Date: September 7, 2016
Source: Central Ornithology Publication Office
"Survival of the fittest" usually means that animals put their own needs first, but occasionally it pays to work together. A new study in The Auk: Ornithological Advances describes an unusual example of cooperative breeding in an introduced pheasant population in Hawaii, where young males help care for chicks and defend against intruders rather than striking out on their own.
Cooperative breeding, where members of a social group provide care to young that are not their own offspring, is rare in "precocial" bird species like pheasants -- those where chicks are already well-developed when they hatch and don't require intense parental effort. However, Lijin Zeng of the University of California-Riverside and her colleagues have discovered that cooperative breeding is the norm among Kalij Pheasants in Hawaii's Volcanoes National Park. While females incubate their eggs alone, all group members, including up to six males as well as the breeding female, feed the chicks after they hatch and defend the group against intruders. Dominant males father the most chicks, but almost a third are fathered by subordinate males within the same group or males from other groups.
This is only the third time cooperative breeding has been observed in the pheasant family, and Kalij Pheasants, introduced in Hawaii in the 1960s, are not known to breed cooperatively in their native range in Asia. Possibly due to a lack of predation and disease, their population density in Volcanoes National Park has grown very high, and overcrowding may prevent young males from being able to establish their own territories. Instead, their best hope to pass on their genes is to stay with the group and wait to move up in the dominance hierarchy, fathering a few chicks in the meantime.