Morphological differentiation of Icelandic Redpolls, <i>Acanthis flammea islandica</i>

<p><b>Capsule</b> The analyses support the grouping of the three <i>Acanthis</i> species, although a large split is observed between the <i>A. hornemanni</i> subspecies.</p> <p><b>Aims</b> To investigate the morphological variation in <i>A. f. islandica</i> among different periods of the year and its morphological differentiation from the other subspecies <i>A. f. flammea</i> and <i>A. f. rostrata</i>, and also from the redpoll species, <i>A. cabaret</i> and the two subspecies of <i>A. hornemanni</i>, <i>exilipes</i> and <i>hornemanni</i>.</p> <p><b>Methods</b> The subspecies status of the Icelandic population was evaluated with Amadon's rule, by comparing its variation of traits to the distribution of the traits in different species/subspecies of the group.</p> <p><b>Results</b><i>A. f. islandica</i> is characterized by intermediate wing, bill and tail lengths. Based on the 75% rule, wing length and bill depth can be used to discriminate <i>A. f. islandica</i> from both extreme morphs of redpolls (currently classified as different species); <i>A. hornemanni</i> and <i>A. cabaret</i>, and tail and wing length can distinguish <i>A. f. islandica</i> from its conspecifics <i>A. f. flammea</i>. The overall morphological divergence within the redpoll complex is not supported by association to the studied nuclear markers.</p> <p><b>Conclusion</b> The taxonomic status of the three redpoll species is supported by Amadon's rule, however the subspecies status of the Icelandic Redpoll remains unclear.</p