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A Rapid Assessment Function To Estimate Common Raven Population Densities: Implications For Targeted Management, Brianne E. Brussee, Peter S. Coates, Shawn T. O'Neil, Seth J. Dettenmaier, Pat J. Jackson, Kristy B. Howe, David Delehanty Jan 2021

A Rapid Assessment Function To Estimate Common Raven Population Densities: Implications For Targeted Management, Brianne E. Brussee, Peter S. Coates, Shawn T. O'Neil, Seth J. Dettenmaier, Pat J. Jackson, Kristy B. Howe, David Delehanty

Human–Wildlife Interactions

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 …


Thinking Like A Raven: Restoring Integrity, Stability, And Beauty To Western Ecosystems, John M. Marzluff, Matthias-Claudio Loretto, Cameron K. Ho, Georgia W. Coleman, Marco Restani Jan 2021

Thinking Like A Raven: Restoring Integrity, Stability, And Beauty To Western Ecosystems, John M. Marzluff, Matthias-Claudio Loretto, Cameron K. Ho, Georgia W. Coleman, Marco Restani

Human–Wildlife Interactions

Common ravens (Corvus corax; ravens) are generalist predators that pose a threat to several rare wildlife species in the western United States. Recent increases in raven populations, which are fueled by increased human subsidies—notably food, water, and nest sites—are concerning to those seeking to conserve rare species. Due to the challenges and inefficiencies of reducing or eliminating subsidies, managers increasingly rely on lethal removal of ravens. Over 125,000 ravens were killed by the U.S. Government from 1996 to 2019, and annual removals have increased 4-fold from the 1990s to mid-2010s. We contend that lethal removal of ravens, while capable …


Spatial Modeling Of Common Raven Density And Occurrence Helps Guide Landscape Management Within Great Basin Sagebrush Ecosystems, Sarah C. Webster, Shawn T. O'Neil, Brianne E. Brussee, Peter S. Coates, Pat J. Jackson, John C. Tull, David J. Delehanty Jan 2021

Spatial Modeling Of Common Raven Density And Occurrence Helps Guide Landscape Management Within Great Basin Sagebrush Ecosystems, Sarah C. Webster, Shawn T. O'Neil, Brianne E. Brussee, Peter S. Coates, Pat J. Jackson, John C. Tull, David J. Delehanty

Human–Wildlife Interactions

Common ravens (Corvus corax; ravens) are a behaviorally flexible nest predator of several avian species, including species of conservation concern. Movement patterns based on life history phases, particularly territoriality of breeding birds and transiency of nonbreeding birds, are thought to influence the frequency and efficacy of nest predation. As such, predicting where on the landscape territorial resident and non-territorial transient birds may be found in relation to the distribution of sensitive prey is of increasing importance to managers and conservationists. From 2007 to 2019, we conducted raven point count surveys between mid-March and mid-September across 43 different field …


A Novel Technique To Improve Capture Success Of Common Ravens, Lindsey R. Perry, Terrah M. Owens, Zachary T. Slick, Jimmy D. Taylor, Jonathan B. Dinkins Jan 2021

A Novel Technique To Improve Capture Success Of Common Ravens, Lindsey R. Perry, Terrah M. Owens, Zachary T. Slick, Jimmy D. Taylor, Jonathan B. Dinkins

Human–Wildlife Interactions

Traditional trapping techniques for common ravens (Corvus corax; raven) require significant effort, often produce low capture rates, and cannot be used in some situations. We designed a 3-m noose pole to secure ravens from nocturnal roost locations while using a strobe spotlight to temporarily disorient them. We collected measures of trapping efficiency and contrasted them with padded leghold traps also used in the study. We effectively implemented our noose pole method in July and August of 2018, 2019, and 2020 in the Baker and Cow Lakes sage-grouse (Centrocercus urophasianus) Priority Areas of Conservation in eastern Oregon, …


Raven Control From A Conservation Biology Perspective, David J. Delehanty Jan 2021

