1. Partridge, L. & Halliday, T. in Behavioural Ecology: An Evolutionary Approach 2nd edn (eds Krebs, J. R. & Davies, N. B.) 222–250 (Blackwell, Oxford, 1984).
2. Parker, G. A. in Mate Choice (ed. Bateson, P.) 141–164 (Cambridge University Press, Cambridge, 1983).
3. Halliday, T. R. in Behavioural Ecology: An Evolutionary Approach (eds Krebs, J. R. & Davies, N. B.) 180–213 (Sinauer, Sunderland, Massachusetts, 1978).
4. Fellers, G. M. Anim. Behav. 27, 107–119 (1979).
5. Arak, A. Nature 306, 261–262 (1983).