| 词条 | Rufous hummingbird | ||
| 释义 |
| name = Rufous hummingbird | image = Selasphorus rufus1.jpg | image_caption = Adult male | status = NT | status_system = IUCN3.1 | status_ref = [1] | genus = Selasphorus | species = rufus | authority = (Gmelin, 1788) }} The rufous hummingbird (Selasphorus rufus) is a small hummingbird, about {{convert|8|cm|in|abbr=on}} long with a long, straight and slender bill. These birds are known for their extraordinary flight skills, flying {{convert|2000|mi|km|abbr=on}} during their migratory transits. It is one of seven species in the genus Selasphorus. DescriptionThe adult male has a white breast, rufous face, flanks and tail and an iridescent orange-red throat patch or gorget. Some males have some green on back and/or crown. The female has green, white, some iridescent orange feathers in the center of the throat, and a dark tail with white tips and rufous base. The female is slightly larger than the male. Females and the rare green-backed males are extremely difficult to differentiate from Allen's hummingbird. This is a typical-sized hummingbird, being a very small bird. It weighs {{convert|2|-|5|g|oz|abbr=on}}, measures {{convert|7|-|9|cm|in|abbr=on}} long and spans {{convert|11|cm|in|abbr=on}} across the wings.[2] They feed on nectar from flowers using a long extendable tongue or catch insects on the wing. These birds require frequent feeding while active during the day and become torpid at night to conserve energy. Because of their small size, they are vulnerable to insect-eating birds and animals. BreedingTheir primary breeding habitats are open areas, mountainsides and forest edges in western North America from southern Alaska through British Columbia and the Pacific Northwest to California,[2] nesting further north (Alaska) than any other hummingbird. The female builds a nest in a protected location in a shrub or conifer. Males are promiscuous, mating with several females.[2] Migration{{refimprove section|date=December 2015}}Western rufous hummingbirds migrate through the Rocky Mountains and nearby lowlands during May to September to take advantage of the wildflower season. They may stay in one local region for the entire summer, in which case the migrants, like breeding birds, often aggressively take over and defend feeding locations. Most winter in wooded areas in the Mexican state of Guerrero, traveling over {{convert|2000|mi|km|abbr=on}} by an overland route from its nearest summer home — a prodigious journey for a bird weighing only 3 to 4 g.{{citation needed|date=October 2016}} Most rufous hummingbirds that migrate to the southeast of the United States and Caribbean Islands are juvenile birds and adult females, with adult males seldom seen.{{citation needed|date=October 2016}} Since juveniles or females are essentially indistinguishable from Allen's hummingbirds unless confirmed by close inspection, eastern rufous migrants may be classified as "rufous/Allen's hummingbirds".[2] Hovering mechanics, metabolism, and sexual dimorphismDigital imaging velocimetry was used to capture rufous hummingbird wing movements on film, enabling determination that the bird supports its body weight during hovering primarily by wing downstrokes (75% of lift) rather than by upstrokes (25% of lift).[3][4] When hovering during fasting, rufous hummingbirds oxidize fatty acids to support metabolism and food energy requirements, but can rapidly switch to carbohydrate metabolism (within 40 minutes) after feeding on flower nectar.[5]Both male and female S. rufus are territorial; however, they defend different types of territories.[6] The more aggressive males fight to defend areas with dense flowers, pushing females into areas with more sparsely populated flowers.[6] Males generally have shorter wings than females, therefore their metabolic cost for hovering is higher. This allows males to beat their wings at high frequencies, giving them the ability to chase and attack other birds to defend their territory.[6] The metabolic cost of short wings is compensated for by the fact that these males do not need to waste energy foraging for food, because their defended territory provides plenty of sustenance.[7] Females on the other hand are not given access to the high concentration food sources, because the males fight them off.[6] Therefore, females generally defend larger territories, where flowers are more sparsely populated, forcing them to fly farther between food sources.[6] The metabolic cost of flying farther is compensated for with longer wings providing more efficient flight for females.[6] The differences in wing length for S. rufus demonstrate a distinct sexual dimorphism, allowing each sex to best exploit resources in an area. ConservationIn 2018, the rufous hummingbird was uplisted from least concern to near threatened on the IUCN Red List, on the basis that due to its reliance on insect prey during the wintering season, it will be heavily affected by the global decline in insect populations due to pesticides and intensified agriculture.[8] Due to climate change, many flowers that the rufous hummingbird feeds on during the breeding season have started blooming two weeks prior to the birds' arrival to their breeding locations, which may lead to rufous hummingbirds arriving too late to feed on them.[8] GalleryReferences1. ^BirdLife International. 2018. Selasphorus rufus. The IUCN Red List of Threatened Species 2018: e.T22688296A131750335. https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T22688296A131750335.en. Downloaded on 19 December 2018. 2. ^1 2 3 {{Cite AllAboutBirds|Rufous Hummingbird}} 3. ^{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/4124666.stm |title=Master fliers of the bird kingdom |publisher=BBC |date=27 June 2005 |accessdate=30 October 2009}} 4. ^{{cite journal|journal=Nature|year=2005|volume=435|issue=7045|pages=1094–7|title=Aerodynamics of the hovering hummingbird|authors=Warrick DR, Tobalske BW, Powers DR|pmid=15973407|doi=10.1038/nature03647}} 5. ^{{cite journal|journal=J Exp Biol|year=2007|volume=210|issue=12|pages=2154–62|title=Oxidation rate and turnover of ingested sugar in hovering Anna's (Calypte anna) and rufous (Selasphorus rufus) hummingbirds|authors=Welch KC Jr, Suarez RK|pmid=17562889|doi=10.1242/jeb.005363}} 6. ^1 2 3 4 5 {{Cite journal|last=Kodricbrown|last2=Brown|title=Influence of economics, interspecific competition, and sexual dimorphism on territoriality of migrant Rufous hummingbirds|journal=Ecology|volume=59|issue=2|pages=285–296|doi=10.2307/1936374|jstor=1936374|year=1978}} 7. ^{{Cite journal|last=Feinsinger|last2=Chaplin|title=On the relationship between wing disc loading and foraging strategy in hummingbirds|journal=The American Naturalist|volume=109|issue=966|pages=217–224|doi=10.1086/282988|year=1975}} 8. ^1 {{Cite news|url=http://www.birdlife.org/sites/default/files/red_list_update_for_birds_-_two_iconic_species_saved_from_extinction_by_conservation_action.pdf|title=Red List update for birds|last=International|first=BirdLife|work=BirdLife|date=22 November 2018|access-date=23 November 2018|language=en-us}} External links{{Commons category|Selasphorus rufus}}{{Wikispecies|Selasphorus rufus}}
5 : Selasphorus|Native birds of Alaska|Native birds of Western Canada|Native birds of the Northwestern United States|Birds described in 1788 |
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