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- Estimating Trends of Common Raven Populations in North America,
1966–2018
Authors: Seth M. Harju et al.
Abstract: 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. We also compared raven abundance within and outside the distributions of 9 sensitive or endangered species. Although we found substantial evidence that raven populations have increased across North America, populations varied in growth rates and relative abundances among regions. We found 73% of Level I (11/15) and II (25/34) ecoregions demonstrated positive annual population growth rates ranging from 0.2–9.4%. We found higher raven abundance inside versus outside the distributions of 7 of the 9 sensitive species included in our analysis. Gunnison sage-grouse (Centrocercus minimus) had the highest discrepancy, with 293% more ravens within compared to outside of their range, followed by greater sandhill crane (Antigone canadensis tabida; 280%), and greater sage-grouse (C. urophasianus; 204%). Only 2 species, least tern (Sternula antillarum) and piping plover (Charadrius melodus), indicated lower raven abundance within relative to outside their distributions. Our findings will help wildlife resource managers identify regional trends in abundance of ravens and anticipate which sensitive species are at greatest risk from elevated raven populations. Future research directed at identifying the underlying regional drivers of these trends could help elucidate the most appropriate and responsive management actions and, thereby, guide the development of raven population management plans to mitigate impacts to sensitive species.
PubDate: Mon, 16 May 2022 12:35:41 PDT
- In the News
Authors: Ike Ionel et al.
Abstract: Items in the news.
PubDate: Mon, 16 May 2022 12:35:40 PDT
- A Novel Technique to Improve Capture Success of Common Ravens
Authors: Lindsey R. Perry et al.
Abstract: 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, USA, which yielded trapping efficiency of 0.48 trap-hours/raven (37 total captured ravens). Our trapping efficiency using leghold traps during the same summer months was 76.42 trap-hours/raven (3 total captured ravens). Our new trapping method constitutes an inexpensive and simple way to safely trap ravens at accessible communal roosts and merits further refinement to increase utility and capitalize on the vulnerability of ravens to capture at night.
PubDate: Tue, 15 Mar 2022 15:28:15 PDT
- Visual Marking of Ground Nests Might Attract Corvids
Authors: Emily M. O'Donovan et al.
Abstract: For ground-nesting birds such as waterfowl, estimating nest survival is a crucial step in assessing population dynamics, and marking nests facilitates continuous monitoring. A conventional method for marking ground nests is to use an inconspicuous rod at the nest bowl and a wooden lathe 10 m away. Nests are visually marked to allow for greater efficiency when revisiting nests and to facilitate subsequent nest searching sessions. Anecdotal evidence suggests that common ravens (Corvus corax) and American crows (C. brachyrhynchos) might learn to recognize these nest markers, resulting in artificially inflated rates of nest predation. In 2017 in central Alberta, Canada, we compared fates of nests marked with the conventional lathe-rod combination versus only a rod. We also tested the prevalence of corvid predation of marked nests in areas with and without high observations of corvid activity, using data from a study of dabbling duck (Anas spp.) nest survival. Our results suggest that marking nests with a lathe can increase predation by corvids and that nests marked with a rod only were more likely to hatch. Evaluation and use of alternate nest-marking methods would be beneficial for future studies of ground-nesting birds in areas where corvids are common. Our work highlights the importance of re-evaluating the efficacy of well-established field methods.
PubDate: Tue, 15 Mar 2022 14:45:21 PDT
- Demography, Morphometrics, and Stomach Contents of Common Ravens Examined
as a Result of Controlled Take
Authors: Corinne M. Gibble et al.
Abstract: 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. Most ravens examined in this study were in moderate to excellent body condition and also exhibited good organ health. There were statistically significant differences between male and female morphometrics (mass, culmen length, and wing length; P < 0.05). Stomach content analysis indicated a varied diet with consumption of animal remains and eggshell fragments, and anthropogenic sources of food (e.g., human food items and human-produced non-food items). Our study provides evidence that lethal control of ravens targeted some individual ravens that were responsible for depredating snowy plover nests
PubDate: Tue, 15 Mar 2022 14:45:11 PDT
- No Difference in Corticosterone Concentrations Between Missouri Three-Toed
Box Turtles Living in an Urban and a Rural Site
Authors: Bennett A. Lamczyk et al.
