During the historic Lewis and Clark expedition, Meriwether Lewis wrote on 20 July 1805, “I saw a black woodpecker (or crow) today… it is a distinct species of woodpecker; it has a long tail and flys a good deal like the jay bird” (sic, Thwaites 1905 ). Subsequent observations of flight and vocalization reminded him of the Red-headed Woodpecker (Melanerpes erythrocephalus) he knew from his home in Virginia. A few years later the ornithologist Alexander Wilson, working with skins that Lewis and Clark's expedition had provided, described this species in his American Ornithology and named it Lewis's Woodpecker in honor of his fellow naturalist ( Snow 1941 , Farrand 1992b , Mearns and Mearns 1992a ).
Since then, Lewis's Woodpecker has continued to intrigue ornithologists. Unlike most woodpeckers, it frequently engages in prolonged glides and complex aerial maneuvers in pursuit of flying insects. It is opportunistic in its feeding habits, eating mostly insects in summer but switching in winter to acorns and other nuts, which it often stores in bark crevices for later consumption. Aggressive encounters, sometimes over stored food, are well documented between Lewis's Woodpecker and its congeners the Acorn Woodpecker (M. formicivorus) and the Red-headed Woodpecker.
Distributed in the United States west of the Great Plains, Lewis's Woodpecker favors open forests, ranging in altitude from low-elevation riparian areas to higher-elevation burns and pine forests during the breeding season. Like all other woodpeckers, it requires snags (standing, dead or partly dead trees) for nesting; because it is not anatomically specialized for excavating in wood, the trees it selects for nesting are generally well decayed. Winter distributions are often associated with storable mast in the form of acorns, nuts or corn.
Key studies of this species include comprehensive research on its ecology and behavior in California ( Bock 1970a ). In addition, important information exists on habitat use ( Raphael and White 1984 , Vierling 1997 , Saab et al. 2007, Saab et al. 2009, Vierling et al. 2009, Newlon and Saab 2011), reproduction and nest survival (Saab and Vierling 2001, Gentry and Vierling 2007, Saab et al. 2011), behavior during the nesting and winter seasons ( Hadow 1973 , Linder 1994 , Vierling 1997), flight performance and anatomy ( Tobalske 1996 ), plumage ( Pyle and Howell 1995 ) and phylogenetic relationships ( Tennant 1991 ).
Nonetheless, many aspects of the biology of Lewis's Woodpecker remain poorly known or known from only limited geographic areas. The sporadic distribution and relatively uncommon status of this species within much of its range present a serious challenge for existing local-scale censusing methods. Broad-scale population trends indicate that numbers have declined markedly throughout the species' range since the 1960s, and several examples of local reductions in distribution have been reported. Possible reasons for the declines include loss of suitable habitat, habitat degradation, and presence of pesticides in the environment. Future research should focus upon determining migration patterns and demographic patterns (survivorship and reproduction) in different habitats and regions to ascertain how factors such as landscape/land use change and climate change will affect the future of this species.