Taxonomy of present species and its close relatives represent one of the most complex challenges in systematic ornithology. The closely related taxa were often treated as a ring of subtle races until the two extremes (L. argentatus, L. fuscus) met in W Europe and did not freely interbreed. Many forms are now treated as separate species, since it is uncertain how to apply the biological or indeed phylogenetic species concept to the complex pattern of variation and interbreeding. Present species is reported as hybridizing extensively with L. hyperboreus in Iceland (disputed, but analysis of mitochondrial and microsatellite data strongly indicate recent hybridization there#R), but rarely with L. fuscus in Europe. Even after several decades of molecular study, uncertainty over the species boundaries of L. argentatus, L. cachinnans and L. fuscus prevails, with many of the identifiable races assigned at one time or another to two or even three of these species. The most extreme lumping has included L. glaucoides, L. fuscus and even L. californicus within L. argentatus; a more traditional treatment included L. armenicus, L. michahellis and L. cachinnans. Owing to sympatry without hybridization in W France, L. michahellis is now seen as a distinct species, further supported by molecular evidence and relatively strong morphological characters#R. Much controversy surrounds the form omissus of the N Baltic region, with pink-legged individuals in a (formerly) predominantly yellow-legged population: it has been treated as a race either of L. argentatus or of L. cachinnans, but is probably simply a morph of L. argentatus (based mainly on voice and primary pattern). Recent trend to separate out smithsonianus as a full species accepted here. See also L. fuscus, L. armenicus, L. cachinnans, L. smithsonianus. Two subspecies recognized.
Food and feeding
Status and conservation
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