Physical-Anthropogenic Influence on House Crow (Corvus splendens) Abundance in Urban Areas with Varying Levels of Urbanization

Simple SummarySeveral bird species like common ravens, carrion crows, hooded crows, and rooks are held responsible for damage to agricultural land and crops. Especially in urbanized areas, they are increasing in abundance and are considered nuisance animals. We estimated the population size of carrion crows over the course of one year in relation to waste and non-waste sites in the federal state Vorarlberg, Austria. The current study showed that several human-related food resources influence the abundance of crows. More crows were observed in survey areas of biogas production and green-waste sites compared to reference sites 3 km distant from waste sites. Continuous hunting activities over the past two decades have not reduced population size. We suggest that the sustainable long-term stabilization and reduction of generalist corvid species populations can only be achieved if anthropogenic food resources are limited.In cities and densely populated areas, several corvid species are considered nuisance animals. In Austria, particularly carrion (Corvus corone) and hooded crows (C. cornix) are regarded as pests by the general public that frequently cause damage to crops, feed on human waste, and thus spread trash. We conducted a detailed one-year field survey to estimate the abundance of carrion crows in relation to potential anthropogenic food sources and reference sites in the Austrian Rhine valley. Our results demonstrated that the number and proximity of waste management facilities, animal feeding areas, and agricultural areas, and the productive capacity of agricultural areas, predominantly influenced habitat choice and abundance of carrion crows. In the current study, the probability of observing more than two carrion crows at a survey site decreased with increasing human population density. Moreover, the abundance of crows increased despite a continuous increase in crow hunting kills registered during the past 25 years. Our study suggests a regionally comprehensive waste management plan could serve as a promising strategy to manage nuisance birds. A reduction in anthropogenic food supply through improved waste management practices is required for long-term, sustainable management to limit the abundance of crow populations in and close to urban environments.

Invasive species such as the Indian House Crow (Corvus splendens) pose a significant ecological threat by disrupting local ecosystems and outcompeting native species. Originally from the Indian subcontinent, this crow has become invasive in Dodoma, Tanzania, where it preys on various organisms, including lizards. Lizards, which are important for pest control and as prey for higher trophic levels, are particularly affected. This study investigates community perceptions of Indian house crows and their impact on lizard populations in Dodoma. Using a combination of cross-sectional surveys and systematic sampling, we assessed local perceptions, lizard diversity and crow abundance. Our results show that approximately 85% of the community is aware of the presence and impact of Indian house crows. The study also shows that lizard diversity, as measured by Shannon's index, is higher in urban areas (1.51) with higher house crow abundance than in peri-urban areas (1.12). However, these urban areas also have significantly higher predation rates, with an average of 12% higher predation on lizards. The study highlights the ecological and socio-economic implications of house crow invasions and stresses the need for targeted management strategies to mitigate their negative impacts on local biodiversity and ecosystems.

Co-breeding involving herons and a potential egg predator, the Indian House Crow (Corvus splendens), in Peninsular India

Corvid populations are increasing worldwide in response to urbanization. We investigated the response of American Crows (Corvus brachyrhynchos) to urbanization by (1) comparing rates of winter population change between urban and nonurban locations (using standard Christmas Bird Counts); (2) quantifying population size along a gradient of urbanization in western Washington; and (3) pooling studies from eastern (New York), midwestern (Wisconsin), and western North America (Washington and California) relating survivorship, reproduction, and space use to urbanization. American Crow populations tend to be densest and increasing most rapidly in urban areas of North America. This appears to be facilitated by small space neEDS of crows in urban relative to suburban, rural, and exurban areas. Crow survivorship is high across the urban gradient, but reproduction and hence population growth, peaks in suburban and rural settings. Local demographic considerations appear unable to account for changing winter crow populations. Rather, we hypothesize that urban crow populations may be increasing primarily as surplus crows from suburban and rural areas disperse into the city where anthropogenic food sources are easily located, rich, and concentrated. This hypothesis likely is affected by local crow sociality. In the western United States, where pre-breeders often form flocks able to exploit urban riches, our dispersal hypothesis may be accurate. But, in midwestern and eastern areas, where crows migrate south for winter or remain on territories to help rather than float as pre-breeders, dispersal may not be adequate to fuel urban population growth. Refuse, invertebrates, and small vertebrates appeared to be more common food items than the nest contents of other birds. This, and the typically diverse suite of nest predators in any area, may explain why the rate of predation on artificial nests we placed throughout the urban gradient was not highly correlated with the abundance of crows. We encourage researchers to study how urbanization affects important mechanisms (like nest predators and predation) so environmental policy will benefit from a detailed, scientific understanding of how avian communities are structured.

