Hooded Crow Corvus Cornix Research Articles

Absence of effects of predator control on nesting success of Northern Lapwings Vanellus vanellus: implications for conservation

The control of generalist predator populations is increasingly adopted as a management tool to combat declines in ground-nesting bird populations. However, compensatory predation by uncontrolled species frequently occurs, so determining the relative impacts of different predatory species, and hence the relative benefits of their control, can be difficult. Islands, with their reduced faunas, provide natural experimental units for investigating specific predator–prey interactions in detail. We studied Northern Lapwing Vanellus vanellus breeding success on an island where feral Ferrets Mustela furo and Hooded Crows Corvus cornix were subjected to trial control regimes over 2 years. In both years, Lapwing hatching success was >80%, with neither Ferret nor Crow control selected as important predictors. Fledging rates in both years were 0.7 young per pair, despite highly effective predator removal, although Crow control potentially resulted in compensatory predation by Common Ravens C. corax. Neither mustelid nor corvid control produced significant immediate benefits for Lapwings. This suggests that mesopredator release of mustelids in mainland situations is unlikely to be a consistent threat to Lapwing, and provides further evidence that declines in this species are unlikely to be tackled successfully through predator management alone.

Predators and nest success of Sky Larks Alauda arvensis in large arable fields in the Czech Republic

Capsule Nest failure owing to a range of predators was high, but the level and specificity of nest depredation cannot be generalised. Aims To determine fates and predators of Sky Lark nests in conventionally managed arable fields in the Czech Republic. Methods Sky Lark nests in large fields (mainly Maize, Sugar Beet and Opium Poppy) were monitored by means of continuous video surveillance. Results Primary nest fates of 42 active nests were fledging (13), depredation (22), desertion (5), nestling death (1), and flooding (1). The overall nest success (Mayfield estimate) was 17% (all mortality factors considered) or 27% (only depredation). Depredation events were caused by Marsh Harrier Circus aeruginosus (11), Hooded Crow Corvus cornix (4), Stone Marten Martes foina (3), Montagu’s Harrier Circus pygargus (2), Red Fox Vulpes vulpes (2), Hedgehog Erinaceus sp. (2) and Eurasian Jackdaw Corvus monedula (1). Successful nests were only slightly more away from field edge than depredated nests; nests taken by birds tended to be closer to field edge than those depredated by mammals. The possible reasons for the absence of a clear edge effect include comparatively large field parcels (about 50 ha) and location of nests far from field edge (median = 195 m). Conclusion Nest survival and composition of nest predators are site‐specific and contingent upon the study method and may not be simply generalised.

Are Changes in Predatory Species Composition and Breeding Performance Responsible for the Decline of CootsFulica atrain Milicz Ponds Reserve (SW Poland)?

Abstract. Both native and non-native predators should strongly affect resident fauna. Nevertheless, because of a lack of defensive mechanisms in potential prey, the influence of non-native predators should have longer-lasting and more deleterious repercussions. The breeding ecology of the Coot was studied in the Milicz Ponds reserve and compared with data from 20 years earlier. In the meantime, non-native, mammalian predators (American Mink Mustela vison, Raccoon Dog Nyctereutes procyonoides and Raccoon Procyon lotor) turned up in this area, while the numbers of Hooded Crow Corvus cornix, the main predator of Coot nests, decreased. Compared with 1980–1982, the number of Coots in 2002–2003 dropped by more than half and mean clutch size decreased. Breeding success and the number of hatchlings per pair remained unchanged; in the 1980s, however, Coots renested more frequently, there was greater nesting synchrony and breeding seasons were demonstrably shorter. Moreover, although predation still remained the ma...

Nest predators of woodland open‐nesting songbirds in central Europe

I used time‐lapse videotaping to identify predators of open songbird nests in fragmented deciduous woodland (nine plots, 2–10 ha each) in the Czech Republic from 2002 to 2006. I documented 22 species of predators at 171 nests of 13 species (mainly Blackcap Sylvia atricapilla, Song Thrush Turdus philomelos, Common Blackbird Turdus merula, Yellowhammer Emberiza citrinella and Chaffinch Fringilla coelebs). The main predators were Pine Marten Martes martes (37% of 178 predation events), Jay Garrulus glandarius (29%), Buzzard Buteo buteo (7%) and Great Spotted Woodpecker Dendrocopos major (7%); mammals accounted for 48% of total predation. At least 3% of nests were depredated by multiple predators. In spite of their local abundance, Hooded Crows Corvus cornix did not present a serious threat for shrub nesting songbirds (< 1% of total predation). No predation by mice was recorded, suggesting that their importance has been overestimated in artificial nest studies. The proportional species composition of predators depended on which species occupied the monitored nest and location (study plot), but not on the year or the time of season. Corvids and raptors accounted for a relatively larger percentage of total predation of small (‘warblers’) and large (‘thrushes’) prey species, respectively, whereas carnivores were important predators of all prey species. Active nests of thrushes were only rarely robbed by Jays (< 4% of 52 events), presumably due to parental nest defence. Predation by woodpeckers was spatially clumped, probably due to individual foraging specialization. Predation by the other major predators was documented on most/all study plots.

