Common ravens disrupt greater sage-grouse lekking behavior in the Great Basin, USA

Joseph Atkinson; Peter S. Coates; Brianne E. Brussee; Ian A. Dwight; Mark A. Ricca; Pat J. Jackson

doi:10.26077/add8-50a4

Home/Archive/USGS

USGS · 70241053

Common ravens disrupt greater sage-grouse lekking behavior in the Great Basin, USA

Joseph Atkinson·Peter S. Coates·Brianne E. Brussee·Ian A. Dwight·Mark A. Ricca·Pat J. Jackson

View original source ↗Export metadata ↓

Abstract

Expansion of human enterprise has contributed to increased abundance and distribution of common ravens ( Corvus corax ; ravens) across sagebrush ( Artemisia spp.) ecosystems within western North America. Ravens are highly effective nest predators of greater sage-grouse ( Centrocercus urophasianus ; sage-grouse), a species of high conservation concern. Sage-grouse population trends are estimated using count survey data of males attending traditional breeding grounds, known as leks. We sought to investigate associations of ravens to sage-grouse lek sites and document interactions between the sage-grouse and ravens as well as those between sage-grouse and other animals observed around leks. First, we used extensive raven point counts and sage-grouse lek observation data collected across Nevada and California, USA, from 2009–2019 to evaluate spatial associations between sage-grouse and ravens while accounting for other environmental covariates. We found that ravens were more likely to be observed closer to lek sites, especially as leks increased in size. Second, we used a subset of the lek dataset from 2006–2019 to describe behavioral changes of male sage-grouse in the presence of ravens and other predators. Our analysis indicated that ravens are attracted to lek sites and were associated with disrupting lekking sage-grouse by causing flushes or ceasing displaying behaviors. These results suggest that adult and yearling sage-grouse perceive ravens as a reason to alter breeding activity, and ravens may adversely influence their reproduction during the lekking stage. Additionally, standardized techniques to count sage-grouse on leks for population trend analyses could be biased low if raven presence during surveys is not accounted for.

Explore related subjects

Human–Wildlife Interactions Article

Source-reported bounding extent: 35.70784567296465° to 42.77372245600145° latitude; -121.36925353163426° to -113.90172172016928° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Joseph Atkinson, Peter S. Coates, Brianne E. Brussee, Ian A. Dwight, Mark A. Ricca, Pat J. Jackson. 2021. Common ravens disrupt greater sage-grouse lekking behavior in the Great Basin, USA. https://doi.org/10.26077/add8-50a4

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2021

A rapid assessment function to estimate common raven population densities: Implications for targeted management

Common raven ( Corvus corax ; raven) populations have increased over the past 5 decades within the western United States. Raven population increases have been largely attributed to growing resource subsidies from expansion of human enterprise. Concomitantly, managers are becoming increasingly concerned about elevated adverse effects on multiple sensitive prey species, damage to livestock and agriculture, and human safety. Managers could benefit from a rapid but reliable method to estimate raven densities across spatiotemporal scales to monitor raven populations more efficiently and inform targeted and adaptive management frameworks. However, obtaining estimates of raven density is data- and resource-intensive, which renders monitoring within an adaptive framework unrealistic. To address this need, we developed a rapid survey protocol for resource managers to estimate site-level density based on the average number of ravens per survey. Specifically, we first estimated raven densities at numerous field sites with robust distance sampling procedures and then used regression to investigate the relationship between those density estimates and the number of ravens per survey, which revealed a strong correlation ( R 2 = 0.86). For management application, we provide access to R function software through a web-based interface to estimate density using number of ravens per survey, which we refer to as a Rapid Assessment Function (RAF). Then, using a simulation analysis of data from sites with abundant surveys and the RAF, we estimated raven density based on different numbers of surveys to help inform how many surveys are needed to achieve reliable estimates within this rapid assessment. While more robust procedures of distance sampling are the preferred methods for estimating raven densities from count surveys, the RAF tool presented herein provides a reliable approximation for informing management decisions when managers are faced with resource and small sample size constraints.

California, Idaho, Nevada, Oregon↗

USGS2021

Occurrence, resource use, and demography of the common raven in North America: A research synthesis

We reviewed the scientific literature to inventory existing studies of common raven ( Corvus corax ; raven) ecology in western North America. We conducted an intial literature review between June 2015 and March 2018. Prior to completing our review, we revisited the published literature for any additional relevant studies in July 2021. Our goal was to identify knowledge gaps and to synthesize the current understanding of environmental features that may support raven populations that pose general threats to biodiversity and sensitive species in particular. We focused our review on studies with direct conservation applications related to 3 processes of raven ecology: occurrence, resource use, and demography. We identified covariates that researchers associated with these processes of raven ecology, and we also quantified the geographic distribution of studies. Our review identified 54 studies, with an increasing number of studies published per decade and a geographic bias characterized by more studies conducted in the Mojave and Columbia Plateau ecoregions than elsewhere. Most studies (44) reported on a single ecological process, but 10 studies reported on multiple ecological processes. Results related to raven occurrence appeared 31 times; demographic results appeared 21 times; and resource use was reported 17 times. We also identified 13 explanatory covariates regularly invoked to explain variation in raven ecological processes. Greater attention was given to covariates including vegetation land cover, human settlement, recreation, and linear rights-of-ways than were used to explain variation in ecological processes. Most demographic studies investigated raven reproduction exclusively, but a small number of studies considered raven survival exclusively or in combination with reproduction. Along with a detailed summary of individual studies provided as an appendix, we intend for our findings to serve as a reference and to help identify future research priorities.

Human–Wildlife Interactions↗

USGS2021

Synthesis of nest predation impacts of common ravens on sensitive avian species

Decades of mounting scientific evidence have revealed that common raven ( Corvus corax ; raven) population numbers have been increasing across nearly all regions of their geographic range in North America. Concomitantly, numerous native wildlife species have experienced elevated predation rates from ravens as populations have increased and expanded their range. Managers are concerned that increased raven predation of many threatened and endangered avian species in the U.S. and Canada during nesting periods may be hampering species recovery. We explored the literature to aggregate existing knowledge and evaluate the impacts of raven predation on nests and young of sensitive avian species. We used this information to develop a simple relative index for each species, the “Raven Impact Index” (RII). The RII incorporated the species demographic rates, abundance of ravens in relation to each sensitive species’ breeding range, and the degree of overlap between raven and sensitive prey distributions. We also developed a second relative descriptor describing our confidence in each RII, termed a “Impact Credibility Index (ICI).” The species ICI was based on the number of published studies and the type of evidence presented (e.g., circumstantial vs. direct). We found evidence of nest predation on 8 sensitive avian species and suspected nest predation on 1 additional species. All species shared aspects of nesting biology that suggested they would likely be susceptible to raven nest predation. The RII varied among prey species, with greater sage-grouse ( Centrocercus urophasianus ) having the highest relative impact values, followed by snowy plover ( Charadrius nivosus nivosus ), marbled murrelet ( Brachyramphus marmoratus ), and Gunnison sage-grouse ( Centrocercus minimus ). Our species RII is intended to inform management decisions regarding actions that mitigate the negative effects of raven predation of sensitive avian species. Although elevated nest predation may be of high conservation concern, it is important to recognize that all of the sensitive native prey species we established an RII for also face multiple conservation threats.

Human–Wildlife Interactions↗