Biometric characterization of the Red-legged Partridges Alectoris rufa of northwestern Italy

The biometrics of the Red-legged Partridge Alectoris rufa has been relatively well studied in the western part of its distribution range (Iberian Peninsula and France), especially due to the available large hunting bag samples. Conversely, the Italian population is poorly characterized. We analysed a sample of 254 live birds trapped and ringed in the northern Apennines (province of Alessandria, northwestern Italy), by measuring body mass and the length of wing, eighth primary, tail, tarsus and bill. We found significant differences in some biometric measurements between sex and age classes. A subsample of birds (n = 112) was genetically tested for introgressive hybridization with A. chukar, an introduced species, showing that 16.1 % of free-living partridge are hybrid individuals. When we analysed separately "pure"and "introgressed"birds we found only small biometric differences in body mass of adult males. Finally, our results were compared with the biometry of other populations from the whole natural range of the species (France, Spain and Portugal) showing a negative biometric trend of wing length from westernmost to southeastern birds of the range. Introgressed birds found in the studied population were not easily distinguishable with biometric criteria from pure A. rufa rufa, so genetic analysis is highly recommended when planning reintroductions or restocking

Disentangling the effects of environmental conditions on wintering and breeding grounds on age-specific survival rates in a trans-Saharan migratory raptor

International audienceMigratory species are subject to environmental variability occurring on breeding and wintering grounds. Estimating the relative contribution of environmental factors experienced sequentially during breeding and wintering, and their potential interaction, to the variation of survival is crucial to predict population viability of migratory species. Here we investigated this issue for the Montagu's harrier Circus pygargus, a trans‐Saharan migrant. We analysed capture‐recapture data from a 29‐yr long monitoring of wing‐tagged offspring and adults at two study sites in France (Rochefort‐RO & Maine‐et‐Loire‐ML). The study period covers a climatic shift occurring in the Sahel with increasing rainfall following a period of droughts (Sahel greening). We found that harriers’ adult survival in RO (between 1988 and 2005) varied over time and was sensitive to the interaction between the amount of rainfall in the Sahel and the annual mean breeding success, two proxies of prey availability. The occurrence of adverse conditions on breeding and wintering grounds in the same year decreased survival from 0.70‐0.77 to 0.48 ± 0.05. Juvenile survival in RO was slightly more sensitive to conditions in Europe than in the Sahel. Unexpectedly, lower survival rates were found in years with higher mean breeding success, suggesting compensatory density feedbacks may operate. By contrast, adult survival in ML, monitored between 1999 and 2017, was higher compared to RO (0.76 ± 0.03 vs. 0.66 ± 0.02), remained constant and unaffected by any proxy of prey availability. This difference seems consistent with the fact that harriers in ML experienced better and especially less variable environmental conditions during breeding and wintering seasons compared to RO. Overall, we showed that survival of a migratory bird is sensitive to the level of variability in environmental conditions and that adverse conditions on wintering grounds can amplify the negative effects of conditions during the previous breeding season on birds’ survival

Recent distribution of Red-legged Partridge Alectoris rufa in Piedmont (North Western Italy): signs of recent spreading.

The red-legged partridge Alectoris rufa in Piedmont (NW Italy) is historically limited to the hilly and low-mountain areas of the southern half of the region, in particular lying in the Langhe and the Apennines on the Ligurian border, in the districts of Cuneo, Asti and Alessandria. In the Cuneo district, on the Maritime Alps, hybrid populations with Alectoris graeca were also known. The distribution of the species has been mapped in some occasions with the \u201cAtlases\u201d projects of the GPSO (Gruppo Piemontese Studi Ornitologici) and special enquiries. On this occasion we tried to update the geographical distribution of the species using data conferred by bird-watchers on www.regione.piemonte.it/aves/, managed by the GPSO, enquiries among hunters\u2019 organizations and specific field researches. The resulting distribution is shown on a 10 km square grid. The species shows signs of distribution dynamism, with the occupation of some lowland areas, where it was totally absent until the \u201890s. A little range expansion is noticeable also in the Western Monferrato. The situation seems to be more stable (or even declining) in the Langhe area and the species is now disappeared from the alpine border. In general we are seeing an areal contraction or density reduction on hills and mountains and an extension on lowlands. The observed changes seem to be attributable mainly to environmental and climate changes

LPMLE3 : a novel 1-D approach to study water flow in streambeds using heat as a tracer

We introduce LPMLE3, a new 1-D approach to quantify vertical water flow components at streambeds using temperature data collected in different depths. LPMLE3 solves the partial differential equation for coupled water flow and heat transport in the frequency domain. Unlike other 1-D approaches it does not assume a semi-infinite halfspace with the location of the lower boundary condition approaching infinity. Instead, it uses local upper and lower boundary conditions. As such, the streambed can be divided into finite subdomains bound at the top and bottom by a temperature-time series. Information from a third temperature sensor within each subdomain is then used for parameter estimation. LPMLE3 applies a low order local polynomial to separate periodic and transient parts (including the noise contributions) of a temperature-time series and calculates the frequency response of each subdomain to a known temperature input at the streambed top. A maximum-likelihood estimator is used to estimate the vertical component of water flow, thermal diffusivity, and their uncertainties for each streambed subdomain and provides information regarding model quality. We tested the method on synthetic temperature data generated with the numerical model STRIVE and demonstrate how the vertical flow component can be quantified for field data collected in a Belgian stream. We show that by using the results in additional analyses, nonvertical flow components could be identified and by making certain assumptions they could be quantified for each subdomain. LPMLE3 performed well on both simulated and field data and can be considered a valuable addition to the existing 1-D methods