After breeding, if you’re a bird, comes molting. Time to discard those old, worn, raggedy flight feathers and start with some fresh ones for the long haul of the fall molt, or replace sparse downy feathers with good warm ones for the cold of winter. This means that around now—from mid-July to September—you may see a lot of birds who aren’t looking their best.
The sun dips low over the bay, its fading rays gilding the avocets as they swish their heads through the water. The egrets eye their own reflections as if in profound self-contemplation. A willet flashes past, its black-and-white wings an exclamation in the dusk.
Faced with such beauty, two words come irrepressibly to mind: niche partitioning.
Something is not quite right here. What is it?
One of the veterinarians at the animal rehabiliation hospital recently lamented to me that so many animals she sees are “killed with kindness.” The most common problem by far is that of feeding baby birds. Well-meaning rescuers find a baby bird in need; they search the internet and find statements like “Baby birds must be fed every hour or they will die.” Terrified that the bird will starve before they can get it to the animal hospital—maybe the hospital is closed for the night; maybe it’s a 40-minute drive away—they feed the bird. It makes intuitive sense that babies need to eat, after all. What is not intuitive to us is how easy it is to fatally injure a baby bird by feeding it incorrectly.
“Nowhere on the internet says ‘It’s okay to not feed baby birds for a while, they won’t starve,'” the vet said. “And then they come in fed on milk or something, because the internet said that was a good idea, and they die.”
So: It is okay to not feed baby birds for a while. They will not starve in the several hours it takes to get them to the animal hospital. They will not starve overnight if you find them at 6pm and the animal hospital doesn’t open until 9am the next morning. Baby birds expect to fast the night: their parents sleep, after all. The risk to the bird of starvation is much smaller than the risk of a human trying to feed it without the necessary expertise.
Hummingbirds wear a public image of fragile, ethereal beauty: tiny jewels whirring through the air, occasionally pausing to drink daintily from a flower. Their unusual appearance supports this: the iridescent feathers, the long dainty bill, the near-invisible feet all make them seem quite apart from the everyday world of animals who don’t shimmer in the sun and do have feet.
But hummingbirds, like all birds, evolved from dinosaurs. Hidden under that glimmering exterior is a tiny, fierce raptorial dinosaur.
The birds are having babies, those babies are learning to fly, and they are flying into our nets at the banding station. They’re not really babies by this point: most of them are independent of their parents. They may have been out of the nest for a month or more, and are technically “juveniles” or “immatures.”
At the banding station we collect data on each bird we catch, including that bird’s age. It’s important to record the age if we can, because the more accurate we are with the age the first time we catch a bird, the more accurate we can be later. If we caught a bird in 2014 and recorded that it was a juvenile, then when we catch it in 2016, we’ll know it’s exactly 2 years old. If we didn’t bother to age it back in 2014, then in 2016 we would only know that it was at least 2. That maybe seems like a small distinction, but the lifespans of wild birds are still an area in which we lack a lot of information, so knowing exact ages is valuable.
How do you tell if a bird is a juvenile or an adult? In some species, the juveniles are dramatically different colors than the adults. Juvenile juncos, brown and streaky, look distinct from adults even from a distance—until they molt, at least. But the differences can be a lot more subtle.
Here is a Common Yellowthroat from the banding station:
How old is it?