West Nile virus (WNV) was first detected in the western hemisphere during the summer of 1999, reawakening US public awareness of the potential severity of vector-borne pathogens. Since its New World introduction, WNV has caused disease in human, avian, and mammalian communities across the continent. American crows (Corvus brachyrhynchos) are a highly susceptible WNV host and when modeled appropriately, changes in crow abundances can serve as a proxy for the spatio-temporal presence of WNV. We use the dramatic declines in abundance of this avian host to examine spatio-temporal heterogeneity in WNV intensity across the northeastern US, where WNV was first detected. Using data from the Breeding Bird Survey, we identify significant declines in crow abundance after WNV emergence that are associated with lower forest cover, more urban land use, and warmer winter temperatures. Importantly, we document continued declines as WNV was present in an area over consecutive years. Our findings support the urban-pathogen link that human WNV incidence studies have shown. For each 1% increase in urban land cover we expect an additional 5% decline in the log crow abundance beyond the decline attributed to WNV in undeveloped areas. We also demonstrate a significant relationship between above-average winter temperatures and WNV-related declines in crow abundance. The mechanisms behind these patterns remain uncertain and hypotheses requiring further research are suggested. In particular, a strong positive relationship between urban land cover and winter temperatures may confound mechanistic understanding, especially when a temperature-sensitive vector is involved.

The alpine grassland on the Qinghai-Tibet Plateau covers an area of about 1/3 of China’s total grassland area and plays a crucial role in regulating grassland ecological functions. Both environmental changes and irrational use of the grassland can result in severe grassland degradation in some areas of the Qinghai-Tibet Plateau. However, the magnitude and patterns of the physical and anthropogenic factors in driving grassland variation over northern Tibet remain debatable, and the interactive influences among those factors are still unclear. In this study, we employed a geographical detector model to quantify the primary and interactive impacts of both the physical factors (precipitation, temperature, sunshine duration, soil type, elevation, slope, and aspect) and the anthropogenic factors (population density, road density, residential density, grazing density, per capita GDP, and land use type) on vegetation variation from 2000 to 2015 in northern Tibet. Our results show that the vegetation index in northern Tibet significantly decreased from 2000 to 2015. Overall, the stability of vegetation types was sorted as follows: the alpine scrub > the alpine steppe > the alpine meadow. The physical factors, rather than the anthropogenic factors, have been the primary driving factors for vegetation dynamics in northern Tibet. Specifically, meteorological factors best explained the alpine meadow and alpine steppe variation. Precipitation was the key factor that influenced the alpine meadow variation, whereas temperature was the key factor that contributed to the alpine steppe variation. The anthropogenic factors, such as population density, grazing density and per capita GDP, influenced the alpine scrub variation most. The influence of population density is highly similar to that of grazing density, which may provide convenient access to simplify the study of the anthropogenic activities in the Tibet plateau. The interactions between the driving factors had larger effects on vegetation than any single factor. In the alpine meadow, the interaction between precipitation and temperature can explain 44.6% of the vegetation variation. In the alpine scrub, the interaction between temperature and GDP was the highest, accounting for 27.5% of vegetation variation. For the alpine steppe, the interaction between soil type and population density can explain 29.4% of the vegetation variation. The highest value of vegetation degradation occurred in the range of 448–469 mm rainfall in the alpine meadow, 0.61–1.23 people/km2 in the alpine scrub and –0.83–0.15 °C in the alpine steppe, respectively. These findings could contribute to a better understanding of degradation prevention and sustainable development of the alpine grassland ecosystem in northern Tibet.

The house crow (Corvus splendens) is globally recognised as a pest. It is an invasive species that can populate Malaysia's urban landscape and urban coastal areas. C. splendens was imported from Sri Lanka to Klang, Malaysia, in the 1890s to control caterpillars on coffee plantations. After a few decades, crows are able to adapt and co-exist with humans as a result of significant growth in the human population and urbanization. These urban pests are important due to the large volume of faecal droppings on buildings and near human dwellings. In other parts of the world, house crows can transmit pathogens and diseases such as chlamydiosis, salmonellosis, colibacillosis, and avian tuberculosis. They also carry human pathogens such as Salmonella spp., Shigella serotypes, Vibrionaceae spp., Newcastle disease virus (NDV), avian influenza virus (AIV) and West Nile virus (WNV) that can be transmitted to humans through their faeces. The first AIV transmission from birds to humans that caused a pandemic was alarming because of the risk of AIV and other avian virus transmission from birds. This prompted investigations into crow populations in urban centres. This review details the potential of C. splendens to spread AIV, NDV and WNV in Malaysia's highly urbanized areas.

