Northern Prairie Wildlife Research Center
Prairie chickens spend over half their life on a roost, especially
in the North with extended winter nights. Roosting sites must provide a measure
of protection from weather but, more importantly, safety from predators. The
latter could involve preventing detection from predators and sites which facilitate
escape from predators in case of detection. On occasion, Svedarsky has flushed
roosting coveys of gray partridge off snow-free gravel roads in the winter
when snow covered the remaining landscape. Certainly, an elevated roadway
is one of the most climatically exposed sites available, but it was initially
thought that their clumped form was a rock and perhaps a great horned owl
would as well! Roosting cover is critical year-round, but perhaps more so
in the winter when it is closely tied to food resources.
Roost sites should be accessible to adequate winter food resources in order
to minimize movements which utilize energy and increase exposure to predators.
Burger (1988:88) noted for Missouri: "Our observations suggest that prairie-chickens
select optimal winter roosting habitat, then make daily feeding movements
radiating as far out from this habitat as necessary to meet energetic demands."
This suggests that roosting habitat may be more of a limited resource than
food in more snow-free areas. Farther north, food may be more limiting, but
still needs to be close to night roosts. For Wisconsin, Schmidt (1936:197)
said, "Food determines what range is habitable in winter, but so does
cover, particularly roost cover." Hamerstrom et al. (1957) believed winter
cover was not limiting since when the herbaceous vegetation got covered with
snow, birds used woody cover (fairly abundant in the Wisconsin prairie chicken
range). In a photo caption (page 57) they noted, "Here bluegrass is (matted)
down, under ten inches of snow, but sedges, quack, timothy and Muhlenbergia
still give roosting cover." Later, using radio-tagged birds, Toepfer
(1988) found 57.1% of 175 winter roosts in "wetland" habitat in
western Wisconsin and 51.8% of 307 locations in "wetland/shrub"
habitats in central Wisconsin.
Manske and Barker (1988) identified the following as winter roosting habitats
at the SNG based on observations of prairie grouse (sharptails and prairie
chickens) roost sites: switchgrass portion of midland community, shelterbelts
and other woody vegetation along cropland edges, and snow when it became >30
cm deep in drifts along shelterbelts and the lee side of hummocks. Toepfer
and Eng (1988) following 20 radio-tagged prairie chickens at the SNG, found
64.0% of 525 night locations in lowland grass and shrubs, followed
by reed canary grass (13.7%), shrubs (11.8%), midland grasses - primarily
little bluestem (7.4%), and quackgrass (7.1%). Manske and Barker (1988) recorded
no winter night roost sites in the "Lowland Grassland" habitat type.
Predator avoidance strategies?
While lowlands tend to support taller vegetation than more upland
areas, there may be advantages in predator avoidance as well. Gratson (1988)
suggested that canid predators likely spend comparatively less time hunting
small mammals in lowlands thus reducing chances of happening on to roosting
prairie grouse. He also suggested that there tend to be fewer trees in wetlands
which could serve as hunting perches for great horned owls, an important nocturnal
and crepuscular predator. Gratson found the greatest preference for lowland
roosting for sharptailed grouse in Wisconsin when birds were snow-burrowing.
This would negate any possible thermal advantages of roosting there compared
to upland sites assuming that snow was equally available in all sites. Gratson
also discussed the possible predator avoidance strategy of birds changing
roost sites often since predators may return to sites of previous prey captures.
Toepfer and Eng (1988) found the average distance between successive
night locations was 922 m (.6 mile), indicating that prairie chickens shift
In northwest Minnesota, Rosenquist and Toepfer (1995) found several habitats
used for roosts but areas with forbs, especially alfalfa and goldenrod, appeared
to provide the best snow burrowing conditions. CRP lands with brome and alfalfa
were used when snow conditions permitted burrowing. Native prairie was used
little due to snow packing and willow areas received little direct use but
the associated herbaceous vegetation within willow complexes was often used
since it tended to accumulate snow providing good burrowing conditions. Birds
rarely roosted under willow branches but, on one occasion, a roosting bird
was apparently depredated when it flushed up into willow branches from a snow
burrow (Eric Rosenquist, personal commun.).
While a snow burrow is ordinarily a good place to roost, it can be disastrous
if extreme conditions cause hard crusting. Lindsay (1967) recounted that in
the winter of 1932-33 in northern Wisconsin, west of Hurley, a mild day with
a misty rain was followed by extreme cold (perhaps down to -40o). The snow
crusted over hard enough to support a horse in many areas. Prairie chickens
had been common in the area but at once became scarce. Several residents found
dead birds under the snow and more after the snow began to melt in the spring.
Lindsay (1967:25) believed: "From my own observations, we must have lost
the entire prairie chicken population of that area at that time. I haven't
seen a chicken in Iron County since."
What constitutes "good" winter roosting cover?
Toepfer and Eng (1988) at the SNG found over 85% of the winter night
locations in cover class III and over (>25 cm). VOR's for 32 vegetation
roosts averaged 2.1 dm. Manske and Barker (1988) did not separate data for
winter roosts but found an average VOR for night roosts throughout the year
of 1.9 dm (range: 1.5-2.2 dm). From these data, they concluded, "1.5
dm is the minimum level for good night roost habitat" Manske
and Barker (1988:18). If one considered the midpoint of a range or a mean
to indicate "good", an alternate view would be to average Toepfer
and Eng's average of 2.1 dm for vegetation sites with Manske and Barker's
overall average of 1.9 which would yield 2.0 dm as a standard of "good"
winter roosting cover. This would not include considerations of snow burrowing
but, for monitoring purposes, (McCarthy et al. 1995a) only vegetation characteristics
Roosting cover in the snow-free period
McKee (1995) collected roost data from all seasons in Missouri and
found an average VOR of about 20.4 cm (range 10-35) but no pattern of site
selection was apparent. In Colorado, Schroeder and Braun (1992:16) indicated
that, "Roosting typically occurred in mid and tall vegetation in relatively
dense grassland areas in all seasons" but presented no quantitative data.
For Oklahoma, Jones (1963) noted the following vegetation heights used for night roosts by season: winter - 13 cm, spring - 4 cm, summer - 32 cm, and fall - 5 cm. These values are perhaps biased towards shorter cover since Jones was not working with radio-tagged birds and roost forms are more difficult to locate in heavier cover. Toepfer (1988), following radio-tagged prairie chickens in Wisconsin, found vegetation shorter than 25 cm was regularly used during the day but not for night roosting when about 90% of locations were in cover >25 cm. "Grass/Forbs" were a major habitat used in all 4 seasons in central Wisconsin followed by "upland grass" (Table 5). At Crex Meadows, in western Wisconsin, "edge" was a major habitat used, followed by "wetland."
a Number of locations.