I seem to be up to my eyeballs in wildlife mysteries these days. Each animal, like each human, is unique to some extent, and there are always some that can be way outside the norm. And I really don’t know much about some species. What I do know is not to assume much of anything and to just keep observing, looking and doing research.
The most recent mystery involves a pair of Carolina chickadees that may or may not be nesting in the bluebird box in my backyard. My landlord put the box back together after a bear smashed it last year and attached it to one of my clothesline poles by way of two-by-fours, putting the box at least 10 feet in the air.
A month or so ago, a bluebird pair checked out the box but apparently found it wonting; then a pair of Carolina chickadees showed up. They were in and out of the house quite a bit for a few days, so I thought they had decided to nest in it. However, during that time, the first batch of phoebes in the nest on my house fledged, and phoebes were suddenly careening all over the place in the edge of the forest around the box.
The chickadees looked disconcerted. They’d already had the adult phoebes using the box to scan the area for prey, as they had been doing all spring. Suddenly, the chickadees disappeared.
Then they returned about a week ago, or at least a pair was at the box and seemed to have taken it over. Often one of them was sitting perched at the entrance, peering out. It didn’t seem to notice when I came near the box. I spent a lot of time over the next couple of days watching the chickadees, trying to figure out what they were up to, and did a lot of research.
Chickadees have only one clutch of eggs per year, with peak breeding time in April, but if they lose a brood, they may have a second clutch. I monitored the pair for about an hour one day to see if they were indeed nesting and, if so, what stage they were in — building the nest, incubating the eggs or feeding hatchlings? Unlike phoebe and Carolina Wren parents, who use a U-shaped flight pattern in their trips to and from the nest to avoid attracting the attention of predators, the chickadees were making straight shots to and from the forest on the other side of the house.
I looked to see if the chickadees were carrying nesting material to the box, such as grass or hair, but instead I saw only small-to-medium, limp, mostly green things that looked like caterpillars or other bug larva in their mouths. Then again, I was mostly seeing the butt end of the birds when they arrived at the box, so I can’t be sure what they were carrying. If it was food for nestlings, that means I missed nest building and almost two weeks of egg brooding, which doesn’t seem possible. Eggs hatch in 14 to 15 days, and the young fledge in 17 to 18 days, remaining with the parents for another two weeks.
During the brooding phase, the nesting behavior of black-capped chickadees is similar to that of bluebirds — the female stays in the box most of the time, incubating the eggs, while the male brings her food. The female usually comes out of the box to accept the food when the male shows up with it. In this case, both birds seemed to be coming and going, each time going into the box briefly, then leaving again.
Chickadees, unlike many bird species, are not dimorphic in terms of gender — males and females look the same. And appearance among individuals also doesn’t vary much, so it’s hard to sort out if just one of the pair was coming and going or both were. I never saw both at the box at the same time.
So, are they feeding nestlings? I saw what appeared to be a fecal sack in the mouth of one of the chickadees as it left the nest on two different occasions. For hygiene reasons, the young of some nesting bird species have evolved to excrete their feces into a membrane-encased sack, which the parent then can easily remove from the nest, so that should indicate there are nestlings in the box.
The next day, there was no sign of the pair. I wasn’t monitoring the box closely, but any time I went out back or looked through my kitchen window, I didn’t see any chickadees. What I did see was one of the adult phoebes sitting on the box — frequently. Chickadees will fiercely defend their nest, so I doubted the phoebe had scared them off. Were the chickadees nesting at all? If they were indeed feeding young, wouldn’t they have to show up more often?
Later I saw what looked like a female robin sitting on the cat guard in front of the entrance to the box. That was new.
The next day, chickadees were all over the place in and around the box, going in and out of the tangled forest edge and sitting on the clothesline, another favorite perch of the phoebes. And most of the chickadees seemed pretty young — or on drugs. One was going from clothespin to clothespin, pecking at each one. Why? In the process, it suddenly bumped into the phoebe, which had been ignoring it but apparently had had enough of its antics and body-slammed the smaller bird to the ground. There seemed to be a lot of small disputes among the chickadees themselves.
Had the chickadees indeed been nesting and their babies suddenly fledged? Had another family moved into the neighborhood with their own fledglings? Was it just a hot housing market and these guys were scouting potential nesting site for next year?
The next day, no sign of chickadees. This mystery may never be solved, but I think I’ll consult with some bird experts.