The Chiricahua Mountains, Arizona, contain at least 15 hummingbird-adapted plant species and 4 breeding hummingbird species, which fall into two size classes (7-8 grams and 3-4 grams). Two closely related claret cup cactus taxa (Echinocereus coccineus and E. triglochidiatus) are unusual in having very large flowers, which are red and trumpet-shaped. We asked whether nectar production rates of these cacti are unusually large, like their corolla sizes. Because E. coccineus has a wider elevation range than other local hummingbird plants, we asked whether nectar production and hummingbird visitation patterns varied from low (1500 m) to medium (2250 m) to high (3000 m) populations. This gradient spans a habitat range from desert scrub to ponderosa pine forest, with annual rainfall varying two-fold. Caged flowers of E. coccineus at 4 sites accumulated on average 29.4 mg sugar/flower in their first day after anthesis, approximately 10 times the production rate of most local hummingbird flowers. High elevation coccineus populations were more productive (averaging 34.5 mg sugar/flower) than low elevation coccineus (22.3 mg/flower) or triglochidiatus populations (21.9 mg/flower). Despite habitat differences, hummingbirds visited cactus flowers at all elevations: large Magnificent Hummingbirds and small Broad-tailed Hummingbirds predominated, occurring at all elevations, whereas small Black-chinned Hummingbirds and large Blue-throated Hummingbirds visited only low populations. Thus there is little variation within this mountain range in size classes of hummingbirds visiting claret cup flowers, although on a larger geographic scale (for example, between northern and southern Arizona) there is considerable variation.

Key words: Echinocereus triglochidiatus (Cactaceae), Echinocereus coccineus (Cactaceae), elevation gradient, floral nectar, hummingbirds, pollination