Chiappe, Luis M. (16 April 2009). "Downsized dinosaurs: The evolutionary transition to modern birds". Evolution: Education and Outreach. 2 (2): 248–256. doi: 10.1007/s12052-009-0133-4. ISSN 1936-6426. S2CID 26966516. The giant hummingbird's wings beat as few as 12 times per second, [150] and the wings of typical hummingbirds beat up to 80 times per second. [151] As air density decreases, for example, at higher altitudes, the amount of power a hummingbird must use to hover increases. Hummingbird species adapted for life at higher altitudes, therefore, have larger wings to help offset these negative effects of low air density on lift generation. [152] In 2004, Gerald Mayr identified two 30-million-year-old hummingbird fossils. The fossils of this primitive hummingbird species, named Eurotrochilus inexpectatus ("unexpected European hummingbird"), had been sitting in a museum drawer in Stuttgart; they had been unearthed in a clay pit at Wiesloch–Frauenweiler, south of Heidelberg, Germany, and, because hummingbirds were assumed to have never occurred outside the Americas, were not recognized to be hummingbirds until Mayr took a closer look at them. [37] [9] Sexual size and bill differences likely evolved due to constraints imposed by courtship, because mating displays of male hummingbirds require complex aerial maneuvers. [63] Males tend to be smaller than females, allowing conservation of energy to forage competitively and participate more frequently in courtship. [63] Thus, sexual selection favors smaller male hummingbirds. [63] Brusatte, SL; O'Connor, JK; Jarvis, ED (October 2015). "The origin and diversification of birds". Current Biology. 25 (19): R888–98. doi: 10.1016/j.cub.2015.08.003. PMID 26439352. S2CID 3099017.

The high metabolic rate of hummingbirds – especially during rapid forward flight and hovering – produces increased body heat that requires specialized mechanisms of thermoregulation for heat dissipation, which becomes an even greater challenge in hot, humid climates. [104] Hummingbirds dissipate heat partially by evaporation through exhaled air, and from body structures with thin or no feather covering, such as around the eyes, shoulders, under the wings ( patagia), and feet. [105] [106] a b c Mayr, Gerald (2004). "Old World fossil record of modern-type hummingbirds". Science. 304 (5672): 861–864. Bibcode: 2004Sci...304..861M. doi: 10.1126/science.1096856. PMID 15131303. S2CID 6845608.Many plants pollinated by hummingbirds produce flowers in shades of red, orange, and bright pink, although the birds take nectar from flowers of other colors. Hummingbirds can see wavelengths into the near- ultraviolet, but hummingbird-pollinated flowers do not reflect these wavelengths as many insect-pollinated flowers do. This narrow color spectrum may render hummingbird-pollinated flowers relatively inconspicuous to most insects, thereby reducing nectar robbing. [58] [59] Hummingbird-pollinated flowers also produce relatively weak nectar (averaging 25% sugars) containing a high proportion of sucrose, whereas insect-pollinated flowers typically produce more concentrated nectars dominated by fructose and glucose. [60] Hummingbirds have the highest mass-specific metabolic rate of any homeothermic animal. [5] [6] To conserve energy when food is scarce and at night when not foraging, they can enter torpor, a state similar to hibernation, and slow their metabolic rate to 1/15 of its normal rate. [6] [7] While most hummingbirds do not migrate, the rufous hummingbird has one of the longest migrations among birds, traveling twice per year between Alaska and Mexico, a distance of about 3,900 miles (6,300km). Hummingbirds host a highly specialized lice fauna. Two genera of Ricinid lice, Trochiloecetes and Trochiliphagus are specialized on them, often infesting 5-15% of their populations. Contrarily, two genera of Menoponid lice, Myrsidea and Leremenopon are extremely rare on them. [138] Reproduction [ edit ] Video of a hummingbird building a nest

The Andes Mountains appear to be a particularly rich environment for hummingbird evolution because diversification occurred simultaneously with mountain uplift over the past 10 million years. [42] Hummingbirds remain in dynamic diversification inhabiting ecological regions across South America, North America, and the Caribbean, indicating an enlarging evolutionary radiation. [42] While hummingbirds rely primarily on vision and hearing to assess competition from bird and insect foragers near food sources, they may also be able to detect by smell the presence in nectar of insect defensive chemicals (such as formic acid) and aggregation pheromones of foraging ants, which discourage feeding. [223] In myth and culture [ edit ] Nazca Lines - hummingbird Hummingbird emblem on Caribbean AirlinesA top may be used to demonstrate visual properties, such as by James David Forbes and James Clerk Maxwell in Maxwell's disc (see color triangle). By rapidly spinning the top, Forbes created the illusion of a single color that was a mixture of the primaries: [3] While their range was originally limited to the chaparral of California and Baja California, it expanded northward to Oregon, Washington, and British Columbia, and east to Arizona over the 1960s to 1970s. [117] This rapid expansion is attributed to the widespread planting of non-native species, such as eucalyptus, as well as the use of urban bird feeders, in combination with the species' natural tendency for extensive postbreeding dispersal. [121] In the Pacific Northwest, the fastest growing populations occur in regions with breeding-season cold temperatures similar to those of its native range. [117] Northward expansion of the Anna's hummingbird represents an ecological release associated with introduced plants, year-round nectar availability from feeders supplied by humans, milder winter temperatures associated with climate change, and acclimation of the species to a winter climate cooler than its native region. [26] [117] Although quantitative data are absent, it is likely that a sizable percentage of Anna's hummingbirds in the Pacific Northwest still do migrate south for winter, as of 2017. [26] Hummingbirds are named for the prominent humming sound their wingbeats make while flying and hovering to feed or interact with other hummingbirds. [71] Humming serves communication purposes by alerting other birds of the arrival of a fellow forager or potential mate. [71] The humming sound derives from aerodynamic forces generated by the downstrokes and upstrokes of the rapid wingbeats, causing oscillations and harmonics that evoke an acoustic quality likened to that of a musical instrument. [71] [72] The humming sound of hummingbirds is unique among flying animals, compared to the whine of mosquitoes, buzz of bees, and "whoosh" of larger birds. [71] [72]