Do Sharp-Tailed Grouse Select Loafing Sites to Avoid Visual or Olfactory Predators?

ABSTRACT Grouse should seek loafing sites hidden from predators; however, good hiding sites from predators that use vision to locate prey differ from good hiding sites from predators that use odor to locate prey. We compared characteristics of control sites to sites used for loafing by sharp-tailed grouse (Tympanuchus phasianellus) to determine whether selection of loafing sites was more influenced by the need to hide from visual or olfactory predators. Sites used for loafing were similar to control sites in characteristics that would help hide a grouse from visual predators (i.e., visual obstruction, lateral visibility, visual obstruction, cover ht, and surface roughness), but loafing sites differed from control sites in characteristics that would help hide a grouse from olfactory predators (i.e., greater updrafts, wind velocities, and atmospheric turbulence).     

Sharp-tailed grouse lek attendance and fidelity in upper Michigan

To assess and improve existing monitoring protocols for sharp-tailed grouse (Tympanuchus phasianellus) in the eastern Upper Peninsula of Michigan, we used data from 58 radio-collared grouse (46 M, 12 F) monitored within 3 openland landscape types: a xeric, conifer-dominated site, a wetland-dominated site, and a site dominated by low-intensity agriculture. We used lek counts and radio telemetry to determine lek attendance rates, factors affecting lek attendance rates, lek fidelity, and inter-sexual variation in these parameters. Our analysis indicated lek attendance varied with respect to sex of bird, day of year, time after sunrise, and wind speed. Peak male lek attendance rates exceeded those of females by up to 40%, and peak lekking activity for both males and females occurred during the second and third weeks of April. Male lekking activity occurred earlier and was sustained longer than that of females. Lekking activity was negatively related to time of day and wind speed. We observed strong lek fidelity as radio-collared birds attended a primary lek 94% of the time, indicating a low probability of multiple counting of individual birds. We also proposed a method to adjust lek count data for the probability that birds are on a lek during lek counts. Our proposed method can be used by researchers and managers to improve estimates of the number of birds attending a lek by reducing the negative bias associated with observed counts. © 2011 The Wildlife Society.     

Phylogeographic structure, gene flow and species status in blue grouse (Dendragapus obscurus)

We investigated the genetic population structure and species status of a relatively sedentary bird that is a permanent resident of western North American forests, the blue grouse (Dendragapus obscurus). Phylogenetic analysis of complete mitochondrial control region DNA sequences resulted in the identification of three basal clades of haplotypes that were largely congruent with well-known biogeographical regions. These clades corresponded to the parapatric sooty (D. o. fuliginosus) and dusky (D. o. obscurus) subspecies groups of blue grouse plus a previously unrecognized division between northern and southern dusky grouse populations; the latter does not correspond closely to any currently recognized subspecies boundary. Approximately 66% of the total genetic variation was distributed among these three regions. Maximum likelihood estimates of gene flow between the regions were low or asymmetric; gene flow has been insufficient to prevent genetic divergence between dusky and sooty grouse. Estimates of gene flow among populations within sooty grouse were large except across the Columbia River valley. Among populations of dusky grouse, estimates of gene flow were heterogeneous and asymmetrical, reflecting large-scale fragmentation of the distribution due to landscape features and associated vegetation. Genetic, morphological and behavioural evidence suggest that sooty and dusky grouse are species-level taxa; the specific status of a third clade remains ambiguous.     

