Rusty blackbird patch use during winter in suburban landscapes

Abstract

The rusty blackbird (Euphagus carolinus) is a species of conservation concern throughout its range because of rapid population decline. During winter, relatively large flocks are in suburban landscapes within the Georgia and South Carolina Piedmont Plateau of the southeastern United States. We studied radio‐tagged blackbirds within flocks that moved daily among 3 distinct patch types: pecan (Carya illinoinensis) and small‐seeded oak (Quercus spp.) groves, shallowly flooded forested wetlands, and residential areas landscaped with turf grass. The patch types used for foraging have varying availability of invertebrate and mast food. We investigated the relationship between daily observations of blackbird flocks and previous, current, and oncoming short‐term weather. Suburban landscapes with the appropriate configuration of shallow wetland, residential lawns, and mast grove patches within a 153–415‐ha area, the size of patch aggregations in this study, likely constitute high quality wintering areas for this species. Blackbird flocks were 1.6–1.8 times more likely to be observed foraging in wetlands with each 10°C increase in current temperature, 1.5 times more likely in wetlands for every 5 days with no previous precipitation, and 3.2 times more likely in wetlands with every 10 extra hours of oncoming cold weather. Blackbirds were 4.1–4.5 times less likely to be observed foraging in forested wetlands with every 5‐mm increase in current precipitation. Blackbirds were 2.2 times more likely to be observed in mast groves with every 5‐mm of oncoming precipitation. Radio‐tagged blackbirds used pecan groves for foraging in 2011 but not 2012, which was an overall warmer winter. Pecan groves may be a sporadically used component of a combination of foraging patches that are rarely near flooded forested wetlands or residential areas. Our results can be used to identify and conserve patch components used by rusty blackbird flocks during winter in suburban nature parks and greenways. © 2018 The Wildlife Society.