Reflex association of feeding and defecation in young birds. (Troglodytes Aedon).

In connection with the problem of visceral reflexes, it is of interest to record an observation on young house wrens (Troglodytes aedon). A brood of six nestlings ranging in age from three to six days was orphaned, and for several hours were fed insects and worms by means of small forceps.

When disturbed, the young bird, if hungry, extended the head and opened its beak. As soon as a morsel of food was swallowed, the bird became very active, scrambling and jostling until it had pushed its head down toward the center of the nest and elevated the anus just over the edge of the nest, in which position defecation always occurred. At once the bird became quiet and could not be induced to take food again for a period of from one and one-half to three minutes. Defecation in this position always followed the taking of food.

Ornithologists have long known that in many species the parent birds carried away excreta after every trip to a nest with food. A parent wren was observed to repeat this operation on an average of 25 times an hour, carrying away the excreta every time food was carried to the nest.

By noting the color of the food and that of the feces it was made certain that each bolus was digested and the waste ready for voiding before the bird could be stimulated to receive food again. The young bird, then, does not take food until the previous bolus has been digested. Immediately upon swallowing a fresh supply a very complicated reflex is set up, which not only leads to defecation but places the young bird in an unusual position in which the parent bird can most easily collect the excreta as voided and remove it from the nest.