Keep nesting boxes clean, too

After addressing the need to keep bird feeders clean in my last column, we received a few questions about cleaning bird nesting boxes. A quick answer is that those boxes are typically only used by a single nesting pair of birds per year, so they don’t act as gathering areas with the potential for disease transmission between many birds like feeders do. This difference means that there is much less need to clean nest boxes, and it can generally be done only once per year.

That leads to the next question, as Bob Hunn wrote in and asked: “When is the best time to clean the nest box?” He’s been seeing baby birds and says, “I do not want to disrupt any current activity.” Ideally you want all nesting to be done which typically means waiting until the fall, but it is good to keep other critters in mind. Mice will frequently use nest boxes in the winter and even cache seeds and other food items to help survive. You may not be thrilled with the idea of encouraging mice near you, but it’s better to have them inside that bird house than in your walls.

As a quick semantic explanation, I try to use “nesting boxes” rather than “bird houses” because the former is a better descriptor of their actual purpose. Once the birds are done nesting, they will not use that box any longer – it isn’t a “house” that they live in. Keeping the purpose in mind helps answer questions like when to clean them, which I usually recommend as March. None of our cavity nesters have started nesting in March, and there isn’t much else getting us through that lengthy part of winter, so keep yourself busy by giving those nest boxes a quick clean.

Tossing out the old nests onto the ground is fine. You can’t keep them, or you’d be violating the Migratory Bird Treaty Act, and potentially bringing mites inside. That is one of the more important reasons for cleaning out the boxes – to help get rid of any parasites that may have moved in and are waiting for new inhabitants. Some birds can handle those parasites themselves. There are also some natural controls as well (like wasps) so it is good to keep in mind that you don’t need to clean nest boxes out. A study in Kentucky found that bluebirds actually preferred boxes with old nests in them, which they’ll just build on top of. Always remember that birds were nesting in cavities for millions of years before humans put nesting boxes up, and no one was going around cleaning those cavities for them.

Where are the birds?!

One very noticeable shift in the natural world right now is how quiet it has gotten in the morning. For months, while the days were getting longer and warmer, the dawn brought us a full chorus of singing birds. But as we head into August birds begin to shift their daily activities and spend less time making themselves known, at least through their loud songs. Even without hearing this drop in the dawn chorus, I know exactly when it is happening because of the number of phone calls or emails we receive at Maine Audubon from people asking “where are the birds?!”

Perhaps the simplest place to start is with how we detect birds. One thing that people notice is the lack of activity at their bird feeders; you may also have noticed a ton of insects, as well as fruit ripening and seeds forming. With natural food nearing its highest level of abundance, birds have less of a need to come to a bird feeder.

We also get a lot of calls and queries from people who are noticing the decrease in the aforementioned dawn chorus. Songs, unlike other noises or vocalizations that birds make, are defined by their purpose: to attract a mate or defend their territory. Since we are heading into the end of the nesting season, most chicks are fledged and parents are focused on molting out of their breeding plumage before they make their migration south, meaning there is no need to be singing anymore. There are always some exceptions, like Carolina wrens that sing all year, or maybe an overly ambitious young male still trying to woo a lady, but for most birds, they’re done with their song until next spring.

Interestingly, there is something paradoxical about a perceived lack of birds in the late summer: when birds are most abundant, they are least detectable. This might be an oversimplification, but think about, for example, a pair of chickadees. They will typically have a single brood with around six eggs. (Mortality is unfortunately high – one reason it’s good to have half a dozen chicks in a single clutch – but within these few weeks since chicks have fledged we can hope for about 80% survival rate given how abundant food is and since they’re still under the care of their parents.) This is a long-winded way to say that, using the chickadee example, we’ve gone from two pretty visible and audible birds in the spring to about seven in that family now, but they’re just harder to find.

It may feel a bit funny to realize there are more birds than ever during the month when people are concerned about how few birds they are seeing and hearing, but if we understand what is going on in the lives of our feathered friends, it helps explain away the mystery.

Do you have a nature question for Doug? Email questions to ask@maineaudubon.org and visit maineaudubon.org to learn more about bird walks, community science projects, and other programs about wildlife and habitat.