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.     

Behavioural responses of male ruffed grouse (Bonasa umbellus,L.) to playbacks of drumming displays

Birds use a variety of sounds in their courtship displays, but the majority of behavioural studies have focused on vocalizations. In contrast, little is known about how non‐vocal sounds, or sonations, are used, even though many avian species produce them. The ruffed grouse (Bonasa umbellus) is a useful species to examine non‐vocal sounds because they lack vocal components in their courtship and rely on a non‐vocal sound to attract mates and defend their territory. Their courtship display, known as “drumming,” is created by the wings, and the number of pulses and speed (pulse rate) varies significantly among males. Anecdotal evidence suggested that males can affect the drumming behaviour of neighbouring males in drumming “duels” in an analogous way to song contests. Here, we test whether males do respond to the playback of drumming sounds of an unfamiliar male. Using a portable speaker system, we played recordings of drumming displays to males that were actively drumming themselves. Throughout each playback, we recorded the drumming behaviour of target males so that we could assess whether drumming activity changes following a playback as well as whether males change the speed of their display. Overall, male grouse were equally likely to approach the speaker or continue drumming following a playback. For those males that continued drumming, their drumming pulse rate was significantly faster following playbacks, but they drummed less often. These results indicate that male ruffed grouse do respond to drumming sounds, but the specific response differs among males. Because the differential response was not related to colour phase or whether a male was drumming in proximity to other males, we suggest that the response of individuals likely varies with other traits, such as hormone levels or behavioural syndrome.     

Evaluating spatially explicit viability of a declining ruffed grouse population

Species associated with early successional habitats have experienced dramatic declines in the eastern United States as a result of land use changes and human disruption of natural disturbance regimes. Consequently, active management is required to create early successional habitat and promote plant and animal communities that depend on periodic forest disturbance. Ruffed grouse (Bonasa umbellus) depend on recently disturbed forest habitat, and have experienced dramatic declines over the last half-century. Although ruffed grouse are extensively studied, little effort has been made to link population dynamics with habitat management at landscape scales. We used stochastic, spatially explicit population models that combined landscape conditions derived from a Geographic Information System with demographic data, and applied the model to a declining ruffed grouse population in Rhode Island, USA. We identified vital rates that influence ruffed grouse population dynamics using baseline models constructed with current demographic rates and landscape conditions, and assessed the effect of landscape-scale forest management alternatives on population persistence by running multiple management simulations. Baseline models typically predicted population decline, and we concluded that vital rates (survival and recruitment) had a greater influence on population persistence than did dispersal capability, carrying capacity, or initial population size. Management simulations predicted greater population persistence under a scenario where high-quality habitat was provided in fewer large blocks as opposed to many small blocks, and the rate at which we allowed ruffed grouse to colonize newly created habitat had a substantial impact on management success. Populations of ruffed grouse in the eastern United States are likely to continue to decline given current disturbance regimes, and our work provides a link between ruffed grouse demography and landscape-scale habitat conditions to support management decisions. © 2011 The Wildlife Society.     

Ruffed Grouse Winter Habitat Use in Mixed Softwood-Hardwood Forests,Québec,Canada

Abstract: Ruffed grouse (Bonasa umbellus) is a popular small game species in northeastern North America. We assessed female ruffed grouse habitat characteristics during winter of 2001-2002 and 2002-2003 in a region dominated by mixed softwood-hardwood forests by comparing used and random locations. We followed 23 radiotagged adult females in 2 forest sites of the Réserve faunique de Portneuf, Québec, Canada, from late November to mid-April. We described grouse habitat using ground surveys and identified selected habitat characteristics using analysis of variance and logistic regression. Females preferred mixed softwood-hardwood stands > 17 m tall and 61-120 years old. Compared with random locations, grouse locations had more well-developed total canopy cover (>4m;75%), canopy (>4m;35%), midstory (1-4 m tall; 35%), and lower-story (<1 m tall; 23%) coniferous cover, and higher coniferous stem density and tree basal area (dbh > 9 cm; 343 stems/ha and 9.0 m²/ha, respectively). Forest management should maintain mature mixed softwood-hardwood stands (50% coniferous), which are adequate winter habitat for ruffed grouse.     

