Fidelity and persistence of Ring-billed ( Larus delawarensis ) and Herring ( Larus argentatus ) gulls to wintering sites

While the breeding ecology of gulls (Laridae) has been well studied, their movements and spatial organization during the non-breeding season is poorly understood. The seasonal movements, winter-site fidelity, and site persistence of Ring-billed (Larus delawarensis) and Herring (L. argentatus) gulls to wintering areas were studied from 2008-2012. Satellite transmitters were deployed on Ring-billed Gulls (n = 21) and Herring Gulls (n = 14). Ten Ring-billed and six Herring gulls were tracked over multiple winters and > 300 wing-tagged Ring- billed Gulls were followed to determine winter-site fidelity and persistence. Home range overlap for individuals between years ranged between 0-1.0 (95% minimum convex polygon) and 0.31-0.79 (kernel utilization distributions). Ring-billed and Herring gulls remained at local wintering sites during the non-breeding season from 20-167 days and 74161 days, respectively. The probability of a tagged Ring- billed Gull returning to the same site in subsequent winters was high; conversely, there was a low probability of a Ring- billed Gull returning to a different site. Ring- billed and Herring gulls exhibited high winter-site fidelity, but exhibited variable site persistence during the winter season, leading to a high probability of encountering the same individuals in subsequent winters.