Space Use and Movements of Southeastern Breeding Double-Crested Cormorants (Nannopterum auritum) in the United States

Abstract

Seasonal movements of Double-crested Cormorants (Nannopterum auritum) have been studied at breeding and wintering sites in the southeastern United States, but little information exists on the movements of these birds within and from their southern breeding sites in lacustrine systems. Since 2001, cormorants have established nesting colonies on islands in Guntersville Reservoir in Alabama, USA. Following the movements of tagged cormorants using satellite telemetry, we found that the mean home range during the 2017 breeding season (May–August) was 41.76 km2, with a core use area of 6.36 km2. The mean home range used by these birds was largest during the period coinciding with incubation: 9–30 May: (98.86 ± 80.64 km2) compared with the chick-rearing 31 May–4 July: 18.30 ± 22.56 km2), and the post-fledge periods (5 July–15 August: 42.04 ± 30.95 km2). There was no significant difference in the metrics of movement and space use between male and female cormorants assessed in this study. Differences in space used by cormorants breeding in Alabama relative to their northern breeding grounds may be explained by landscape characteristics and availability of prey.