Nesting of Anna's Hummingbirds in San Diego, CA

Temporal Analysis of Nest-Building, Egg-Laying, Hatching & Fledging

Oct 27, 2009

Little is known about the life spans and timing of nesting events of hummingbirds. Eight different nests made in the same tree from 2003-2009 provide some information.

The remarkable ability of Mexican monarch butterflies, San Juan Capistrano swallows, and California gray whales to return to the exact same breeding grounds every year after migrating thousands of miles is a true wonder of nature. But no less wondrous to many coastal Californians is the annual nesting of resident, non-migratory, Anna's hummingbirds that build their nests in the exact same places year after year. This article reviews observations made for eight different Anna's hummingbird nests that were built in the same Tasmanian tree fern in San Diego, California from 2003-2009.

Nest Locations and Periods

The eight nests were not only built in the same tree but in the same part of the tree. Not exactly the same branch, because tree fern branches are continually replaced by newer sprouts. These branches are strong enough to support a nest and a few 3-4 gram hummingbirds (a nickel weighs about 5 grams) but not the weight of cats or other predators. Over the seven year period, six of the eight nests were established between the end of February and the beginning of March and one nest each was built on April 23 and May 22. A ninth nest was started on December 22 but was abandoned for unknown reasons before being completed.

Nest Maintenance

The mother hummingbird builds the nest, incubates the eggs, and feeds the chicks on her own. Only once was a male hummingbird observed near a nest; an unsuccessful attempt to frighten away a predatory raven. People are more likely to frighten ravens, hawks, and other hummingbird predators which may be one reason that Anna's hummingbirds build their nests so close to people. The observed nests were ~15 feet from the front door and only 3-5 feet from the head of any person passing by on the walkway. However, hardly anyone noticed the nests because they were so well hidden and camouflaged in the fern fronds.

Nest Construction and Timing

Beautiful nests of lichens, moss, twigs, lint, and spider silk were constructed in just four days and two pearl white, jelly bean-size eggs appeared five days later, on the average. From the onset of nest-building, both eggs hatched 24 days later and both chicks fledged their nest by 45 days on average. The mother only sleeps on a nest when it is occupied by eggs or chicks. Although it's unknown if the same mother built all eight nests from 2003-2009, it's a possibility because Anna's can live 7-10 years.

While not as well known as the more famous California Grey whales, Capistrano swallows, and Monarch butterflies, the cute little Anna's hummingbirds are wondrous creatures in their own right that instill a great appreciation of nature equally well.

Reference

Kaiser, Don, Announcing an Anna's Annual Arrivals, Analysis of Data, 2003-2009

The copyright of the article Nesting of Anna's Hummingbirds in San Diego, CA in Bird Watching is owned by Don Kaiser. Permission to republish Nesting of Anna's Hummingbirds in San Diego, CA in print or online must be granted by the author in writing.