Gonadosomatic index infers the breeding season of the House Crow Corvus splendens in Dar es Salaam, Tanzania

Abstract

The House Crow Corvus splendens is native to the Indian subcontinent but also has a broad invasive range which includes the coast of East Africa. House Crows (HC and HCs throughout this paper) were introduced in Zanzibar in the 1890s from where they later spread to mainland Tanzania. Their negative socioeconomic and ecological impacts have necessitated the instigation of population control programmes using avicides and trapping. Although knowledge on the reproductive biology of HCs, in particular the breeding status, is important for successful control programmes, little is known about it in Dar es Salaam. To establish the HC breeding status, a total of 83 female and 100 male birds were collected from August 2013 to July 2014 from traps operated by the Ministry of Natural Resources and Tourism population control programme. All birds were euthanized, dissected, and sex determined by gonad examination. The gonadosomatic index (GSI) was determined as the ratio of gonad weight upon total body weight. The GSI, which is an index of gonad development relative to the bird’s sexual maturation, peaked from October to December suggesting that this period is the main breeding season. The HC population control could be intensified during the onset of gonad development when the demand for resources is high.

Keywords: breeding season, gonadosomatic index, House Crow, Dar es Salaam