Intake of Buds and Catkins of Birch by Captive Hazel Grouse in Winter

Abstract

The intake of buds and catkins of birch, Betula platyphylla, by captive Hazel Grouse, Bonasa bonasia, was measured from December 1987 to March 1988, March 1991, from November 1991 to March 1992, and November 1992 to March 1993. Buds included 15.3% crude protein, 32.9% crude fat, 14.1% crude fiber and 4.1% sugar. The corresponding values for catkins were 14.1, 20.7, 22.6, and 5.8%, respectively. The amount of buds and catkins eaten by pairs of Hazel Grouse ranged from 8.3 ± 2.7 g/day (dry weight) in January to 11.8 ± 3.2g/day in December. In single-bird trials, the amounts eaten ranged from 6.2 ± 1.7g/day in November to 7.0 ± 1.5g/day in January for males and from 5.7 ± 1.2g/day in March to 6.6 ± 1.9g/day in November for females. Mean gross energy values did not show significant seasonal and sexual variations, being 232.94 ± 102.92kJ/day for pairs and 154.69 ± 38.08kJ/day for single birds. The gross energy obtained by eating buds and catkins in captivity was lower than that expected for wild birds, around 410kJ/day. This was probably because captive birds were accustomed to artificial foods and required less amount of foods than wild birds.