Costa's Hummingbird (The True Desert Hummingbird)
Costa's hummingbird (Calypte costae) is a bird species in the hummingbird family Trochilidae. It breeds in the Sonoran and Mojave Deserts of California and Arizona. While it naturally occurs in the western United States and Mexico, it is known to wander towards the east and north as far as Alaska and Canada. It leaves the desert at the peak of summer and moves to chaparral, scrubs, or woodland habitat.
This species is very small, a mature adult growing to only 7.6–8.9 cm in length, a wingspan of 11 cm, and an average weight of 3.05 g for males and 3.22 g for females. The male Costa’s Hummingbird has mostly green upper parts, its back, sides, and belly. It has an iridescent violet crown and white patches under its gorged throat and tail. The throat patch extends to the sides of the throat. Its wings are small and have black tails and wings. Its vibrant purple cap and throat, with throat feathers flaring out and back behind its head, is cited as its most remarkable feature. The female, which is comparably larger in size, is not that remarkable as male. It has a greyish-green crown and back, and a white belly and breast. Its flanks are ‘buffy’ and the tips of its outer tail feathers are white. Sometimes, its throat has some dark feathers. The juvenile Costa’s Hummingbird closely resembles the adult female, with tray-buff edging on the feathers of the upper body. Also, instead of having a singly rounded tail, juvenile Costa’s Hummingbird has a doubly rounded tail.
Like all other hummingbird species, Costa's hummingbird feeds on flower nectar and any tiny insects that it happens to find in the flower petals. At flowers, usually feeds while hovering. They would visit desert natives like agave, chuparosa, desert honeysuckle, and fairy-duster. To catch small insects, may fly out and capture them in midair, or hover to pluck them from foliage.
The male Costa's hummingbird's courtship display is a spirited series of swoops and arcing dives, carefully utilizing a proper angle to the sun to show off his violet plumage to impress prospective mates. Males perform a looping dive display to entice females to mate with them and also to threaten intruding hummingbirds. They fly straight towards the female, make several loops around her and then fly straight up into the air, returning in a broad U-shaped dive. During the dive, they sing a high-pitched whistle. They continue to loop around and perform dives for the female without pause, sometimes for up to 4 minutes, but usually, the display lasts for about 35 seconds. If that was not enough to attract the female’s attention, they also hover directly in front of her with their gorget flared.
One male may mate with several females. Nest site is in rather open or sparsely left shrub or small tree, sometimes in yucca or cactus, usually 2-8 feet above the ground. Placed on a horizontal or diagonal branch. The female constructs a small cup-shaped nest out of plant fibers, down, and at times spider silk, coated with lichen to hold it together. The nest is situated on a yucca stalk or tree limb. The female lays just two eggs, which are white in color, which she will incubate for 15 to 18 days before the young hatch. The young leave the nest after 20 to 23 days. Amazingly, the mother Costa can survive without water throughout the nesting period. Egg and nest predation is the major source of mortality at most sites. Important predators are snakes, small mammals, jays, orioles, and lizards. Adults may be preyed on by Greater Roadrunners and thrashers.
All hummingbirds have a super-fast metabolism and can die quickly if their body temperature isn’t maintained. In the desert at night, the temperatures sometimes dip low. They have a special adaptation called Torpor, a semi-hibernation-like state which allows the body temperature to reduce and the heart rate to slow to 50 beats per minute. A normal heartbeat is 500 to 900 beats per minute. Slowing down their metabolism in this way allows these birds to survive the cold nights.
The Costa’s Hummingbird has a ‘Least Concern’ status under the IUCN Classification System. The IUCN says that the species appears to have a stable population trend and a very large range, which signifies that it does not approach the thresholds for vulnerability. Of all the states in the US where the Costa’s have been observed, only New Mexico has listed the species as threatened.
The most serious threat to the species is loss of habitat, primarily coastal scrub and Sonoran desert scrub. A lot of these areas have been converted for human uses, such as agriculture and residential development.
#Wildlife #SonoraDesert #Mating
