Assessment of bird collisions with deer fences in Scottish forests.
Bird collisions along 135 km of deer fences were monitored for 1 yr (April/May 1992 to April/May 1993) at 27 sites in the Scottish Highlands. The majority (93%) of recorded collisions were by grouse species and at least 16% were fatal (carcasses found). In a trial testing how long carcasses would remain beside fences, 18 out of 20 were not relocated after 1 month. Red grouse (Lagopus lagopus scoticus) collisions were more frequent on fences surrounding pre-thicket plantations, while capercaillie (Tetrao urogallus) collisions were more frequent on fences in native pinewoods. The distribution of collisions differed seasonally. Two-thirds of both red grouse and black grouse (T. tetrix) collisions occurred between February and May, while capercaillie collisions occurred later, with a peak in September. Collisions by capercaillie were positively associated with areas of Vaccinium spp., whereas those by black grouse were negatively associated with grass and heather. This study adds weight to previous findings that fences are a frequent cause of mortality in capercaillie. Further work aimed at reducing collision rates is needed, but a policy of deer culling to achieve (natural and artificial) tree regeneration without deer fencing would be desirable wherever practicable, and especially within the range and main native pinewood (Pinus sylvestris) habitat of capercaillie.