Descrizione
Descrizione
REAZIONI DI CORNACCHIE GRIGIE Corvus corone cornix A CONSPECIFICI MUMMIFICATI IN PARTICOLARI POSTURE E PRESENTATI IN CAMPAGNA
GIOVANNI CORSETTI e TIZIANO LONDEI
Riassunto - Un particolare metodo di conservazione per esemplari di volatili è stato utilizzato per preparare oggetti-stimolo da presentare in campagna al fine di misurare le risposte di Cornacchie grigie selvatiche. Dalle prove effettuate è emersa una evidente discriminazione, da parte dei selvatici, nei riguardi della postura imposta agli oggetti-stimolo e nell'appartenenza di questi ultimi a sottospecie e specie differenti, suggerendo l'esistenza di un meccanismo contro l'ibridazione.
Abstract - Reaction ofwild Hooded Crows to conspecific mummified in particolar postures and exposed in the field. A method for preparing bird specimens to be used as stimulus-objects in the field was tested by measuring the response of wild Hooded Crows, Corvus corone cornix. In a first series of experiments, Hooded Crows specimens were tested for generai responsiveness and posture discrimination by conspecific. More approaches were consistently made to Bristle-head posture than to Sleeked posture. In a combination of bristlehead specimens of different subspecies and species, C.c. corone was approached more times than C.c. cornix, whereas C.frugilegus elicited intermediate interest. In a different combination of bristle-head specimens, C.c. corone was more attractive than C. c. cornix, whereas a hybrid C.c. corone x cornix was less attractive than each pure form. The approaches were usually aggressive. Bristle-head posture was confirmed to be a self advertising posture and the comparisons between subspecies provided suggestions about the mechanism against hybridation.