Does bird predation influence the spot-number variation in Maniola jurtina (Lepidoptera)?

For six years samples of the satyrine butterfly Maniolajurtina L. were collected on small islands in southern Sweden and scored for beak marks, i.e. damage on wings presumably resulting from attacks by birds; in the present study area mainly Red-backed Shrike Lanius collurio L. An overall mean of 8% (5–1496 in different years) of the females and 1396 (10–2296) of the males had beak marks. Both sexes of M. jurtina show variation in spot-number on the hindwings and there is some evidence that in some years the frequencies of different spot-number phenotypes with beak marks differ significantly from randomness. Although it is not known how beak mark frequencies are related to predation pressure (reflecting rates of predation or escapes?) it is suggested that, due to behavioural differences of spot-number phenotypes, birds act as a selective factor influencing the spot-number variation. The results are discussed in relation to a recent model proposed by Brakefield attempting to account for variation in spot-number in M. jurtina.