Nature News: Warblers are small, but colorful insect eaters

published May 17, 2021 in the York Weekly, Porstmouth Herald, Foster’s Daily and other Seacoast Media Group local papers

I have a friend who has had bird feeders for years and is fairly knowledgeable about most of the birds that visit her feeders.  However, the other day I was telling her about the warblers that were coming through my yard and she asked me what exactly a warbler is. She had heard of warblers but had never knowingly seen one at the feeder.  But, warblers are small and quick and if you didn’t know what to look for your brain might lump them in with other small birds that are difficult to identify.  Another reason my friend might have missed encountering warblers is because most of the warblers in the United States and Canada (over 50 species breed up here) don’t visit bird feeders.

Warblers are neotropical migrants lured here by our bugs.

Warblers are among the smallest birds in our woods and can be among the most colorful.  They are neotropical migrants, meaning they overwinter in the new-world tropics (hence neo-tropics) migrating to North America in the spring to breed.  Starting perhaps mid-April they have been moving into and through New England on their way north.  Why come up here?  Why leave balmy Central and South America?  Insects!  It’s black fly season! I also heard my first mosquitoes today.  The lure of a high-protein bug-diet, necessary for raising young, is what brings these insect-eaters north. 

This palm warbler is one of the many warblers that migrate through in the spring. photo

What is a warbler? According to Encyclopedia Britannica, warblers are “any of various species of small songbirds belonging predominantly to the Sylviidae, Parulidae, and Peucedramidae families of the order Passeriformes. Warblers are small, active insect eaters found in gardens, woodlands, and marshes.” (According to The Cornell Lab’s Bird Academy warbler course I’m taking there are actually 8 different families of birds with the name warbler!).   When we talk about warblers here in the U.S we are referring to the new world warblers (also known as wood warblers).  The wood warblers are more closely related to orioles but got the name warbler from their physical and behavioral resemblance to the old world warblers. 

Some tips on how to identify the confusing array of warblers.

While warblers have a wide variety of colors and patterns you can learn to recognize them by their overall shape-small with narrow insect-eating bills, short to medium tails, and, as mentioned before, they are active foragers, always moving about looking for their next meal.  If you want to take the plunge, the next step is to try to identify some.  This group is notoriously difficult to identify.  Because they are so active it can be hard to get a good look so you have to train yourself to look for a variety of features–color, wing bars, eye rings vs eye lines, breast markings or patterns on the tail.  Paying attention to where they are foraging is also helpful as many have divided up available habitat into different foraging areas to avoid direct competition for food (this is called resource partitioning).  A famous example of resource partitioning is from a 1958 study by Robert MacArthur in which he described how 5 different northeastern warbler species had divided up their foraging area-blackburnian and Cape May warblers preferring the tops of trees, while black-throated green warblers stuck to the inner branches around the middle. 

Watch for new warblers to show up at feeders throughout the spring

Spring is the best time to be looking for warblers.  Just like the spring wildflowers that are welcoming in the season, the arrival of these tiny migrants to our woods heralds the warmer days to come.  And, if the bears haven’t yet forced you to take down your bird feeders some might come by to check out the suet.  We’ve had yellow-rumped warblers, blue-winged warblers and palm warblers drop by this spring and have been hearing many more in the trees. So, while I am lamenting the arrival of the black flies and mosquitoes  I am also happy about it-more bugs means more warblers.