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

Priorities for Future Research

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Introduction

The population on Grand Bahama Island—in particular its status and its subspecific distinctness—needs immediate study. Hayes et al. (2004) argued that this population should be recognized as a distinct species, but a petition to do so was rejected by the AOU for insufficient evidence (Banks et al. 2006). Phylogenetic analyses of mitochondrial DNA revealed significant geographic differentiation between the Grand Bahama population and mainland U.S. populations (Lloyd et al. 2008). Additional gene-sequencing of island and mainland birds as well as detailed follow-up on the vocal differences suggested in Hayes et al. (2004) will help determine how much these populations have diverged.

Equally important will be the development and implementation of surveys adequate to generate robust estimates of population size on Grand Bahama I. and monitor trends over time. Much of the concern over the island population stems from the conclusion in Smith and Smith (1994) that this population had declined by > 90% since the late 1960s, but more recent surveys have yielded conflicting results and showed clearly that survey results were strongly dependent on survey methodology, with passive surveys producing very low rates of detection that produce gross underestimates of abundance (Hayes et al. 2004, Lloyd and Slater 2011).

Museum and/or molecular work to determine the extent of differentiation of the Bahamas population might also address differences between birds from northern and southern Florida -- to resolve the issue of subspecific status for S. p. caniceps (currently not recognized – see Systematics).

Other conservation priorities involve determining more precisely the factors that limit population growth (e.g., habitat degradation, nest predation, cavity competition) and management steps crucial to sustaining populations (e.g., prescribed burning, habitat preservation, reintroductions). Additional studies of marked populations would be especially useful in this regard. For example, estimates of important demographic rates such as survival and emigration, and analyses of the role they play in influencing population growth rate, would help to identify appropriate targets for habitat management (Lloyd et al. 2009).

Continued monitoring and research of the population reintroduced to Long Pine Key, Florida, is also warranted given concerns over the viability of that population (Lloyd et al. 2009). Studies of particular importance to this population include the role of fire in the dynamics of snag populations and whether nest predation limits population size.

Ongoing range expansion along the Tennessee River on the west side of the Appalachian Mountains (Renfrow 2003) offers an opportunity to test many current hypotheses regarding the natural history of this species, including our understanding of habitat selection, the factors influencing cooperative breeding, and the factors that limit or promote dispersal. Particularly interesting is the possibility that this range expansion is driven by the planting of loblolly pine outside of its native range and subsequent bark-beetle infestations that create suitable habitat in these plantations (Roy et al. 2001, Renfrow 2003).

Further work on cooperative breeding is needed to determine its role in the ecology and behavior of the species and to illuminate the factors that have driven its evolutionary origin and maintenance. Further study of the benefits of cooperative breeding may also help reconcile conflicting findings regarding the effect of helpers on breeding success (49, Cox and Slater 2007).

More study of tool use would be helpful—in particular, whether it is more prevalent in years of poor cone crops, and how it contributes to foraging success. Perhaps tool use is an adaptation to deal with low seed availability, similar to nomadism in Red-breasted Nuthatch, given that the Brown-headed Nuthatch is more constrained to a sedentary lifestyle.

The voluminous work of Norris (1) provided a wealth of information on many aspects of this species' biology. Nevertheless, the work's admirable breadth meant that many of Norris's conclusions were based on small sample sizes. Thus, more narrowly focused work in the future will no doubt contribute substantially to our knowledge of the species.

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