Raven Control From A Conservation Biology Perspective, David J. Delehanty

Human–Wildlife Interactions

The common raven (Corvus corax; raven) is a large, highly intelligent passerine songbird with a Holarctic distribution attributable to a high degree of plasticity in its foraging and nesting behavior. Historically, ravens have received special attention in human culture, being either respected or vilified. In the western United States, ravens are exploiting the expanding human enterprise, which provides them with unintended subsidies of food, water, and breeding locations, allowing ravens to expand their range and increase in population density and resulting in raven depredation threatening species of conservation concern. From a conservation biology perspective, increased raven populations present …


Increased Abundance Of The Common Raven Within The Ranges Of Greater And Gunnison Sage-Grouse: Influence Of Anthropogenic Subsidies And Fire, Jonathan B. Dinkins, Lindsey R. Perry, Jeffrey L. Beck, Jimmy D. Taylor Jan 2021

Increased Abundance Of The Common Raven Within The Ranges Of Greater And Gunnison Sage-Grouse: Influence Of Anthropogenic Subsidies And Fire, Jonathan B. Dinkins, Lindsey R. Perry, Jeffrey L. Beck, Jimmy D. Taylor

Human–Wildlife Interactions

The common raven (Corvus corax; raven) is native to North America and has increased in abundance, especially throughout western North America, during the last century. Human subsidies have facilitated raven dispersal into less suitable habitats and enabled these populations to maintain higher annual survival and reproduction. Concomitantly, overabundant raven populations are impacting other native at-risk species such as the greater sage-grouse (Centrocercus urophasianus) and potentially the Gunnison sage-grouse (C. minimus). Using Breeding Bird Survey data from 1995–2014, we evaluated raven count data to quantitatively describe changes in abundance and expansion into sagebrush (Artemisia …


Influence Of Anthropogenic Subsidies On Movements Of Common Ravens, Adam E. Duerr, Peter H. Bloom, Kerry Ross, Tricia A. Miller, Melissa A. Braham, Amy L. Fesnock, Todd E. Katzner Jan 2021

Influence Of Anthropogenic Subsidies On Movements Of Common Ravens, Adam E. Duerr, Peter H. Bloom, Kerry Ross, Tricia A. Miller, Melissa A. Braham, Amy L. Fesnock, Todd E. Katzner

Human–Wildlife Interactions

Anthropogenic subsidies can benefit populations of generalist predators such as common ravens (ravens; Corvus corax), which in turn may depress populations of many types of species at lower-trophic levels, including desert tortoises (Gopherus agassizii) or greater sage-grouse (Centrocercus urophasianus). Management of subsidized ravens often has targeted local breeding populations that are presumed to affect species of concern and ignored “urban” populations of ravens. However, little is known about how ravens move, especially in response to the presence of anthropogenic subsidies. Therefore, subsidized ravens from distant populations that are not managed may influence local prey. To …


Efficacy Of Manipulating Reproduction Of Common Ravens To Conserve Sensitive Prey Species: Three Case Studies, Corina A. Sanchez, Brianne E. Brussee, Peter S. Coates, Kerry L. Holcomb, Seth M. Harju, Timothy A. Shields, Mercy Vaughn, Brian G. Prochazka, Steven R. Mathews, Steffen Cornell, Chad V. Olson, David J. Delehanty Jan 2021

Efficacy Of Manipulating Reproduction Of Common Ravens To Conserve Sensitive Prey Species: Three Case Studies, Corina A. Sanchez, Brianne E. Brussee, Peter S. Coates, Kerry L. Holcomb, Seth M. Harju, Timothy A. Shields, Mercy Vaughn, Brian G. Prochazka, Steven R. Mathews, Steffen Cornell, Chad V. Olson, David J. Delehanty

Human–Wildlife Interactions

Expansion of human enterprise across western North America has resulted in an increase in availability of anthropogenic resource subsidies for generalist species. This has led to increases in generalists’ population numbers across landscapes that were previously less suitable for their current demographic rates. Of particular concern are growing populations of common ravens (Corvus corax; ravens), because predation by ravens is linked to population declines of sensitive species. Ecosystem managers seek management options for mitigating the adverse effects of raven predation where unsustainable predator–prey conflicts exist. We present 3 case studies examining how manipulating reproductive success of ravens influences …