Temporal changes in age and sex ratios of forest grouse harvested in northeastern oregon

Ratio of immature (young of the year) grouse to adult birds (I:A) in the harvest of upland game birds is commonly used as an index to annual reproduction; however, I:A ratios can vary as the season progresses producing biased estimates. We analyzed I:A ratios in the daily harvest of dusky grouse (Dendragopus obscurus) and ruffed grouse (Bonasa umbellus) in northeastern Oregon over 28 years (1981–2008) and found that I:A ratios in the harvest declined for both species as the hunting season progressed. We also analyzed ratios of adult female to adult male (AF:AM) grouse to determine if female and male grouse were harvested in equal numbers throughout the harvest season. We found that more males than females of both species were harvested, but that AF:AM ratio of both dusky and ruffed grouse did not change during most of the hunting season. Approximately 50% of the annual harvest occurred during the first 14 days of the hunting season. Therefore, we recommend using the ratios of I:A birds in the first 14 days of the harvest season as the best index to annual reproduction of forest grouse in northeast Oregon. © 2011 The Wildlife Society.     

Habitat occupancy by riparian muskrats reveals tolerance to urbanization and invasive vegetation

Wildlife communities are being altered by rapid environmental change including habitat loss and fragmentation, urbanization, and spread of invasive species. To predict consequences of these anthropogenic changes to landscapes, it is necessary to identify not only species that are negatively affected, but also species that are unaffected or even thrive. We used occupancy modeling to examine the spatial distribution of muskrats (Ondatra zibethicus) in riparian habitat within an agricultural region of east-central Illinois from 2007 to 2008. We examined whether site occupancy was related to local habitat conditions and anthropogenic landscape alterations including urbanization and dominance of invasive reed canary grass (Phalaris arundinacea). We sampled 90 study sites (200-m stream segments) for occupancy by muskrats based on presence of tracks, scat, and feeding sign. Per-survey detection probability was 0.79 (SE = 0.04) in 2007 and 0.76 (SE = 0.04) in 2008. Detection was related positively to Julian date and negatively to abundance of woody debris and emergent rocks. Site occupancy by muskrats was 0.59 (SE = 0.09) in 2007 and 0.69 (SE = 0.06) in 2008, a year with above-average precipitation. Occupancy was related positively to urban land cover surrounding sites, which could reflect higher baseflows and reduced risk from predation and trapping in urban areas. Occupancy was unrelated to site dominance by invasive reed canary grass, but muskrats occurred more often at larger, deeper streams and those with greater bank heights and less sandy bank soils. Turnover between years was driven by stream size and water availability. Muskrats exhibited tolerance to key aspects of environmental change, and muskrats might even be urban adapters when occupying riparian habitat that remains adequately connected in urbanizing landscapes. © 2011 The Wildlife Society.     

