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In page Heron:

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The night herons could warrant separation as subfamily Nycticoracinae, as it was traditionally done. However, the position of some genera (e.g. Butorides or Syrigma) is unclear at the moment, and molecular studies have until now suffered from a small number of studied taxa. Especially, the relationships among the subfamily Ardeinae are very badly resolved. The arrangement presented here should be considered provisional.