A Decision Tool To Identify Population Management Strategies For Common Ravens And Other Avian Predators, Andrea F. Currylow, Brenda J. Hanley, Kerry L. Holcomb, Timothy Shields, Stephen Boland, William I. Boarman, Mercy Vaughn Jan 2021

A Decision Tool To Identify Population Management Strategies For Common Ravens And Other Avian Predators, Andrea F. Currylow, Brenda J. Hanley, Kerry L. Holcomb, Timothy Shields, Stephen Boland, William I. Boarman, Mercy Vaughn

Human–Wildlife Interactions

Some avian species have developed the capacity to leverage resource subsidies associated with human manipulated landscapes to increase population densities in habitats with naturally low carrying capacities. Elevated corvid densities and new territory establishment have led to an unsustainable increase in depredation pressure on sympatric native wildlife prey populations as well as in crop damage. Yet, subsidized predator removal programs aimed at reducing densities are likely most effective longer-term when conducted in tandem with subsidy control, habitat management, and robust assessment monitoring programs. We developed decision support software that leverages stage structured Lefkovitch population matrices to compare and identify treatment …


A Desert Tortoise–Common Raven Viable Conflict Threshold, Kerry L. Holcomb, Peter S. Coates, Brian G. Prochazka, Timothy Shields, William I. Boarman Jan 2021

A Desert Tortoise–Common Raven Viable Conflict Threshold, Kerry L. Holcomb, Peter S. Coates, Brian G. Prochazka, Timothy Shields, William I. Boarman

Human–Wildlife Interactions

Since 1966, common raven (Corvus corax; raven) abundance has increased throughout much of this species’ Holarctic distribution, fueled by an ever-expanding supply of anthropogenic resource subsidies (e.g., water, food, shelter, and nesting substrate) to ecoregion specific raven population carrying capacities. Consequently, ravens are implicated in declines of both avian and reptilian species of conservation concern, including the California (USA) endangered and federally threatened Mojave desert tortoise (Gopherus agassizii; desert tortoise). While ravens are a natural predator of desert tortoises, the inter-generational stability of desert tortoise populations is expected to be compromised as annual juvenile survival is …


Common Raven Impacts On Nesting Western Snowy Plovers: Integrating Management To Facilitate Species Recovery, Cheryl Strong, Kriss K. Neuman, Jenny L. Hutchinson, Jamie K. Miller, Amber L. Clark, Lena Chang, Joanna Iwanicha, Elizabeth Feucht, Matthew J. Lau, David J. Lauten, Sarah Markegard, Benjamin Pearl, David L. Sherer, Rachel Tertes, Susie Tharratt, Travis Wooten Jan 2021

Common Raven Impacts On Nesting Western Snowy Plovers: Integrating Management To Facilitate Species Recovery, Cheryl Strong, Kriss K. Neuman, Jenny L. Hutchinson, Jamie K. Miller, Amber L. Clark, Lena Chang, Joanna Iwanicha, Elizabeth Feucht, Matthew J. Lau, David J. Lauten, Sarah Markegard, Benjamin Pearl, David L. Sherer, Rachel Tertes, Susie Tharratt, Travis Wooten

Human–Wildlife Interactions

The U.S. Pacific coast population of the western snowy plover (Charadrius nivosus nivosus; plover) has declined due to loss and degradation of coastal habitats, predation, and anthropogenic disturbance. The U.S. Fish and Wildlife Service listed the subspecies in 1993 as threatened under the Endangered Species Act due to the population declines and habitat loss. Predation of nests and chicks has been identified as an important cause of historic population declines, and thus, most predator management actions for this subspecies are focused on reducing this pressure. In recent years, common ravens (Corvus corax; ravens) have become the most …


Estimating Trends Of Common Raven Populations In North America, 1966–2018, Seth M. Harju, Peter S. Coates, Seth J. Dettenmaier, Jonathan B. Dinkins, Pat J. Jackson, Michael P. Chenaille Jan 2021

Estimating Trends Of Common Raven Populations In North America, 1966–2018, Seth M. Harju, Peter S. Coates, Seth J. Dettenmaier, Jonathan B. Dinkins, Pat J. Jackson, Michael P. Chenaille

