Predicting the breeding success of large raptors in arid southern Africa: a first assessment

Abstract

Raptors are often priorities for conservation efforts and breeding success is a target measure for assessing their conservation status. The breeding success of large raptors in arid southern Africa is thought to be higher in years of high rainfall. While this correlation has been found in several studies, it has not yet been shown for data from a wider geographical area. In conservation research, it is important to explore the differences between spatially-separated populations to estimate and to compare their conservation status, and to deduce specific management strategies. Using a theoretical approach, we develop a simplistic model to explain the breeding success-rainfall relationship in large African raptors at larger spatial scales. Secondly, we validate this model and we show that the inclusion of field data leads to consistent predictions. In particular, we recommend that the average size of the ‘effective territory' should be included in the relationship between annual rainfall and breeding success of raptors in arid southern Africa. Accordingly, we suggest that breeding success is a function of precipitation and inter-nest distance. We present a new measure of territory quality depending on rainfall and territory size. We suggest that our model provides a useful first approach to assess breeding success in large raptors of arid southern Africa. However, we strongly emphasise the need to gather more data to further verify our model. A general problem in conservation research is to compare the status of populations assessed in different study areas under changing environmental conditions. Our simplistic approach indicates that this problem can be overcome by using a weighted evaluation of a target measure (i.e. breeding success), taking regional differences into account.

Ostrich 2006, 77(1&2): 22–27