Effects of Rain on Palm Springs Ground Squirrel Occupancy in the Sonoran Desert

ABSTRACT Long-term monitoring programs must use informative yet cost-effective methods. Occupancy estimates that incorporate detection probabilities are used with increasing frequency to describe species status and make management recommendations. Estimating changes in the occupancy of points over time in response to management actions or environmental changes may be especially useful for management of the Palm Springs round-tailed ground squirrel (Spermophilus tereticaudus chlorus), a subspecies covered under the Coachella Valley Multiple Species Habitat Conservation Plan and Natural Community Conservation Plan. In 2002 and 2003, we estimated occupancy and detection probability of ground squirrels across lands modeled as ground squirrel habitat by the Scientific Advisory Committee for the Habitat Conservation Plan and tested a priori hypotheses about how occupancy varied among vegetation and substrate types. In the 2003 study, we asked whether these associations were affected by winter rains after the 2002 drought year. Occupancy in 2003 was estimated at 0.99 (SE = 0.01) in Western honey mesquite (Prosopis glandulosa) on dunes and hummocks, and occupancy of the remaining modeled habitat was best described by distance to mesquite, with the occupancy probability decreasing with increasing distance from mesquite on dunes or hummocks. The best-supported model in 2002 described the distribution of ground squirrels as a function of only vegetation and substrate type. However, the best-supported models in 2003 suggested that distance to mesquite was a component of the occupancy of non-mesquite vegetation. Mesquite seems to provide high-quality habitat that can support ground squirrels at high occupancy probabilities that may breed successfully every year. In contrast, other vegetation types provide low-quality habitat that can only support ground squirrels at low occupancy probabilities that may only breed occasionally. Mesquite could be an essential refugium during drought years, and the 4 best-supported models in 2003 suggest that restoration of mesquite beginning near currently occupied mesquite patches could be critical for maintaining ground squirrel populations on the preserves.     

Ruffed Grouse Bonasa umbellus habitat selection in a spatially complex forest: evidence for spatial constraints on patch selection

Drumming display sites of male Ruffed Grouse Bonasa umbellus serve as activity centres and occur in a variety of forest types and age classes. We used a case‐control study design and model selection to evaluate a set of predictions about habitat constraints placed upon Grouse given the habitat where their breeding season activity centres were located. We located 110 individual Grouse activity centres near Cloquet, Minnesota, between 2002 and 2005, and 40 activity centres at two other sites in northern Minnesota in 2005. Our most parsimonious model indicated that Ruffed Grouse used logs more than other potential drumming structures (e.g. stumps, dirt mounds or roots) and sites with a higher density of shrubs as compared with unused sites. Predicted values from this model correlated with observed values from independently sampled areas. Structures used by Grouse for their drumming display were characterized by a greater density of aspen stems than unused sites when in young aspen and mature pine, but not when in other forest types. The patterns of habitat selection that we observed supported predictions (1) that the differences in habitats at larger spatial scales (e.g. forest stands or breeding territories) may impose certain constraints on specific sites selected for their drumming display, and (2) that some of these constraints may vary by forest type.     

Mourning dove reporting probabilities for web-address versus toll-free bands

Federal migratory bird bands have been inscribed with a postal address and toll-free telephone number (toll-free bands) since 1995 for their reporting, but in 2007 the postal mail address was replaced with an internet address (web-address bands). The reporting rate of web-address bands is unknown, and knowledge of band reporting probabilities is an integral part of bird band-recovery studies designed to obtain unbiased estimates of harvest rates and recovery rates if use of band types differs across space and time. We estimated web-address band reporting probabilities for mourning doves (Zenaida macroura) in the United States by comparing the relative recovery rate (ratio) of web-address to toll-free bands and applying this as an adjustment factor to the known reporting probabilities of toll-free bands. Cooperators banded 132,386 doves representing 57,982 (44%) web-address and 74,404 (56%) toll-free bands in July and August during 2008–2010 across 34 states, 12 regions, and 3 management units. Of the birds banded, 4,642 (3.5%) were direct recoveries, as a result of being shot, and all but 3 were reported via telephone or internet. Nationally, internet reporting accounted for 16.3% of toll-free bands and 42.9% of web-address bands recovered. Web-address bands had a greater recovery rate than toll-free bands (ratio = 1.081, SE = 0.027). We found some evidence of spatial variation in ratio estimates at management unit and regional scales, but the variation was primarily at the regional level where it was not great (range = 1.015–1.213) and statistical support for this variation was not particularly strong (SE = 0.129). Nationally, the web-address band reporting probability was 0.535 (SE = 0.021), an absolute increase of 0.040 compared to the reporting probability of toll-free bands. The additional reporting probability of web-address bands relative to toll-free bands must be accounted for in band-recovery studies used to obtain estimates of harvest rates and recovery rates if use of band types differs across space and time for mourning doves and possibly other species. © 2011 The Wildlife Society.     

