2.5. Museum data

Skin and bone samples of the Northern Goshawk were used in the morphological analysis from the collection of the Zoological museum of the University of Oulu. In total, 258 specimens were used in the analysis. The collection originates from northern Finland in 1961-1997. From each skin the following measurements were taken: body, length, tail, bill, tarsus and total length. Wing lengths were taken from flattened and straightened wings and tail length from the root of central retrics to the tip of them. Because these measurements were made during the preparation by several people, they are open to criticism. However, the same people have prepared hawks of both sex and age categories. When possible all measurements were checked from the museum skins. Skeletons were measured as follows: sternum length: from the tip of the spina to the median back edge of the sternum, breadth (median) and height (maximum), maximum lengths of coracoid and femur, humerus: from the proximal tip (caput humeri) to the tip of the trochlea, length of the pelvic bone (length of the sacrum) and breadth of it: distance between the lower (outer) edges of acetabulum (see Bährmann 1974). The outer bones of limbs were excluded from the analysis, because these bones are mostly left on the skin.

All birds were classified according to plumage, adults and juveniles. Cause of death was considered by grouping the sample together, birds in normal condition and starved birds. If the cause of death was not accurately determined we considered the adult male starved or under the risk of starvation if it weighed less than 700 g and a juvenile when weighing less than 650 g. The respective limits for females were 1100 g for adults and 1000 g for juveniles. If starvation was caused by injury, such birds were excluded from the analysis.