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Introduction
This series of preliminary reviews continues with the Sittidae, including nuthatches and the wallcreeper. These were treated by Greenway (1967) in volume XII of Peters’s Check-list of Birds of the World. His arrangement, not explained at the time, is examined and comments herein draw on more recent publications, including three associated papers in this issue of this journal.
The accompanying ‘sister paper’ on types (Dickinson et al., 2006: this issue) also covers tree-creepers (Certhiidae), which receive their own separate preliminary review (Martens & Tietze, 2006: this issue).
The Sittidae, about 26 species[1] in total, are essentially Holarctic in distribution, but also occur in the Indian subcontinent and South-east Asia. Vaurie (1957) provided a general background to the family, noting disagreements then current over whether the Australian sittellas belonged to the family Sittidae. Since then, molecular studies (cited by Schodde & Mason, 1999: 426-427), have led to the conclusion that similarities between the sittellas and the nuthatches are due to convergence. The true affinities of the sittellas, especially with other Australasian passerines, remain uncertain. The wide ranging species Sitta europaea Linnaeus, 1758, and a few associated, closely similar birds were reviewed by Voous & van Marle (1953), with whom Vaurie (1957) disagreed quite widely. The nature of these disagreements is discussed below, together with consideration of the alternative treatment given in Peters’s Check-list by Greenway (1967). However, Greenway published no details of any independent studies that he had made which might support his decisions to disagree with Vaurie. The most recent major work on the nuthatches is that of Harrap (1996) who, as with the titmice, thoroughly discussed the relationships of the various species and depicted and described them well. While there has been much subsequent work on the titmice (Eck & Martens, 2006) study of the relationships among nuthatches has progressed rather little, and not much will be added here to what Harrap wrote.
Molecular sampling in the family is still limited to only a few taxa. It is possible, nevertheless, that some generic names not employed in the last 50 years will prove worth reintroducing.
Progress is also lacking in the collection and analysis of acoustic evidence. Vaurie (1957) wrote that Dr Löhrl had tape recordings that demonstrated the differences in their calls between Sitta castanea Lesson, 1830, and Sitta europaea; much later Harrap (1996) added that Löhrl published about Sitta cashmirensis Brooks, 1871, in 1969, and that Roberts (1992) had added to our knowledge of that taxon’s calls. More evidence is still needed at the local level, especially in the Himalayas and China, to help resolve remaining concerns about species limits.