Costa’s is a bright little hummer, a bird that, once seen, you could not mistake for anything else. Arguably the prettiest North American hummer, the male has a brilliant purple throat with trailing feathers and a white line above the eye. Combined with a head-on look, this gives you the impression that you are in a stare-down with an angry bird. But that only lasts for a short time, especially if you’re lucky enough to see a male displaying for a female.
In his display, he erects his purple throat feathers into six- or eight-finger-like projections, making it look like an octopus has attached to his throat and making his appearance a little more comical – and impressive.
As this species will come to feeders, you can increase your chances of seeing Costa’s hummingbirds in your backyard if you put a feeder out. However, they are usually subordinate to other species of hummers, and so this may put them at a disadvantage. Interspecific (between-species) interactions were a focus of my scientific research for years.
I still am keen to learn about species where aggressive behavior affects their ability to access food, especially when humans create this situation. Let’s explore the world of Costa’s hummingbirds!
Bottom Line Up Front
This desert-loving species is a tiny brilliant jewel, as the males have a bright purple throat with elongated trailing feathers. They feed on numerous species of flowers in dry habitats, and in areas where flowers get scarce, they migrate to Mexico during the winter. You can see it in urban areas because it is a species that will use feeders, and it seems to be expanding its range, perhaps in response to this new food supply.
Costa’s hummingbirds are classified using the following taxonomy:
- Kingdom Animalia
- Phylum Chordata
- Class Aves
- Order Apodiformes
- Family Trochilidae
- Genus Calypte
Costa’s hummingbirds can hybridize with the closely-related Anna’s hummingbird (C. anna), the only other species in the same genus. However, they can also hybridize with broad-tailed (Selasphorus platycercus) and black-chinned (Archilochus alexandri) hummingbirds in different genera.
Species can sometimes breed with other species in the same genus but rarely with species in a different genus. These inter-generic hybrids indicate that the taxonomy of these groups may need to be revisited, and these species may be more closely related than currently thought.
How to Identify Costa’s Hummingbirds
These small birds are 3-3.5 inches long and weigh just over 3 grams.
The throat patch is most distinctive aspect of the male Costa’s hummingbird. Like all hummers, the throat feathers are reflective, so the throat patch’s color depends on the angle of the light, which means it can look magenta, amethyst purple, violet-blue, or even greenish or reddish. These reflective purplish feathers extend to the forehead and crown, and you can usually see a white stripe above the eye. When resting, the elongated throat feathers form an inverted V.
The feathers extend along the breast’s sides, overlapping each other. It’s only when the male is displaying for a female that you realize it’s not just a single set of long feathers, but instead, each side has three to four projections, so when fanned out, it looks vaguely octopus-like.
If you look at the rest of the bird, you’ll see the lower throat is grayish, and these feathers continue down the middle of the belly, framed by metallic bronze-green feathers like a vest. The metallic green-bronze feathers are also found on the back and wing coverts, and the flight feathers are brown-gray.
Adult females can also have metallic throat feathers; otherwise, their throat and belly are pale brownish gray, and they have a dull white eye stripe above and behind the eye. Juveniles look similar to adult females but have a grayish-buff edging to the feathers of the throat and back, and the tail is slightly notched at the center in contrast to an adult’s rounded tail. Juvenile males usually have a few metallic throat feathers and dusky spots on their throats that distinguish them from juvenile females.
Anna’s hummingbirds, especially females or juveniles, can be confused with Costa’s hummingbirds. On a perched bird, look at the end of the wingtips compared to the tail: on Costa’s hummingbirds, they are equal in length, whereas on Anna’s hummingbirds, the tail is longer than the wings. For males, Anna’s hummingbirds have red throats with no elongated throat feathers, which looks quite different from the purple, elongated throat feathers of a male Costa’s.
Where Does Costa’s Hummingbird Live: Habitat
This species prefers dry, xeric, arid brushy habitats. They are common in the Lower Sonoran zone of the Sonora desert (up to 3,000 feet) and are less common in the Mojave desert (up to 4,000 feet) and will use city parks and gardens as well. They will also use coastal chaparral, sage or desert scrub, and woodlands near streams.
