profiles of birds occurring in Britain & Ireland (BTO Research Report 407). Thetford: British Trust for Ornithology. 2015 [13 February 2015]. (原始内容存档于1 April
profiles of birds occurring in Britain & Ireland (BTO Research Report 407). Thetford: British Trust for Ornithology. 2014 [30 March 2014]. Pravosudov, Vladimir