Capsule Declines of upland waders were associated with habitat cover, forest edge exposure, grouse moor management intensity and crow abundance. Aims To explore whether changes in the abundance of five wader species in the uplands correlate with the three key hypotheses proposed for their declines. Methods Using data from repeat upland bird surveys, we examined at two spatial scales (region and plot) if population changes correlate with vegetation cover, forest edge exposure, grouse moor management intensity or crow abundance. Results For Northern Lapwings Vanellus vanellus and Eurasian Curlews Numenius arquata, there was an association between declines and broad‐scale vegetation cover; declines being greatest on heather‐dominated plots. Exposure to forest edge was associated with declines of European Golden Plovers Pluvialis apricaria and Common Snipe Galinago galinago at the plot scale, and of Northern Lapwings at the regional scale. More intensive grouse moor management was associated with lower declines in Northern Lapwings at both the plot and regional scale, but with greater declines in European Golden Plovers at the plot scale. Northern Lapwings also declined most on plots with the highest Carrion Crow Corvus corone abundance. Conclusion These analyses represent the first attempt to assess empirically the balance of evidence for different broad‐scale land‐use and habitat‐related drivers of upland wader population declines, providing pointers to their respective roles in driving these declines.

The Indian house crow (Corvus splendens) has successfully invaded tropical and subtropical regions well beyond its native range, reaching pest proportions in many areas. The invasive population of house crows in Singapore (Southeast Asia) has increased at least 30-fold since 1985 and now numbers in excess of 130,000 birds. To understand the population ecology and behavior of the house crow in Singapore, we undertook regular population size and roost surveys, dissections of birds shot (to provide age structure and breeding status), detailed nestsite observations, and monitoring of coastal dispersal. Using a discrete-time, density-dependent population model to synthesize this information, we demonstrated that at least 41,000 crows will need to be culled in the first year of a control program, and equivalent effort committed each year thereafter, to be confident of suppressing the Singapore population from its 2001 density of 190 birds/km(2) to the management target of <10 birds/km(2) within a 10-year period. This figure drops to 32,000 if culling is combined with other management strategies such as resource limitation and nest destruction. Complete eradication of the house crow from Singapore may be an unrealistic goal due to potential difficulties in detecting crows at IOW population densities and influx of migrants from neighboring Malaysia. Our study has implications for pest-bird management in other cities in Asia, Africa, and the Middle East, and presents it surrogate population-dynamics management tool for use in regions where the house crow has become established as a pest species, but where limited local field data is available.

Conditioned food aversion reduces crow nest predation: An improved framework for CFA trials

The House Crow (Corvus splendens) is a useful study system for investigating the genetic basis of adaptations underpinning successful range expansion. The species originates from the Indian subcontinent, but has successfully spread through a variety of thermal environments across Asia, Africa and Europe. Here, population mitogenomics was used to investigate the colonisation history and to test for signals of molecular selection on the mitochondrial genome. We sequenced the mitogenomes of 89 House Crows spanning four native and five invasive populations. A Bayesian dated phylogeny, based on the 13 mitochondrial protein-coding genes, supports a mid-Pleistocene (~630,000 years ago) divergence between the most distant genetic lineages. Phylogeographic patterns suggest that northern South Asia is the likely centre of origin for the species. Codon-based analyses of selection and assessments of changes in amino acid properties provide evidence of positive selection on the ND2 and ND5 genes against a background of purifying selection across the mitogenome. Protein homology modelling suggests that four amino acid substitutions inferred to be under positive selection may modulate coupling efficiency and proton translocation mediated by OXPHOS complex I. The identified substitutions are found within native House Crow lineages and ecological niche modelling predicts suitable climatic areas for the establishment of crow populations within the invasive range. Mitogenomic patterns in the invasive range of the species are more strongly associated with introduction history than climate. We speculate that invasions of the House Crow have been facilitated by standing genetic variation that accumulated due to diversifying selection within the native range.

