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Long-tailed Duck Research: Details
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Long-tailed Ducks landing on Nantucket Sound. Photo copyright Dave Larson. |
Background
In late 2001, Cape Wind wind energy project (WEP) was proposed for Horseshoe Shoal in Nantucket Sound (the Sound), and comprehensive environmental review process began almost immediately. During the scoping phase of this project, Mass Audubon and others recommended that the environmental review include comprehensive surveys of avian use of the Sound. One of the focal areas was the use by winter waterfowl of the Sound and the proposed project area in order to gauge the risk of the project to this particular group of birds. Mass Audubon conducted aerial surveys of the Sound during the winter months to supplement studies conducted by the applicant (e.g., Perkins, et al. 2004).
The view from the plane - thousands and thousands of ducks on Nantucket Sound (with closeup inset). Photo copyright Simon Perkins. (See full size image)
The Sound is the winter home of 100,000’s of sea ducks, particularly Long-tailed Duck, all three North American scoters, and Common Eider. For Long-tailed Duck, this wintering congregation also is thought to represent a large, but unknown, fraction of the total North American population of this species and is probably greater than 5% of the global population (del Hoyo, et al. 1992).
The land-based Christmas Bird Count on Nantucket Island, coordinated nationwide by the National Audubon Society, have counted as many as a half million individuals (525,505 in 2002). As the Sea Duck Monitoring Working Group noted in their recommendations for North American waterfowl, nearly every sea duck is inadequately monitored, and accurate estimates of the number of sea ducks in various “stocks” or “management units” are lacking.
The effect of wind turbines and wind energy projects on birds, particularly WEPs constructed offshore, is not well known. Studies of offshore wind facilities in Europe that are slightly smaller than the proposed WEP in Nantucket Sound indicate little direct mortality of sea ducks, but suggest that the turbines can cause behavioral changes such as alteration of offshore habitat use (e.g., Petersen 2005; Tulp et al. 1999); the European studies often had only one year of pre-construction survey data to compare with post-construction “response”. An understanding of the shifting geographic pattern of winter habitat use of sea ducks will improve our ability to understand the ecological significance of post-construction shifts.
The abundance of birds in the Sound indicates a need for a multi-year study to gather reliable baseline data in order to assess the impact of the construction and deployment of this WEP on the avian species that use the Sound for winter habitat.
Methods
Our telemetry methods required several steps: 1) capture of LTDUs, 2) surgical implantation of transmitters, 3) tracking of ducks, 4) mapping of locations of ducks.
1) CAPTURE OF WATERFOWL
Ducks were located from a boat with the use of powerful spotlights as the birds rested on the water at night. When a bright spotlight was trained on ducks in darkness, they became somewhat disoriented, making them easier to approach. Under these conditions, they were captured from the bow of the boat with large, long-handled hoop nets. The capture team consisted of at least one capture person, one assistant, and one boat operator.
2) TRANSMITTER IMPLANTATION
Once the ducks were captured, they were transported to a local veterinary clinic (MSPCA Animal Care and Adoption Center, 21 Crooked Lane, Nantucket, MA), where Dr. Glenn Olsen, USFWS veterinarian, and Scott Ford, DVM, performed surgical implantation of transmitters into each of the ducks. Implantation (vs. an external harness) was necessary to prevent abnormal behavior that has been observed with other diving ducks rigged with external loop harnesses (see Perry et al. 2004 for more information on sea duck telemetry). Following surgery, the ducks were kept for observation for at least one day and then released during morning hours.
3) TRACKING/LOCATING
Transmitters also provide information on the accuracy of the satellite fix and the internal body temperature of the instrumented ducks. The temperature data allowed us to determine whether the duck was still alive. If the internal body temperature of the duck dropped suddenly, indicating that the duck had died, the transmitter automatically switched to a “Ground Track” mode that enabled us to relocate the duck and its transmitter. We used this function successfully to relocate and reuse several transmitters.
4) LOCATION MAPPING
Geographical and diagnostic data (e.g., internal body temperature) were downloaded weekly from the Argos web site. Mass Audubon staff plotted the geographical coordinates of each duck using ArcGIS software to create distribution maps of the birds on a regular basis.
Results
Through the first two field seasons, twenty-one Long-tailed Ducks were instrumented with Satellite transmitters and from these we plotted more than 1500 geographic fixes. The following transmitters each provided a minimum of 65 accurate fixes.
2007-08- Season #1
2008-09- Season #2
(“Rush Hour” is period around sunrise and sunset during which most ducks are “commuting” between the Nantucket Sound and Nantucket Shoals)
Our data addressed several questions about LTDU distribution around Nantucket. These conclusions are presented briefly below:
- There is no direct evidence that LTDUs used Horseshoe Shoals as a nighttime roosting site (Figure 1 and Figure 9).
- Individual ducks may have a “preference” for certain regions at night, but collectively the ducks appear to use mainly the southeastern quadrant of Nantucket Sound, in an area bounded by Nantucket and Tuckernuck Islands to the south and Tuckernuck Shoals to the north.
