Research - Caspian terns


Laterality and a chick's introduction to prey


Laterality, or the preferential use of one or the other side of the body, is associated with differential brain activity and increased specialization of brain function. Historically, lateralization has been considered a uniquely human trait. Within the past 30 years, however, motor and sensory directional lateralization (i.e. right or left side bias) at the population level has been shown to be widespread among vertebrates, from bony fish, to amphibians, reptiles, birds and mammals.

On East Sand Island (~9,000 breeding pairs, the largest known Caspian Tern colony in the world), we recorded more than 2000 chick-feeding events for analysis of lateralization of prey within the bills of adult birds, size and shape of prey items delivered to chicks in relation to chick age, and the development of prey-handling skills among chicks.

This study not only adds to the growing body of evidence for lateralization in wild animals, but places lateralization within the much larger context of a chick's introduction to prey. The ability to manipulate and consume prey items is intimately entwined with tern life and evolutionary history, because fitness in chicks and adults depends not only on how well parents are able to deliver prey, but also how well chicks are able to consume the prey.

This research was published in Animal Behaviour 75:2005-2011.