How many leks does it take? Minimum samples sizes for measuring local-scale conservation outcomes in Greater Sage-Grouse

Abstract

Monitoring population response to conservation actions, such as habitat management, is critical to evaluate conservation outcomes. Greater Sage-Grouse (Centrocercus urophasianus) has been the recipient of substantial recent conservation efforts in North America. Sage-Grouse are often surveyed using counts of males displaying on breeding leks, and these lek counts offer a practical method for monitoring Sage-Grouse population trends. Although substantial work has assessed the utility of lek count data for largescale population monitoring, there has been comparably little effort focused on the use of lek counts to evaluate local-scale management. We used Greater Sage-Grouse lek count data from Oregon, USA, combined with simulation, to evaluate the sample sizes (number of leks, years of monitoring) required to detect a positive outcome of habitat management on population growth. We further assessed assumptions associated with male detection, and compared analyses that both did (N-mixture models) and did not (Poisson regression) account for detection probability. We found that when treatments produced a 5% increase in annual population growth, and leks were monitored for at least 10 years, lek counts produced unbiased and detectable estimates of treatment effects with as few as seven treatment and seven control leks. Using an unbalanced design with a greater number of control leks (n = 16) permitted inference from even fewer treatment leks (n = 4), however, we found no scenarios where use of more control leks permitted detection of smaller treatment effects or allowed shorter duration studies. We found that N-mixture models and Poisson regression of the maximum of three repeated counts produced equivalent results when detection probability was constant, but at the small sample sizes we evaluated, confounding between detection probability and habitat management compromised the accuracy of all analysis methods. Our results show that lek counts hold promise for efficient monitoring of local-scale conservation, but further work is needed to understand the mechanisms that affect male detection during lek surveys. Combien de leks sont nécessaires? Taille d'échantillon minimum requise pour mesurer les retombées de conservation à l'échelle locale chez le Tétras des armoisesRÉSUMÉ. À la suite de l'instauration d'activités de conservation, telles que l'aménagement d'un habitat, le suivi des populations est essentiel afin qu'on puisse évaluer les retombées sur la conservation. Le Tétras des armoises (Centrocercus urophasianus) a fait l'objet d'efforts considérables récents de conservation en Amérique du Nord. Le dénombrement des mâles nicheurs qui paradent aux leks constitue une méthode d'inventaire fréquente chez le tétras, et ces comptes aux leks s'avèrent pratiques pour suivre les tendances de population. Bien qu'il y ait eu de nombreux travaux attestant de l'utilité des comptes aux leks pour le suivi de population à grande échelle, peu d'efforts ont ciblé l'utilisation de comptes aux leks pour évaluer la gestion à petite éc...

Sage‐Grouse Population Dynamics are Adversely Affected by Overabundant Feral Horses

“…Nevada Department of Wildlife (NDOW) and the California Department of Fish and Wildlife (CDFW) along with numerous personnel from private, non‐profit, and governmental agencies (state and federal) administered and led collection of lek data. Lek counts followed standardized established protocols approved by interagency collaboration (Connelly et al 2003, Western Association of Fish and Wildlife Agencies [WAFWA] 2015, Blomberg and Hagen 2020). Briefly, observers counted sage‐grouse each spring during maximum lek attendance periods (Mar–Apr; Wann et al 2019) from 2005–2019.…”

Large-scale wildfire reduces population growth in a peripheral population of sage-grouse

“…For wildlife and resource managers, the continued use of lek sites by sage-grouse for courtship provides opportunity for annual monitoring of sage-grouse populations. Lek counts are the most common and cost-effective method for tracking sagegrouse abundance at various spatial scales (Patterson 1952;Connelly and Schroeder 2007;Blomberg and Hagen 2020). Lek counts were implemented as early as the 1930s (Johnson and Rowland 2007), so in many cases long-term population trends can be established from these datasets.…”

Landscape Conservation Forecasting for Data-Poor at-Risk Species on Western Public Lands, United States

“…GSG experts were not convinced that RSFs from the north applied to the Black Mountains, but collecting more demographic data would require significant funding and a decade of field work in southwest Utah to achieve significant statistical power to define RSFs. Therefore, experts were willing to propose the strongest RSFs in a three-hour workshop that applied to all populations of GSG, which were later revised using statistically defensible demographic data from southern populations in central Nevada [2,33,34]. (b).…”

“…Local demographic data help guide management actions to improve at-risk species habitat, but it is uncommon to have complete demographic data on at-risk species for more than one drought cycle (e.g., seven-year El Niño cycle) reflecting highs and lows of reproductive effort in most western states-it is even uncommon for the simplest demographic data [2]. Where demographic, behavior, and landscape data are available, habitat suitability and per capita population growth rates can be statistically estimated [3,4].…”

“…Public land managers preparing plans to conserve whole multiple-use landscapes may be concerned with the following questions [5]: (1) What is the current condition of vegetation? (2) What is the current condition of the habitat for at-risk species? (3) Is vegetation likely to get worse over time under status quo (hereafter, custodial) land management?…”