Number Of Crows Research Articles

Trapping efficacy of invasive crows is affected by environmental factors and deployment history

AbstractHouse crows (Corvus splendens) are considered an invasive species and are prevalent in parts of Europe, Africa, and Southeast Asia. Existing crow management measures include food limitation, habitat modification, and direct population control. The latter method provides a more immediate solution, particularly in nesting locations where crow attacks occur more frequently. Crow ladder traps are widely adopted to capture crows, but a thorough examination of the environmental conditions that optimize trapping efficacy is lacking. We assessed factors affecting crow trap efficacy in Singapore to better advise future deployment strategies of crow traps. We obtained data from 170 crow trapping operations including the identities of the contractors conducting the trapping operations, operation start date, crow density, intensity of bird feeding, various land use cover proportions, and an index to quantify the spatial‐temporal proximity to previous trapping operations. We used a spatial gamma generalized linear mixed model (GLMM) to determine the factors affecting the daily number of crows captured and a spatial binomial GLM to determine the factors affecting the probability that crows will be captured. The number of bird‐feeding incidents had a negative effect on crow trap efficacy suggesting that crows are probably less inclined to enter traps if proximate anthropogenic food abundance is high. Trapping efficacy increased if traps were placed in high crow‐density areas, likely because more crows could detect the traps. The probability of capture also declined if the traps were placed closer to prior trapping locations or with a shorter time interval from previous trapping operations. Capture rates of crows can be increased by placing traps in high crow density areas, limiting bird‐feeding incidences, and lengthening the spatial and temporal proximities to previous trapping operations. The deployment of ladder traps is a viable means to control the population of house crows and consideration of environmental conditions and trapping history can improve capture rates.

The impact of population management on urban and rural Hooded Crow populations

Hooded Crow (Corvus cornix), originally native to agricultural areas, has become widespread in urban areas in recent decades. However, this process has negative consequences on urban animals and humans. Due to these problems, the control of urban crow populations is needed. Crows also cause significant damage to wildlife management, and are constantly being controlled in rural areas as well. In this study, we compare rural and urban populations to find out whether hunting activities have a population reduction effect. In the rural population, the reduction is carried out by weapons and traps, while the urban crows are controlled using traps only. In both sample areas, crow nests were surveyed during the nesting period. 29 active nests were monitored in the rural area in 2021, and 39 in 2022. In the urban area, 44 nests were recorded in 2021 and 35 nests in 2022. In 2021, 30 individuals were removed in the rural area, and 84 in 2022. In the urban area, 223 individuals were removed in 2021 and 144 in 2022. Results show that the number of crows removed follows the number of active nests, so that the reduction of a given year is likely to have an effect on the following year's nesting population. Because traps mostly capture juvenile birds, reducing the breeding population in the city can only be achieved in the long-term. Considering this, it is likely that increased attention to population control can effectively maintain crow populations and reduce the problems they cause.

Population Size and Habitat Occupancy by the Endangered Mariana Crow

I present data on the Mariana Crow for an extensive but previously unavailable set of population and habitat surveys from 1992 to 1993. From these, I (1) compute a series of population estimates from that period during which Mariana Crow numbers were first entering a precipitous decline, (2) quantitatively assess the habitats occupied by individual birds and thereby provide a view of the range of habitats occupied during a time when the species was still widespread, and (3) provide the first direct wet-dry season comparisons of populations and habitat occupancy. Surveys yielded significantly different wet (943) and dry season (459) population estimates, which suggested wet season courtship activity preceding dry season nesting when birds became more secretive. Moreover, they indicated that the critical turning point in population decline was after 1995. Forest was the principal habitat type occupied during both wet and dry seasons, with savanna present less than half as often as forest, although birds occupied a range of additional habitats. The species was more versatile in habitat use than is often assumed, as rates of habitat occupancy and availability were similar. Versatility is an advantage for populations confined to small islands that periodically suffer catastrophic habitat damage due to typhoons.

