. The Canadian field-naturalist. BATE 19 26 3 K) 17 24 31 7 JUNE I JULY lAUGUST. 10 17 24 31 7 14 21 28 JULY I AUGUST |mS£CTS ^^TMEB ANIMALS [ ^:uLTI\ftTEB GRAJHS ||^WILD FRUITS ^^RASS a LEAVES |]i|i§SEEOS (a) (b) Fig. 2. Left. Foods eaten by 55 juvenile pheasants of Group I, hatched from June 9-19. Right. Foods eaten by juvenile pheasants of Group II, hatched from July 10-24. a change in nutritional requirement on the part of the bird, or a change in the availability of the food. Whether or not food is available depends of course not only on the season but on the mobility of the bird. Those f
. The Canadian field-naturalist. BATE 19 26 3 K) 17 24 31 7 JUNE I JULY lAUGUST. 10 17 24 31 7 14 21 28 JULY I AUGUST |mS£CTS ^^TMEB ANIMALS [ ^:uLTI\ftTEB GRAJHS ||^WILD FRUITS ^^RASS a LEAVES |]i|i§SEEOS (a) (b) Fig. 2. Left. Foods eaten by 55 juvenile pheasants of Group I, hatched from June 9-19. Right. Foods eaten by juvenile pheasants of Group II, hatched from July 10-24. a change in nutritional requirement on the part of the bird, or a change in the availability of the food. Whether or not food is available depends of course not only on the season but on the mobility of the bird. Those from one to three vi^eeks of age, and to a lesser degree those of four and five weeks, are dependent upon the food in their immediate surround- ings, while birds six weeks and older can travel some distance to a source of supply. Fig. 2 (a) shows graphically the foods eaten by 55 birds, hatched between June 9 and ;19. This figure illustrates in more detail the change from animal to plant food and the date at which this took place. In Fig. 2 (b) appears a similar plot for 48 birds hatching between July 10 and 24. Although Group II .has hatched at least three weeks later than I, the picture is somewhat the same. The change from animal to plant food still occurred be- tween the fourth and the sixth week despite ^he fact that the wheat was combined by July 24 and thus waste wheat became avail- able in quantity to the birds of Group II when they were only three weeks old. It is evident that at this date they were still largely insectivorous, while those of Group I were eating a considerable amount of wheat. It can also be seen that grass and leaves were not taken until the fourth week. Since these are available throughout the summer, this also might indicate a selection determined perhaps by nutritional requirement beginning at four weeks of age. However, availability of food does play a part in determining what is eaten. For ex- ample, at six weeks of age the later-hatched birds a
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