Some birds are known to nest alone when conditions are suitable, but not somtimes. The white-winged dove of southwestern North America was known to nest in large colonies when foraging areas could support such numbers. In 1978, in Tamaulipas, Mexico, researchers counted 22 breeding colonies of white-winged doves with a collective population size of more than eight million birds. But as habitat was transformed through urbanization or agriculture, the doves apparently spread out into smaller, less long-lived colonies. Today, these doves are observed to nest singlyin both urban and not urban areas.