Distribution and Habitat Use of King Rails in the Illinois and Upper Mississippi River Valleys

ABSTRACT The migratory population of the king rail (Rallus elegans) has declined dramatically during the past 40 years, emphasizing the need to identify habitat requirements of this species to help guide conservation efforts. To assess distribution and habitat use of king rails along the Illinois and Upper Mississippi valleys, USA, we conducted repeated call-broadcast surveys at 83 locations in 2006 and 114 locations in 2007 distributed among 21 study sites. We detected king rails at 12 survey locations in 2006 and 14 locations in 2007, illustrating the limited distribution of king rails in this region. We found king rails concentrated at Clarence Cannon National Wildlife Refuge, an adjacent private Wetlands Reserve program site, and B. K. Leach Conservation Area, which were located in the Mississippi River floodplain in northeast Missouri. Using Program PRESENCE, we estimated detection probabilities and built models to identify habitat covariates that were important in king rail site occupancy. Habitat covariates included percentage of cover by tall (>1 m) and short (>1 m) emergent vegetation, percentage of cover of woody vegetation, and interspersion of water and vegetation (2007 only) within 50 m of the survey location. Detection probability was 0.43 (SE = 0.12) in 2006 and 0.35 (SE = 0.03) in 2007 and was influenced by observer identity and percentage of cover by tall herbaceous vegetation. Site occupancy was 0.11 (SE = 0.04) in 2006 and 0.14 (SE = 0.04) in 2007 and was negatively influenced most by percentage of cover by woody vegetation. In addition, we found that interspersion of vegetation and water was positively related to occupancy in 2007. Thus, nesting king rails used wetlands that were characterized by high water-vegetation interspersion and little or no cover by woody vegetation. Our results suggest that biologists can improve king rail habitat by implementing management techniques that reduce woody cover and increase vegetation-water interspersion in wetlands.     

Teasing out biological effects and sampling artifacts when using occupancy rate in monitoring programs

ABSTRACT.   Recent declines in biodiversity stress the need for rigorous and reliable multispecies monitoring programs. A potential weakness of monitoring programs is a reliance on raw counts and the assumption either of complete detection or of constant detection probability for each species, regardless of the sampling situation. Until recently, these assumptions have largely remained untested and, therefore, to help insure accuracy, bird-monitoring programs have depended on standardization of counts and counts of longer duration. We tested the effectiveness of these strategies for providing unbiased occupancy rates using a method designed to accommodate situations where species detection probabilities are less than one and heterogeneous. We tested the effect of potential sources of heterogeneity in detection probability (vegetation structure, wind velocity, cloud cover, date, and time) on occupancy rate estimates of 13 bird species in southern France. We compared adjusted and raw occupancy rates for two sampling durations (10 and 20 min). Differences between raw and adjusted occupancy rates were low even for the shorter count duration, suggesting that standardized long counts should produce reliable estimates of occupancy rates even in the absence of correction by an appropriate method. This enhances the value of past monitoring programs where long standardized counts were used, but with designs that do not allow corrected estimates. However, we found that detection probability was heterogeneous for most species and that vegetation structure was an important source of heterogeneity. The possible effects of habitat on detection probability should be of special concern for long-term monitoring programs conducted in landscapes where habitats vary across time or space.     