Abstract: Baseline health data for species of conservation concern are important for understanding threats to the long-term viability of populations. One indication of health is physiological stress among individuals. Corticosterone (CORT) is frequently used to quantify stress in free-living reptile populations, as high values may be associated with reduced fitness. Herein, we describe and validate methods for quantifying blood CORT levels in three-toed box turtles (Terrapene mexicana triunguis). We subsequently use this information to evaluate stress levels in 2 populations of free-living three-toed box turtles in Missouri, USA. To our knowledge, this is the first quantification of CORT levels in the three-toed box turtle. In 2012 we collected blood samples from 11 three-toed box turtles in human care at the Saint Louis Zoological Park (zoo), St. Louis, Missouri for assay validation, and from 2012 to 2016 we collected 220 samples from 144 free-living three-toed box turtles at 2 sites, 1 urban and 1 rural. In the zoo turtles, mean CORT concentration was 0.71 ± 0.10 ng/mL. Following a handling experiment, CORT concentration increased to 3.14 ± 0.72 ng/mL (P = 0.011). Mean CORT levels between free-living turtles at the urban and rural sites did not differ (urban = 0.54 ± 0.08 ng/mL, rural = 0.37 ± 0.02 ng/mL, F pr = 0.12). Sex did not influence CORT levels (F pr = 0.29). These results suggest that the turtles living in the urban environment did not experience chronic elevated glucocorticoid production and supports urban parks as potential habitat for box turtles.
PubDate: Thu, 10 Mar 2022 14:59:54 PST
- Evaluating Common Raven Take for Greater Sage-Grouse in Oregon’s Baker
County Priority Conservation Area and Great Basin Region
Authors: Frank F. Rivera-Milán et al.
Abstract: 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; i.e., trmsy= 0.01-0.60). We fit a Bayesian state-space logistic model to estimate abundance based on the Breeding Bird Survey route-level count data for the PAC during 1997-2019 and Great Basin Region (GBR) during 1968-2019. We predicted abundance for 2019-2030 and evaluated potential take levels (PTL) for the PAC and GBR. Abundance averaged 682 (SE = 93) for the PAC during 1997-2019 and 333,027 (SE = 20,504) for the GBR during 1968-2019. With take rates between 0.41 and 0.60, predicted abundance averaged 308 (SD = 405) for the PAC and 142,258 (SD = 53,474) for the GBR during 2019-2030. With management factor F = 0.75-2 for takes ranging from below to above the MSY, the PTL 50th percentiles were 150-401 yr-1 for the PAC and 60,457-161,219 yr-1 for the GBR. Our modeling framework is flexible and can be part of a comprehensive management strategy for ravens in the western United States.
PubDate: Tue, 08 Mar 2022 14:34:58 PST
- Raven Control from a Conservation Biology Perspective
Authors: David J. Delehanty
Abstract: 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 a difficult challenge in managing human–wildlife conflict. Some raven control measures are effective empirically but present ethical dilemmas, are economically expensive, or are socially divisive. Current studies seek to better understand raven population dynamics in relation to human land use and to identify socially acceptable ways to ameliorate raven impacts on biodiversity in the American West. The purpose of this paper is to provide readers with summaries of important constraints in the search for how to address deleterious effects of an expanding raven population. Specifically, I describe ethical, legal, social, and biological constraints in relation to calls for lethal control of ravens. Despite these constraints, a conservation strategy may emerge through modeling the relationship between raven presence and reproduction of sensitive prey species, and developing a clearer understanding of raven ecology. Papers in this special issue explore raven population dynamics, conservation consequences, and conservation solutions in detail and reveal innovative ways to address the complex human–wildlife conflict presented by ravens.
PubDate: Tue, 08 Mar 2022 14:11:25 PST
- Why Advertise in HWI'
Abstract: The benefits of advertising with Human–Wildlife Interactions and how to do so.
PubDate: Tue, 22 Feb 2022 15:02:57 PST
- Follow Us on Social Media
Abstract: How to follow HWI on social media.
