Ardea
Official journal of the Netherlands Ornithologists' Union

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Voipio P. (1969) Geographical variation in Corvus monedula in Finland. ARDEA 57 (1-2): 48-63
The objective of the present paper is to investigate the taxonomic status of the Finnish Jackdaws, particularly with reference to the two main characteristics used in the subspecific discrimination of the species, viz. (1) the general hue of the silvery collar and, especially, (2) the frequency of occurrence and the average size of the white neck patch. Within the Finnish population, the white neck-patch is present in about 70% of the individuals. However, the frequency and the average size of the white patch generally increase from the Southwest to the Northeast and, especially, the East. The populations living on the +land Isles, the south-western Finnish mainland, and on the south coast, are more closely related to each other than to that of Lappeenranta in south-eastern Finland. Further, the populations of Tavastland (HSme), north of the south-western-southern populations, somewhat deviate from the latter in the 'eastern' direction. The south-eastern population of Lappeenranta differs from the other populations of Finland in that the white patch is present in 100% of the specimens (against 60-70% in the others). In addition, the average size of the white patch is 2-3 times larger than within the south-western and Tavastland areas, and, finally, the average colour of the silvery collar is significantly lighter than in the west. Consequently, the population concerned should be classified as belonging to the eastern subspecies soemmerringii. In respect to the properties concerned, the south-western and the Tavastland population are intermediate between the Swedish and south-eastern Finnish populations. Their coefficients of variation are high (more than two-, and nearly threefold, respectively, as compared with the south-eastern population) indicating that they consist of heterogeneous material. This is reflected also in the two-peaked frequency distribution of the different size classes of the white patch. They are, thus, preferably to be considered as secondary intergradations between the two northern subspecies, or monedula <> soemmerringii. Factors affecting the origin of several properties that characterize individual, local populations have also been considered.


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