Theoretical aspects of the calculation the main design parameters of the electric bird repeller

The problem of scaring away birds was born in ancient times and remains relevant to this day. Birds tend to places where they are comfortable and stay there. Therefore, to achieve maximum effect, new and effective designs of electric bird repellers are needed. Currently, the territories of cities and their outskirts serve as a habitat not only for people and domestic animals, they are also a habitat for numerous species of wild birds. In the settlements and in their vicinity, a specific fauna of birds has formed. Its main features are a limited number of species and a large number of individuals. This is due to the fact that few bird species were able to adapt to the specific living conditions in the city. However, those who were able to adapt found in the city a favorable environment for rapid and mass reproduction. The number of synanthropic birds in large cities reaches tens and hundreds of thousands of individuals [2]. Synanthropic birds are wild birds that constantly live in the vicinity of humans or have found favorable nesting conditions in the territory of settlements and their environs. Many spheres of life of synanthropic birds are directly related to human activities, since the food of synanthropic birds is anthropogenic in nature, because their diet usually includes seeds of cultivated plants and all kinds of food waste [3]. In each region, different species of birds prevail, but there are patterns that are characteristic of the entire territory of Russia. Almost everywhere, the main representatives of the synanthropic are house sparrows and doves. In the central part of the country, you can safely add the hooded crow to this list. When moving towards the west, the number of crows decreases markedly.

Why do zoos attract crows? A comparative study from Europe and Asia.

Crows have successfully colonized many cities, and urban zoos have been important in this process. To evaluate why zoos attract crows, we quantified crow numbers and behavior in three zoos in Europe (Debrecen, Edinburgh, Vienna) and one in Asia (Sapporo). Data were collected in 445 surveys over 297 days in summer 2014 and winter 2014–2015. We found that crow numbers were highest in Vienna, intermediate in Debrecen and Edinburgh and lowest in Sapporo, increased significantly from summer to winter (Debrecen, Edinburgh, Vienna), and from mornings to afternoons (Debrecen, Sapporo, Vienna), and were higher in sunny weather than in cloudy weather with precipitation and when visitor numbers were low (Debrecen, Vienna). The crows' use of natural food was highest in Vienna, intermediate in Edinburgh and Sapporo, and low in Debrecen. The use of anthropogenic food was high in Debrecen and Sapporo, where the availability of open grassy areas typically used by crows for natural foraging was low. In Sapporo, food availability was more limited than in other zoos, resulting in strong territoriality and few crows in summer, which decreased further in winter. Our study indicates that crows are primarily attracted to zoos by food availability and secondarily by breeding opportunities and that the relative importance of natural versus anthropogenic food sources may vary with zoo habitat structure. Our study draws attention to a previously overlooked role of zoos in urban biodiversity conservation. It may also provide useful information for the management of crow populations, if necessary, and for the planning of urban areas.

Capturing Crows for the Protection of Threatened and Endangered Shorebird Species

ABSTRACTCorvids are highly intelligent and capable of thriving in anthropogenic ecosystems. American crows (Corvus brachyrhynchos) regularly depredate threatened and endangered avian species. Live capture is a common component of crow management programs; however, crows are notoriously difficult to capture. Here, we report previously undocumented crow capture techniques, utilizing a modified goshawk (Accipiter gentilis) trap design as part of a shorebird conservation project in San Diego, California, USA, 2012–2017. A negative binomial generalized linear model showed a significant relationship between number of crows removed and number of endangered California least tern (Sternula antillarum browni) eggs predated by crows. Of the total number of crows in that analysis, 67% were removed via goshawk trap. Therefore, we attribute the same percentage of reduction in egg loss to the success of that trap type. We tested 2 goshawk trap designs that differed by number of capture chambers (single and double). Double‐chambered traps were nearly twice as effective at capturing crows compared with single‐chambered traps. We performed McNemar's χ2 tests with continuity correction to determine whether traps were more effective with the use of conspecific lure‐birds and obtained significant results for single and double‐chambered traps. The modified goshawk trap has an efficient design that can improve crow control programs, especially when constructed with 2 chambers and deployed with lure‐birds. © 2018 The Wildlife Society.

