Uncle Doug, can we touch birds’ nests? I found one in our Christmas tree!

– Johnny Enright, 4, Bedford, Massachusetts

One of my favorite things about this time of the year is seeing all the birds’ nests, which had been hidden among the leaves, now exposed. You might see some right on the edge of your yard, or in a bush you walked past 100 times this summer. And it isn’t uncommon to encounter them if you’ve had trees or branches fall down in a nor’easter, or even as my nephew Johnny did, discovered in the branches of a Christmas tree that his family had brought home. As tempting as it may be to take one of these engineering marvels, it is illegal to possess one.

Empty bird nests often come into view after trees and bushes shed their leaves. But the Migratory Bird Treaty Act makes it illegal to possess one. Photo courtesy of Maine Audubon

Despite these nests now being “abandoned”— in almost all cases, typical cup nests are only used once — they are still protected by the Migratory Bird Treaty Act. I wrote about this last summer when a Portland resident had nesting birds that were “making a mess all over (a tenant’s) brand new truck” and though that nest was still being used, the law also applies to vacant nests. Under the treaty act, it is illegal to collect, possess, or by any means transfer possession of bird nests.

This might seem strict, but the treaty act is perhaps the most important piece of legislation that has protected and brought about a rebound in many birds that were nearly wiped out. A much younger version of myself, who was not aware of the treaty act, would probably still be paying off the fines if a warden ever saw the walls of my childhood bedroom. Though that “collection” may have helped shape my appreciation for nature, there is plenty to be learned by observing nests in nature — from the placement in a tree to the materials used in construction. Plus, Johnny, that nest could have mites or other critters living in it that I’m sure your mother wouldn’t want brought in the house!

A Baltimore oriole. Cornell Lab of Ornithology photo via Tribune News Service

BIRD’S DILEMMA: MIGRATE OR STAY PUT?

Our female oriole is still here. She uses the tray feeder for sunflower seed but spends most of her time on the suet. She has been here since Oct 20. Will she be able to survive the winter if she stays? Thanks!

– Sue Shaw, Penobscot

Perhaps the most common question about a lingering or especially vagrant bird, maybe after “Where is it?!” is about its chances of survival. This has been a good year for birders, with lots of rare sightings, and since this question comes up so often, I want to talk about some of the theories around these anomalies and what the real threats to their survival are.

Using Sue’s Baltimore oriole as an example, one reason that a bird may try to overwinter farther north is because of the risks of migration. It takes a lot of energy for the 2,000-plus miles that an oriole will travel each spring and fall, so there is a lot to be gained by not putting all that effort into a long flight. One great benefit would be the time/effort saved come next spring, when that bird is already closer to its breeding grounds than one traveling from Panama. Earlier arrival could mean better breeding habitat, access to more resources, etc.

There are also a lot of threats to birds as they migrate. We know that 624 million birds die each year in the U.S. and Canada from collisions with windows, with most of these occurring during migration. While there may be risky windows around Sue’s neighborhood, the hidden threat of large glass buildings mostly in cities between here and Central America is tremendous. Perhaps the only larger threat comes from outdoor cats, accounting for 2.6 billion bird deaths each year. Though there are too many outdoor cats in Maine killing birds, there are even more feral, and lethal, populations to be encountered where it is warmer. Add to windows and cats the many natural causes, like starvation and predation, that cause high mortality, especially in the first year of life for many birds.

Getting back to Sue’s oriole: For this one and many of these other lingering birds, food availability is probably going to be the greatest limiting factor to survival. In most cases they are equipped to survive the cold, but generally the food they need is not present in our cold winters. That meal at your feeder may be the fuel that allows them to migrate a little farther south, or it may provide just enough calories to get them through another chilly night. One thing we should keep in mind is that distributions in many birds are changing rapidly with our changing environment. Birds will do their best to adapt, testing limits on either end, and we should do our best to help, especially by limiting the damage we already do. Keep cats inside, put stickers on your windows, and keep those feeders full!

Do you have a nature question for Doug? Email questions to ask@maineaudubon.org and visit maineaudubon.org to learn more about virtual and backyard birding, online classes and other programs about wildlife and habitat.