Our data addressed several questions about long-tailed duck distribution around Nantucket Sound, and revealed no direct evidence that long-tailed ducks used Horseshoe Shoals as a nighttime roosting site or regularly spent time there during daylight hours. Several breeding areas north of Hudson Bay were identified, as were migratory stopover sites.
Some of the specific findings from the study included:
- Many ducks exhibited local movements between roosting and foraging sites, but ducks apparently do not commute every day.
- Tracked birds appeared to use a large area of the Sound for nighttime roosting sites, and roosting locations often changed.
- Horseshoe Shoal does not appear to be a major nighttime roosting site for long-tailed ducks. No satellite-tracked ducks were observed on the Shoal–day or night. Long-tailed ducks were observed on the Shoal during daytime aerial surveys, but numbers were quite small relative to their overall abundance.
- Satellite-tracked long-tailed ducks consistently used the same spring staging area locations in the mouth of the St. Lawrence River. Limited data suggest these same areas are used as stopovers during the fall migration, but perhaps not consistently.
- Long-tailed ducks wintering in Nantucket Sound appear to breed in a relatively confined geographic area in northern Canada that includes eastern Nunavut and northwestern Quebec provinces.
- Long-tailed ducks arrive on their winter range by mid-November, depart for their breeding areas by mid-April, and reach breeding areas by the end of June. They subsequently depart their breeding areas for their winter range by early October.
- Long-tailed ducks take about two months to travel from the winter range to their summer range, including the stopover at staging areas. The return from summer to winter range takes about one month. The stay on the winter range lasts for five and one-half months, and the stay on the summer range lasts for approximately three and one-half months.
- Preliminary analyses suggested little or no genetic structuring of long-tailed duck populations. Birds from Nantucket Sound, Russia, Alaska, and Nunavut share a high level genetic diversity, reflecting historically large population sizes and ongoing gene flow among populations. Given this lack of structure on a continental scale, it is unlikely that birds from different breeding populations wintering together in Nantucket can be discriminated on the basis of genetic data.