Sunday, October 2, 2011

Harlequin Duck Secrets

Harlequin Duck pair in McDonald Creek, Glacier National Park (c) John Ashley
A pair of Harlequin Ducks on McDonald Creek, in Montana's Glacier National Park.
In Glacier National Park, Harlequin Ducks are twice as rare as grizzly bears. So in the early-1970's, Harlequins were the subject of a three-year study on McDonald Creek in the park. What the researchers soon learned was that these ducks are very secretive nesters, and no Harlequin nests were found.
Twenty years later, surveys for Harlequins were repeated throughout the 1990's by using the same methodology as before, visual surveys and monitoring.  But after working on the creek for 10 breeding seasons, researchers were unable to locate a single Harlequin nest.

This summer - almost 40 years after that first study - a new 3-year research project began on this population of Harlequin Ducks.  By this time, however, technology had improved.  Researchers attached tiny, temporary radio transmitters to a dozen of the females in an attempt to learn where they nested. The transmitters were designed to fall off a few months later.

Armed with the most modern technology, what the researchers have learned so far is this - Harlequin Ducks are still reluctant to reveal their secrets.

Harlequin Duck pairs migrate eastward from the Pacific coast, arriving at their Rocky Mountain breeding streams in mid-April. The new research project on McDonald Creek started in late-April with the capture of fewer than half of the Harlequin pairs. Each bird captured was fitted with an aluminum U.S. Fish and Wildlife Service band on one leg, and the other leg received a plastic band with a unique two-digit code.

With the leg bands, individual ducks can be identified at a distance by using a spotting scope. With the radio transmitters, female harlequins can be tracked to a general area and then visually followed through the scope.

Sounds relatively straight-forward, right?

One of the most interesting discoveries was that, during pre-nesting, Harlequins spent lots of time in backwater beaver ponds, away from the main stream. Swampy, muddy, brushy beaver ponds.

This behavior was reported during the 70's and 90's but was apparently underestimated. That's because visual observations are incredibly difficult in ponds that are overgrown with willows all around the edges. When the duck detects a person in the area, they often just vanish into the willows.

Another interesting discovery this year was the Harlequins' roosting behavior at night.

After dusk, the ducks flew downstream to Lake McDonald (in some cases covering many miles) where they spent the night rafted up in open water. At or just before first light, the Harlequins flew back upstream. By dawn, they were feeding in the same creek sections where they were last seen. You would never know that they had left - if you were only monitoring them visually.

Roosting on lakes at night during the breeding season was interesting behavior, but not totally unexpected.  Harlequins do the same thing out on the coast.  Just after dark, they fly about a mile away from shore and raft up into small groups for the night. At dawn, they're back along the shoreline.

Probably the most unexpected behavior detected - so far - was where the female Harlequins decided to nest.

By following signals from the tiny radio transmitters, the researchers were finally able to locate a grand total of two Harlequin nests.  In spite of many years of previous research, these were the first Harlequin Duck nests officially documented in Montana.

The catch?  Neither nest was located on McDonald Creek, where the females spent their time feeding and raising their broods.

Instead, both nests were found by radio-tracking the two females miles up smaller side streams that feed into McDonald Creek.  And in spite of the new technology, it required a ton of earnest effort over one entire breeding season before the researchers were finally able to find the nests.

Montana's first documented Harlequin Duck nests never would have been found using the old methods of visually following the ducks.  Discovery required radio telemetry, which also revealed glimpses into the harlequins' nighttime roosting behavior and their extensive use of beaver ponds.  It also required a dedicated team of researchers and volunteers just to glean these kernels of insight, which will now be used to protect and conserve these Harlequins.

How's that for holding on to your secrets?

Harlequin Duck brood using a backcountry beaver pond in Glacier National Park, Montana (c) John Ashley
Harlequin Duck brood on a backwater beaver pond in GNP