Common Magpie Pica pica, Western Jackdaw Corvus monedula and Hooded Crow Corvus cornix in Some Towns in North-eastern Slovenia (Central Europe)

Common Magpie Pica pica, Western Jackdaw Corvus monedula and Hooded Crow Corvus cornix in Some Towns in North-eastern Slovenia (Central Europe)

Mås- och kråkfågelförekomsten på en soptipp

The present study presents results from counts of gulls and corvids once a week on a refuse dump just outside the city of Skövde in southwestern Sweden during 1992—1999. The most common gull was Herring Gull Larus argentatus, which visited the dump during the whole year. The most common corvid was Jackdaw Corvus monedula with a peak in late June and July. All species except Jackdaw and Raven Corvus corax were found in small numbers during August. High numbers of gulls and corvids were seen on the refuse dump during the winter months. After that the community stopped dumping food rests on the refuse dump in January 1999, Herring Gull, Jackdaw, Hooded Crow Corvus cornix, and Black-headed Gull Larus ridibundus decreased during the spring and summer 1999, however not significantly. In the same time the number of Magpies Pica pica, Great Black-backed Gulls Larus marinus and Ravens increased.

Nest predation and nest site selection among EidersSomateria mollissima:the influence of gulls

Hooded Crows Corvus cornix, Great Black‐backed GullsLarus marinusand Herring Gulls L. argentatus were the main nest predators in an Eider population in southwest Sweden. The clutch sizes of Eider nests within gull colonies did not differ from those outside gull colonies. The proportion of Eider nests destroyed by predators was significantly lower within than outside gull colonies, especially on islands with Lesser Black‐backed Gulls L. fuscus. Although the difference was not significant, the survival time of simulated Eider nests was higher within than outside gull colonies. On Eider islands with gull colonies, foraying crows spent more time within the colony area than expected by chance. However, crows apparently avoided an area around each gull nest, and we suggest that the colonies, to some extent, protected Eider nests against predation. The density of Eider nests was higher on gull islands than on gull‐ free islands, and higher within than outside the gull colonies. However, the association with gulls was weak compared to that displayed by some other waterfowl.

Habitat selection and feeding activity in the MagpiePica pica

Habitat selection and feeding activity was studied in the MagpiePica pica for a three year period during 600 hours of observation. The species was solitary except for communal roosting in the non-breeding season and social gatherings throughout the year. Flocking was rare even though interspecific competitors (Hooded CrowsCorvus cornix), which induce flocking in some areas, was found in high numbers. It is suggested that the dispersed occurrence of food in territories led to dispersion of Magpies. Feeding habitats were utilized to an increasing extent with probably increasing productivity and accessibility of the habitat. Interference with Hooded Crows was common. Aggressive encounters between the two species were common outside the productive summer months both during the breeding cycle and outside that period. Thus, interspecific competition for food may be the primary cause of the antagonistic behaviour. Magpies preferred feeding habitats near tree-cover and houses, probably due to the placing of territories in these areas and due to the infrequent occurrence of Hooded Crows. Magpie predators were rare and they did probably not influence the distribution of birds. Preferred habitats were frequented by Magpies during favourable weather conditions annually as well as during winter.

Reproduction in a population of the hooded crow Corvus cornix

Nest density was stable during the 8‐year study period. The mean clutch size was 4.3, and the production of fledglings was 2.0 per pair. Incubation started, on average, when there were still two eggs to be laid and lasted for 18 days. Few eggs were lost but 23% of all broods of nestlings were lost to predators. Single nestlings in a brood were not lost to predators but often starved to death, this applied to 25% of all nestlings. A large proportion of the nestlings were probably infected by Syngamus tracheae, and some of these succumbed during the first weeks after fledging. A comparison with other studies of crow populations shows that the major causes of breeding failure are different in different populations. The causes of variation in breeding success between populations are discussed, especially considering the role of nonbreeding crows.

Nest Distribution in a Population of the Hooded Crow Corvus cornix

Nest Distribution in a Population of the Hooded Crow Corvus cornix