Of the many species of hummingbirds found in British Columbia, only one stays throughout the winter – the Anna’s Hummingbird. The Anna’s Hummingbird (Calypte anna) is a medium-sized hummingbird with green and gray plumage on the back and head and a striking rose-pink throat and crown. Here are some key facts about the overwintering behavior of the Anna’s Hummingbird in B.C.:
Key Questions
Why does the Anna’s Hummingbird stay in B.C. for winter while other hummingbirds migrate? The Anna’s Hummingbird is able to withstand colder temperatures and lower availability of food compared to other hummingbird species. Its ability to enter torpor allows it to conserve energy on cold nights. Also, human feeders provide a reliable winter food source.
How do they survive the winter? Anna’s Hummingbirds enter a state of torpor at night, slowing their metabolism and body temperature. During the day, they feed on nectar from winter-blooming plants and feeders provided by humans. They are aggressive and territorial, allowing them to monopolize feeder resources.
What is their winter distribution in B.C.? The Anna’s Hummingbird can be found along the full extent of coastal B.C. during winter, including Vancouver Island, the Gulf Islands, and the mainland coast. Their range extends inland along river valleys on the mainland.
Where do they nest in winter? Anna’s Hummingbirds build nests and raise young during the winter months. Nests are typically found in trees and shrubs near human habitation where feeders are present.
Overwintering Behavior
Of all the hummingbird species found breeding in British Columbia, only the Anna’s Hummingbird regularly spends the winter in this region. Several behavioral and physiological adaptations allow this species to survive cold temperatures and reduced food availability.
Ability to Enter Torpor
A key adaptation is the Anna’s Hummingbird’s ability to enter a state of torpor overnight. Their metabolic rate and body temperature drops dramatically during torpor, allowing them to conserve energy on cold nights. Studies have shown their body temperature can decrease from 107°F to as low as 48°F overnight, resulting in up to a 25% energy savings.
Feeding Adaptations
Anna’s Hummingbirds have a faster feeding rate than other hummingbirds, allowing them to take advantage of brief warming periods on winter days. They also dominate feeders, aggressively excluding other wintering birds. Their diet shifts during winter to rely more heavily on sugar-rich foods like nectar and tree sap to provide energy.
Cold Hardiness
Physiologically, Anna’s Hummingbirds are better equipped to handle cold weather than other hummingbird species. They are able to elevate their metabolism rapidly after torpor to raise their body temperature and become active on winter days. Their feathers provide excellent insulation to retain body heat.
Winter Distribution
During winter, Anna’s Hummingbirds can be found across much of coastal British Columbia as far north as the Queen Charlotte Islands. Their range extends inland along major river valleys on the mainland. Here is a summary of their winter distribution in B.C.:
Vancouver Island
Abundant across Vancouver Island during winter, with concentrations near urban and suburban areas where feeders are present.
Gulf Islands
Common and widespread across the Gulf Islands, including Salt Spring Island, Galiano Island, and Gabriola Island.
Mainland Coast
Found along the full extent of the mainland coast from the Vancouver area north to the Queen Charlotte Islands. Flocks congregate in urban areas.
Inland Valleys
Breeding birds are present year-round in interior river valleys including the Okanagan Valley, Thompson River, and Fraser River east to Hope.
| Region | Winter Distribution |
|---|---|
| Vancouver Island | Abundant across the island, concentrated near urban areas |
| Gulf Islands | Common on all major Gulf Islands |
| Mainland Coast | Found along entire coast north to Queen Charlotte Islands |
| Inland Valleys | Year-round in Okanagan, Thompson, and lower Fraser Valleys |
Winter Nesting
Anna’s Hummingbirds build nests and raise young during the winter months in British Columbia. This sets them apart from all other hummingbird species that breed in B.C.
Nest Sites
Anna’s Hummingbird nests are typically found in conifers and deciduous trees near human habitation. Favorite nest sites include Douglas fir, western redcedar, maple, and willow. Nests may be placed from 3 to 100 feet above ground.
Nest Description
The nest is small, about 1.5 inches across and 1 inch high. It is constructed using spider webs and lichens bound together with plant down. The exterior is camouflaged using bits of bark, moss, and lichens.
Clutch Size
Typical clutch size is just two tiny white eggs measuring 0.5 x 0.25 inches. The female incubates the eggs for 16-18 days before they hatch.
Broods
Anna’s Hummingbirds will produce up to three broods per year. Second and third broods are timed to take advantage of spring and summer flowering.
| Nest Fact | Description |
|---|---|
| Placement | 3 to 100 feet up in conifers and deciduous trees |
| Construction | Spider webs, lichens, plant down |
| Camouflage | Adorned with bark, moss, lichens |
| Eggs | Typically 2, white, 0.5 x 0.25 inches |
| Incubation | 16 to 18 days |
| Broods | Up to 3 per year |
Identification
Distinguishing the Anna’s Hummingbird from other species during winter can be challenging. Here are some key identification tips:
Size and Shape
Medium-sized with a short, straight bill. Longer primary feathers produce a round-tipped tail.
Color Pattern
Males have iridescent rose-pink feathers covering the head and throat. The back and tail are mostly green. Females lack the pink throat and are overall grayish-green.
Behavior
Aggressive behavior and vocalizations help identify Anna’s. They aggressively defend winter feeders from other birds and humans. Male display dives make whistling or popping sounds.
| Identification Feature | Description |
|---|---|
| Size and Shape | Medium-sized, short straight bill, round-tipped tail |
| Color (Male) | Rose-pink head and throat, green back and tail |
| Color (Female) | Grayish-green overall |
| Behavior | Aggressive defense of feeders, vocalizations, display dives |
Conclusion
The Anna’s Hummingbird is a fascinating year-round resident of coastal British Columbia. Its ability to tolerate cold winters through adaptations like torpor and its aggressive nature allow it to monopolize winter feeding resources. This species can be found across Vancouver Island, the Gulf Islands, mainland coast, and inland river valleys throughout the winter. Watch for them defending feeders, building nests, and raising young – even in the middle of winter!
