Acorn Woodpeckers live in close-knit family groups and have one of the most complex breeding systems of any bird in the world. In about 20 percent of family groups, up to 3 related females may lay eggs in the same nest. They raise the chicks cooperatively with one or more related males. This behavior is known as joint nesting or "cooperative polyandry." Only five other species of birds worldwide are known to do this. The reasons that may be driving the behavior are outlined in a study recently published in The American Naturalist.
* This article was originally published here
