Seasonal patterns in home range and habitat use of the Grey-headed Woodpecker Picus canus as influenced by the availability of food

Abstract

Seasonal patterns in diet, home range and habitat use of the Grey-headed Woodpecker Picus canus were recorded at the Varaldskogen study area, a managed boreal forest located on the Swedish-Norwegian border in southcentral Scandinavia. One successfully breeding pair was radio-monitored throughout a year . Additional telemetry data were collected in summer from a male in a pair that failed breeding. In summer the birds almost exclusively preyed upon ant colonies in soil and rotten stumps located in young conifer plantations. In winter, when snow or frost prohibited ground feeding, birds were feeding on bark-dwelling insects in old pine and dead trees . The winter shift in diet and feeding behavior was accompanied by an approximately 100 times enlargement in home range size, increasing from 50-100 ha (n = 3) in summer to 4 500- 5 400 ha (n = 2) in winter . With reservations due to small sample size, our data suggests that availability of winter food is critical to the Grey-headed Woodpecker when snow or frozen ground prevents ground-feeding for soil-dwelling ants .