We use decals (that we bought at Maine Audubon) on our windows to prevent bird strikes, but sometimes birds still hit the windows. What’s going on?

– Carol Beyna, Cumberland

I wrote about cats a few weeks ago, and how important it is that they are kept indoors to save birds. Cats are the No. 1 source of human-caused mortality in birds at an estimated four billion birds per year in the United States alone.

The No. 2 cause is birds striking windows, with an estimated 365 to 988 million birds dying annually in the United States. A 2014 study by Scott Loss and others in The Condor (a scientific journal published by the American Ornithological Society) that produced this estimate showed 44% of collisions happened at residences, which I’ll focus on to answer Carol’s question.

One of the best ways to keep birds from hitting windows is to put something, like a sticker or decal, on the outside to break up the reflective pattern on it. Glass is a great reflector, especially when you are looking at it from the brighter side. For our diurnal birds, that tends to be most of their waking hours. That reflection, depending on where you live and the orientation of the window. It may include the sky, trees, shrubs, or any number of places that might attract a bird. I need to emphasize and reiterate that any solution needs to be on the outside of the window. Putting something up on the inside will not stop this reflection and in some cases could even make it worse.

I’ve also written about a similar issue where territorial birds will attack their reflections in a window, perceiving it as a competitor for their turf. There are some easy solutions, and you can start by installing a screen or putting up some creative artwork in front of the window. At our Nature Store, at our Gilsland Farm location in Falmouth, we sell decals that are semi-transparent but reflect light in the ultraviolet spectrum, which birds can see but humans cannot. Many of these decals come in pleasing shapes, like flowers, birds, or butterflies, but they have two downsides that many people may not realize. One of these could be what’s happening at Carol’s house: 1) The decals need to cover a large portion of the window, so in most cases one decal won’t cut it. The recommended spacing for window treatments is no more than four inches apart, otherwise birds may still try flying into those “open” spaces; and 2) They need to be replaced more often than most people realize. Make sure you check to see how long they last. Some of the more popular brands recommend replacing every three to four months.

My favorite products currently available are by CollidEscape (collidescape.org), especially their BirdTape or Dot Patterns. These are easy to apply, visually appealing, have a 10-year lifespan rating. When applied in a 2-inch-by-4-inch pattern, it can reduce strikes by more than 80%. If we could all treat our “problem windows” at home, we could be saving over 200 million birds per year!

For a different discussion, I’d love to talk about improvements coming along for the other 56% of bird collisions, which come from striking low-rise buildings. Conversations have been started in Portland, and other cities in Maine, to require that buildings be “bird safe.” In December 2019, New York City’s City Council passed a bill that requires all new construction to use bird-friendly glass, a huge win for birds and a wonderful precedent for the rest of the country to follow.

That swarm of swallows is migration in action

On Aug. 28, in the afternoon, we (saw) upwards of two dozen swallows circling above the house and yard for a couple of hours almost like a swarm of bees. We have nesters in a bird house every year, but that would only account for a half dozen or so. All I could think of was perhaps a flock getting together to begin their migration south for the winter. It seems like August is early to migrate, but where they’re small birds with a very long way to go, perhaps it’s the answer. Is that plausible?

– Geoff Cartmell, Arrowsic

What a treat to see migration in action! Visible migration, or “vismig” as the hipsters like to say, is often thrilling, if not awe inspiring, when you get to see birds, typically in large numbers, as they are moving along their migrations, sometimes with thousands of miles behind and ahead of them.

Tree swallows are especially well known for some of their large congregations during migration, often called “staging events,” and August is not too early. From mid-August to mid-September, there are often reports of several thousand tree swallows flocking up, especially along the coast from Biddeford Pool down to Ogunquit. The largest group I’ve seen was an estimated 12,300 swallows, mostly in a swarm over Richmond Island, on Sept. 7, 2018, while birding at Kettle Cove in Cape Elizabeth. I echo the comment that it was like a “swarm of bees,” an especially challenging group to try to count. Using my spotting scope I was able to estimate groups, passing at a rate of about 100 every 4 seconds. When I first noticed this group, they appeared to be diving frequently over the tops of the spruces on Richmond Island, apparently feeding on something.

A bird’s primary focus is feeding, both before and during migration. Think of it as going on a road trip and stopping at a gas station (or EV charging station) along the way. Those swallows seen in Arrowsic may have been focused on a swarm of flying ants, a good source of protein before they move toward the coast and mass up with others. Keep this in mind, particularly when walking along the beach – especially if you have a dog with you – where you may encounter shorebirds (sandpipers, plovers, etc.) that are stopping over on their several-thousand-mile migration. Every time you get too close and cause them to fly, they are burning valuable energy, which for these birds is measured in grams of fat rather than gallons of fuel (or kWs of electricity). Those grams can be the difference between life or death for many migrants, so give them their space and enjoy the spectacle that is vismig!

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