Lu X. & Zheng G.M. (2005) Cooperative young-caring behaviour in a hybrid population of White and Tibetan Eared-pheasants in Tibet. ARDEA 93 (1): 17-24

In the mountains of eastern Tibet lives a wild population of hybrids between White Eared-pheasants Crossoptilon crossoptilon and Tibetan Eared-pheasants C. harmani. We studied the social behaviour of this locally dominant galliform, living in oak and juniper forests on high mountains and deep canyon slopes. When winter flocks broke up early in the breeding season, adult males and females established monogamous mating bonds. Non-breeders either stayed solitarily, joined with other non-breeders or associated with a pair. Females incubated the eggs alone. Breeding males were never observed guarding the nests, but instead joined the flocks of non-breeders. A post-hatching social unit included either one single brood, or several (mixed) broods. Mixed-brood units were only encountered late in the season, and probably resulted from the aggregation of several single-brood units. Out of 13 observed single-brood units, one was accompanied by the female parent only, four by two parents, and another eight by two parents plus non-parent individuals. Each of the six mixed-brood units included a pair and other (sub)adult individuals. In multi-member brood units, often more than one adult and subadult male fed the chicks. We conclude that as young grew up, the separate brood units tended to merge and both parents and non-parent birds cooperatively cared for the young. The cooperative brood care in this species, which represents a rare example of cooperative breeding in a socially monogamous species, may be linked with the association of male breeders and non-breeders during the female incubation period.