Nature seems to be on a streak of articles about brood parasitism, in this case intraspecific. Last week's issue reports recent results from Bruce Lyon's work with American Coots (Fulica americana) in Riske Creek, B.C.

Coots are indeterminate layers, like domestic chickens; that is, they will continue laying even if eggs are removed from the nest until they reach the "right" number of eggs. Their eggs are speckled with brown, but vary considerably in ground color. The variability is sufficient that often a parasitized female can distinguish her own eggs from those laid by another bird. Her usual defense is to bury the suspected egg, but only after a few days.

The surprising finding of this paper is that the hen can adjust her clutch size while the parasitic eggs are still present, before she has buried them. In other words, in a nest with distinguishable parasite eggs, she can "count" the number of eggs that are hers and continue laying. Only then does she reject the intruders.

posted: 11:33:17 PM