Conspecific and heterospecific social learning in shiny cowbirds

We tested whether shiny cowbirds, Molothrus bonariensis, can improve the acquisition of a feeding response by observing a demonstrator of their own species or a species with which they share roosts and foraging flocks. We trained birds to peck a transilluminated response key using a classical conditioning procedure (the key was transilluminated for 10 s and then food was delivered to a hopper). We compared the efficiency in acquiring the pecking response in four experimental groups: (1) birds that could observe a conspecific demonstrator peck the key and then eat the food, (2) birds that could observe a heterospecific demonstrator (a screaming cowbird, Molothrus rufoaxillaris) peck the key and then eat the food, (3) birds that could observe the apparatus working automatically ('ghost' demonstrator) and (4) birds that learned the task alone. Birds in the conspecific demonstrator group required fewer trials to learn to peck the key than did birds in the groups with a ghost demonstrator or without a demonstrator. Birds in the group with a heterospecific demonstrator also required fewer trials to learn the task than did birds in the group without a demonstrator. There were no differences between the groups with a conspecific and a heterospecific demonstrator. Our results show that shiny cowbirds can acquire behaviour by observing other individuals, and that they learn from heterospecifics with which they share roosts and foraging flocks as readily as they do from conspecifics. (c) 2005 The Association for the Study of Animal Behaviour Published by Elsevier Ltd. All rights reserved.