Public willingness to participate in actions for crow management

Context Large-scale human modification of the environment has caused an overall loss of biodiversity; some species, such as crows, do benefit from these changes. Increased crow numbers in Slovenia in the past two decades have caused one of the main human–wildlife conflicts. To reduce these conflicts, successful and effective wildlife management is needed that is rooted in an evaluation of general public opinions and attitudes towards action. Aims The purpose of the present study was to identify factors that affect the willingness of the public to participate in actions for crow management. With knowledge about the factors that affect the willingness to participate in management actions, we can enhance public intention and behaviour. Methods A research model based on variables from a public survey was set up and tested with ordinal regression analysis. Key results The willingness to participate in crow management was influenced by (1) attitudes towards action, (2) interest in crows and conflicts in interaction with the moderator variables of education level or place of residence, (3) perceived behavioural control, (4) fear towards damage caused by crows, and (5) trust in experts in with the moderator variables of gender, education level, or utilitarian behaviour. Conclusions Public do not possess sufficient competences for crow management. With additional information and awareness, they could decide more clearly about their participation in management. Implications To increase the number of participants in actions, we need to educate the public about critical skills and competencies, provide explanations why some actions are effective and feasible, and convey the importance of public participation. With low confidence about their competences and low, or even no, trust in decision-makers, the willingness to participate was found to decrease.

The effect of infrastructure on the invasion of a generalist predator: Pied crows in southern Africa as a case-study

Corridors can favour range expansion of generalists. Specifically, roads have been suspected of facilitating invasion. In southern Africa, pied crows (Corvus alba) have either colonised or increased in abundance, perhaps because climate warming has shifted their available habitat, assisted by roads. We investigated the link between abundance of this generalist bird species and roadkill, taking into account whether road infrastructure, socio-economics and driving habits influence roadkill. We surveyed 1170km of principal roads in South Africa (SA), Botswana, and Zimbabwe. SA has the most complex economy incorporating good roads, fast vehicles and more human activity. The economy of Botswana is intermediate and Zimbabwe's is smallest. Crows were sighted nearly 10 times more often in SA than Zimbabwe, although crows were historically rare in 60% of the SA area we surveyed. They were five times more abundant in Botswana than Zimbabwe. Roadkill was 20 times more frequent in SA and eight times more frequent in Botswana, than Zimbabwe. The average number of vehicle occupants in Zimbabwean vehicles was 5.5 and 2.8 times that of SA and Botswana, respectively. That is, the number people transported per roadkill was 4.5 in South Africa, compared to 433 in Zimbabwe. There was an interaction between roadkill and country. SA had the greatest increase in crow numbers per roadkill, indicating that crow densities were greater in SA because roads are particularly important for crows compared to the surrounding environment, and/or that the regular supply of roadkill on South African roads builds a “reservoir” of crows. Increased crow abundance places additional predation pressure on mammals, reptiles, birds and insects in the surrounding scrub-vegetation. Telegraph poles contribute to the problem, providing nest sites in an environment that provides few other nests and perches. An approach to socioeconomic development that considers contributing factors can be expected to reduce the spread of opportunist species.

Attitudes toward and Acceptability of Management Strategies for a Population of Hooded Crows (Corvus cornix) in Slovenia

ABSTRACTRecently, the number of hooded crows (Corvus cornix) in Slovenia has increased, which has resulted in a higher number of situations perceived as human–wildlife conflicts. The purpose of our survey was to provide a basis for population management measures of hooded crows that would be both feasible and acceptable to the public. An online survey based on snowball sampling received 1,042 responses, representing about 0.05% of the total and 0.13% of the active human population of the Republic of Slovenia. The major findings are that the majority of respondents were interested in learning more about problems caused by crows and think that crow numbers should be reduced, but by measures that would not cause their death. About one-third of respondents would be willing to participate in measures directed to controlling the crow population; however, about one-third would actively oppose such measures. They would even sign a petition regarding control measures. From the results, we conclude that the most suitable strategies in terms of acceptability would be passive, by educating people about how to avoid conflict with crows, and by better management of the resources affecting their foraging success.

AN EPIZOOTIC OF EMERGING NOVEL AVIAN POX IN CARRION CROWS (CORVUS CORONE) AND LARGE-BILLED CROWS (CORVUS MACRORHYNCHOS) IN JAPAN.

