Factors Influencing Harlequin Duck Survival and Recruitment in Glacier National Park

Hansen, Warren

The objective of this project is to study life strategies of Harlequin Ducks in Glacier National Park over a two-year period by examining a range of possible factors influencing survival and recruitment. Through the use of radio-telemetry, we will greatly expand our knowledge of where Harlequins nest, the factors affecting their nest success, and the factors affecting chick survival. The year 2011 marked the beginning of a 2.5 year research project on harlequin ducks in the park. Warren Hansen, the graduate student on the project, is currently researching several aspects of the duck's life history and ecology along Upper McDonald Creek (UMC) as the main focus of his Masters of Science thesis. He is enrolled at the University of Montana (UM) with Creagh Breuner as his major professor.With a team of NPS employees, researchers and volunteers we successfully banded a total of 47 ducks in 2011: 18 females, 15 males,and 14 juveniles. Radio transmitters were attached to 12 breeding females to aid in locating their nests. Two nests were found. One was located upstream on Snyder Creek, the other was on Hidden Creek; neither successfully fledged chicks. Two other nests were probable based on female behavior, but both of these were thought to have been flooded. A fifth nest was never found although we knew the female was incubating. In late August, we successfully recaptured her. She had six chicks, all of which we banded.With the use of telemetry we have learned that although many females use UMC initially upon their return in the spring, some of them retreat to smaller tributaries to nest. In addition, we have learned that harlequins travel to Lake McDonald to roost on the open water at night, returning to UMC at first light. Presumably, they make this daily trip to avoid predation at night.Trapping and banding is scheduled to begin again the last week of April 2012. We have 12 more radios to attach to females and the same veterinarian, Dan Savage, will attach the radios in 2012. No ducks were lost or injured due to our trapping, banding, and telemetry efforts in 2011. One female retained her radio long enough to migrate and was observed off Puget Sound in Washington in September for over a week diving, preening, and roosting with the flock.In addition to our banding and telemetry efforts, we conducted 13 standard harlequin duck surveys along the 15.6 km stretch of UMC between Lake McDonald and Logan Creek from 26 April and 23 September 2011. Over the course of 13 surveys, the total number of harlequins observed during a single survey ranged from 3 to 42 ducks. Pair surveys (one male, one female) began 26 April and ended7 June. During six pair surveys we detected a total of 51 harlequin duck pairs. The high count for pairs occurred on May 18 with 15 pairs detected. The high count for individuals was 42 and occurred on the same date. This was significantly higher than the historic average kept since 1991. Brood surveys (female with young) began 22 July and ended 23 September. The high count for broods occurred on September 7 with four broods and 10 chicks detected. This is the same as the 20 year average. Overall, we observed 15 chicks during standard surveys.More than 25% of all Harlequin Duck chicks produced in Montana are raised along the 9.7-mile stretch of McDonald Creek from Lake McDonald to Logan Creek, in Glacier NP, making Upper McDonald Creek (UMC) one of the most significant Harlequin breeding streams in Montana (Montana Natural Heritage Program 2010). In 2010, however, we failed to detect any chicks. All female Harlequin Ducks born on UMC subsequently return to nest there once they reach breeding age. Although systematic stream surveys have been conducted along UMC since 1991, only one Harlequin nest has ever been found in the park due to the secretive behavior and cryptic coloring of these birds.