Costa’s Hummingbird Diet and Feeding
They utilize desert plants since that is their habitat; favored plants are chuparosa and ocotillo, but they are not specialists. They use at least 22 plant species, from tiny desert lavender (usually visited by bees) to large saguaro flowers (usually visited by bats). Males maintain feeding territories, whereas females do not. In urban environments, males will maintain territories year-round; in the absence of feeders, males will disperse and follow nectar sources.
These hummingbirds will also catch insects while flying, such as flies and mayflies; this is an essential source of protein, especially necessary for females to feed their growing chicks. They get most of their water needs through nectar but sometimes drink from streams.
Costa’s Hummingbird Breeding
They begin breeding in March in California and February in Baja California, but breeding peaks in May. Recent records of them nesting into December suggest that human-provided nectar feeders and non-native plants have extended their breeding season, with unknown consequences.
Costa’s hummingbirds are polygynous (males mate with multiple females), and females enter a male’s territory to decide whether to mate. To try and woo the female, the male initially flies close to her and flashes his throat patch while singing. Then he proceeds to do a full shuttle display, where he quickly flies back and forth repeatedly in front of the perched female, erecting his throat and crown feathers – remember, this is when the octopus appears!
Because these feathers are reflective, the angle of the male compared to the sun and the watching female affects how bright the feathers appear.
If the female stays, males will perform a U-shaped breeding flight, where they fly about 30m high and then dive rapidly toward the ground, making a whistle-like sound at the bottom with their outer tail feathers. Since males dive slightly offside of the female, males twist their tail feathers to direct the mechanical sound towards the females.
These behaviors mean the male can affect how bright his throat feathers look (by changing his angle) and the loudness of his tail feathers (by twisting the feathers) to convince the female that he is the one with whom to mate.
Costa’s Hummingbird Nesting
Nests are located 2-9 feet off the ground, averaging around 4 feet. The placement of nests is often near the end of branches, possibly to make them less accessible to climbing mammals, with trees such as netleaf hackberry (Celtis reticulata) used as nesting sites. The nests are made from plant fibers and small stems, lined with soft plant down and feathers, and are attached to the branch with spider webs.
The female camouflages the nest by attaching bark or plant material with spider webs. Though early studies found no evidence of the reuse of nests or nesting sites, other studies found that females did reuse nest sites; it is unclear when females chose to reuse nests versus make new ones. Their nests, often described as flimsy, are less well-built than other species and can be wrecked by inclement weather.
Only a few hummingbird species nest more than once a year. Though Costa’s hummingbirds typically only raise one brood per year, they can successfully raise two or even three within a season. When a female raised a second or third clutch, she was usually still feeding older or recently fledged nestlings as she started a new nest, which meant she was feeding nestlings and incubating new eggs at the same time – pretty impressive for a 3 g bird!
Costa’s Hummingbird Eggs
They lay 2 eggs, like all hummingbirds, with the second egg laid 2 days after the first. The female may continue building the nest while the first egg is laid, but the nest is usually completed by the time she has laid the second egg. Interestingly, the female starts incubation after laying the first egg, which creates a 1-2 day age gap between the two chicks. Incubation length seems very variable, lasting from 9-18 days, with 16-18 days probably being typical; this is longer than most other hummingbirds. The shorter incubation lengths seem biologically unreasonable and should be viewed with caution.
The nestlings fledge at 20-23 days. The adult female will continue to feed the fledglings for 1-2 weeks once they leave the nest.
Costa’s Hummingbird Population
The range of Costa’s hummingbird is fairly small, and they are migratory in parts of their range. Their breeding range extends from southern Nevada to southwestern Utah, western Arizona, barely into southwestern New Mexico, and mid-Sonora (Mexico). They overwinter along the west coast of Mexico, mainly Sinaloa and Nayarit, with a few individuals recently seen in Jalisco outside the described range.
We don’t know a lot about the details of migration; does post-breeding migration lead to individuals overwintering in the year-round or winter parts of the range? Information about migration is further complicated because, in some areas, some individuals move while others stay (a pattern termed partial migration), and individuals also have irregular movements in response to nectar availability which can look like migration.
Year-round they are found in southern California, southwestern Arizona, Baja California, and western Sonora. Overall, some areas have decades between sightings, whereas, in other areas, they are becoming increasingly common.
Costa’s hummingbird has been seen quite far outside its accepted range, with sightings in Texas, Kansas, Colorado, Oregon, Washington, Idaho, Alberta, British Columbia, and even Alaska. Most northern sightings were adult males in late spring, which may reflect male dispersal after mating.
