“It is better to be seen and not heard” is advice often given to children. Among young birds, the advice might be “it is better to be neither seen nor heard.”
Consider the red-tailed hawk. Young birds have a dull brown tail with some black barring. They don’t don the bright orange tail of an adult until their second summer marking them as an adult ready to hold territory and breed.
Their first year of life can be miserable. They get chased from territory to territory and are often left with a rather poor piece of land to try to eke out a living until they enter the adult world. Having rather cryptic plumage often allows them to pass unnoticed by cranky adults for a short time in more productive habitats. They even tend to perch low when they do trespass to help escape detection before discovery and a rude send-off.
Young bald eagles wear less than bright, regal plumage until reaching adulthood at four years of age.
Smaller birds such as male tanagers also wear cryptic plumage until they are old enough to proclaim a territory and rear young. A first-year male western tanager is hardly going to set any fashion trends. Drab is the word.
This brings us to the rather confusing case of downy woodpeckers and close relatives. As adults, they wear a tidy red patch on the back of their head. Females have no red feathers at all. This makes it simple come courtship time. To a female: “I see you have no bright patch of red on the back of your head. You are no threat. Care to join me in my woodlot?”
It also can help when advertising and defending a territory. To another male: “I am owner of this woodlot. See my bright red patch. I will fight to defend this territory if you insist.”
All this makes sense until it comes time to rear young. A healthy brood of hungry young wears a lot of red on the head. Young males wear a sizable patch of red feathers on their forehead and crown. Even some young females wear a bit of red on their forehead. OK, the red isn’t in the same place on the head as the red patch of an adult male, but it is red and it is on the head. I would think this banner would be enough to confuse the adult male and trigger aggressive behavior. What happened to the edict that it is better to be neither seen nor heard?
Young birds lose the “inappropriate” red by the end of summer as they molt into adult plumage. The loss of red is in plenty of time before the next breeding season, when adults become strongly territorial and look for mates, but why the red in the first place? As much time as I have spent mulling over this question, I have come to no conclusion that makes sense to me. I doubt that it is a developmental accident that serves no real purpose. Maybe it prompts the male to encourage dispersal once the young fledge. If this is the case I would expect to see this pattern repeated in other birds. I don’t see it. For now, I just have to add this to my growing list of life’s mysteries.
— Stewart Janes is a biology professor at Southern Oregon University. He can be reached at firstname.lastname@example.org.