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Dryad

The desert exploiter: an overabundant crow species exhibits a neighborhood diffusion pattern into the southern region of Israel

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May 18, 2021 version files 7.69 MB

Abstract

Overabundant species are considered drivers and passengers of profound anthropogenic disturbance in ecosystems, resulting in uneven communities. Understanding the causes of spread and establishment of such species may help decipher invasion mechanisms, while providing managers targeted management tools. The objective of this research was to quantify the spread of Corvus C. cornix in Israel, while attempting to elucidate the causes of its spread. Long-term occurrence data of crow sightings was used to analyze the species expansion. This data-set was correlated with a suit of climatic, NDVI and land-use variables. Results showed new hotspots of hooded crow activity in the north-western Negev desert and Jerusalem regions. A diffusion equation model revealed an expansion rate of 1.60 km year -1. Land-use analysis revealed an affinity of sighted individuals towards urban and low vegetation land types. Hooded crows sightings were positively correlated with annual precipitation, while being negatively correlated with precipitation during the wettest quarter. These findings suggest the species has established new source populations and is situated in the range expansion stage. The comparatively slow rate of dispersal is consistent with a neighborhood diffusion pattern, corresponding to the species life history traits. Human- altered land-use types, including low cover agriculture provide a habitat rich in constantly available food and nesting trees, both allow the hooded crow to thrive throughout the year. Precipitation may aid in enhancing hooded crow tolerance towards other unfavorable physical conditions. In light of these new findings, short term actions require pruning of tall trees in population hotspots. Intermediate term policies should focus on removal of existing stepping stones, and on farmer-ranger cooperation with the goal of limiting available food and water supplies. Long-term plans ought to recognize centers of hooded crow activity as indicators of highly disturbed and uneven communities. This should emphasize the need to establish Agri- environmental schemes (AES) in such areas, which would raise community resistance to invasive species. As AES are currently not in place in the national scale, and since their creation has the power to improve landscape connectivity of native species, this last plan is especially in need.