The Survival of Bullfinches on Cultivated Fruit Buds

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Abstract
To study their ability to survive on the buds of different pear cultivars, captive bullfinches were fed diets of fruit buds of Doyenne du Comice or Conference cultivars. Controls received a diet of mixed seeds. Bulfinches on all diets lost up to 8.7% body weight overnight. They regained weight during the day when eating seeds, but continued to lose weight when eating buds. Weight losses after 24 h were the same for birds eating either cultivar. When the buds began to swell in Jan. and some tests were run for 48 h, bullfinches eating ''Comice'' buds lost significantly more weight than those eating ''Conference''. The number of buds eaten per day increased from Dec.-Feb. but did not differ between cultivars. The calorific value of the 2 pear cultivars was also similar but, since a greater proportion of a ''Comice'' bud is inedible, fewer calories were ingested by birds that ate ''Comice''. Bullfinches must keep the time and energy spent feeding on buds to a minimum. Thus the proportion of a bud that is edible and the ease with which it can be eaten may be important factors in determining feeding preferences.

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