SPECIES

Brown-headed Nuthatch Sitta pusilla Scientific name definitions

Gary L. Slater, John D. Lloyd, James H. Withgott, and Kimberly G. Smith
Version: 1.1 — Published August 18, 2021

Systematics

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Systematics History

The Brown-headed Nuthatch and Bahama Nuthatch (Sitta insularis) were considered conspecific under Brown-headed Nuthatch until 2021 (3, 4). The Bahama Nuthatch was recognized as a distinct species based on differences in vocalizations (5, 6) and responses to playback (7), though morphometric (5) and genetic differences are also significant (26, 6). The Bahama Nuthatch has a distinctly longer bill and tarsi and shorter wings than does the Brown-headed Nuthatch (5), and there is a 1.37% difference in mitochondrial DNA between the two species, suggesting that they diverged from a common ancestor around 685,000 years ago (26, 6).

Geographic Variation

Populations of the Brown-headed Nuthatch exhibit a generally smoothly clinal trend in body size, with northern birds larger than southern birds, although there is a relatively abrupt step in the cline between populations in Maryland and in Virginia (Norris 1958). Neither its plumage (Norris 1958) nor its mitochondrial DNA (Lloyd et al. 2008) varies relative to geography.

Subspecies

The Brown-headed Nuthatch is monotypic.

Related Species

The family Sittidae, the nuthatches, was long considered to be allied with Paridae (tits and chickadees) and Certhiidae (creepers), but molecular phylogenies (Sheldon and Gill 1996, Ericson and Johannson 2003) have placed the nuthatches in a group with the creepers, wrens (Troglodytidae), and gnatcatchers (Polioptilidae), in a radiation separate from that of Paridae. Despite similarities in morphology and behavior, the Australian creepers (Daphoenosittidae) are not closely related to the nuthatches. By contrast, the monotypic Wallcreeper (Tichodroma muraria) of the southern Palearctic, which is often placed in its own family, is closely related to the nuthatches and as such is sometimes placed in a subfamily (Tichodrominae) of Sittidae.

Relationships within the genus Sitta have not been completely resolved, though hybridization among the five North American species is unknown (McCarthy 2006). Nevertheless, the Pygmy Nuthatch (Sitta pygmaea) and the Bahama Nuthatch (Sitta insularis) are clearly sister species of the Brown-headed Nuthatch, and the three taxa constitute a superspecies (27, 6) and have, in the past, been treated by some authorities as conspecific (28). The Bahama Nuthatch was only recently recognized as a distinct species, Bahama insularis (see Systematics History, above).

Fossil History

No information.

Recommended Citation

Slater, G. L., J. D. Lloyd, J. H. Withgott, and K. G. Smith (2021). Brown-headed Nuthatch (Sitta pusilla), version 1.1. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.bnhnut.01.1