Anna’s and Costa’s hummingbirds are two similar looking hummingbird species found along the west coast of North America. They can be difficult to tell apart, especially for amateur birdwatchers. This article will go over the key identification features, habitat, diet, behaviors and other differences between these two hummingbirds.
Quick Identification Tips
Here are some quick tips for identifying Anna’s vs Costa’s hummingbirds:
- Anna’s males have rose-pink throats and crowns. Costa’s males have purple crowns and gorgets (throat patches).
- Females of both species are similar with green backs and grey undersides. Anna’s have more spotting on the throat.
- Anna’s have longer tails and larger size overall.
- Costa’s have shorter bills that are more curved.
- Costa’s prefer hot arid climates while Anna’s thrive in cooler climates.
- Anna’s make a lower pitched sound compared to Costa’s high pitched song.
Identification
Now let’s go over the identification features and differences between Anna’s and Costa’s hummingbirds in more detail:
Male Plumage
The most striking difference between adult males of these species is in their plumage:
- Anna’s males have iridescent rose-pink feathers on their throats (known as their gorget) and crowns. When the light hits them just right, they can appear bright pink or even orangey-red.
- Costa’s males have a violet-purple gorget and crown. Their purple coloring is deeper and more uniform compared to the flashy Anna’s.
Both species have green backs and flanks with grayish undersides. However the Costa’s gray underparts are whiter and less washed out.
Female Plumage
Females of both Anna’s and Costa’s are much harder to differentiate. They are nearly identical with green upperparts and grayish white underparts. The best distinguishing feature is:
- Anna’s females typically have some small magenta or pink colored spots on their throat feathers. Costa’s females lack any spotting or markings on the throat.
Females in both species may also show some reddish-pink on the base of the outer tail feathers, but this is variable and not a reliable ID feature.
Shape and Size
Anna’s hummingbirds have a larger body size and longer tail compared to Costa’s:
- Anna’s measure 3.5-4.3 inches long with a wingspan of 4.7 inches. Their tail is fairly long at 1.1-1.3 inches.
- Costa’s measure 3-3.75 inches in length with a 3.75 inch wingspan. Their tail measures 0.8-1.1 inches.
The Costa’s smaller size means they have shorter wings that are more rounded compared to the longer pointed wings of Anna’s. Their flight is faster and more direct due to the short wings.
Bill Shape
The bill shape also differs:
- Anna’s have straight, medium length bills.
- Costa’s have very short bills that are distinctly decurved or curved downwards.
This curved bill correlates to the Costa’s shorter wings and body, giving it a more petite and compact appearance compared to Anna’s more elegant proportions.
Habitat Differences
These two hummingbirds occupy broadly overlapping ranges along the Pacific Coast and desert Southwest. However they frequent different habitats within this range:
- Anna’s hummingbirds prefer open woodlands, scrubland, chaparral, and suburban gardens, parks and backyards.
- Costa’s hummingbirds are more closely tied to hot desert climates including desert scrub, palo verde and mesquite thickets, and oasis gardens.
A main habitat difference is that Costa’s are rare or absent from cooler coastal and mountain locations inhabited by Anna’s. Costa’s require hot conditions and do not tolerate cold weather or frost.
Backyard Feeders
In urban and suburban areas, Anna’s readily visit backyard nectar feeders year-round. Costa’s may visit feeders in winter but less commonly stay throughout summer. Anna’s are one of the most common urban hummingbirds, while Costa’s are rare around feeders outside the Sonoran Desert region.
Elevation
The elevation ranges occupied by each species also differs:
- Anna’s occur from sea level up to 10,000 ft elevation in mountain ranges.
- Costa’s are rarely found above 5,000 ft and occupy lower elevations in hot desert regions.
Range and Distribution
Anna’s and Costa’s hummingbirds have broadly overlapping ranges along the west coast and Southwest deserts. However there are some key differences:
Year Round Ranges
- Anna’s residential range covers coastal California and the Pacific Northwest. They occur year-round west of the Sierra Nevada range.
