European Bee-eater (Merops apiaster) Science Article 1
This example of bigamy is interesting, because it does not fit with current hypotheses about the adaptive value of polygyny. Orians (1969) argued that females may sometimes gain by being the second female on a good territory rather than a lone female on a poor territory, and Pleszczynska (1978) was able to manipulate territory quality to produce polygyny.
M. I. Avery, J. R. Krebs, and R. E. Hegner, Auk, Vol. 101: 609-610