Key points are not available for this paper at this time.
Kevin J. Gaston, Tim M. Blackburn, Global Scale Macroecology: Interactions between Population Size, Geographic Range Size and Body Size in the Anseriformes, Journal of Animal Ecology, Vol. 65, No. 6 (Nov., 1996), pp. 701-714
Gaston et al. (Fri,) studied this question.