It’s that time of year when the songbirds sing, and this House Finch male is part of the morning concert. He perched higher up in the same tree where I saw the Lesser Goldfinches (see “Tiny Finch,” March 6 2022). As House Finch males go, this one is only about average in color intensity, and may have to sing quite a while and expand his repertory before he finds a female who likes him. They tend to go for the reddest.
House finches get their red from the carotenoids in certain foods. Both sexes may eat the same food but only the males develop the intense color. I haven’t found a clear explanation of the gender difference, and I’m not sure that I would understand it if I saw it, since it’s very likely a matter of complicated biochemistry that does not have to do with testosterone. (These birds have been studied extensively and testosterone levels in color-intense males were not higher than in drab males.) In any event, the gendered color development in finches is unlike flamingoes, for example, which also get their color from food, but the sexes look alike.
Finches learn songs from resident older males during their first two months after hatching. They may also copy songs of nearby species such as canaries and sparrows. As they mature, their songs become more individual. California finches don’t have stable regional dialects, and birds develop personal song styles. Females also sing occasionally, particularly when ready to mate. It’s a females’ market, as there are typically more males than females. Females generally pair up with only one male. Polyandry happens rarely, but the odd casual hookup with a different male is not unknown, and in different flocks, somewhere between five and 50 percent of nests contained at least one egg from a different father. Once paired, the couple typically stays together for the rest of the season and often for a year or two beyond that; the record among researched birds is seven years.
The female does all the nest building. Researchers saw males bringing nesting material to a nest construction site, but the female never used it. Nest building is a learned skill; young females have to learn it from older females. During the mass die-off of House Finches in the early oughts due to mycoplasmosis, young females in one location could not build nests and humans introduced artificial nests that the birds quickly adopted and padded out. Nest sites are generally up in trees or shrubs or on walls, not on the ground.