Estimating occupancy dynamics in an anuran assemblage from Louisiana,USA

Effective monitoring programs are designed to track changes in the distribution, occurrence, and abundance of species. We developed an extension of Royle and Kéry's (2007) single species model to estimate simultaneously temporal changes in probabilities of detection, occupancy, colonization, extinction, and species turnover using data on calling anuran amphibians, collected from 2002 to 2006 in the Lower Mississippi Alluvial Valley of Louisiana, USA. During our 5-year study, estimates of occurrence probabilities declined for all 12 species detected. These declines occurred primarily in conjunction with variation in estimates of local extinction probabilities (cajun chorus frog [Pseudacris fouquettei], spring peeper [P. crucifer], northern cricket frog [Acris crepitans], Cope's gray treefrog [Hyla chrysoscelis], green treefrog [H. cinerea], squirrel treefrog [H. squirella], southern leopard frog [Lithobates sphenocephalus], bronze frog [L. clamitans], American bullfrog [L. catesbeianus], and Fowler's toad [Anaxyrus fowleri]). For 2 species (eastern narrow-mouthed toad [Gastrophryne carolinensis] and Gulf Coast toad [Incilius nebulifer]), declines in occupancy appeared to be a consequence of both increased local extinction and decreased colonization events. The eastern narrow-mouthed toad experienced a 2.5-fold increase in estimates of occupancy in 2004, possibly because of the high amount of rainfall received during that year, along with a decrease in extinction and increase in colonization of new sites between 2003 and 2004. Our model can be incorporated into monitoring programs to estimate simultaneously the occupancy dynamics for multiple species that show similar responses to ecological conditions. It will likely be an important asset for those monitoring programs that employ the same methods to sample assemblages of ecologically similar species, including those that are rare. By combining information from multiple species to decrease the variance on estimates of individual species, our results are advantageous compared to single-species models. This feature enables managers and researchers to use an entire community, rather than just one species, as an ecological indicator in monitoring programs. © 2011 The Wildlife Society.     

Occupancy of Random Plots by White-Tailed and Gunnison's Prairie Dogs

ABSTRACT Areas occupied by white-tailed prairie dogs (WTPD; Cynomys leucurus) and Gunnison's prairie dogs (GPD; C. gunnisoni) are not well-known in Colorado (USA) and elsewhere. Suitable methodology for monitoring changes in populations of WTPD and GPD over broad areas also has not been well established. We evaluated occupancy modeling methodology to establish baseline occupancy rates for WTPD and GPD in Colorado. We estimated that WTPD occupied 24.1% (SE = 12.8) of 47,710 0.25-km² plots and GPD occupied 7.5% (SE = 1.3) of 158,225 0.25-km² plots in Colorado during 2004 and 2005. Areas reported as colonies in the Colorado Division of Wildlife's database were not good predictors of WTPD and GPD occupancy. Occupancy rates were highest for GPD at intermediate elevations. We estimated detection probabilities for surveys from the ground of 0.760 (SE = 0.042) for WTPD and 0.786 (SE = 0.060) for GPD. Probability of detection for WTPD improved with lower temperature and earlier Julian date, whereas no covariates improved detection rates for GPD. We recommend that wildlife managers use occupancy monitoring to establish status and trends in populations of WTPD and GPD across their range.     

Towards the automated detection and occupancy estimation of primates using passive acoustic monitoring

Recent advancements in technology have made possible the use of novel, cost-efficient biomonitoring techniques which facilitate monitoring animal populations at larger spatial and temporal scales. Here, we investigated using passive acoustic monitoring (PAM) for wild primate populations living in the forest of Taï National Park, Côte d’Ivoire. We assessed the potential of using a customized algorithm for the automated detection of multiple primate species to obtain reliable estimates of species occurrence from acoustic data. First, we applied the algorithm on continuous rainforest recordings collected using autonomous recording units (ARUs) to detect and classify three sound signals: chimpanzee buttress drumming, and the loud calls of the diana and king colobus monkey. Using an occupancy modelling approach we then investigated to what extent the automated, probabilistic output needs to be listened to, and thus manually cleaned, by a human expert, to approach occupancy probabilities derived from ARU data fully verified by a human. To do this we explored the robustness of occupancy probability estimates by simulating ARU datasets with various degrees of cleaning for false positives and false negative detections. We further validated the approach by comparing it to data collected by human observers on point transects located within the same study area. Our study demonstrates that occurrence estimates from ARU data, combined with automated processing methods such as our algorithm, can provide results comparable to data collected by humans and require less effort. We show that occupancy probabilities are quite robust to cleaning effort, particularly when occurrence is high, and suggest that for some species even naïve occupancy, as derived from ARU data without any cleaning, could provide a quick and reliable indicator to guide monitoring efforts. We found detection probabilities to be most influenced by time of day for chimpanzee drums while temperature and, likely, poaching pressure, affected detection of diana monkey loud calls. None of the covariates investigated appeared to have strongly affected king colobus loud call detection. Finally, we conclude that the semi-automated approach presented here could be used as an early-warning system for poaching activity and suggest additional techniques for improving its performance.     

