EDELAAR P, ROBB M, EERDE K VAN, TERPSTRA K, BIJLSMA R & Maassen E (2004) Are there several species of 'Common' Crossbill Loxia curvirostra in The Netherlands?. LIMOSA 77 (2): 31-38.

Recent studies have shown that in The Netherlands the Common Crossbill occurs in several 'vocal types'. Vocal types are discrete groups of individuals that are categorised by their flight and excitement calls (Fig. 1). The biological and taxonomic status of these vocal types is currently unknown. In North America, crossbill vocal types differ in biometry, are ecologically specialised, are (at least partly) reproductively isolated, and are therefore most likely separate species. Our preliminary results suggest that the European vocal types are also ecologically specialised (we found significant differences in bill depth; Fig. 2) and reproductively isolated (we found strong assortative mating), and hence the European vocal types may also represent separate species of crossbill. We discuss and partly refute alternative explanations and highlight which important questions remain to be tackled. Furthermore we call for vocal recordings and information on food of Eurasian crossbills. Common Crossbill Loxia curvirostra Parrot Crossbill Loxia pytyopsittacus Scottish Crossbill Loxia scotica Two-barred Crossbill Loxia leucoptera

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