Substrate influences foraging selection by Eurasian Green Woodpeckers Picus viridis in autumn and winter: observations in Hungary over a 20-year period

The foraging behaviour and habitat use of the Eurasian Green Woodpecker Picus viridis at various sites in Hungary over a 20-year period was documented. Detailed observations were recorded on foraging behaviour at hard substrates; in quarries, cliffs and human made structures of brick and stone construction. Using Chi-square tests on the frequency of observations of birds at hard substrates foraging sites, we compared usage during periods of snow cover and those without. Birds were found to be more frequently observed at hard substrates during periods of snow cover because these remained largely free of snow. We supposed that this response was due to invertebrate prey becoming increasingly scarce generally across typical foraging sites, i.e. grasslands and meadows during harsh winter conditions. Accessibility to the alternative sites became important as a source of food because availability of prey was more reliable. Vertical surfaces of hard substrates such as those associated with quarries, cliffs and buildings may be important to sustain Eurasian Green Woodpeckers in periods of snow cover where these provide a valuable foraging resource.