Separation of Willow Tit and Marsh Tit in Britain: a review

Separation of the British races of Willow Tit Poecile montana and Marsh Tit P. palustris is notoriously difficult. Numerous identification criteria have been proposed during the past 50 years, based primarily on information gained from examination of birds in the hand, although none are judged to be wholly reliable.The best separation feature for birds in the field is considered to be voice, yet the vocal repertoires of both species have not been fully documented. Despite some work to assess the reliability of distinguishing characteristics, some current texts continue to place emphasis on discredited criteria for field identification, or on those of use only for in-hand examination. This paper reviews the separation criteria in the current literature in order to clarify the most important and reliable characters for the separation of this species pair. New information is provided from examination of skins and live birds, and on diagnostic vocalisations. A clarification of the races occurring in Britain is also provided. Recommendations are made for the key criteria to be used for field, photographic and in-hand identification, with a primary focus on voice, bill marks, cheek pattern, plus wing and tail measurements and the presence or absence of a clear wing panel