- Costa’s are permanent residents only in the Sonoran and Mojave desert regions of California, Arizona, and Mexico.
Breeding
- Anna’s breed along most of their Pacific coast range and inland west of the mountains.
- Costa’s breed in the desert Southwest and Mexico. Their breeding range extends slightly farther north than where they reside year-round.
Wintering and Migration
- Anna’s are one of few hummingbird species that do not migrate. They tolerate cold winters provided they have access to feeders.
- Costa’s migrate north in spring to breed and south in fall to winter primarily in Mexico. Their winter range extends along warmer Gulf coast areas farther east than where they breed.
Vagrants
Both species may turn up well outside their expected ranges. This occurs most often with younger birds in their first migrations. Anna’s vagrants may reach eastern North America. Costa’s vagrants occur most often in southeastern Arizona, Texas, and Louisiana.
Diet and Feeding
Anna’s and Costa’s rely on many of the same flower nectar, tree sap, and small insect food sources. However there are some subtle differences:
- Anna’s take more tree sap especially during winter when flowers are scarce. They also more readily visit backyard feeders year round.
- Costa’s depend more heavily on desert flowers and less on feeders or sap outside the breeding season. Their shorter bills are adapted to arid climate flowers.
Both species feed heavily on small insects and spiders to meet their high protein requirements during the breeding season. Some favorite prey includes gnats, midges, mosquitoes, caterpillars, and spiderwebs.
Breeding and Nesting
Anna’s and Costa’s hummingbirds share some key traits as breeding species, but also have notable differences:
Breeding Season
- Anna’s nest from November to June and occasionally have two broods per season.
- Costa’s nest from January to July with just one brood.
So while their breeding seasons overlap broadly, Anna’s begin and end a little earlier in the year compared to Costa’s.
Courtship Displays
Males perform elaborate courtship displays to attract females in both species. Costa’s are famous for their “pendulum display” where they fly in U-shaped or figure-8 patterns over breeding areas. Anna’s have similar display dive flights but their patterns may be more erratic.
Nest Materials
Female hummingbirds gather all nest materials. Anna’s and Costa’s build very similar tiny nests on branches using soft plant down held together with spiderweb silk and camouflaged with lichens.
Nest Placement
Typical nest placement locations:
- Anna’s often nest in high open branches of trees including eucalyptus, oak, sycamore, pine, and cypress. They may also nest on wires, posts, or other manmade structures.
- Costa’s typically nest lower in small desert trees and shrubs like palo verde, acacia, mesquite, and yucca. Cholla cactus is another favorite nest site.
The lower nest placement of Costa’s correlates to the smaller desert trees in their habitat compared to larger trees used by Anna’s.
Clutch Size
Another difference is typical clutch size:
- Anna’s lay 2-3 eggs per clutch.
- Costa’s lay just 2 eggs per clutch.
The smaller clutch of Costa’s may be an adaptation to hot desert conditions where it is more difficult to provision larger broods.
Behavioral Differences
Some key differences in behavior between the species:
- Temperature regulation – Anna’s tolerate colder temperatures. Costa’s require hot conditions.
- Aggression – Anna’s males are highly territorial. Costa’s rarely exhibit aggression.
- Vocalizations – Anna’s have lower pitched calls. Costa’s make very high pitched squeaky songs.
- Wariness – Anna’s are tamer and more tolerant of humans. Costa’s are shy around people.
- Displays – Costa’s have a famous pendulum display flight. Anna’s displays are less consistent.
These behaviors reflect adaptations to their different environments and resources.
Conclusion
While Anna’s and Costa’s hummingbirds appear very similar at first glance, a closer look reveals key differences in their identification features, habitats, distribution, diet, nesting biology, and behaviors that allow them to thrive in their respective ranges along the Pacific Coast and desert Southwest.
Anna’s hummingbirds are better adapted to cooler climates from the coast to mountain ranges. Costa’s hummingbirds require hot desert conditions where they alone can survive year-round. Understanding these differences helps birdwatchers accurately identify these often confused species.