Like most cases of extralimital movements, we don’t know if this is a true range expansion or just more sightings of vagrants (or, for females, better species identification from Anna’s hummingbird, whose range extends up the west coast). As more hummingbird feeders are left out, especially year-round, these sightings may become more common if these artificial food sources are why this species is moving north and east.
Is Costa’s Hummingbird Endangered?
No. Overall, they are listed as Least Concern, with a population estimate of 3.4 million. However, in New Mexico, they are listed as Threatened because their population is small and has a limited range in that state. Threats to their population are most likely those related to habitat loss: development (agricultural and urban) and grazing (particularly converting scrub and forests to South African buffelgrass for cattle).
It is also possible that diseases could become an issue, as 20% of dead Costa’s hummingbirds tested positive for West Nile virus. This mosquito-borne disease has severe consequences for some species.
Costa’s Hummingbird Habits
The sister species of Costa’s hummingbird, Anna’s hummingbird, learns its complex song. Because Costa’s hummingbird has a simple song, it was thought this must be inherited, not learned. However, Costa’s hummingbirds learn their very simple song. All males sing the same song: a single syllable that can be repeated up to 8 times.
However, the high-energy elements of the song (such as frequency and duration) vary among individuals, and males with larger throat patches sing faster songs. This variation means that song and throat patches may reflect the quality of males or may be involved in competition between males for territories, as both songs and displays are used in both contexts.
To learn their song, birds must hear the correct song during specific sensitive periods, usually early in their lives. Juvenile Costa’s hummingbirds require the sight and sound of an adult male to learn the proper adult song; without this, it never develops properly. They have a long learning period, which begins early (at the age of 23-35 days) and continues late (at the age of 115-125 days).
Females also sing on occasion. The purpose of female songs is not known.
Both sexes give call notes which are a high, light tic, several running together in a rapid twitter when excited. These call notes are used when other hummingbirds are intruding.
Costa’s Hummingbird Predators
Perhaps because of their small size and willingness to feed on small flowers close to the ground, at least two species of birds are likely opportunistic predators – greater roadrunners (Geococcyx californicus) and curve-billed thrashers (Toxostoma curvirostre). How often these other birds successfully capture fast little hummingbirds is not known.
Nests are very vulnerable to predation. In one study, predation was the cause of all nest failures recorded, and in another study of 11 nests over three years, only 1 chick fledged; the rest were predated, though the species of predator was not known. The predator was believed to be spotted skunks in one case; birds and snakes probably account for the others. In another study, on average, a female needed to lay three eggs for every chick that successfully fledged.
Costa’s Hummingbird Lifespan
Their maximum lifespan is unknown, but the closely-related Anna’s hummingbird can live at least 8 years, so we can assume that the lifespan would be similar for Costa’s hummingbird.
Answer: This bird was named after Louis Marie Pantaleon de Costa, the Marquis de Beau-Regard, a French collector interested in hummingbirds. It was suggested in 1927 that the species be named the California hummingbird; this species is mainly found there, but its name was never changed.
Answer: Yes, probably to their advantage, as more areas will warm. One estimate is that Costa’s hummingbird will lose 9% of its southern range but gain 43% at the northern edge. This change, however, would still require that the new areas have suitable flowers for food, bushes for nesting, and low competition from other species – all unknowns.
Answer: Torpor is a physiological response to conserve energy. Some hummingbirds will do this, especially at night, including Costa’s hummingbird. It involves lowering oxygen consumption, heartbeat, and body temperature. Body temperatures can drop to as low as 10 C (compared to a normal body temperature of 35 C), and their heartbeat to 50 beats/min (compared to a normal rate of 500-900 beats/min) – pretty impressive!
It’s amazing that a bird this small, with high energetic requirements, can survive and thrive in desert habitats. As a biologist, I’m fascinated by the questions that this generates.
To what extent does competition with other species drive this distribution? What adaptations do they have to survive the desert environment, and what are the trade-offs? Why are they present in such variable numbers, especially at the edges of their range? Will supplemental artificial feeders help or hurt them, as feeders often attract multiple species and may increase competition?
Like many hummingbird species, there is still much to learn about this tiny purple-throated bird, but we need to conserve its habitat to have the chance.
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