Assessing breeding success in common woodland birds using a novel method

Capsule Repeated counts of fledged broods can provide a useful estimate of breeding success for most common woodland birds.

Aims To assess the efficacy of comparing fledged-brood survey data with territory mapping using simple mark–recapture analysis techniques to provide an estimate of breeding success for common woodland birds that does not involve finding nests.

Methods Three observers undertook territory mapping surveys of adults, followed by counts of fledged broods four times a week during May–July 2007 in two 15 ha woods each, both in southern England. Using known fledging to maturity periods, these counts were used to calculate daily detection probabilities for broods of ubiquitous species. These enabled fledged brood territory occupancy probabilities (i.e. brood to territory ratios) to be estimated that take account of the possibility that broods were present but missed by surveys.

Results Of the 19 species found in all six woods, mean daily detection probability estimates for fledged broods of 17 species ranged from 0.17 to 0.50 with significant variation between woods for 12 species, but within region/observer for four species. The mean probability of detecting a brood at least once was over 75% using four visits per week and over 50% using two visits. Only for Great Spotted Woodpeckers Dendrocopos major and Garden Warblers Sylvia borin was the fledging period too short and the daily detection probability too low to provide a reasonable estimate of the territory occupancy probability.

Conclusion Daily detection probabilities for fledged broods of most common woodland birds were sufficiently high to enable useable estimates of fledged-brood territory occupancy probabilities to be made based on a survey programme involving two or three visits per week between late May and the end June. The method used may have application as a means of providing a relatively easily derived productivity index for woodland bird monitoring programmes or for research studies.     

Front Cover

Courtship displays are typically comprised of the same behavioral pattern, or patterns, repeated several times by males. Both the quantity and quality of the displays produced by a given male bird are not, however, constant. The number and/or quality of displays can decrease over time, indicating fatigue, or males can increase the number and/or quality as they display more, indicating a warm-up period. Although there is evidence for fatigue or warm-up periods for many types of courtship displays, data on motor components of avian courtship are scant, despite how commonly they are used. Here, we test whether drumming, a non-vocal motor display, in male ruffed grouse (Bonasa umbellus) changes in relation to the number of displays executed. Using a large number of recordings, our linear mixed models yielded a significant effect of cumulative number of drumming displays on the number of wingbeats per second, referred to as pulse rate. Across males, pulse rate is slowest when males begin drumming each day and increases until approximately 50 drumming displays have been produced. The rate of increase is also modulated by the nighttime low temperature such that cooler conditions are associated with lower pulse rates and a slower increase in pulse rate relative to the cumulative number of displays. Further, the maximum pulse rate recorded and average pulse rate after 50 displays is inversely correlated with body mass such that larger males are slower than smaller males. We suggest that the daily changes in pulse rate likely reflect a warm-up period based upon the effects of cumulative drumming count and temperature on pulse rate. Whether these dynamic changes in the production of a motor display are informative to female grouse is unknown. However, we propose that daily changes in how motor displays are performed may be a common feature of avian courtship that has gone relatively unnoticed, despite the potential for motor performance to be a trait that is important for female mate choice.     

