Co-operative breeding

Genetic parents found in 220 species of birds and 120 species of mammals. Approx. 3.2% of birds, 12% of all Australian species. Help for kin selection. Hamilton’s principle genetic relatedness times additional benefit must outweigh cost. May be used as practice, to gain future mates by proving ability to parent when unsuccessful in mating that season, may be due to limited resources to colonies take turns, may be sneakers who are secretly genetic parent.