Trochilidae

Hummingbirds are polygynous; males interact with females only to breed and provide no parental care. Females are responsible for nest building, incubation and post-hatching parental care. Males attract mates using song, iridescent plumage and dramatic display flights. Depending on the species, males display at lekking grounds, defended territories, traditional display grounds, or singing posts.

Mating System: polygynous

Hummingbirds breed during the season with peak nectar availability. Most hummingbirds build cup nests, but a few build domed or semi-domed nests that provide more protection than an open cup nest. Nest height ranges from a few centimeters above the ground to 10 to 30 meters. Nests are camouflaged with lichen, moss, dead leaves, bark, etc. and are held together with spider webs. They are sometimes lined with feathers, fur, hair, or plant down. Nests take 5 to 10 days to build and are often re-used year to year.

Clutch size is two and eggs are white, non-glossy and an elliptical oval shape. Because some species of hermits will lay eggs in another female’s nest, clutches of more than two can sometimes be found. There is a 48-hour interval between egg laying. The size of hummingbird eggs range from 8 by 11 mm in bee hummingbirds (Mellisuga helenae) to 12 by 20 mm in giant hummingbirds (Patagona gigas). The average weight of an egg is 0.4 to 1.4 g. Incubation usually lasts 16 to 19 days. If females begin incubating after the first egg is laid, hatching of the two eggs can occur 48 hours apart. If she waits until the second egg is laid, hatching occurs synchronously. Nestling period is 23 to 26 days; hatchlings are altricial with almost no feathers and eyes closed. Females brood young for 7 to 12 days, at which point the young are able to control their own body temperature. Fledglings continue to be fed by the female for 18 to 25 days after they have left the nest.

Female hummingbirds can have two broods per year when conditions permit and will re-nest if a brood is lost. Most nest failure is due to depredation.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal )

Only female hummingbirds are involved in parental care; they must incubate eggs, brood young hatchlings, and feed the chicks as nestlings and fledglings. Hummingbird chicks are altricial and stay in the nest for 23 to 26 days. When they first hatch, young hummingbirds have few feathers and cannot thermoregulate. The female must brood the young for 7 to 12 days until they can maintain their body temperature. Females feed nestlings nectar and arthropods approximately twice every hour. Fledglings are fed by the female for 18 to 25 days and gradually learn to forage by themselves.

Parental Investment: altricial ; female parental care

Microstructures produce iridescent colors: hummingbird
 

The feathers of hummingbirds are iridescent due to the inhomogeneous interference structure of platelets on feather barbules.

"To summarize, hummingbird iridescence is due to interference colors  produced by a stack of about three films whose optical thickness is  one-half the peak wave length. Each film is a mosaic of platelets of  elliptical form. Each platelet is about 2.5 microns long and one micron  wide. The platelets are not homogeneous and consist of air bubbles  encased in a matrix of refractive index about two. The different  hummingbird colors are produced by a combination of effects. The  platelet thickness decreases moderately as one passes from red through  green to blue, and the air content increases simultaneously. In theory,  of course, platelet thickness could remain constant and the color change  would arise solely by variation in air content. Conversely air content  could be constant and the platelet thickness varied. Nature for reasons  best known to herself has elected to vary both factors together.”  (Greenewalt et al. 1960:253)

"First, we repeated the examination of barbular surfaces with the optical microscope. We confirmed the presence of the platelet mosaic on the iridescent surfaces of fifty or so hummingbird species. Only the platelets are colored; the interstices are dark. The platelets are minute, about 2.5 microns across the long axis of the ellipse, and one micron across the short axis. Ten thousand of them laid end to end would measure a little over an inch. Their size varies little throughout the hummingbird species which we have examined. The length of 2.5 microns is a good average and the limits of variation would be no more than 30 per cent either way. Along its length the barbule is divided into cells separated by diagonal lines crossing the width of the barbule. At the points where the barbule joins the ramus and where the pennulum develops, the colored platelets disappear and one sees only a few random uncolored or faintly colored ellipses in these areas. The barbule proper then has a surface which is 15-20 microns wide and 100 microns long, divided by diagonal boundary lines into a series of cells which look like parallelograms, each cell made up of a mosaic of 100 or more beautifully colored elliptical platelets”  (Greenewalt et al. 1960:250).

   
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Intestines absorb glucose fast: hummingbird
 

Intestines of hummingbirds rapidly take up glucose by using glucose transporters in intestinal mucosa.

 
  "Intestinal transit time is about 15 minutes, during which time, using a high density of glucose transporters in the intestinal mucosa, some 99% of ingested glucose is absorbed." (Fowler and Miller 2003: 235)
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Hummingbirds are found only in the New World in the Nearctic and Neotropics. Their range extends from Alaska to Labrador in the North to Tierra del Fuego in the south and from Barbados to the Juan Fernandes islands. Most species are tropical and sub-tropical and live between 10 degrees N and 25 degrees S lattitude. More than half of all species of hummingbird are found in Brazil and Ecuador.

Biogeographic Regions: nearctic (Native ); neotropical (Native )