Ruffed Grouse Brood Habitat Use in Mixed Softwood-Hardwood Nordic-Temperate Forests,Quebec, Canada

Abstract: Adequate cover is a critical component of ruffed grouse (Bonasa umbellus) habitat during the brood-rearing period when chick mortality is high. We assessed habitat use by ruffed grouse during the brood-rearing period by comparing characteristics of tree, shrub, and ground layers at ruffed grouse brood and random locations. We captured and radiomarked 29 females with broods in 2 forest settings of the Réserve faunique de Portneuf, Quebec, Canada. We described grouse habitat using ground surveys and forest maps, and we identified the used habitat characteristics using analysis of variance and logistic regression. Females with broods used mixed and regenerated clearcut stands that were 1.5–7 m tall and 11–20 years old. Compared with random locations, grouse locations had higher lateral obstruction (76% vs. 68%), higher small-stem density (29,085 stems/ha vs. 19,340 stems/ha), and were closer to roads and trails. Percentage of coverage by ground vegetation was not higher at grouse locations as often reported in previous studies. Results from this study will help orient ruffed grouse habitat management on Quebec public land and elsewhere in nordic—temperate mixed hardwood—softwood forests to maintain suitable brood habitat after logging operations. Forest management should promote growth of young mixed stands with high horizontal and vertical cover provided by high small-stem density, which offers protection against aerial and terrestrial predation. Edges such as roadsides are also important in brood habitat as they provide food and cover.     

Effects of rangeland management on the site occupancy dynamics of prairie-chickens in a protected prairie preserve

We investigated the site occupancy dynamics of greater prairie-chickens at Konza Prairie Biological Station, a protected site in northeastern Kansas that is managed for ecological research. We surveyed the site during mid-Mar to mid-May, 1981–2008, and recorded detections of birds in a grid of 6.3 ha survey plots (n = 187 plots). We used multiseason occupancy models to estimate the probabilities of occupancy (ψ) and detection (p), and tested whether land cover in woody vegetation, and land use with prescribed fire or grazing management influenced the dynamic processes of site colonization and local extinction. Probability of detection per site was consistently <1 and varied among years (p = 0.12–0.82). Site occupancy of prairie-chickens declined 40% over the study period from a high of ψ = 0.19 ± 0.02 SE in 1981 to a low of 0.11 ± 0.03 in 2008, despite protection from disturbance at leks and losses to harvest. We found that different sets of environmental factors impacted the probabilities of colonization and local extinction. Probability of colonization for an unoccupied site was negatively associated with the proportion of site occupied by woodland cover (β = −1.25), and was lower for grazed sites (β = −0.62). In contrast, probability of local extinction was affected by a weak interaction between grazing and average frequency of prescribed fire (β = −1.01), but model-averaged slope coefficients were not statistically different than 0. To conserve prairie-chickens, we recommend prairies be managed with combinations of prescribed fire and grazing that maintain a heterogeneous mosaic of prairie habitats, while preventing woody encroachment. To assess biotic responses to land management practices, field sampling should be based on occupancy models or similar techniques that account for imperfect detection. © 2011 The Wildlife Society.     

Factors affecting detectability of river otters during sign surveys

Sign surveys are commonly used to study and monitor wildlife species but may be flawed when surveys are conducted only once and cover short distances, which can lead to a lack of accountability for false absences. Multiple observers surveyed for river otter (Lontra canadensis) scat and tracks along stream and reservoir shorelines at 110 randomly selected sites in eastern Kansas from January to April 2008 and 2009 to determine if detection probability differed among substrates, sign types, observers, survey lengths, and near access points. We estimated detection probabilities (p) of river otters using occupancy models in Program PRESENCE. Mean detection probability for a 400-m survey was highest in mud substrates (p = 0.60) and lowest in snow (p = 0.18) and leaf litter substrates (p = 0.27). Scat had a higher detection probability (p = 0.53) than tracks (p = 0.18), and experienced observers had higher detection probabilities (p > 0.71) than novice observers (p < 0.55). Detection probabilities increased almost 3-fold as survey length increased from 200 m to 1,000 m, and otter sign was not concentrated near access points. After accounting for imperfect detection, our estimates of otter site occupancy based on a 400-m survey increased >3-fold, providing further evidence of the potential negative bias that can occur in estimates from sign surveys when imperfect detection is not addressed. Our study identifies areas for improvement in sign survey methodologies and results are applicable for sign surveys commonly used for many species across a range of habitats. © 2010 The Wildlife Society