Table 3: Some of the main original data used and calculation performed for estimation of raptor predation impact on juvenile grouse (only mean values are presented).

Weight of black grouse hen, g ( )Both raptors950
Weight of black grouse chick, g ( )Both raptors350

Weight proportion of the black grouse hens and chicks, % (WPhc)GoshawkHens17.3

Grouse body weight utilised by raptors, % (U)Both raptors75

Daily food requirements of male (m), female (f) and juvenile (j) raborts, g/day (DFRmfj)Goshawk 130190196
Buzzard 100126138

Ratio of the black grouse among grouse chicks in the diet of raptors, % (P)Goshawk60

Length of the study period (L)Goshawk60

Maximum density of raptor population nests/100 km2 (D)GoshawkSO10

Occupancy rate of the territory (Or)Goshawk, buzzard56, 33
Productivity chicks/occ. terr. (Prod)Goshawk, buzzard2.1, 1.2

Clutch size (Cs)Black grouse8
Brood size (Bs)Black grouse6
Density of hens in August ( )Black grouse3.2
Density of chicks in August ( Black grouse10.5
Density of hatchlings = ( Cs)Black grouse25.4
Loss of chicks ( )Black grouse20.5

Consumption of a hawk familyC = DFRm + DFRf + Prod × DFRj
Kill rate of adult hensKRh = (C × U × )/
Kill rate of chicksKRc = (C × U × P × )/
Total kill rate of black grouse chicksTKRc = OrD × (0.5KRhBs+KRc) × L