In 2006-10, an epizootic of emerging avian pox occurred in Carrion Crows ( Corvus corone ) and Large-billed Crows ( Corvus macrorhynchos ), leading to mortality of juvenile crows in Hokkaido, the northernmost island of Japan. We diagnosed 27 crows with proliferative skin lesions (19 carcasses and eight biopsied cases [one in zoo captivity]) as avian pox clinically, histopathologically by detection of Avipoxvirus-specific 4b core protein (P4b) gene, and epidemiologically. The fatal cases demonstrated intensively severe infection and aggressive lesions with secondary bacterial infection. Since the first identification of avian pox in Sapporo, Japan, in 2006, the frequency of mortality events has increased, peaking in 2007-08. Mortalities have subsequently occurred in other areas, suggesting disease expansion. In Sapporo, prevalence of avian pox evaluated by field censuses during 2007-12 was 17.6% (6.6-27.2%), peaked during 2007-08 and 2008-09, and then decreased. All diseased crows were juveniles, except for one adult. The number of crows assembling in the winter roosts had been stable for >10 yr; however, it declined in 2007-08, decreased by about 50% in 2008-09, and recovered to the previous level in 2009-10, correlated with the avian pox outbreak. Thus, avian pox probably contributed to the unusual crow population decline. All P4b sequences detected in six specimens in Sapporo were identical and different from any previously reported sequences. The sequence detected in the zoo-kept crow was distinct from any reported clades, and interspecies transmission was suspected. This report demonstrates an emerging novel avian pox in the Japanese avifauna and in global populations of Carrion Crows and Large-billed Crows. Longitudinal monitoring is needed to evaluate its impact on the crow population.

Electric crows: powerlines, climate change and the emergence of a native invader

AbstractAimClimate change and other anthropogenic global change drivers act in complex, mutually exacerbating ways to alter the abundance and distribution of species. In South Africa, pied crows Corvus albus have increased in numbers and range in recent decades. Popular opinion links these changes to urbanisation and infrastructure development, but there has been no empirical test of this idea. We aimed to clarify the drivers of pied crow population changes in South Africa.LocationSouth Africa.MethodsWe used publicly available long‐term datasets, the Southern African Bird Atlas Project and University of Delaware Gridded Climate Database, and spatial data from government bodies, to assess relationships between pied crow population and range changes, land use, infrastructure, urbanisation and climate change.ResultsPied crow numbers have increased significantly in the past three decades, but rate of increase varied geographically, with crows declining in the northeast and increasing in the south‐west of South Africa. Pied crow population changes were strongly correlated with climate change. Crows have benefited most from climate warming in the shrubland biomes of south‐western South Africa. Pied crows are tree nesters, and within these shrublands, there is a strong positive relationship between the rate of population increase and the density of powerline infrastructure, which may facilitate pied crows’ increase by providing nesting sites.Main conclusionsPied crow numbers have increased in response to climate warming, with their spread facilitated by electrical infrastructure in south‐western South Africa, providing a clear example of compound influence of multiple global change drivers promoting a significant change in species range and reporting rate. Pied crows are generalist predators and there is popular concern about their ecological impact in areas where increases have occurred. We highlight the importance of understanding the ecosystem‐level implications of increased numbers of pied crows in South Africa's shrubland biomes.

The highest-ranking rooster has priority to announce the break of dawn.

The “cock-a-doodle-doo” crowing of roosters, which symbolizes the break of dawn in many cultures, is controlled by the circadian clock. When one rooster announces the break of dawn, others in the vicinity immediately follow. Chickens are highly social animals, and they develop a linear and fixed hierarchy in small groups. We found that when chickens were housed in small groups, the top-ranking rooster determined the timing of predawn crowing. Specifically, the top-ranking rooster always started to crow first, followed by its subordinates, in descending order of social rank. When the top-ranking rooster was physically removed from a group, the second-ranking rooster initiated crowing. The presence of a dominant rooster significantly reduced the number of predawn crows in subordinates. However, the number of crows induced by external stimuli was independent of social rank, confirming that subordinates have the ability to crow. Although the timing of subordinates’ predawn crowing was strongly dependent on that of the top-ranking rooster, free-running periods of body temperature rhythms differed among individuals, and crowing rhythm did not entrain to a crowing sound stimulus. These results indicate that in a group situation, the top-ranking rooster has priority to announce the break of dawn, and that subordinate roosters are patient enough to wait for the top-ranking rooster’s first crow every morning and thus compromise their circadian clock for social reasons.

