Natural History and Behavior of the Aldabra Rail (Dryolimnas [Cuvieri] Aldabranus)

Abstract

The Aldabra Rail (Dryolimnas [cuvieri] aldabranus) is endemic to Aldabra Atoll, Seychelles and is the last remaining flightless bird in the tropical western Indian Ocean. We studied it over two breeding seasons from 1999 to 2001. Pairs formed strong bonds, defended territories year-round, and were mate and territory faithful across seasons. Reproductive duties are shared by males and females. Breeding was closely tied to the rainy season and pairs responded to favorable conditions by increasing clutch size and clutch frequency. Clutches contained 1–4 eggs and replacement clutches were laid if nests failed early in the season. The incubation period was 19–24 days and hatching was usually synchronous. Mayfield estimates of daily survival of eggs and nesting success were 98.8% and 77.0%, respectively. Hatching success was 60.9% and 57% of chicks that hatched were successfully reared to independence. Chicks are sub-precocial and fledged chicks were cared for in the natal territory for at least 2 months, after which they were forcibly evicted. A large repertoire of behaviors and ritualized displays are described including pseudo-copulation and reverse mounting.