By Jeanne Church
During the months of May and June this year, a few local birding enthusiasts posted pictures of black-billed cuckoos that they had seen at the Wolf Lake State Fish Hatchery in Mattawan. Up until a few years ago, I didn’t even know we had cuckoos in Michigan! My first sighting took place in May of 2018 while I was walking through the Asylum Lake Preserve in Kalamazoo. There was an unfamiliar bird perched high in a nearby tree and I took a picture.
After I got home and was able to use an app to identify it, I discovered that my mystery bird was a black-billed cuckoo! I had seen and heard cuckoos while hiking in Scotland, but never in Michigan. This one looked different than the Scottish cuckoos and, I later learned, the two birds have totally different songs. The cuckoos in Scotland sound exactly like a cuckoo clock! Michigan cuckoos do not.
A few weeks after my cuckoo surprise at the Asylum Preserve, I was walking through the Bernard Baker preserve in Bellevue, and found another mystery bird. That bird turned out to be a yellow-billed cuckoo! Apparently, we have two different cuckoos in Michigan!
The black-billed cuckoo and the yellow-billed cuckoo are very similar. Both are slender, dove-sized birds with relatively long, slightly curved bills and very long tails. The black-billed cuckoo, however, has a slightly smaller bill and a somewhat shorter tail. Both birds have white spots on the underside of their tails, but the spots on the yellow-billed cuckoo are much larger. The most obvious difference between the two birds is the color of their bills: one black, one yellow.
After my first sightings in 2018, I have never seen another cuckoo. I was quite surprised, then, and very interested in knowing why several birders in the area had recently reported multiple sightings. The answer has everything to do with diet! Cuckoos LOVE spongy moth caterpillars (formally known as gypsy moth caterpillars) and they follow the spongy moth caterpillar outbreaks. Cuckoos will even delay having babies to coincide with when the caterpillars are most succulent!
Last year, spongy moth caterpillars completely defoliated mature trees here in southwest Michigan. So, the fact that more and more people were seeing or hearing cuckoos in our area was not a particularly good sign. It meant we were having another heavy infestation of spongy moth caterpillars! Hopefully, these cuckoos will put a significant dent in the spongy moth population so that next year, they can follow the invasion somewhere else!
Not many birds like to eat these hairy caterpillars, but cuckoos love them, and they have a natural adaptation to digest them! Cuckoos can eat more than 100 hairy caterpillars in less than 10 minutes but they don’t actually have to digest the hairs. Instead, the hairs form a dense felted mass in the cuckoo’s stomach which the bird gets rid of by shedding its entire stomach lining, hairs and all! It then regurgitates this mess as a packet—much like a cat coughing up a hairball. There’s a new stomach lining all ready to go and the cuckoo can keep on gulping down caterpillars to its heart’s content.
It’s highly unlikely that you will ever see either of these cuckoos, but you might very well hear one. They are extremely secretive and prefer hiding in dense vegetation and sitting motionless for long periods of time. Cuckoos are more often heard than seen, so it’s particularly helpful to know what they sound like.
The song of the black-billed cuckoo has been described as series of three to five toots all on the same pitch that can be repeated many, many times over the course of several minutes. The yellow-billed cuckoo has a somewhat different sound. I find it much more helpful to go online and listen to recordings of their various songs and calls than to decipher a sound from a written description. One of my favorite sites for bird calls is Cornell Lab’s All About Birds, https://www.allaboutbirds.org. There’s also a free app called Merlin where you can make a sound recording of the birds you hear and Merlin will identify them immediately. I have the app on my phone and use it frequently when I’m out walking the trails or sitting in my backyard with a cup of tea.
Enjoy your birding adventures wherever they may lead you!
By Jeanne Church