Solomonoff Induction Violates Nicod's Criterion

Nicod's criterion states that observing a black raven is evidence for the hypothesis H that all ravens are black. We show that Solomonoff induction does not satisfy Nicod's criterion: there are time steps in which observing black ravens decreases the belief in H. Moreover, while observing any computable infinite string compatible with H, the belief in H decreases infinitely often when using the unnormalized Solomonoff prior, but only finitely often when using the normalized Solomonoff prior. We argue that the fault is not with Solomonoff induction; instead we should reject Nicod's criterion.Comment: ALT 201

Influence of Anthropogenic Subsidies on Movements of Common Ravens

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 better understand this issue, we deployed global positioning system – global system for mobile communications transmitters to track movements of 19 ravens from September to December 2020 relative to 2 land cover types that provide subsidies: developed areas and cultivated crops. On average, ravens moved 41.5 km (±30.5) per day, although daily movement distances ranged from 0.13–206.1 km. Raven movement among cover types during the non-breeding season varied widely, with 100% of individuals each using land cover types that provide subsidy and other types at least once in the season. On 100% of days ravens used areas that did not provide subsidy, on 86.7% of days they used developed areas, and on 20.5% of days they used cultivated crops. Although on some days a raven would stay exclusively in areas that did not provide subsidy, there were no days in which a single raven ever stayed exclusively in developed or cultivated crops. Ravens moved shorter distances on days when they used subsidies more frequently. Further, time spent in developed areas and cultivated crops increased when ravens roosted closer to them, although this effect was greater for developed areas than for cultivated crops. Individual ravens were not associated exclusively with either of the subsidy-providing landscapes we considered, but instead all birds used both subsidized and other landscapes. Our research suggests that management of ravens during the non-breeding season and possibly during the breeding season, intended to reduce risk of predation on desert tortoises, will be most effective if conducted on a broad scale because of distances the birds travel and the lack of separation between putative “urban” and “natural” populations of ravens

Winter Ecology and Spring Dispersal of Common Ravens in Wyoming

Numbers of Common Ravens (Corvus corax) have increased in western North America, and these high abundances are the source of problems throughout the species\u27 range. Little is known about the winter ecology of ravens. We studied a population of ravens in Wyoming during the winters of 2013–2015; our goals were to examine use of landfills for foraging and use of anthropogenic structures for roosting, as well as dispersal patterns of ravens from these landfills in the spring. On average, 22% of radio-marked ravens foraged at landfills on a given day and 68% roosted at anthropogenic sites (e.g. on buildings or underneath bridges) each night. Daily counts at an anthropogenic roost and at the nearest landfill were positively correlated. Decreased temperatures increased raven use of landfills and anthropogenic roost sites. In the spring, radio-marked and GPS-marked ravens (n = 56) dispersed an average of 38 km from the landfills where they were captured. Use of landfills and anthropogenic roost sites in the winter likely contributes to an increase in the number of ravens by improving survival and body condition of breeding-age birds. In the spring, ravens moved outward from these locations, and the area most susceptible to raven damage was localized within a 40-km radius of where ravens wintered

Demography, Morphometrics, and Stomach Contents of Common Ravens Examined as a Result of Controlled Take

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 \u3c 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 nest

Common Ravens Disrupt Greater Sage-grouse Lekking Behavior in the Great Basin, USA

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

Efficacy of Manipulating Reproduction of Common Ravens to Conserve Sensitive Prey Species: Three Case Studies

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 demographic rates of 2 sensitive prey species. Two case studies examine impacts of removing raven nests or oiling raven eggs on nest survival of greater sage-grouse (Centrocercus urophasianus; sage-grouse) within Wyoming and the Great Basin of California and Nevada, USA, respectively. The third case study uses Mojave desert tortoise (Gopherus agassizii; tortoise) decoys to examine effects of oiling raven eggs on depredation rates of juvenile tortoises in the Mojave Desert in California. Initial trial years from all 3 case studies were consistent in finding improved vital rates associated with the application of strategies for reducing reproductive success of ravens. Specifically, removal of raven nests resulted in increased nest survival of sage-grouse within treatment areas where predation by ravens was the primary cause of nest failure. In addition, nest survival of sage-grouse and survival of juvenile tortoise decoys was higher following a treatment of oiling the eggs of ravens in their nests at 2 sites within the Great Basin and 4 tortoise conservation areas in the Mojave Desert in California. Along with specialized technologies that can make techniques such as egg-oiling more feasible, these findings support these management practices as important tools for managing ravens, especially in areas where breeding ravens have negative impacts on sensitive prey species

