A Woodpigeon (Columba palumbus) Feeding Preference Explained by a Digestive Bottle-Neck

Woodpigeons foraging at brassica sites spent around 50% of their time resting. They tended to move from brassicas to clover sites during the day. A higher proportion of birds was found at brassicas after cold nights and spells of cold weather. Feeding at brassicas was associated with low body weight, and juveniles which had made least progress with their post-fledging moult tended to accumulate there. These observations can be interpreted differently according to whether or not there is a bottle-neck in the digestion of brassicas. A laboratory experiment favours the bottle-neck hypothesis. The limiting digestion rate (0 5 g per minute) is estimated to be insufficient for wild woodpigeons subsisting on brassicas to maintain weight in mid-winter.