First Description of Nesting Behavior of a Same-Sex Pair of Whooping Cranes (Grus americana) in the Reintroduced Eastern Migratory Population

Abstract

Accounts of same-sex nesting behaviors have been observed in several wild and captive bird species, but the evolutionary adaptation of this behavior remains unclear. There have been reports of male-male and female-female territorial pairs of Whooping Cranes (Grus americana) in two reintroduced populations. However, this is the first documentation of nesting behavior of a same-sex pair of Whooping Cranes. The incubation rhythm and nesting behaviors of a female-female Whooping Crane pair nesting at McMillan Marsh Wildlife Area in Marathon County, Wisconsin, USA, were documented using a nest camera. The female-female pair displayed comparable nest constancy (99.7%) and incubation behaviors to male-female Whooping Crane pairs in the same population. Both females of the pair incubated the nest; however, the older female incubated for longer periods of time than the younger female (235.8 ± 20.7 min and 168.3 ± 17.2 min, respectively). The pair exchanged incubation duties 5.7 ± 0.2 and 1.1 ± 0.2 times daily during daylight hours and nighttime hours, respectively. The two females incubated the nest for at least 28 days, but fate of the eggs was not determined. Ultimately, the cause of this pairing remains unknown. This behavior could have implications for the breeding success of this small, reintroduced population of Whooping Cranes.