The geological, geomorphic conditions of a mountainous environment along with precipitation and human activities influence landslide occurrences. In many cases, their relation to landslide events is not well defined. The scope of the present study is to identify the influence of physical and anthropogenic factors in landslide activity. The study area is a mountainous part of the northern Peloponnesus in southern Greece. The existing landslides, lithology, slope angle, rainfall, two types of road network (highway-provincial roads and rural roads) along with land use of the study area are taken into consideration. Each physical and anthropogenic factor is further divided into sub-categories. Statistical analysis of landslide frequency and density, as well as frequency and density ratios, are applied and combined with a geographic information system (GIS) to evaluate the collected data and determine the relationship between physical and anthropogenic factors and landslide activity. The results prove that Plio-Pleistocene fine-grained sediments and flysch, relatively steep slopes (15°–30°) and a rise in the amount of rainfall increase landslide frequency and density. Additionally, Plio-Pleistocene fine-grained sediments and flysch, as well as schist chert formations, moderate (5°–15°) and relatively steep slopes (15°–30°), along with the amount of rainfall of &gt;700 mm are strongly associated with landslide occurrences. The frequency and magnitude of landslides increase in close proximity to roads. Their maximum values are observed within the 50 m buffer zone. This corresponds to a 100 m wide zone along with any type of road corridors, increasing landslide occurrences. In addition, a buffer zone of 75 m or 150 m wide zone along highway and provincial roads, as well as a buffer zone of 100 m or 200 m wide zones along rural roads, are strongly correlated with landslide events. The extensive cultivated land of the study area is strongly related to landslide activity. By contrast, urban areas are poorly related to landslides, because most of them are located in the northern coastal part of the study area where landslides are limited. The results provide information on physical and anthropogenic factors characterizing landslide events in the study area. The applied methodology rapidly estimates areas prone to landslides and it may be utilized for landslide hazard assessment mapping as well as for new and existing land use planning projects.

This study reports on the perspectives of local farmers on predation on chickens by the invasive House Crow Corvus splendens, together with their coping strategies, in Dodoma, Tanzania. A survey was conducted among 391 farmers of free-range chickens in urban and peri-urban areas. Using a questionnaire and point counts, the study revealed that urban areas had a higher abundance of House Crows than peri-urban areas, largely attributable to increased availability of disposed waste. There was significantly greater predation in peri-urban than urban areas. Chicks and eggs had the highest predation rates, with chicks being the preferred prey. There was a negative correlation between the predation rate and the numbers of hens and chicks. To deter House Crows, farmers used techniques such as chasing and shouting. Effective predation control strategies should consider both the predation intensity and proximity to urban areas. While the farmers’ methods were environmentally friendly, innovations are needed to optimise their efforts to control House Crow predation on backyard poultry. Further research is therefore essential for sustainable solutions in this context.

Community roosting is the aggregation of more than two species of birds in the same tree for nocturnal roosting or nighttime residence. Mixed species community roosting mostly formed during the non-breeding season of birds. We recorded eighteen communal roosting sites of birds in the suburban region of Salem city, and the most dominant communal roosting birds are the large-billed crows (Corvus macrorhynchos) and house crows (Corvus splendens), along with other birds. The communal roosting site varies from a single large tree, like Ficus religiosa to a group of five to six trees in the case of Tamarindus indica, Azadirachta indica and Peltophorum pterocarpum. We recorded eighteen community roosting sites of birds in Salem and 26 species of trees were used for the community roosting. The roosting birds were dominated by large-billed crows and house crows. A positive correlation was found between the canopy cover and the number of birds roosting at the community roosting sites (r = 0.991, P &lt; 0.01). Further, there was a significant variation found between the time spent by large-billed crows and house crows within the communal roosts (t (46) = 4.997, P &lt; 0.01). Other birds that share the communal roosts with crows were common myna, red-vented bulbul and coppersmith barbet. The communal roosting sites are helpful for protection from nocturnal predators, and they also act as sites for information transfer.

Predation is one of the major challenges threatening chicken farmers, hindering the livelihood potentials in the poultry sector. We employed a cross-sectional design to assess the economic burden and strategies for overcoming predation by Indian House Crows (IHC) among farmers of indigenous chickens in Dodoma City, Tanzania. Data were collected through semi-structured interviews, focus group discussions, and key informant interviews. Quantitative data were analyzed using International Business Machines Statistical Package for the Social Sciences (IBM SPSS) version 26, while qualitative data were analyzed through content analysis. The mean flock size was 24±5 chickens, kept mainly under a free-range system. Depredation of chickens by IHC was high (210 chickens, 35.8%) during the dry season, with chicks being largely affected (461 individuals, 78.7%) compared to other age groups. Factors influencing depredation included the free-range system, young age of chickens, diseases, the dry season, and large flock sizes. Farmers perceived chicken depredation by IHC as a burden that impoverished their livelihood efforts. The main prevention measures against IHC predation were locking chickens up and chasing and shouting at crows. This study recommends further research on effective mechanisms to control IHC in the district and other areas with high crow populations to ensure the sustainability of chicken production and the poultry sector at large.