Bay-Delta, California: trophic pathways, bioaccumulation, and ecotoxicological risk to avian reproduction

“…San Francisco Bay winters typically are mild and cold induced stress in diving ducks may be less common than on other major sea and bay duck wintering areas. 47 …”

Spatiotemporal associations between Pacific herring spawn and surf scoter spring migration: evaluating a ‘silver wave’ hypothesis

“…For highly mobile scoters, the generally continuous availability of herring spawn and abundant alternative foraging habitat likely gives them flexibility to modify their migration timing and habitat use. Surf scoters might use a combination of stopover sites that provide varying habitat resources (Lok et al 2011). The location data suggest that although some surf scoters do appear to generally follow a silver wave of herring spawn availability, they are likely making use of alternative food sources at sites during migration as well.…”

“…Habitat use by surf scoters during winter is related to shoreline characteristics and associated bivalve prey distribution and densities (Žydelis et al 2006). Recent habitat mapping in SEAK indicates that the distribution of blue mussels is more continuous along shorelines closer to the mainland coast (ShoreZone Program 2006), which could provide predictable food resources for scoters (Lok et al 2011).…”

“…Lynn Canal is the most northeastern marine waterbody in SEAK, creating a natural break and stopover area for migrating birds. This area provides scoters with the last access to marine resources along their coastal migration route before they turn inland to breed (Lok et al 2011). Not all spring migration habitats serve the same resource function (Mehlman et al 2005), and Lynn Canal may be distinct as a final migration staging area before inland migration.…”

“…Along the Pacific coast, surf scoters are known to congregate and forage at herring spawning events during late winter and early spring (Vermeer 1981, Vermeer et al 1997, Sullivan et al 2002, Lok et al 2008. Proximity to herring spawn has been identified as a strong predictor of stopover habitat use (Lok et al 2011). However, unlike other food resources, the silver wave of herring spawn is restricted to only a few weeks and along a very small proportion of the available coastline (Hay & McCarter 2007).…”