This indicator tracks population numbers of willow ptarmigan and three species of grouse: spruce grouse, sharp-tailed grouse, and ruffed grouse. These are all major prey species in NWT tundra and taiga ecosystems.
Willow ptarmigan nest on the tundra, and perform a mini migration to just below the treeline – on the taiga – every winter. Other species of ptarmigan occur in the NWT but are not part of this indicator: spruce grouse are present year-round in forested parts of the NWT. They are most numerous in coniferous forests. Ruffed grouse and sharp-tailed grouse are also year-round residents and are most numerous in the taiga plains, mostly in deciduous forests as far north as the Sahtu.
The information for this indicator is obtained from the Christmas Bird Count (CBC)1 a volunteer-based program with count sites across North America, including in the NWT, and from the NWT Resident Hunter Survey.
This indicator offers insight into changes in small-sized prey populations in NWT ecosystems. Grouse numbers do not cycle everywhere in their range in North America. Cycles of about 10 years are recorded only in populations in the NWT, as well as other northern populations in Yukon and Alaska2. Tracking cycles in ptarmigan and grouse populations in NWT ecozones, and comparing these to other 10-year cycles such as snowshoe hare cycles (see Trends in small mammals and hares in NWT ecosystems), help increase our understanding of annual changes in the availability of medium-sized prey species, and changes in behaviour, dispersal, and productivity of NWT’s predator species.
Current view: status and trend
All ptarmigan and grouse species tracked in the NWT show large fluctuations in numbers. Willow ptarmigan numbers seem to fluctuate every 10 years or so. Numbers were high around 1985, 1996-1997 and 2006-2007. This 10-year cycle is most apparent in the 30-year data set from the CBC in Yellowknife. This cycle is also reflected in the hunting success of NWT resident hunters.
A similar cycle in hunting success for spruce grouse is detected. Ruffed grouse and sharp-tailed grouse were apparently syncronized with willow ptarmigan in the 1990s but the data from the NWT Resident Hunter Survey has not detected any large increase in hunting success since then. It is unclear why this is occurring.
Large-scale synchronized population fluctuations suggest ecosystem-level causes may be at work, such as climatic fluctuations3 or changes in predator numbers linked to changes in other prey species such as snowshoe hares2. These hypotheses still require study. In the NWT, ptarmigan and grouse numbers started to peak during the decadal low in hare numbers (1995, 2005: see Trends in small mammals and hares in NWT ecosystems) then declined sharply during the year when hare also declined. Why this occurs is unknown. There is little NWT data to track the effects of these large fluctuations on most predator numbers.
If the current pattern continues, the next peak in population numbers for grouse and ptarmigan should occur around 2016-2017. Differences in the timing of peak numbers of ptarmigan and grouse in different regions of the NWT may be tracked as more information is gathered using the CBC, hunter surveys, and local knowledge.
Cycles in numbers every 10 years have been noted for willow ptarmigan, spruce grouse, and ruffed grouse in Yukon2, for spruce grouse in Alaska2, and for rock ptarmigan in Norway. In Yukon, numbers of grouse increased slightly before (1-2 years) peaks in snowshoe hares2. In the NWT, both grouse and ptarmigan numbers peaked in the middle of the lows in snowshoe hare populations. These regional differences remain unexplained.
Find out more
Other focal points
- See NATURAL CLIMATE FLUCTUATIONS and CLIMATE AND WEATHER for indicators on weather-climate events that may drive or influence population cycles in northern species.
- More information on the resident hunter survey can be found in references below.
- Raw data from the CBC can be downloaded from the Christmas Bird Count.
- Raw data from the resident hunter survey are available under request from ENR.
Ref. 1. National Audubon Society. 2008. Christmas Bird Count.
Ref. 2. Krebs,C.J., S. Boutin, and R. Boonstra. 2001. Ecosystem Dynamics of the Boreal Forest - The Kluane Project. Oxford University Press. 511pp.
Ref. 3. Stenseth N. C. et al.2002. Ecological Effects of Climate Fluctuations. Science 297:1292-1296
Updated: June 9, 2015