Anna’s hummingbirds (Calypte anna) are small, colorful birds that are found along the west coast of North America. The males are known for their iridescent throat feathers that shine in brilliant magenta and rose-pink when the light hits them just right. This coloration makes them one of the most striking and recognizable backyard birds in their range. But did you know that the colors of the male Anna’s hummingbird actually change throughout the year? Unlike some other bird species that molt into a less colorful non-breeding plumage, Anna’s hummingbirds undergo changes in their vibrant throat feathers as the seasons change from breeding season to non-breeding season. Here we’ll look at the fascinating color shifts that Anna’s hummingbirds display and what causes these spectacular changes.
Breeding Season Colors
During the breeding season, which runs from November to June in most parts of their range, male Anna’s hummingbirds sport their most brilliant and eye-catching colors. Their throat and crown feathers erupt into an iridescent fuchsia-rose with an amazingly complex mix of colors from orange to violet dancing across the surface as the bird moves. This coloration results from plate-like melanin structures within the feathers that reflect light. By displaying these flashy feathers, male hummingbirds communicate to females about their fitness. The more intense and vibrant the colors, the better their chances of attracting a mate.
Non-breeding Season Colors
But this dazzling display doesn’t last year round. After breeding season ends, Anna’s hummingbird throat feathers molt and are replaced. The new feathers that grow in are much duller and lack the same complex structure that creates the colorful iridescence. These non-breeding feathers are mostly grey-green to orange with just a small amount of dull pink or purple iridescence in the center. Essentially, they lose the brilliant, metallic coloring that makes the males’ throats appear to glow as if lit from within. The difference is dramatic between breeding season and non-breeding season plumages.
What Causes the Color Change?
So why do Anna’s hummingbirds bother with this seasonal shift in color? It takes energy for the birds to grow colorful new feathers each year, so there must be some benefit. It turns out the color change is likely driven by a few factors:
Saving Energy
The vibrant breeding plumage is energetically costly to produce. By moulting into more subdued non-breeding colors, the birds save energy during the seasons when they don’t need fancy feathers to attract mates.
Camouflage
The duller non-breeding colors also provide better camouflage outside of the breeding season when the birds are not trying to attract attention. This helps hide them from predators.
Social Signalling
The seasonal color change could also function as a social signal indicating breeding status. Females may not be stimulated to breed by the non-breeding colors.
When Do the Colors Change?
The timing of Anna’s hummingbird molts and color changes varies across their range:
Southern Populations
– In Southern California and southwestern Arizona, males undergo two molts per year – one in early summer after breeding and one in early winter before the next breeding season.
– Colors are brightest February through May and dullest in July through August.
Pacific Northwest Populations
– Farther north, the birds only molt once before breeding season.
– Males are dullest September through November and brightest April through July.
– Their iridescence peaks later than southern populations.
Year-round Residents
– Some males in coastal central and southern California and Arizona are year-round residents that may retain breeding colors all year, only showing slight dulling.
Comparing Molts and Color Changes
Here is a table summarizing the key differences in molt timing and color changes for Anna’s hummingbird populations across their range:
Population | Number of Molts | Dullest Colors | Brightest Colors |
---|---|---|---|
Southern CA, AZ | 2 molts/year | July – August | Feb – May |
Pacific Northwest | 1 molt/year | Sept – Nov | April – July |
Some year-round residents | No molt | Slight dulling in winter | Bright year-round |
Why Do the Colors Change?
In summary, Anna’s hummingbirds display a fascinating annual cycle of iridescent color change as their breeding season comes and goes. While breeding-age males sport flashy fuchsia throat feathers to attract mates from November to June, these bright plumes are replaced by subdued grey-green feathers during the non-breeding season. This color shift likely conserves energy, provides camouflage, and acts as a social signal of breeding status. The timing and extent of color change varies across the bird’s range, but typically results in the dullest colors from July to November and the brightest colors from February to May. Whatever the driver, this incredible seasonal color change is a unique and beautiful phenomenon of nature. When you see a vibrant male Anna’s hummingbird gracing your garden in spring, appreciate that his dazzling colors will soon dull as breeding season ends. But keep watching and next winter his throat will flush with color once more as preparations for another season of courtship begin.
Conclusion
In this article, we explored the fascinating color changes that male Anna’s hummingbirds undergo over the course of a year. While their throat feathers erupt in brilliant iridescent fuchsia during the breeding season to attract mates, this flashy plumage is replaced by dull grey-green feathers during the non-breeding months. Molt timing and the extent of seasonal color change varies across the bird’s range, but typically results in the dullest colors from July to November and peak brilliance from February to May. This annual shift between vibrant and subdued colors likely serves to conserve energy, provide camouflage, and communicate breeding status. The color change is a unique adaptation that allows Anna’s hummingbirds to capture our attention with their dazzling hues when they need it most to carry on their species. By appreciating this and other wonders of nature, we gain insights into both the natural world and our own human lives.