However, the gray catbird exhibits a behavior during the nesting season that baffles ornithologists. It seems occasionally gray catbirds will visit thrasher nests and actually break, and eat eggs. Several theories have been developed to explain this activity. Some experts are of the opinion catbirds are trying to discourage much larger brown thrashers from nesting in that location. Others suggest that catbirds consider thrasher eggs to be a source of food. Who knows?