Many hummingbird species are long distance migrants travelling between the USA, Canada, and Mexico; therefore, a tri-national partnership is critical for effective hummingbird conservation in North America. Seventeen species regularly occur in the USA and Canada, of which thirteen are neotropical migrants that overwinter in Mexico (US Fish and Wildlife Service 2008). Hummingbirds live only in the western hemisphere, where they are the second most diverse family of birds (approximately 340 species). Their diversity is well represented among North American bird families with 57 species, of which 40% are endemic to North America, 14% are substantially shared among the nations, 30% are migratory, and 14% are of high conservation concern (Berlanga et al., 2010).
Hummingbirds are specialized nectar feeders with morphological, ecological, and physiological adaptations for this diet, and serve as pollinators for a wide array of native plants (Stiles 1981, Brown and Bowers 1985, Rosero 2003, Temeles and Kress 2003, Gegear and Burns 2007). They depend almost completely on nectar for their energetic supply, and their survival depends upon a reliable supply of suitable nectar-producing plants that are frequently associated with early successional stages of forest re-growth. Almost 300 plant species identified from the literature were listed by Ornelas et al. (2007) as producing nectar used by hummingbirds. Most of the data come from geographic areas in the USA, Mexico, Costa Rica, and Brazil. In western USA, about 130 plant species are pollinated by hummingbirds (Johnsgard 1997).
In addition to nectar, hummingbirds prey upon insects, which provide an important source of protein (Schuchmann 1999). For many hummingbird species, aquatic insects are important prey items during the nesting cycle; thus, management of water resources in the arid west is likely an important conservation issue. Although insects are critical components to hummingbird diets, the real dietary importance of insects remains largely unknown and is under studied.
Forests are the primary habitat for over 80% of hummingbird species (Stotz et al. 1996). In the tropics, the diversity of hummingbirds is highest in montane/sub-montane forests (Schuchmann 1999). This pattern of forest-associated diversity continues northward, where the highest diversity of hummingbirds in the USA occurs in the pine/oak woodlands of southeastern Arizona (Wethington et al. 2005). These woodlands are included in the montane evergreen forest classification (Stotz et al. 1996), which has the highest number of at- risk hummingbird species (Wethington and Finley 2009). There are many unknowns regarding the needs of the various species of hummingbirds, particularly related to habitat requirements for insect prey, timing of nectar resource availability, nest sites, and other habitat requirements at different temporal and spatial scales.
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