Winter ecology of the Rusty Blackbird (Euphagus carolinus)
Newell, Patricia Jean
MetadataShow full item record
The Rusty Blackbird (Euphagus carolinus) is the fastest declining songbird in North America likely due to loss, modification, and conversion of wetland habitat in their winter range in the southeastern United States. The species uses suburban landscapes for wintering habitat, although forested bottomland wetlands historically provided the necessary resources for wintering. Suburban landscapes used by Rusty Blackbirds are composed of a mosaic of patches including forested wetlands, residential lawns, and pecan groves. The patches act together to provide Rusty Blackbirds with pre-opened mast that includes both small-seeded red oak (Quercus spp.) acorns and pecans (Carya illinoinensis), terrestrial non-native earthworms (Lumbricus spp.), aquatic wetland worms (Tubifex spp.), and invertebrates other than worms like snails, dragonfly (Odonata) and fly (Diptera) larvae, and Isopods. This is the first study that documents significant worm-use by Rusty Blackbirds. Current and short-term past and future weather, and particularly precipitation, largely drives patch use, body mass regulation, and incorporated diet items, indicating habitat-use is likely driven by invertebrate availability in suburban landscapes. Therefore, managing water fluctuations in wetlands used by Rusty Blackbirds may be an important technique to increase invertebrate abundance and availability during the winter and especially during times when invertebrates have low availability during periods of drought. This research is the first to document precipitation as a driver of habitat use and food incorporation for songbirds during winter. Rusty Blackbirds use mast to overcome times when invertebrates have low availability such as during current and future cold weather and times without precipitation. Red oak trees in wetlands and residential areas provide mast and habitat for suburban gray squirrels (Sciurus carolinensis), which are an important facilitator in providing pre-opened nuts throughout the winter. Small-seeded red oak trees in residential areas and wetlands also provide leaf litter for cover and forage of terrestrial and aquatic worms. Rusty Blackbirds also use abandoned pecan orchards extensively during cold weather. Providing all components in the landscape is necessary for successful management of the species. Managing Rusty Blackbirds in suburban landscapes may be complex because the diet in the eastern population consists of non-native components (i.e., pecan and non-native terrestrial earthworms).