An Investigation into the Pattern of Bird Damage to the Plastic Stretch Film on Baled Silage in Ireland

Abstract

Baled grass silage is an important ruminant feedstuff in Ireland. Bird attacks to the plastic stretch film surrounding the bales are a considerable problem. We carried out a national survey of bird activity in silage fields and a local crop utilisation survey and made observations of harvested plots containing bales to examine this problem. For the observations of harvested plots, groups of ten bales were made in a series of 0.5ha field plots throughout the summers of 1999 and 2000. Bales were individually wrapped in black plastic stretch film and remained in the field for 24h. Observations during this time indicate that rooks (Corvus frugilegus) and jackdaws (Corvus moneduala) were the primary users of grass silage stubbles and the main species that damaged the plastic film. The incidence of damage was sporadic, but when it occurred was often substantial. Behavioural observations suggest that their primary activity in the field was feeding on the grass stubble and that attacks to the plastic stretch film surrounding bales were a secondary behaviour.