Golden Eagles are one of the main predators of grouse on the lek. Although we’ve only seen a handful of successful attacks, a fairly large proportion of “flushes” (i.e. rapid departures of most or all of the males on the lek) seem to be due to an eagle passing by or attacking the lek. We’ve had a string of such events on Chugwater recently. Very exciting for us, although frustrating when we aren’t able to do an experiment because the birds have all left!

Andrea Aspbury and colleagues studied lek placement and hypothesized that leks form in spots where grouse will be more able to detect approaching eagles. In their analysis, they found the placement of these traditional display grounds balance the need to force eagles to approach from the air (where they are more visible) and the need to make displaying males as conspicuous as possible to prospecting females.