Il comportamento di "foraging" del gracchio alpino e del gracchio corallino è modulato dalla composizione dello stormo.

The Alpine Chough (Pyrrhocorax graculus) and the Red-billed Chough (Pyrrhocorax pyrrhocorax) have Palearctic distribution ranges which overlap to a large extent. In the western Italian alps both species are present and under syntopic Alpine conditions, interspecific competition for food, nesting sites or other resources could be severe. The foraging behaviour of the two different species was assessed through the stay-times analysis: the duration of the birds’ stay in each site (or patch) was measured by selecting one individual in the middle of a landing group and recording the time for which it foraged before flying to a new patch. The time was recorded through a stopwatch but other numerous variables were assessed visually like the flock dimension and composition, the distance between the observed bird and the nearest one, the activity displayed (Feeding/Resting) and the habitat coverage (grassland, scree, mix). The final target was to assess any change in the foraging behaviour and interaction between the two species. On field analysis were carried out in two different periods in the great Basin of Dondena: from July to September in 2021 and 2022. Field work took place for 3-4 consecutive days every ten days: by doing so, with two different operators, the data acquired was a representative sample of Alpine Choughs and Red-billed Choughs behaviour during summertime. In 2022, changing in temperatures and rainfall events may have affected birds behaviour. Overall, results suggest that the Alpine Chough feeding behaviour is modulated by the flock size, the hour of the day and by year 2022 in which temperature were hotter and there were less rainfall events. The Red-billed Chough flock composition is partly modulated by being in a mixed-species flock with the Alpine Chough and, as happened for the Alpine Chough, by the year conditions found in 2022.