Pygmy Nuthatch Sitta pygmaea Scientific name definitions

A noisy, chattering, social species, the Pygmy Nuthatch lives in long-needled pine forests—in the United States, principally ponderosa pines (Pinus ponderosa). Frenetic movements—head first, up tree, down tree, along branches, right-side up and upside down—accompanied by constant chatter, convey the busyness and nervous activity of this gregarious bird as it searches for food.

Because it uses cavities for roosting and for breeding, the Pygmy Nuthatch reaches its highest densities in mature pine forests little affected by logging, firewood collection, and snag removal. It feeds mainly on weevils and leaf and bark beetles (but also eats pine seeds), and is one of the few cooperatively breeding passerines in North America and one of only two cooperatively breeding nuthatch species worldwide. A third of the breeding pairs have 1–3 male helpers, usually progeny or other relatives. Helpers feed incubating females, nestlings, and fledglings and participate in defense of the nest site. Breeding units and their offspring form the nucleus of winter flocks. During the nonbreeding season, family groups flock with other Pygmy Nuthatch families that range over a foraging territory. They also join with other flocking birds of the conifer forests. Pygmy Nuthatches generally dominate these species in the social hierarchy and in volubility.

The Pygmy Nuthatch roosts in cavities, which it selects depending on season and weather. It picks roosts based on insulation and ventilation provided by roost cavities and relies on hypothermia to survive cold winter nights. Although a few other North American birds are capable of controlled hypothermia, only the Pygmy Nuthatch links hypothermia with protected roost sites and communalism. Pairs roost together; juveniles roost with parents, and collectives of several flocks roost together. Stacks of 6, 8, and 10 birds, and more, roost together in formations of squares, oblongs, triangles, diamonds, wedges, and tiers. Two articles report more than 150 individuals roosting in a single tree (Knorr 1957 Knorr, O. A. (1957). Communal roosting of the Pygmy Nuthatch. Condor 59:398. Close , Sydeman and Güntert 1983 Sydeman, W. J. and M. Güntert. (1983). Winter communal nesting in the Pygmy Nuthatch. Flagstaff: Snag Habitat Management Symposium. Northern Arizona Univ. Close ).

Robert A. Norris (Norris 1958b Norris, R. A. (1958b). Comparative biosystematics and life history of the nuthatches Sitta pygmaea and Sitta pusilla. University of California Publications in Zoology 56:119-300. Close ) conducted the most extensive research on Pygmy Nuthatches. His thorough monograph covers all aspects of the biology of this species and compares it to its sister species, the Brown-headed Nuthatch (Sitta pusilla). Russ Balda and associates have addressed many aspects of Pygmy Nuthatch biology, such as cooperative breeding, roosting behavior, physiology, flocking behavior and hierarchy, feeding strategy, and habitat use (Balda 1967 Balda, R. P. (1967). Ecological relationships of the breeding-birds of the Chiricahua Mountains, Arizona. Ph.D. thesis, Univ. of Illinois, Urbana. Close , Balda 1969 Balda, R. P. (1969). Foliage use by birds of the oak-juniper woodland and ponderosa pine forest in southeastern Arizona. Condor 71:399-412. Close , Balda 1975 Balda, R. P. (1975). The relationship of secondary cavity-nesters to snag densities in western coniferous forests. Southwest Region Wildl. Habitat Tech. Bull. 1, Albuquerque: U.S. Dep. Agric. For. Serv. Close , Szaro and Balda 1979a Szaro, R. C. and R. P. Balda. (1979a). Bird community dynamics in a ponderosa pine forest. Studies in Avian Biology 3. Close , Szaro and Balda 1982 Szaro, R. C. and R. P. Balda. (1982). Selection and monitoring of avian indicator species: an example from a ponderosa pine forest in the southwest. Fort Collins, CO: U.S. Dep. Agric. Close , Balda et al. 1983 Balda, R. P., W. S. Gaud and J. D. Brawn. (1983). Predictive models for snag nesting birds. U.S. Dep. of Agric., For. Serv. Gen. Tech. Rep. Close , Hay 1983 Hay, D. B. (1983). Physiological and behavioral ecology of communally roosting Pygmy Nuthatch (Sitta pygmaea). Phd Thesis, Northern Arizona Univ., Flagstaff. Close , Brawn 1985 Brawn, J. D. (1985). Population biology, community structure, and habitat selection of birds in ponderosa pine habitat. Phd Thesis, Northern Arizona Univ., Flagstaff. Close , Brawn 1987 Brawn, J. D. (1987). Density effects on reproduction of cavity-nesters in northern Arizona. Auk 104:783-787. Close , Brawn 1988 Brawn, J. D. (1988). Selectivity and ecological consequences of cavity nesters using natural vs. artificial nest sites. Auk 105:789-791. Close , Brawn and Balda 1988a Brawn, J. D. and R. P. Balda. (1988a). Population biology of cavity nesters in northern Arizona: do nest sites limit breeding densities? Condor 90:61-71. Close , Brawn and Balda 1988b Brawn, J. D. and R. P. Balda. (1988b). "The influence of silvicultural activity on ponderosa pine forest bird communities in the southwestern United States." In Bird conservation 3., edited by J. A. Jackson. Madison: Int. Council for Bird Preservation U.S. section. Univ. of Wisconsin Press. Close , Güntert et al. 1988 Güntert, M., D. B. Hay and R. P. Balda. (1988). Communal roosting in Pygmy Nuthatches: a winter survival strategy. Proceedings of the International Ornithological Congress 19:1964-1972. Close , Löhrl 1988 Löhrl, H. (1988). Etho-ökologische untersuchungen an verschiedenen kleiberarten (Sittidae), eine vergleichende Zusammenstellung. Bonn: Bonner Zoologische Monographien Nr. 26. Zoologisches Forschungsinstitut und Museum Alexander Koenig. Close , Sydeman et al. 1988 Sydeman, W. J., M. Güntert and R. P. Balda. (1988). Annual reproductive yield in the cooperative Pygmy Nuthatch (Sitta pygmaea). Auk 105:70-77. Close , Sydeman 1989 Sydeman, W. J. (1989). The effects of helpers on nestling care and breeder survival in Pygmy Nuthatches. Condor 91:147-155. Close , Sydeman 1991 Sydeman, W. J. (1991). Facultative helping by Pygmy Nuthatches. Auk 108:173-176. Close , Szaro et al. 1990 Szaro, R. C., J. D. Brawn and R. P. Balda. (1990). Yearly variation in resource-use behavior by ponderosa pine forest birds. Studies in Avian Biology 13:226-236. Close , Ghalambor 1998 Ghalambor, C. K. (1998). Ecological and evolutionary determinants of incubation strategies in three coexisting nuthatches (Sittidae). Phd Thesis, Univ. of Montana, Missoula. Close , Martin and Ghalambor 1999 Martin, T. E. and C. K. Ghalambor. (1999). Males feeding females during incubation, I. Required by microclimate or constrained by nest predation? American Naturalist 153:131-139. Close ).