By Acrocephalus_palustris_(Marek_Szczepanek).jpg: https://commons.wikimedia.org/w/index.php?curid=8439437
Sanger
(*) https://en.wikipedia.org/wiki/Marsh_warbler
(*) https://ebird.org/species/marwar3
(*) https://search.macaulaylibrary.org/catalog?taxonCode=marwar3