My almost nine-year-old was feeding ducks recently (mid-August) when she asked me, "Where are all the boy ducks?" I don't know much about birds, but I thought I at least knew that a male Mallard had a green head. Sure enough, no green heads. This seemed to be true in another place we looked. Oh no, was this another symptom of climate change? Pharmaceuticals in the water? Too much fatty food?
Birds of a feather
Turns out that this is situation normal for male Mallards (Anas platyrhychos) in the summer. After the breeding season in the spring; and after all that migrating, courting and nesting, both males and females go for a new wardrobe. Males, however, make a more significant change, because they lose the bright green head and bright wing colours and take up an eclipse plumage of basic brown, so that they resemble females. They are no longer trying to impress the opposite sex and avoiding predators becomes a high priority. Longer daylight hours, in the presence of male hormones, trigger the change.
Dese guys disguise
As male Mallards go through this moult, they lose their primary feathers, so they can't fly and usually go into hiding. This is just as well because they look scruffy until the feathers smooth out. In eclipse plumage, the bills of males are light olive green or yellow, while the females' are orange marked with black.
Fly the coop
Where high-protein food is scarce, the males and unsuccessful nesting hens leave the breeding grounds to reduce competition for food. This is because feathers make up almost one third of the protein in a duck's body and they require lots of protein-rich foods to maintain their feathers. In the city where people are feeding them all the time, they tend to hang around.
Birds and the bees
When the fall comes and the mating season begins, the males need to dress to impress. They moult and grow their fancy feathers again. These contain thin layers of melanosomes that creates the iridescent colours. Researchers found that brighter bills were also more attractive to females. And the females are not just being superficial. Males with brighter bills turn out to have more robust sperm and semen with antibacterial properties.
Brown out
When my daughter was out feeding the ducks, I didn't take pictures and didn't know to look at the beaks. So our all-brown flock may have either been missing males or could have included males in eclipse plumage.
Have you spotted any brown male Mallards?