- The location data provide no evidence of major nighttime concentrations of ducks. Rather, the roosting ducks appear to be rather widely dispersed within the area described above.
- Not all LTDUs commute on a regular basis. Some ducks rarely if ever make the commute (Figure 4 and Figure 5), and in some cases may remain in a small area around Nantucket, Tuckernuck, or Muskeget Islands for most of the winter (Figure 2 and Figure 5). More typically, however, individual ducks frequently change their daytime and nighttime locations- either within a single day or night, or over the course of several days.
- It is hypothesized that LTDUs commute to Nantucket Shoals to feed during the day and return to the shelter of Nantucket Sound at night, but it appears that LTDUs will also occasionally spend the night offshore on Nantucket Shoals.
Eleven instrumented ducks survived the first two winter seasons (six in season 1 and five in season 2). The ducks departed Nantucket Sound in April each year, and spent the summers of 2008 and 2009 in areas north of Hudson Bay, Canada, presumably on their breeding grounds. In both years, their spring migration routes took them via the Gaspe Peninsula, Quebec, and Hudson Bay (Figure 8 and Figure 18).
Two ducks returned to Nantucket in the fall of 2008 and one of these continued to provide fixes for another full winter season before the battery finally lost power in April 2009. A comparison between this bird’s two winter seasons reveals that it behaved very differently: in its first winter it rarely commuted between the Sound and Nantucket Shoals, whereas in its second season, it commuted often (Figure 12). Three ducks returned from the Arctic to Nantucket in the fall of 2009, and two of these continued to provide location data into winter 2010.
Our successes during the first two winters led to our continuing the telemetry study for a third season. In November 2009, we instrumented an additional 10 ducks, which brought the total number of instrumented ducks to thirty-one (10 in 2007, 11 in 2008, and 10 in 2009).
In partnership with the Biology Department of Boston University we are also conducting DNA analyses of instrumented ducks to determine whether LTDU breeding populations can be delineated to specific geographic areas, and if so, what populations are represented by the hundreds of thousands of LTDUs wintering around Nantucket.
Literature Cited:
del Hoyo, J. A. Elliott, and J. Sargatal. 1992. Handbook of the Birds of the World. Vol. 1. Lynx Edicions, Barcelona, 696 pages.
Everaert, J. 2003. Wind Turbines and birds in Flanders: Preliminary study results and recommendations. Natuur. Oriolus 69(4): 145-155.
Janss, G. 2000. Bird behavior in and near a wind farm at Tarifa, Spain: Management Considerations. In: Proceedings of the National Avian-Wind Power Planning Meeting III, pp. 110-114, http://www.nrel.gov.
Langston, R. H. W. and J. D. Pullan. 2002. Wind farms and birds: an analysis of the effects of wind farms on birds, and guidance on environmental assessment criteria and site selection issues. BirdLife International and the Bern Convention, 38 pages
North American Waterfowl Management Plan (NAWMP). 1998. Expanding the Vision. 1998 Update. United States Department of Interior, SEMARNAP Mexico, and Environment Canada, 43 pages.
Orloff, S. and A. Flannery. 1992. Wind turbine effects on avian activity, habitat use, and mortality in Altamont Pass and Solano County Wind Resource Areas 1989-1991. Biosystems Analysis Inc. California Energy Commission, 160 pages.
Perkins, S., G. Sadoti, T. Allison, and A. Jones. 2004. Relative waterfowl abundance within Nantucket Sound, Massachusetts during the 2003-2004 winter season. Final report. Massachusetts Audubon Society, Lincoln, MA. 24 pp. http://www.massaudubon.org/PDF/advocacy/2003_2004Seaducks.pdf
Perry M.C, E.J.R. Lohnes, A. M. Wells, P. C. Osenton, and D. M. Kidwell. 2004. Atlantic Seaduck Project, USGS Patuxent Wildlife Research Center, Laurel, MD.
http://www.pwrc.usgs.gov/resshow/perry/scoters/default.htm
Petersen, I. K. 2005. Bird numbers and distributions in the Horns Rev offshore wind farm area Subtitle: Annual status report 2004. National Environmental Research Institute Ministry of Environment, 38 pp.
Sea Duck Joint Venture. 2005. Recommendations for monitoring North American sea duck populations. August 2005. Available at http://seaduckjv.org or U. S. Fish and Wildlife Service, Anchorage, Alaska or Canadian Wildlife Service, Sackville, New Brunswick.
Thelander, C. G. and Rugge, L. 2000. Avian risk behavior and fatalities at the Altamont wind resource area. National Renewable Energy Laboratory Report, 28 pages.
Tulp, I. H. Schekkerman, J. K. Larsen, J. van der Winden, R. J. W. van de Haterd, P. van Horssen, S. Dirksen, and A. L. Spaans. 1999. Nocturnal flight activity of sea ducks near the windfarm Tuno Knob in the Kattegat. IBN-DLO Report No. 99, 30 pages.
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