tion, lack of pugnacity, lack of fear, and many other apparent

disturbances may be just the condition which shall allow the other birds, those not opening the door, to give evidence that they have the capacity to learn vicariously or through Imita- tion.

In the present series the female Sparrow was not in normal condition much of the time. The male Sparrow was- very wild. The Cowbirds were not nearly so active as the Sparrows and usually made very few efforts. The later photographs show, however, that they learn to be present when the door is opened. They are certainly more attentive and interested if behavior is any criterion.