Plombières-lès-Dijon, France
Plombières-lès-Dijon, France

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Konovalov A.,Estonian University of Life Sciences | Kaldma K.,Estonian University of Life Sciences | Bokotey A.,Ukrainian Academy of Sciences | Brossault P.,Direction Territoriale Bourgogne Champagne Ardenne | And 9 more authors.
Journal of Ornithology | Year: 2014

Sex ratio is an indicator of population health as unexpected biases may indicate potential threats. We studied nestling sex ratio in Black Stork Ciconia nigra populations in order to check potential biases and differences along east–west and north–south gradient across its distribution range in Europe. We also studied variation between years, and checked potential correlations with weather variables. The overall sex ratio of nestlings in Europe was nearly equal with a non-significant deficiency (47.1 %) of males, the larger sex. Although yearly fluctuations in sex ratio were detected, no significant effect of the year alone was found, only simultaneously with population and brood size. There was a tendency to have a higher proportion of female nestlings in larger broods, but the pattern was probably scattered by the effect of reduction of largest broods. Compared to Western and Eastern Europe, a significant deficiency of male nestlings was found in Central Europe (Poland), whereas no differences were found along the north–south gradient. We did not find any effect of temperature, but rainfall during the incubation period was negatively correlated with the proportion of male nestlings in Central (Poland) and Western Europe (France) whereas in North-Eastern Europe (Latvia) the same effect of the precipitation in pre-breeding period was found. © Dt. Ornithologen-Gesellschaft e.V. 2014.

Common Kestrels have been monitored from 1973 to 2012 on the same sample of 41 breeding sites in Côte d'Or, in an area of 1600 km2 (tab. 1). From 1992 to 2012, a 20 km2 area was exhaustively monitored (fig. 2): breeding pairs range between 2 and 11. We conclude that breeding population of Kestrels in the area was stable, despite fluctuations, over the last 40 days and discussed the importance of long term survey for estimating accurate trends of breeding Kestrel population in France.

In France, the number of attacks (physical contact between the species and men) on humans by the Common Buzzard from 2007 to 2014 was of 48 at 37 different sites (a mean of 6 more or less 3.5 attacks/year). Over the studied period, those attacks have significantly increased, partly due to a better knowledge and a greater publicity. These attacks however remain marginal in relation to other problems due to wild animals on human health and must be treated with caution rather than by persecution.

The history of the population trend of this species in Burgundy can be divided in 6 time-periods: before 1940 (no known breeding record), 1950-1960 (first breeding records and spreading), 1961-1978 (decline), 1978-1984 (stagnation), 1984-2003 (a slow colonization process at the beginning and afterwards a rapid one), 2003-2008 (slowing down). Protection measures played in some ways a role in the overall trend: they consisted in raptor protection laws, nest guarding, site protection and rock climbing regulation. It is not easy to predict the future of this population: slowing down or decline? Since 2003 slowing down in breeding numbers and decreasing productivity are the rule but these values are hardly significant. The observed trend should be the consequence of habitat saturation, the best habitats being all occupied. Moreover, some pairs breed outside rocky areas and predation by Eurasian Eagle-Owl Bubo bubo has been recorded.

The effects of nest type on breeding success of Kestrels living in rural areas were studied over a period of 21 years (1992-2012) in Burgundy (East France). Five nest types (n = 35 different nests) were used by the species: cavity in domestic buildings, nest-box, cliff cavity, nesting in old crow nest and on the top of agricultural silo. Based on a sample of 123 breeding records, laying date, clutch size, brood size at hatching, and number of fledglings per pair were not significantly affected by nest type. Nest desertion (due to food shortage or infertile eggs) accounted for 60 % in nest failures. The nest prédation rate was low in all nest types. In fact, individual quality of birds may play the crucial role in breeding success.

A field survey ot a Common Kestrel population was carried out in Burgundy (France) from 1992 to 2005 using individual colourmarked birds captured with bal-chatri traps. Thus 402 individuals have been , marked on 937 attempts. Main results are: sex-ratio and age-ratio varied according to annual cycle of the species. Age-ratio was biased towards adults. Males are much more prone to be recaptured than females, particularly the more they are old and light. Handling stress is low with only 6.9 % of stressed birds. After their release, birds often behave as before their capture. Bias in age-ratio is due to young birds which show less developed hunting techniques (especially with respect to mammals) and field knowledge. This study appears to be the first conducted in Europe that presents detailed results about bal-chatri trapping as a sampling method to study Common Kestrel.

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