Effect of food patch discovery on the number of American Crows (<em>Corvus brachyrhynchos</em>) using a flight lane

In winter, American Crows (Corvus brachyrhynchos) move back and forth between night roosts and foraging sites along flight lanes. If communal roosts act as information centres, we would expect more birds to use a particular flight lane after discovery of a new food patch on that route. In this study, I investigated how the number of crows using different flight lanes was affected by the establishment of artificial food patches, as well as how crows responded to multiple days of provisioning and to the location of the food patch relative to the flight lane. After discovery of a food patch, the number of crows using the flight lane closest to it increased, while numbers using adjacent flight lanes remained the same or decreased, particularly when the patch was in the path of the flight lane and when food provisioning occurred for 2 consecutive days. These results support the idea that crows using winter roosts may make use of information on food availability obtained at the roost.

Pomen in vplivi vran, s poudarkom na sivi vrani (Corvus cornix), v (sub)urbanem okolju

In recent decades, the increase in number of crows, particularly the hooded crow (Corvus cornix), in the (sub)urban environment has resulted in the ever-increasing conflicts with humans. Consequently, this has resulted in growing demands for solving problems with crows and for significant reductions in abundance of these birds (particularly in the urban environment), which happened also in Slovenia. However, Slovene professional-scientific literature does not provide any scientific data that would confirm or even evaluate possible negative impacts of crows on humans, society or ecosystems. For this reason, a comprehensive review of foreign studies on interactions among humans and crows is presented in this paper, which aims to contribute to a better understanding of conflicts with (especially hooded) crows in the urban and rural environment and therefore also to suitable management of species. Due to (rather stigmatised) opinion on negative impacts of crows on populations of other bird species, an overview of studies on the effects of (hooded) crows as predators is also provided. It is very evident from the literature that crows certainly play an important role in ecosystems, and are also involved in many conflict situations with human both on agricultural land (damages on crops and infrastructure) and in urban ecosystems (damage on property, attacks on humans, disturbing peace of residents, pollution in urban areas). In order to make suitable and reasonable management decisions, it would be necessary to systematically study comprehensive ecosystem values of (hooded) crows and their conflicts with humans both in agricultural and urban areas of Slovenia. Based on these findings, appropriate measures to reduce both the number and volume of negative interactions as well as to increase the tolerance of crows in public should be implemented.

Identifikasi Marka Bioakustik Suara Kokok Ayam Kokok Balenggek di Kandang Penangkaran “Agutalok”, Kabupaten Solok

Kokok Balenggek chicken is a genetic resources from West Sumatra Province, Indonesia, well known as song fowl which has high economic commodity for Minang Kabau tribes. There is an important need to identify bioacoustic marker of Kokok Balenggek song fowl in Solok regency of West Sumatra, Indonesia. This research was aimed to collect basic data of crow characteristics of Kokok Balenggek song fowl. This research was conducted in a captive breeding farm “Agutalok”, Solok Regency, Indonesia. The number of 21 heads of adult male Kokok Balenggek chicken were selected as samples in this project. Song characteristics of Kokok Balenggek chicken was observed using time sampling method. Time observation was performed in three time period; Morning (4-6 a.m), Noon (11 a.m – 1 p.m) and Afternoon (4-6 p.m) for three days consecutively. Some parameters such as number of crows, number of phrase crows, time of crows, duration of crows, and frequency of crows were recorded during the observation. The results showed that the number of crows were ranging 5-11 crows, number of phrases crow were 8-14 phrases, time of crows were happened more frequent in the morning, duration of crows were 3.22 seconds happened frequently at Noon with frequency of crows were 9.39 times/10 minutes.

Shifting Synanthropy of the Crow in Eastern North America

The American crow (Corvus brachyrhynchos) falls into a category of wild organisms, called “synanthropes,” that have developed an affinity for, or dependency on, human interventions in the landscape. The distribution and numbers of crows in North America east of the Mississippi River have been largely tied to the anthropogenic fragmentation of the forest. As ground feeders, crows need open space for foraging, but they also need trees for nesting and roosting. Conflicts between corvids and people centered on the former's damage to agriculture. Both Native American peoples and Euro‐American settlers sought to thwart corvine preference for maize through a series of ingenious measures. After 1950 rural concern about corvine depredations greatly diminished. The appearance of large winter roosts in cities shifted the conflict with crows. Like humans, crows have undergone change, and their synanthropic character can be seen as fundamental to their biogeography.

