Tuesday, October 23, 2012

2012 Harlequin Duck Production

Harlequin Duck brood (c) John Ashley
Female Harlequin Duck (right) follows her six juveniles downstream, in Glacier Nat. Park
By now, most if not all of Glacier's Harlequin Ducks should be sitting on salt water, somewhere out on the Pacific Coast - not that anyone in Glacier is still looking for them.

The sample sizes gets smaller as the Montana summer progresses, but generally the adult males head west in June, soon followed by young females that didn't nest. During August, females who nested unsuccessfully also migrate. And in September, roughly two-thirds of the broods will migrate with their mothers; about one-third of the successful females will also head west, leaving their juveniles behind. Finally, in October, a few juvenile stragglers will be the last to leave Montana's breeding streams and head for the coast. How these juveniles know where to go without adult guidance is still a mystery.

And speaking of mysteries, 2012 was the second of three field seasons for the Harlequin Duck research project ongoing in the upper McDonald Creek drainage, in Glacier National Park. One of the research goals is to locate the ducks' ultra-secretive nest locations. And after two years I can honestly report back that the ducks are kicking our cold and wet butts.

Last year, we attached tiny radio transmitters to 12 females and found two nests. In 2012 we attached transmitters to 13 females and found a grand total of one nest - and those eggs were predated before hatching. But in spite of our human, technological short-comings, the Harlequins did quite well this year.

The 2012 Harlequin high count occurred on the August 8th survey, when a minimum of 34 juveniles in 8 different broods were documented in the drainage. This means that those secretive females managed to hide at least eight successful nests from predators - and from duck biologists as well. So we probably won't be able to meet all of our research objectives but, to a person, we were thrilled to see so many female Harlequins meeting objectives of their own.