Breeding cycle of Indian house crow (corvus splendens) and efficacy of special traps in population control in Tanzania

The Indian House Crow (IHC) (Corvus splendens) belongs to the Corvidae family; native to the Indian subcontinent but invasive to other countries especially in Asian and African coast. IHCs were introduced in Zanzibar (Tanzania) in 1890s where they later became pest and invasive. Their negative socioeconomic and ecological impacts have necessitated many countries to instate control programs, using mostly trapping. However, the efficacy of trapping is not well established in many countries. It is however, hypothesised that control programs could be enhanced by understanding IHC breeding cycle. To ascertain this, a total of 716 IHCs from ‘crow traps’ in Dar es Salaam were euthanized by chloroform in the Zoology Laboratory, University of Dar es Salaam from August 2013 to July 2014. All birds were dissected to establish sex and gonads were weighed (g) on Mettler balance AE 100 to establish Gonadosomatic Index (GSI). Before dissection, morphometric measurements were taken including weight (g) and length (mm). Age of each crow was determined based on palate colour. Mean, standard deviation and range for each morphometric measurement were calculated using univariate statistics. Discriminant statistical analyses were conducted to find out morphometric character which could be used to discriminate sex of IHC. Mean adult GSI peaked from October to December suggesting a breeding season. Subadults were more trapped than young (q = 8.170, p<0.001) and adults (q = 6.307, p<0.001), while there were no significant differences between young and adult numbers captured in traps (q = 1.863, p>0.05). There were also no significant differences between female and male IHCs numbers trapped (t =1.78, p = 0.09). All morphometric measures were significantly higher in males than females but beak length was a more influential discriminant character for sexing IHC. This study recommends IHCs control efforts to be intensified from October to December which is a noticeable breeding season particularly in Dar es Salaam. ‘Crow traps’ seems to be of efficacy as it removes most of the subadults that would potentially contribute very much to the IHCs population growth.