The direct and indirect effects of predation by Hen Harriers Circus cyaneus on trends in breeding birds on a Scottish grouse moor

Two phases of an experimental reduction in management at Langholm Moor in southwest Scotland provided an insight into factors that determined trends in the abundance of moorland birds. In 1992 the historical control of breeding Hen Harriers Circus cyaneus stopped and in 2000 grouse moor management was discontinued. Golden Plover Pluvialis apricaria, Lapwing Vanellus vanellus, Curlew Numenius arquata and Red Grouse Lagopus lagopus scoticus declined, whilst Carrion Crow Corvus corone and Snipe Gallinago gallinago increased. Hen Harriers increased from two to 20 breeding females, then declined back to two. Lapwing abundance was positively associated with that of Hen Harriers, and moorland passerines (Skylark Alauda arvensis, Meadow Pipit Anthus pratensis and Stonechat Saxicola torquata) were negatively associated. Golden Plover, Lapwing, Curlew, Red Grouse, Skylark and Hen Harrier were more abundant when the moor was managed for grouse, whilst Carrion Crow, a common predator of clutches of ground‐nesting birds, increased during the second half when management ceased. Increased Crow numbers, together with an increase in Red Foxes Vulpes vulpes, probably contributed to the observed bird declines.

Non-Lethal Management to Reduce Conflicts with Winter Urban Crow Roosts in New York: 2002 - 2007

American crow populations have increased steadily since 1966 in many parts of the U.S. Large winter congregations of crows in urban environments have resulted in an increased number of requests for assistance in managing nocturnal roosts in New York. In 2002, the USDA APHIS Wildlife Services program initiated a large-scale non-lethal winter roost dispersal program in Troy, New York. Since that time, similar programs have been implemented in 4 other cities in New York to manage crow roosts ranging in size from 8,000 - 63,000 individuals. The goals of the programs were to minimize noise, accumulations of crow feces around residences, strong odors associated with droppings, property damage, clean-up costs, and potential threats to human health and safety. The primary management strategy relied on dispersing concentrated crow populations from high-impact high-conflict areas, to low-impact low-conflict areas. An integrated management program using pyrotechnics, amplified recorded crow distress calls, and hand-held lasers was implemented to successfully disperse local crow roosts, reducing populations at the majority of core roost sites each year by more than 98%. In some instances, significant reductions in crow numbers and associated damage persisted >8 weeks after management without additional interventions, although most sites required multiple additional “spot treatments.” High-profile urban wildlife management projects of this type require multiple meetings with key stakeholders and the public and often attract intense media interest, adding complexity to these programs. We provide summary information from 5 cities in New York documenting crow management techniques, intensity of effort, number of interventions required to relocate crow populations, and key lessons learned regarding sciencebased project documentation, project transparency, communication, and the need for long-term adaptive management strategies to meet project goals.

Individual roosting strategies in a flock-living bird: movement and social cohesion of hooded crows ( Corvus corone cornix ) from pre-roost gatherings to roost sites

The function of the conspicuous pre-roost gathering in communally roosting birds is poorly known. We studied movement and social cohesion of radio-tagged hooded crows (Corvus corone cornix) from their daytime location via pre-roost to roost in autumn and winter. With increasing snowfall the previous 24 h, the crows attended pre-roosts farther from the territory, and moved longer from pre-roost to roost. The crows became more likely to roost communally as distance to their territory increased. Attending a pre-roost on average almost doubled the travel distance to a communal roost. Crows were much more likely to join the same roost when they had attended the same pre-roost than otherwise. Breeding mates were more likely to keep together from pre-roost to roost than were other assigned pairs of a territorial male and female. For assigned pairs of non-mates, cohesion from pre-roost to roost decreased with increasing distance to roost, and was higher when both crows roosted communally compared to when at least one of them roosted in its territory. When both roosted communally, cohesion decreased with increasing snowfall and increasing number of crows attending the pre-roost, increased with increasing snow depth, and became higher among two females, compared to other combinations of two crows, with increasing number of crows attending the pre-roost. These patterns may be interpreted as supporting several of the current hypotheses on the function of pre-roost gathering.

Risk factors for Johne's disease in Scotland - the results of a survey of farmers

The reported incidence of Johne's disease has been increasing in the east of Scotland since 1993. A postal questionnaire survey was sent to 127 farms to identify potential risk factors...