Winter Ecology of Common Ravens in Southern Wyoming and the Effects of Raven Removal on Greater Sage-Grouse Populations

My research focused on common raven (Corvus corax; hereafter raven) winter ecology and removal, and how raven removal aids Greater sage-grouse (Centrocerus urophasiansu; hereafter sage-grouse) populations. Raven winter ecology in the western US has not been described in detail. I researched raven use of landfills for foraging and raven use of anthropogenic structures for roosting, as well as dispersal of ravens in the spring. In all 22% of radio-marked ravens (n=73) used landfills during the day, and 68%(n=73) roosted at anthropogenic roost sites during the evening. Correlations between landfill and roost counts of ravens were stronger (0.4\u3err20 km. In the spring, ravens dispersed, on average, 38 km from landfills where they were caught. Large congregations of ravens at a few sites in winter may present opportunities to initiate raven population reduction methods to alleviate later problems. I analyzed raven survival and behaviour when USDA/APHIS Wildlife Services (WS) removed ravens using DRC-1339 during winter months. The number of ravens killed annually was 7-34% of the local population. Ravens did not avoid landfills, yet they switched roosts more frequently after an application of the toxicant. Raven removal improves sage-grouse nest success; however, data were not available to examine how raven removal improves sage-grouse abundance. I analyzed changes in raven density with regard to WS removal, and then related these changes with changes in sage-grouse lek counts the following year. Raven densities decreased by 50% from 2008-2014 where WS conducted removal programs. Sage-grouse lek counts improved in area where WS lowered raven abundance, in comparison to areas farther away, during the latter half of the study (2013-2015), when WS removal efforts intensified. Thereafter, a 10% decline in raven abundance was associated with a 2% increase in sage-grouse lek counts. Overall, ravens in souther Wyoming used anthropogenic resources during the winter, and removal of ravens at these locations, combined with removal in the spring, minimally impacted raven populations annually and was associated with increases in sage-grouse abundance

Space Use and Nesting Ecology of Common Ravens (Corvus Corax) in Central Washignton State

The ecology and space use of Common ravens (Corvus corax; hereafter ravens) is not well understood in the shrub-steppe of central Washington State. Raven populations have increased by more than 254% since 1990 in Washington State (North American Breeding Bird Survey; www.mbr-pwrc.usgs.gov/bbs/). Ravens in central Washington are implicated as top predators of a small endemic population of greater sage-grouse (Centrocercus urophasianus). Researchers have related increased raven populations to anthropogenic subsidies such as landfills, agriculture, and livestock operations. Analyzing movement can help researchers understand the characteristics of habitat that are important and potentially drive population fluctuations. We found that daily and monthly movement distances for ravens were 19 kilometers (range = 3–238.5 km) and 505 kilometers (range = 102–1,575.4 km), respectively. Calculating Brownian Bridge home ranges shows that the average non-breeding raven home range size was 1,746 km2 (range= 104–6,675 km2), which is like home ranges from other studies. Annual reproductive output of ravens on YTC has been documented through nest monitoring since 2011. To better understand the factors that may be influencing raven reproduction, nest success was modeled against parameters thought to be important for ravens. YTC has a relatively high density of nesting ravens compared to other regions, and averages iv 51.5% annual nest success. We found that no habitat variables used for this analysis influenced raven nest success

Black ravens, white shoes and scientific evidence : the Ravens Paradox and/in scientific practice

1BLACK RAVENS, WHITE SHOES AND SCIENTIFIC EVIDENCE.THE RAVENS PARADOX AND/IN SCIENTIFIC PRACTICEErik Weber, Mathieu Beirlaen&Inge De BalCentre for Logic and Philosophy of ScienceGhent University (UGent)Blandijnberg 2, B-9000 Gent , BelgiumAbstractA well-known consequence of Hempel’s account of confirmation is the RavensParadox. In this paper we discuss this paradox from the viewpointof scientific practice. The main worry, when looking at this paradox from a scientific practiceperspective, is that it seems to lead to problematic methodological advice for scientists: it seems to licence ‘indoor ornithology’. We show that this problematic advice only follows from Hempel’s account if one adoptsa suboptimal viewof what counts as evidence for anhypothesis. We present and defend a more sophisticated viewof what counts as evidence, whichtakesrandom sampling–an important methodological principle in scientific practice–into account. On this sophisticated view, the problematic methodological advice connected tothe RavensParadox is avoided