Inability of Biometry to Discriminate Iberian and Common Chiffchaffs During the Autumn Migration Period

摘要: The Iberian Chiffchaff Phylloscopus ibericus has recently been accepted as a full species, but is still very difficult to distinguish from the Common P. collybita when molecular and acoustic evidence lacking. Distinguishing these cryptospecies essential for obtaining accurate population estimates each, which especially important in case of due its restricted distribution. We re-assessed discriminant methods available literature propose some alternative traits both species. used information 24 morphological measured c. 6,700 individuals two species trapped during autumn migration period Donana National Park, Spain, between 2004 2015. Discriminatory were unable efficiently. Despite biometric differences, measurements showed high degree overlap so could not Chiffchaffs. best discriminatory factor at our study site was passage date, since 90% Chiffchaffs have already departed first arrive. Those associated with migration, such wing size shape fat deposits, also able discriminate albeit weakly. This result fully concurs trans-Saharan contrast Chiffchaff, chiefly winters Mediterranean latitudes. In conclusion, are useless discriminating we do recommend their use. A comprehensive examination colouration plumage seems be only reliable way guaranteeing correct identification hand.