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Wintering Anna’s Hummingbirds

We’re studying overwintering Anna’s Hummingbirds in Idaho. Help us by sharing any hummingbird sightings from October-mid March!

Contact us at or 208-426-2223

Share the word with friends by downloading a PDF of our “Wanted Poster”
Share the word with friends by downloading a PDF of our “Wanted Poster” for print.


The Anna’s Hummingbird has a history of range expansion in the west. Their well-documented range expansion began in the 1930’s when this species, previously known to breed only in Baja California, began to spread into Arizona and California. From California, this species continued to grow its range, and by the 1970’s was seen breeding as far north as British Columbia.

Sep25,2013f 018 Anna's Hummingbird juvenile
A Juvenile Anna’s Hummingbird in north Idaho. Photo by Terry Gray

In Idaho, this species was first recorded in 1976. Sightings continued to be somewhat rare (37 between 1976-2005). However, they have become increasingly common (more than 30 records in just 10 years). They are now seen annually in the Idaho Panhandle and Southwestern Idaho.

In the Treasure Valley, birdwatchers have seen a number of Anna’s in recent years. The range map below shows winter sightings of 20+ Anna’s.

ANHU range map

Documenting population growth

With the start of this apparent range expansion in Idaho, we would like to document the progress of the population growth.

Birdwatchers have been an excellent resource for documenting Anna’s sightings, but there are limits to what we can learn by observing birds at feeders. At some feeders there are adult birds of different sexes, making identification of individuals simple. In many cases, multiple individuals have been found visiting one feeder. However, if multiple females or young birds are present it is difficult to determine whether there is more than one hummingbird visiting a feeder because they all look the same. It is also difficult for a birdwatcher to say whether the individual they spotted in September is the same individual they saw in March.

Thanks to reports from birdwatchers, during our first winter (2015-2016) studying Anna’s Hummingbirds in Idaho we (along with collaborator and hummbander Franceen Rudeen in eastern Idaho) confirmed reports of at least 55 individuals in the state! In 2016-2017 we documented 39 individuals. Through banding, our original estimate of 2 individuals at one home turned out to be 6 different individuals that couldn’t be distinguished from each other through feeder-watching alone.

You can learn more about winter hummingbirds in The Cornell Lab of Ornithology’s “All About Birds” article: There’s a hummingbird at my feeder in the dead of winter

For more Idaho-related Anna’s information, check out this publication by fellow hummingbird banders, Carl Rudeen and Fred Bassett: Apparent Breeding by Anna’s Hummingbird in Idaho.

IBO project goals:

Our goal is to get the best documentation to-date on the occurrence of Anna’s in Idaho. We would like to get information on any winter hummingbird sightings.

We will also work with other hummingbird banders in the state to band as many Anna’s Hummingbirds as possible and solve these mysteries.

Young Male Anna’s Hummingbird. Boise, Idaho. Photo by Heidi Ware Carlisle

By tagging these birds, we hope to answer some of these questions:

  • Are these sightings “accidental” or “vagrant” in nature, or a sign of true range expansion?
  • Are the majority of these birds inexperienced young birds, or experienced adults?
  • Are there more females than males?
  • Do individuals return year after year?
  • How many individuals are actually visiting each feeder?
  • Do they move long distances or visit multiple feeders?
  • Are these birds in good body condition? What level of fat stores do they maintain to survive?
  • Do multiple sightings at a feeder throughout the winter represent single individuals, or a number of individuals passing through during the winter season?
  • At what rate is this overwintering population expanding?

For this study, we will rely on dedicated birdwatchers to document presence of birds at their feeders, and return visits from color-marked birds.

Project FeederWatch is also working to answer these questions on a larger scale by using citizen science data. Read their 2017 Anna’s update on page 4 of this newsletter.


Here are a few ways you can help us with this project:

  • If you maintain feeders this winter watch them closely, and keep an eye out for hummingbirds visiting late-flowering plants.
  • Submit your winter hummingbird sightings to eBird.
  • Email us if you see any hummingbird between October-March:
    • Send information on location, species (if known), timing and frequency of visits, and photos if possible.
    • Indicate whether you would like us to try and band your hummer, or if you’d rather just submit sighting reports.
  • Track how long your hummingbird stays (take notes of sightings, or submit to eBird).
  • Tell your birdwatching friends about our project.
Unlikely Friends
An Anna’s Hummingbird and a Dark-eyed Junco enjoying the feeders on a snowy day in Boise, Idaho. Photo by Heidi Ware


What if I don’t want you to band my hummingbird?

That’s fine! We respect homeowner privacy and would love to hear about your sighting whether we end up banding the bird or not.

How do I keep a feeder in cold weather?

For those living in the Treasure Valley, Wild Birds Unlimited in Boise sells heated feeders. Call them to check on availability.

There is another heated feeder on the market called the Hummers Heated Delight! We have tested it in single-digit temps and it has worked great so far, and has received good reviews from others who have tried it. Heidi has used a heated dog bowl at her house with great success, though this method is only safe in a completely cat-free area such as an elevated deck.

female (adult?) ANHU at feeder. High temp of 18F today!
A female Anna’s Hummingbird uses the heated dog bowl on a cold 18 degree F day!

Here are some articles with information about feeding hummingbirds in winter:

Winter hummingbirds: Project Feederwatch

What if I saw a hummingbird but can’t tell what species?

We are interested in all winter hummingbird sightings. Please email us with as much information as possible. Keep your feeder up, take notes about field marks, and if you can, snap a photo. We would love to help you confirm the ID of your hummingbird.

You can still enter your unidentified hummer sighting into eBird by submitting a report of a “Hummingbird sp.”. This still provides valuable scientific information.

What are key field marks for Anna’s Hummingbirds?

Although a hummingbird found in Idaho between October and March is most likely an Anna’s, it’s a good idea to try to confirm what species you are seeing.

The strangest vagrant hummingbird species often show up in winter (such as this Bahama Woodstar and the Xantus’s Hummingbird made famous by the book and movie “The Big Year”) so it’s good to keep your eyes out!

Photo Album

This album of Anna’s Hummingbirds in Idaho includes photos of adult females, young females, and young males.

An adult male Anna’s hummingbird is easy to identify by it’s bright fuchsia head (but be careful: in shade their heads can appear black). Unlike Idaho’s other hummer species, it is the only one with iridescence on both its throat and forehead.

Female or young male Anna’s can be more difficult to identify.

Adult females and young males usually have a small central patch of fuchsia on their throat that is visible in direct sunlight. In the shade, they often appear to have a small gray or black triangular ‘smudge’ on their throat. Young females sometimes lack a throat patch.

Unlike female Rufous and Calliope Hummingbirds, Anna’s do not have any warm buffy, brown, or cinnamon colors on their tail or chests.

Unlike female Black-chinned Hummingbirds, Anna’s chests are smudged with greenish feathers and their crowns are green (Black-chinned’s have less smudgy, gray chests, and more gray crowns).

Overall, Anna’s are more stocky than other species, weighing a few tenths of a gram more than other Idaho hummers. Their bills are proportionately shorter than Black-chinned’s and they have a small white mark above and behind their eye.

Visit the Anna’s Hummingbird page on Cornell’s All About Birds website to learn more.

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