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Wing shape variation of Finnish and Central European Willow Warblers Phylloscopus trochilus and Chiffchaffs P. collybita
Author(s) -
TlAINEN JUHA,
HANSKI ILPO K.
Publication year - 1985
Publication title -
ibis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 80
eISSN - 1474-919X
pISSN - 0019-1019
DOI - 10.1111/j.1474-919x.1985.tb05078.x
Subject(s) - warbler , subspecies , willow , sexual dimorphism , sexual selection , biology , juvenile , wing , zoology , feather , ecology , habitat , engineering , aerospace engineering
Wing shape variation of European Willow Warblers Phylloscopus trochilus and Chiffchaffs P. collybita was studied using indices calculated from wing formulae. Our data were from free‐living local populations of P. t. acredula and P. c. abietinus from southern Finland, and P. t. trochilus and P. c. collybita from southwestern Germany. There were no significant shape differences between the subspecies of the Willow Warbler in which sexual dimorphism was pronounced. The subspecies of the Chiffchaff were significantly different while the sexes were not. There were also significant differences between adult and immature individuals in the autumn. The intrapopulation variation must be considered in attempts to recognize different subspecies or populations in data on birds caught during migration. In the Willow Warbler at least, the difference between age‐groups was larger in males than in females. If the change in wing formula due to the complete pre‐nuptial moult is similar in both sexes, juvenile males intermediate between adult females and adult males suffer disproportionately high mortality. It was earlier suggested that sexual selection increases body size in Willow Warbler males, but the present results imply additional selection pressures for increasing sexual dimorphism.