Population genetic structure of male black grouse (Tetrao tetrix L.) in fragmented vs. continuous landscapes

We investigated the association of habitat fragmentation with genetic structure of male black grouse Tetrao tetrix. Using 14 microsatellites, we compared the genetic differentiation of males among nine localities in continuous lowland habitats in Finland to the genetic differentiation among 14 localities in fragmented habitats in the Alps (France, Switzerland and Italy). In both areas, we found significant genetic differentiation. However, the average differentiation, measured as theta, was more than three times higher in the Alps than in Finland. The greater differentiation found in the Alps is probably due to the presence of mountain ridges rising above natural habitats of the species, which form barriers to gene flow, and to a higher influence of genetic drift resulting from lower effective sizes in highly fragmented habitats. The detection of isolation by distance in the Alps suggests that gene flow among populations does occur. The genetic variability measured as gene diversity HE and allelic richness A was lower in the Alps than in Finland. This could result from the higher fragmentation and/or from the fact that populations in the Alps are isolated from the main species range and have a lower effective size than in Finland. This study suggests that habitat fragmentation can affect genetic structure of avian species with relatively high dispersal propensities.     

The Influence of Ecological Factors on Detecting Drumming Ruffed Grouse

Abstract: We surveyed drumming ruffed grouse (Bonasa umbellus) to estimate the probability of detecting an individual, and we used Bayesian model selection to assess the influence of factors that may affect detection probabilities of drumming grouse. We found the average probability of detecting a drumming ruffed grouse during a daily survey was 0.33. The probability of detecting a grouse was most strongly influenced by the temperature change during a survey (_{temp change} = 0.23, 95% probability interval [PI] = 0.13 ≤ ≤ 0.33) and its interaction with temperature at the start of the survey (_interaction = 0.01, 95% PI = 1.42 × 10⁻³ ≤ ≤ 0.03). Although the best model also included a main effect of temperature at the start of surveys, this variable did not strongly correlate with detection probabilities (_{start temp} = −0.03, 95% PI = −0.06 ≤ ≤ 9.80 × 10⁻⁵). Model assessment using data collected at other sites indicated that this best model performed adequately (i.e., positive correlation between observed and predicted values) but did not explain much of the variation in detection rates. Our results are useful for understanding the historical drumming index used to assess ruffed grouse populations and for designing auditory surveys for this important game bird.     

Museum samples provide novel insights into the taxonomy and genetic diversity of Irish red grouse

The taxonomic status of red grouse in Ireland has been the subject of considerable debate over the past century. Irish red grouse are usually classified as Lagopus lagopus scoticus, which is the same subspecies as that found in Britain, but some ornithologists believe that native Irish red grouse constitute an endemic subspecies, namely L. lagopus hibernicus. The considerable decline of Irish red grouse over the past century, along with possible hybridization with introduced grouse from Britain, have highlighted the need to resolve their taxonomic status as part of a biodiversity management plan. However, genetic analysis of samples from a single point in time will provide limited insight into potentially confounding historical events such as hybridization and introgression. We therefore compared mtDNA sequences from both current and historical samples of the two putative subspecies, scoticus and hibernicus, to see if they are or were genetically distinct. Red grouse from Britain and Ireland shared mitochondrial haplotypes, and our historical data suggest that this is unlikely to be the result of recent hybridization and introgression. These findings, combined with a general lack of documented differences in behaviour and ecology, suggest that Irish red grouse should remain classified as L. lagopus scoticus. At the same time, we found evidence that a significant amount of genetic diversity has been lost from Irish red grouse over the past century, presumably as a result of diminishing population sizes and fragmentation of extant populations. A loss of habitat, combined with the declining numbers and genetic diversity of Irish red grouse, justify their designation as an All-Ireland Priority (Red List) species and a Northern Ireland Priority Species for conservation.     

Divergent color signals from homologous unfeathered ornaments in two congeneric grouse