Human–Wildlife Interactions

Over the last half century, common raven (Corvus corax; raven) populations have increased in abundance across much of North America. Ravens are generalist predators known to depredate the eggs and young of several sensitive species. Quantifying raven population increases at multiple spatial scales across North America will help wildlife resource managers identify areas where population increases present the greatest risk to species conservation. We used a hierarchical Bayesian modeling approach to analyze trends of standardized raven counts from 1966 to 2018 using Breeding Bird Survey data within each Level I and II ecoregion of the United States and Canada. …


Common Raven Nesting And Spatial Distancing On Power Lines In Southeast Idaho, Usa, Quinn R. Shurtliff, Jericho C. Whiting Jan 2021

Common Raven Nesting And Spatial Distancing On Power Lines In Southeast Idaho, Usa, Quinn R. Shurtliff, Jericho C. Whiting

Human–Wildlife Interactions

Common raven (Corvus corax; raven) abundance and distribution have increased in western North America in recent decades, facilitated by anthropogenic subsidies and other environmental changes. Electrical power transmission line structures provide nesting substrates for ravens. When these structures transect landscapes where natural nest substrates are limited, they may facilitate raven predation on eggs and juveniles of sensitive avian and reptile species. Little information is available regarding raven nest density trends on adjacent power lines or how raven territorial behavior influences spatial partitioning of nests, and hence, nest density. This knowledge would be valuable for managers of sensitive prey …


Occurrence, Resource Use, And Demography Of The Common Raven In North America: A Research Synthesis, William C. Webb, Peter S. Coates, Seth J. Dettenmaier, David J. Delehanty Jan 2021

Occurrence, Resource Use, And Demography Of The Common Raven In North America: A Research Synthesis, William C. Webb, Peter S. Coates, Seth J. Dettenmaier, David J. Delehanty

Human–Wildlife Interactions

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 …


Synthesis Of Nest Predation Impacts Of Common Ravens On Sensitive Avian Species, Peter S. Coates, William C. Webb, Seth J. Dettenmaier, Seth M. Harju, David J. Delehanty Jan 2021

Synthesis Of Nest Predation Impacts Of Common Ravens On Sensitive Avian Species, Peter S. Coates, William C. Webb, Seth J. Dettenmaier, Seth M. Harju, David J. Delehanty

Human–Wildlife Interactions

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 …


Common Ravens Disrupt Greater Sage-Grouse Lekking Behavior In The Great Basin, Usa, Joseph L. Atkinson, Peter S. Coates, Brianne E. Brussee, Ian A. Dwight, Mark A. Ricca, Pat J. Jackson Jan 2021

Common Ravens Disrupt Greater Sage-Grouse Lekking Behavior In The Great Basin, Usa, Joseph L. Atkinson, Peter S. Coates, Brianne E. Brussee, Ian A. Dwight, Mark A. Ricca, Pat J. Jackson

Human–Wildlife Interactions

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 …


Demography, Morphometrics, And Stomach Contents Of Common Ravens Examined As A Result Of Controlled Take, Corinne M. Gibble, Kriss K. Neuman, Jessie Beck Jan 2021

Demography, Morphometrics, And Stomach Contents Of Common Ravens Examined As A Result Of Controlled Take, Corinne M. Gibble, Kriss K. Neuman, Jessie Beck

Human–Wildlife Interactions

Common ravens (Corvus corax; ravens) are known nest predators that have the ability to negatively impact nesting birds, including imperiled species of seabirds and shorebirds. We conducted systematic necropsies of ravens that were lethally controlled in Monterey Bay, California, USA during 2013–2015, in or near western snowy plover (Charadrius nivosus nivosus) nesting areas, in an effort to better understand body condition, overall health, and diet of individual ravens. Raven predation of snowy plover nests has increased over the years in the Monterey Bay study area, and lethal removal of ravens has been employed to reduce predation. …


Evaluating Common Raven Take For Greater Sage-Grouse In Oregon’S Baker County Priority Conservation Area And Great Basin Region, Frank F. Rivera-Milán, Peter S. Coates, Jacqueline B. Cupples, Michael Green, Patrick K. Devers Jan 2021

