There’s method in red-winged blackbirds’ mating behavior
Last time, I introduced you to Carl, a male red-winged blackbird who lives a life of romance and intrigue — never looking back, never second-guessing himself. You may admire Carl for his method of dealing with the ladies, but you also may see him as a scoundrel.
This week we’ll look at the world through the eyes of a female red-winged blackbird. We’ll call her . . . Brooke. What kind of challenges does she face? What decisions does she have to make? After this, you may decide that Carl isn’t such a cad after all.
When Brooke arrives on the breeding grounds, in early April, the males will have already set up territories. The most robust males occupy the best territories, while the less attractive areas may only have one or two younger males in residence. Upon her arrival, Brooke begins a tour of the local males.
Since Carl is an older male, he will have an impressive territory. Brooke notices him immediately and, for the sake of our story, let’s say that Brooke and Carl get cozy. It’s at this point that the common motive of maximizing reproduction will drive Carl and Brooke to very different behaviors.
The male urge
Male red-wings want to father as many babies as possible. To succeed, they need to mate with as many females as possible, so they spend most of their time drawing attention to themselves. They fight with other males, attract females, and fight off predators. Males never incubate eggs, or build nests, so they can afford to look flashy.
Females also want to produce as many offspring as possible, which is limited by the number of eggs they can lay. So the feminine goal is to find the highest-quality male to father babies. Females build nests, incubate eggs and feed babies. So the last thing they need is to attract attention. Thus, their feathers provide camouflage.
Once Brooke becomes Carl’s primary female, he will attempt to attract another. Early in the year, to ensure the survival of her first brood when resources are limited, Brooke will attack any female that enters Carl’s primary territory. As soon as she lays a full clutch of eggs, however, the game is on.
Carl will search out another female and if Brooke puts up any fuss he may actually turn on her. But fear not, Brooke will prevail. Her chicks will hatch first and Carl will actually help to feed them. He won’t assist his secondary female in this manner. This is where potential “second wives” have an important decision to make: is it better to be the secondary female to an impressive male, or the primary female to a lesser male?
Once Brooke’s first batch of chicks fledges, her self-centered behavior kicks in. The only way to have more offspring is to abandon her family and start a new nest. This is where being Carl’s main squeeze pays off again.
Since he will feed these chicks, Brooke can hand them over and start anew. Carl’s secondary females do not have this advantage and, as a result, they will not have as many offspring. Brooke won’t even bother fighting with other females because Carl’s territory provides abundant resources and the other females will be busy so late in the season.
At the end of the year, Brooke may have up to three sets of chicks (many more than any secondary females) and Carl will have fathered them all. This winning combination of genes will proliferate and the chicks will exhibit the strong qualities of their parents.
Bill Danielson is a professional nature photographer and author living in Altamont. Contact him at www.speakingofnature.com.