Color‐based visual signals are important aspects of communication throughout the animal kingdom. Individuals evaluate color to obtain information about age and condition and to behave accordingly. Birds display a variety of striking, conspicuous colors and make ideal subjects for the study of color signaling. While most studies of avian color focus on plumage, bare unfeathered body parts also display a wide range of color signals. Mate choice and intrasexual competitive interactions are easily observed in lekking grouse, which also signal with prominent unfeathered color patches. Most male grouse have one pair of colorful bare part ornaments (combs), and males of several species also have inflatable air sacs in their throat. Previous studies have mostly focused on comb color and size, but little is known about the signaling role of air sac color. We measured comb size and the color properties of combs and air sacs in the Lesser and Greater Prairie‐Chickens (Tympanuchus pallidicinctus and T. cupido, respectively), and investigated whether these properties varied with age and mass. We found that mass predicted color properties of air sacs and that age predicted comb size in the Greater Prairie‐Chicken, suggesting that these ornaments indicate condition dependence. No conclusive relationships between color and age or size were detected in the Lesser Prairie‐Chicken. Color properties of both ornaments differed between the two species. Further research is needed to determine mechanisms that link condition to color and whether the information advertised by color signals from these ornaments is intended for males, females, or both.     

Highest densities of mountain hares (Lepus timidus) associated with ecologically restored bog but not grouse moorland management

Over the last 20 years, ecological restoration of degraded habitats has become common in conservation practice. Mountain hares (Lepus timidus scoticus) were surveyed during 2017–2021 using 830 km of line transects in the Peak District National Park, England. Historically degraded bog areas were previously reported having low hare numbers. Following bog restoration, we found hare densities of 32.6 individuals km⁻², notably higher than neighboring degraded (unrestored) bog with 24.4 hares km⁻². Hare density on restored peatland was 2.7 times higher than on bogs managed for grouse shooting at 12.2 hares km⁻² and 3.3 times higher than on heather moorland managed for grouse shooting at 10.0 hares km⁻². Yearly estimates varied most on habitats managed for grouse, perhaps indicative of the impact of habitat management, for example, heather burning and/or possible hare culling to control potential tick‐borne louping ill virus in gamebirds. Acid grassland used for sheep farming had a similar density to grouse moorland at 11.8 hares km⁻². Unmanaged dwarf shrub heath had the lowest density at 4.8 hares km⁻². Hare populations are characterized by significant yearly fluctuations, those in the study area increasing by 60% between 2017 and 2018 before declining by ca. 15% by 2020 and remaining stable to 2021. During an earlier survey in 2002, total abundance throughout the Peak District National Park was estimated at 3361 (95% CI: 2431–4612) hares. The present study estimated 3562 (2291–5624) hares suggesting a stable population over the last two decades despite fluctuations likely influenced by weather and anthropogenic factors. Mountain hares in the Peak District favored bog habitats and were associated with restored peatland habitat. Wildlife management should be cognizant of hare density variation between habitats, which may have implications for local extinction risk.     

Intra-sexual competition alters the relationship between testosterone and ornament expression in a wild territorial bird

In a reliable signalling system, individual quality is expected to mediate the costs associated with ornamental displays, with relatively lower costs being paid by individuals of higher quality. These relative costs should depend not only on individual quality, but also on levels of intra-sexual competition. We explored the current and delayed effects that testosterone implants have on bird ornamentation in populations with contrasted population densities, as a proxy for intra-sexual competition. In a replicated experiment, we manipulated testosterone in 196 yearling male red grouse Lagopus lagopus scoticus in autumn in populations of high and low levels of intra-sexual competition. Males were assigned to one of three exogenous testosterone (T) treatments: empty implants (T0), small T implants (T1) or larger T implants (T2). We monitored subsequent changes in testosterone levels, ornament size and carotenoid-based colouration, carotenoid levels and body condition from autumn to spring. Testosterone implants increased testosterone levels, comb redness and comb size, and decreased body condition but these effects depended on levels of intra-sexual competition. Specifically, T2-implanted birds increased testosterone levels and comb size more, and reduced body condition more, in populations where intra-sexual competition was low. In the following spring, testosterone levels of T2-treated birds kept increasing in populations where intra-sexual competition was high but not in populations where intra-sexual competition was low. Our results highlight that levels of intra-sexual competition alter the relationship between testosterone levels and ornament expression, influencing their condition-dependence; they also indicate that the outcome of standard hormone manipulation conducted in free-living animals vary depending on the population context.