Evaluating Common Raven Take For Greater Sage-Grouse In Oregon’S Baker County Priority Conservation Area And Great Basin Region, Frank F. Rivera-Milán, Peter S. Coates, Jacqueline B. Cupples, Michael Green, Patrick K. Devers

Human–Wildlife Interactions

The common raven (Corvus corax; raven) is a nest predator of species of conservation concern, such as the greater sage-grouse (Centrocercus urophasianus). Reducing raven abundance by take requires authorization under the Migratory Bird Treaty Act. To support U.S. Fish and Wildlife Service’s take decisions (e.g., those that authorize killing a specified proportion or number of individuals annually in a defined area), including the most recent one for Oregon’s Baker County Priority Area for Conservation (PAC), we modeled raven population dynamics under hypothetical scenarios with take rates ranging from below to above the maximum sustained yield (MSY; …


Inter- And Intra-Annual Effects Of Lethal Removal On Common Raven Abundance In Nevada And California, Usa, Shawn T. O'Neil, Peter S. Coates, Julia C. Brockman, Pat J. Jackson, Jack O. Spencer Jr., Perry J. Williams Jan 2021

Inter- And Intra-Annual Effects Of Lethal Removal On Common Raven Abundance In Nevada And California, Usa, Shawn T. O'Neil, Peter S. Coates, Julia C. Brockman, Pat J. Jackson, Jack O. Spencer Jr., Perry J. Williams

Human–Wildlife Interactions

Populations of common ravens (Corvus corax; ravens) have increased rapidly within sagebrush (Artemisia spp.) ecosystems between 1960 and 2020. Although ravens are native to North America, their population densities have expanded to levels that negatively influence the population dynamics of other wildlife species of conservation concern, such as greater sage-grouse (Centrocercus urophasianus) and desert tortoises (Gopherus agassizii). For this reason, lethal removal, such as the application of the avicide DRC-1339, has been used to manage raven numbers at local scales and under certain circumstances. Because the relative effectiveness of DRC-1339 in reducing raven …


Common Raven Impacts On The Productivity Of A Small Breeding Population Of Snowy Plovers, Matthew J. Lau, Benjamin H. Becker, David T. Press Jan 2021

Common Raven Impacts On The Productivity Of A Small Breeding Population Of Snowy Plovers, Matthew J. Lau, Benjamin H. Becker, David T. Press

Human–Wildlife Interactions

Common ravens (ravens; Corvus corax), an adaptable, synanthropic generalist, have thrived coincident with increasing human landscape modifications and fragmentation, consequently affecting their prey, which are often sensitive native and protected species. Ravens are a conservation concern for the protected western snowy plover (plover; Charadrius nivosus nivosus), causing low nest and chick survival in some breeding areas along the Pacific coast of North America. We used a long-term dataset from a breeding snowy plover monitoring program in Point Reyes National Seashore (PRNS) to investigate potential impacts of ravens on snowy plover nest and fledging success. Between 2002 and 2020, …


Smart: A Science-Based Tiered Framework For Common Ravens, Seth J. Dettenmaier, Peter S. Coates, Cali L. Roth, Sarah C. Webster, Shawn T. O'Neil, Kerry L. Holcomb, John C. Tull, Pat J. Jackson Jan 2021

Smart: A Science-Based Tiered Framework For Common Ravens, Seth J. Dettenmaier, Peter S. Coates, Cali L. Roth, Sarah C. Webster, Shawn T. O'Neil, Kerry L. Holcomb, John C. Tull, Pat J. Jackson

Human–Wildlife Interactions

Large-scale increases and expansion of common raven (Corvus corax; raven) populations are occurring across much of North America, leading to increased negative consequences for livestock and agriculture, human health and safety, and sensitive species conservation. We describe a science-based adaptive management framework that incorporates recent quantitative analyses and mapping products for addressing areas with elevated raven numbers and minimizing potential adverse impacts to sensitive species, agricultural damage, and human safety. The framework comprises 5 steps: (1) desktop analysis; (2) field assessments; (3) comparison of raven density estimates to an ecological threshold (in terms of either density or density …