Anna’s Hummingbird

Calypte Anna

It is hard to spot a 4-gram mass in the wide-open refuge. Usually, it is the buzz of their wings that gets your attention. Anna’s Hummingbird, named for the Countess of Rivoli (Italy) in the 1829, can be found year-round on the Refuge. It’s genus name, Calypte, is Greek for hood in reference to the male’s iridescent crown.

Having recently seen an Anna’s on the nest, it is the female I want to talk about today. The pair-bonding is brief. The male attracts attention through their elaborate dive displays, in which they can ascend over 100 feet and then plummet toward their target making a variety of complex song and tail feather sounds. The female associates with the male-only long enough to copulate then she is on her own. If you have hummingbird feeders at home, you probably have witnessed the males fighting off other males, females, and young birds. They are not social. No wonder she is a single mother. The female selects a nest site after she locates and begins to defend a nearby source of nectar. The nest is usually placed on a horizontal surface of a twig or branch. Nest height above ground can be as low as 5 feet to about 30 feet. Anna’s use a wide variety of tree, bushes, and shrubs for nesting, though generally not conifers. And it is not infrequent that they will nest along a sidewalk or trail with high human activity as in our case this year along the trail leading to the blind.

Nesting is generally timed with increased availability of nectar and small insects for food. She begins building the nest by alternating between plant down and spider webs. The sides and rim of the nest develop as she sits in the nest, pushing material with her breast while turning. She fashions a cup structure about 1.5 to 1.7 inches wide by 1.25 to 1.6 inches high with the interior width being a snug one inch.  The inside is lined loosely with downy material (plant, feathers, hair). Then she decorates the outside with bits of lichens, mosses, and dead leaves as you can see in the photo taken by Jim Bradley on May 7^th along the trail to the blind. Researchers have found nests decorated in paint chips too!

When the eggs are laid, they are about .5 grams, or 12% of the female’s body weight. Generally, she lays two eggs about 48 hours apart. Eggs are incubated approximately 16 days. The female doesn’t have a vascularized brood patch seen on other species, but it has been noted that their legs swell at this time and speculated that this might be a mechanism for keeping the eggs warm.

As you know, our hummingbirds are frequently moving to and from our home feeders. They have a high energy use and consequently, need to feed frequently. With this lady being on her own both during incubation and rearing, she is very busy. On May 13^th I had an interesting conversation with a photographer who had been observing the mother for several hours. He said she would fly off for about 10 minutes then come back, immediately feed the hatchlings, then sit on them for a while and fly off again. Her routine was quite predictable. Also, given the dates of observation, the eggs were likely laid sometime between April 20^th and April 27th, give or take. Hatchlings are fed immediately, and besides nectar, the female brings in protein in the form of insects. The nestling period varies a lot from field studies, starting from 18 days up to 30 days. Possibly weather or other environmental factors contribute to the variation.

I find it interesting that Anna’s Hummingbird has expanded its range dramatically since the mid-1930s. It once nested only on the Pacific slope of northern Baja California and California north to the San Francisco Bay area. Now it breeds north to Vancouver Island. It is postulated that their effective use of cultivated urban and suburban exotic plants and feeders has contributed to its increased numbers and expanded range.

After reading in some depth about the female Anna’s Hummingbird, I have a lot more respect for her tenacity in bringing more of these lovely birds into the world. You go girl.

-Susan Setterberg, Contact Station Volunteer