Abstract
The food of willow grouse chicks, based on the content of 96 crops from 1974 and 1975, is given. The food items eaten were studied in relation to the availability. Highly preferred plant spp. were Vaccinium myrtillus, V. uliginosum and Polygonum viviparum. Adult Diptera and Hemiptera and Lepidoptera larvae were the most important animal food. Percent dry weight of animal food declined from some 60 in chicks 0-3 d [day] old, to < 5 in chicks older than 3 wk. Choice of invertebrates depended more on availability than did the choice of plants. The activity of the insects did not seem to affect the chicks'' choice of these food items, but very fast insects like Phoridae were little eaten. Willow grouse chicks selected for bigger than average-sized insect prey.