Blue Ridge Naturalist: The Warbler Guide App

A Nashville Warbler searches for insects on late-blooming goldenrod in mid-October. Photo: Dick Rowe, VMI Biology Department.

A perpetual motion machine is one that can do unending work without an input of energy—an apparatus greatly desired by mankind. However, the laws of physics tell us that such a machine isn’t possible because energy is always expended and thus lost from the system. Without an additional input of energy, then, the machine will eventually run out of the energy it requires to keep moving.

In my mind, warblers seem to be biological perpetual motion machines because they almost always seem to be moving! It’s as if they possess an unlimited internal supply of energy. If you spot one in a shrub or tree, it’s likely to be constantly hopping around or flying from one branch to another, as if it hasn’t time to waste as it searches for its next insect meal.

Birders find these birds of particular interest because they are often brightly colored and thus lovely and enjoyable to see. Unfortunately, it can be very difficult to get a good look at a warbler because of its almost constant motion.

The best time to see them is early spring when deciduous trees and shrubs are either leafless or have leaves just emerging so they are still very small. Even so, some species are very similarly colored, making identification a challenge even when you do get a good long look.

If you’ve experienced the frustration of trying to tell warblers apart, especially in fall when they may not be in their much more colorful and distinctive breeding plumage, there’s a nice new tool you can use that combines a real world manner of usage with an electronic one.

Princeton Press has published “The Warbler Guide App”, a lightweight, water-resistant, folding card that shows North American warblers with their identifying features.  Brief written descriptions of field marks inform you what to look for and the warblers are shown from the side as well as from below (a belly view), which is especially useful in spring when they tend to be located high above you.

The card itself is useful for the few folks such as I who have not embraced the latest in technology, but it’s only a starting point for those who are never far from their electronic devices.

If you want more information and have a mobile device, you can make use of the small black-and-white square that accompanies each species account. When you scan the square (formally known as a “QR Code”), you are taken directly to the species’ page that is located at a website. There you can view a rotating 3D model of the bird to really get an idea of what it looks like.

Additionally, the bird’s primary songs (the ones most often heard in the field) can be played, courtesy of the Cornell Lab of Ornithology. And if you are into sonograms (graphs that show the distribution of energy at different frequencies for a particular bird’s song), they are provided at the web site as well.

The real-world beauty of the folding card is that it works no matter where you are birding, unlike the electronic features that are unavailable in locations too far from a cell tower to get web-site access. It fits easily into a glove compartment and is made of sturdy, plastic-coated paper to withstand the inevitable degradation associated with use.

You can find out more about this app at You can purchase the app from Apple’s App Store.

I think the folding card itself would be extremely helpful to beginning birders who are new to warbler identification and the difficulty of telling these birds apart. In contrast to a book where images are spread out over many pages, the card places all of the images right into your hands on just two sides of an easy-to-hold card.  Therefore you can quickly search over one side of the card and then the other for the bird you want to identify.

The only criticism that I have of this app is the arrangement of the warbler species on the card. For identification purposes, it’s always helpful to have similar-looking birds close together for side-by-side comparison. Instead, these warblers are in alphabetical order, as if you’ve already made your identification and know the name!

So where do you find warblers? If you’ve landscaped properly, you should be able to see them right at home, especially in spring and fall when they are migrating through the area. Because they are insect eaters, they need to leave the northern areas of our country in fall to head south because insects will disappear from view once very cold temperatures have arrived. But these birds return in spring to breed as insects once again become active.

If you want to assist warblers on their migration in fall, be sure to keep spent flower stalks standing. Often these withering plants will have aphids on them that can nourish warblers very well.

I often notice warblers and other bird species in my gardens going go up and down and all around old stalks searching for these tiny insects that are usually the last insects easily available to insectivorous birds as temperatures become ever colder.  Because warblers are especially easy to see at ground level on my dried, browned herbaceous plants, fall is my favorite time to look for them.

There’s far less frustration trying to get a nice look because they aren’t hidden by leaves way up high. I don’t have to crane my neck towards the sky, which is always more comfortable. And the birds tend to stay in view much longer, making it easier to spot their identifying features.

With this Princeton Press foldout guide at my fingertips, I’m more able to quickly match field marks on each bird to the photos in the guide with much less effort than when searching through a book. So even, or perhaps especially, if you’re not as “into” the digital age as most folks tend to be these days, you might like this old-fashioned basic method for quick assistance identifying warblers.


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