PubDate: Tue, 22 Feb 2022 15:02:53 PST
- Monograph Reduced Box Price: Managing Human–Deer Conflicts
Abstract: Order form for HWI monograph, Methods for Managing Human–Deer Conflicts in Urban, Suburban, and Exurban Areas. This monograph identifies challenges and benefits associated with many human–deer conflict mitigation actions as well as methods to monitor the response of deer populations to management actions. Deer exploit urban, suburban, and exurban areas where human populations provide anthropogenic attractants, either intentionally or inadvertently, which often leads to human–deer conflicts. Mitigating actions have varying degrees of efficacy and may not be effective or accepted in every situation. Wildlife and municipal managers must work together to seek methods to reduce attractants, mitigate conflicts, and perpetuate the conservation of wildlife species that adds to the appreciation of nature in our lives.
PubDate: Tue, 22 Feb 2022 15:02:49 PST
- In the News
Authors: Ike Ionel et al.
Abstract: Items in the news.
PubDate: Tue, 22 Feb 2022 15:02:45 PST
- COVID-19: The Spearpoint of Human–Wildlife Interactions
Authors: Terry A. Messmer
Abstract: This is the letter from the editor-in-chief.
PubDate: Tue, 22 Feb 2022 15:02:41 PST
- Cover, Editorial Staff, Journal Information
Abstract: This includes the cover, editorial staff, and journal information.
PubDate: Tue, 22 Feb 2022 15:02:34 PST
- Extended Submission Deadline for Special Topic: Island Invaders
Authors: S. Nicole Frey
Abstract: This is an extended submission deadline for the call for papers for the special issue on island invaders.
PubDate: Mon, 06 Dec 2021 08:03:20 PST
- Why Advertise in HWI'
Abstract: The benefits of advertising with Human–Wildlife Interactions and how to do so.
PubDate: Tue, 24 Aug 2021 09:19:51 PDT
- Follow Us on Social Media
Abstract: How to follow HWI on social media.
PubDate: Tue, 24 Aug 2021 09:19:47 PDT
- Monograph Reduced Box Price: Managing Human–Deer Conflicts
Abstract: Order form for HWI monograph, Methods for Managing Human–Deer Conflicts in Urban, Suburban, and Exurban Areas. This monograph identifies challenges and benefits associated with many human–deer conflict mitigation actions as well as methods to monitor the response of deer populations to management actions. Deer exploit urban, suburban, and exurban areas where human populations provide anthropogenic attractants, either intentionally or inadvertently, which often leads to human–deer conflicts. Mitigating actions have varying degrees of efficacy and may not be effective or accepted in every situation. Wildlife and municipal managers must work together to seek methods to reduce attractants, mitigate conflicts, and perpetuate the conservation of wildlife species that adds to the appreciation of nature in our lives.
PubDate: Tue, 24 Aug 2021 09:19:44 PDT
- Wild Boar in Flanders, Belgium: (Dis)agreements Between Key Stakeholders
on Wild Boar Management Objectives, Actions, and Legal Provisions
Authors: Caroline Geeraerts et al.
Abstract: Wild boar (Sus scrofa) reappeared in Flanders, Belgium in 2006 after more than half a century of absence. Besides being a native and highly valued game species in Europe, wild boar are also known to be responsible for car collisions, crop damage, disease transmission, and ecological damage at high densities. The management of wild boar therefore seeks to balance these positive and negative impacts. Given the highly fragmented landscape in Flanders and its multifunctional use, coexistence with wild boar is only possible through integrated management involving relevant stakeholder groups. However, to be successful, this requires that the management objectives, the overall wild boar policy of the Flemish authorities, and management actions are supported by the stakeholders. To assess the support for the current management, we conducted a survey among members of the 3 key stakeholder groups: farmers, hunters, and conservationists. Our survey assessed the importance stakeholders attribute to different management objectives, their support for the current legal provisions, and how desirable the different stakeholder groups considered possible management actions. The potential for conflict index was used to analyze the (dis)agreement between and within stakeholder groups. Reducing or preventing crop damage and the risk for car accidents are indicated as being the most important management objectives by all 3 stakeholder groups. Stakeholder groups differ strongly in their support for the current legal provisions. Those stakeholders that have to implement the legal provisions or are mostly affected by these laws are less supportive than others. The desirability of the possible management actions strongly varied according to the different stakeholder groups. Contrary to other studies, the desirability of a possible management action was hardly influenced by the management objective it tried to achieve.
PubDate: Tue, 24 Aug 2021 09:19:22 PDT
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