Reproductive Ecology of Sharp-Tailed Grouse on the Pine Barrens of Northwestern Wisconsin
File(s)
Date
2001-04Author
Connolly, Timothy T.
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
Metadata
Show full item recordAbstract
Sharp-tailed grouse were once abundant throughout Wisconsin, but only a few
isolated populations presently exist due to the loss of early successional habitat they
require. Most populations are found on savanna reserves managed for sharp-tailed
grouse or recent large clearcut areas of industrial and public forestland in the
northwestern part of the state. Populations on large clearcuts are of high numbers and
densities, but on some managed savanna reserves numbers and densities are low. I
studied nesting success, hen survival, chick survival and production, and vegetation and
habitat characteristics associated with nest site selection and nesting success on 6 study
sites in northwestern Wisconsin. Study sites were classified as a managed landscape or
unmanaged landscape.
Nesting success (P = 0.015) and hen survival during the reproductive period (P =
0.035) and entire study period (P = 0.045) were significantly greater on unmanaged
landscapes than managed landscapes. Chick survival (P = 0.11) and production (P =
0.47) were not significantly different between landscape types. Predation of brood hens
accounted for the loss of most broods on managed landscapes, but adverse weather
during the early brood period was suspected as the primary cause of brood losses on
unmanaged landscapes. Large clearcut areas in northwestern Wisconsin may have higher
numbers and densities of sharp-tailed grouse than managed savanna reserves due to
higher nesting success and hen survival.
Vegetation and habitat characteristics were examined at 3 scales: landscape, small
scale, and microhabitat. On managed landscapes, hens preferred adjacent clearcut areas
for nesting habitat to managed savanna reserves (P = 0.001). Hens selected nest sites in
areas with greater fragmentation (P = 0.014) and further from tall trees (P = 0.001) at the
landscape scale. Coniferous tree cover (P = 0.043), heath-type cover (P = 0.010), and
deciduous woody cover (P = 0.016) were positively correlated with nest site selection at
the small scale, and forb cover (P = 0.078) and non-woody and heath-type vegetation
height (P = 0.011) were negatively correlated. Microhabitat vegetation characteristics
positively associated with nest site selection were grass cover at the nest bowl (P =
0.007), coniferous tree cover (P = 0.021), heath-type cover (P = 0.091), and deciduous
woody cover (P = 0.016). Grass cover near the nest (P = 0.049) and woody vegetation
height (P = 0.017) were negatively correlated with nest site selection.
Hens on unmanaged landscapes selected nest sites in areas of lower fragmentation
(P = 0.002) and closer to forest edges (P = 0.013) at the landscape scale. Raspberry cover
(P = 0.003) and heath-type cover (P = 0.017) positively influenced nest site selection at
the small scale, but forb cover (P = 0.014) and non-woody and heath-type vegetation
height (P < 0.001) were negative influences. Grass cover (P = 0.015) and grass height (P
= 0.002) at the nest bowl, coniferous tree cover (P = 0.003), visual obstruction
measurements (P = 0.018) and height of non-woody and heath-type vegetation (P =
0.013) were microhabitat vegetation characteristics positively associated with nest site
selection. Grass cover (P = 0.031) near the nest was negatively correlated with nest site
selection.
On managed landscapes, nests nearer to tall trees (P = 0.074) were less successful.
At the microhabitat scale, deciduous woody cover (P = 0.057), and grass cover (P =
0.092) near nests were negatively correlated with nesting success. Height of non-woody
and heath-type vegetation (P = 0.079) at the small scale was negatively correlated with
nesting success on unmanaged landscapes.
Nesting success was significantly greater on unmanaged landscapes than managed
landscapes, but was not different between adjacent clearcut areas and managed savanna
reserves on managed landscapes (P = 0.78). Fragmentation at the landscape scale may
influence nesting success through nest site selection, and woody vegetation may
influence nesting success on managed landscapes through nest density and distribution.
Lengthening prescribed burning rotations on managed landscapes may increase preferred
nesting habitat and nesting success on managed landscapes, but landscape scale
management utilizing clearcut habitat is necessary to maintain populations of sharp-tailed
grouse into Wisconsin's future.