do any birds eat gypsy moth caterpillars

Now before you think I’m well typecast because I once played the catatonic character in “One Flew Over the Cuckoo’s Nest,” I must assure you that cuckoos are for real.

In fact there are five cuckoo species that have been sighted in North America with two species quite common in Michigan. They may take some effort to locate since they aren’t typically found in your back yard, unless you live on the border of a large, wild woodlot. Cuckoos sound and look nothing like their namesake clock that was popular when some of us were children but they are a highly important creature at this time in natural history. Let’s take a look at the yellow-billed cuckoo species and learn where and how they can be found locally.

The yellow-billed cuckoo is a medium-sized bird that is roughly the size and shape of a brown thrasher. They have gray-brown upperparts with cinnamon-colored primary wing feathers (the trailing edge of the wing), white undersides, yellow eye ring, and the bill is, you guessed it, black with a yellow lower mandible.

The long tail has white spots that show as white on gray-brown stripes when perching. The less common black-billed cuckoo differs with a solid black bill, red eye ring, solid brown wings, and smaller white tail spots. They average 12 inches in length with a 16 inch wingspan and weigh in at just under 4 ounces. The song is a harsh, rattling “ka-ka-ka-ka-kow-kowp” and they also have a “coo” call that is repeated several times, not at all like the couplet rhythm of the clocks .

This bird has tremendous range and is found throughout North America, and in many Central American and Caribbean locations. There are also vagrant populations in parts of Europe, Northern Africa, and the UK. The global population is estimated at 9.2 million individual birds.

They are migratory birds that are found in most of the United States only during the summer breeding season (except for extreme southwestern Arizona). They winter from Mexico to Central America, and the Caribbean. The preferred habitat is moist woods and thickets, overgrown pastures, and orchards and they have an affinity for willows.

The nest is a flimsy saucer of twigs built in bushes or small saplings. The monogamous parents lay one to five light blue green to yellow green eggs that are incubated by both sexes. Cuckoos occasionally lay their eggs in another cuckoo’s nest and rarely in the nest of other bird species. They are not considered to be serious brood parasites.

Food choices are the feature that makes yellow-billed cuckoos very beneficial to us. They eat mainly insects, foraging in dense shrubs and trees and also catch their prey in flight. They have a strong preference for tent caterpillars, cicadas, and gypsy moth caterpillars and they sometimes congregate near outbreaks of these exotic and devastating pests. They will also eat berries and can be found enjoying Mulberries from mid-to-late summer.

Look for yellow-billed cuckoos in the Port Huron State Game area or anywhere locally where woods and water meet in a natural state. They are common along much of the Black River, Mill Creek, and other local wetland woods.

A unique and interesting fact: on day six or seven after hatching, the feathers emerge from their sheaths and the nestlings then become fully feathered in two hours. I close by stating…a group of cuckoos are collectively known as an “asylum” of cuckoos!

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Given that caterpillars are active during bird nesting seasons and that fledglings are often fed caterpillars due to their high protein content, it stands to reason that the caterpillar life stage of the gypsy moth is the most significant to birds (Smith and Lautenschlager 1981). According to Gale, DeCecco, McClain, Marshall, and Cooper (2001), there are a variety of immediate effects of an influx of gypsy moth caterpillars on bird abundance. For instance, local abundance of the well-known caterpillar specialists Black- and Yellow-billed Cuckoos rose two years prior to the gypsy moth outbreak reaching epidemic levels, and they vanished as soon as the outbreak subsided. Prior to an outbreak, the population of Indigo Buntings increased similarly; however, it took approximately five years for the population to return to normal.

The cuckoo is a notable woodland bird that feeds on the caterpillars of gypsy moths. Cockoos with yellow and black bills are experts at eating caterpillars; they consume both hairy and spiny ones. They are able to consume these caterpillars because they have developed the amazing capacity to regenerate the linings of their stomachs. The cuckoo regurgitates the used stomach lining in the form of pellets, eliminating all the hairs and spines from the caterpillars it has eaten once its lining is fully clogged with them (Forbush 1907, cited in Bent 1940). When gypsy moth infestations occur, cuckoo species, grackles, and Red-winged Blackbirds are drawn to the area and will expand their avian population once the caterpillars reach epidemic proportions (Leonard 1981). These birds arrive and start eating a lot of the caterpillars. Crows, Chipping Sparrows, starlings, and cowbirds are among the other opportunistic species that have been linked to gypsy moth caterpillar infestations (Smith and Lautenschlager 1981). However, Smith (1985) observed that the Chipping Sparrows he caught did not contain any gypsy moth caterpillars within their stomachs. Additionally, there is a second group of birds that regularly consume caterpillars from the gypsy moth, which helps to keep the pest population at a low level until an outbreak happens. These birds don’t just show up when outbreak levels are high. The Black-capped Chickadee, Blue Jay, Eastern Towhee, Baltimore Oriole, and Gray Catbird are among the species in this group (Smith and Lautenschlager 1981). These are all fairly common species that feed in a range of habitats and frequently raise two or more broods in a season.

The light brown egg masses that the female psylla moths lay, mostly on tree trunks and branches but also occasionally on outdoor furniture and other structures, are where psylla moths begin their life cycle. The egg masses are made up of both eggs and hairs from the female moth’s body. Early to mid-May sees the caterpillars emerge from the eggs, and during their earliest instars, they can be seen hiding on the undersides of leaves that are largely still intact. The caterpillars’ hairs are thinner and smaller at this stage than the thicker bristles that appear later in the instars, when the caterpillars are bigger and getting closer to pupation. In late June or early July, the caterpillars pupate and produce dark brownish-red pupal cases, which are frequently found in clusters on tree trunks, fences, or the sides of buildings. After roughly two weeks, the adult moths emerge from the pupal cases. Male moths are grey in color, and during major outbreak years, you can see them flying or drawn to lights at night. Despite having wings, the white females are larger than the males and are unable to fly. Rather, they typically hover around their pupae’s release site until a male shows up to begin a mating dance.

The most noticeable immediate result of a large-scale gypsy moth infestation is the loss of leaves on trees and shrubs. We must first comprehend what defoliation means for plants before we can examine the potential effects on birds. More than 500 different kinds of trees, shrubs, and vines—including broadleaf and coniferous species—will have their leaves eaten by gypsy moth caterpillars. Oak, birch, poplar, willow, alder, basswood, and apple are their favorite targets. They have also been seen consuming hornbeam, elm, cherry, hickory, maple, sassafras, and numerous other common hardwood forest plants in Massachusetts. Coniferous species like pine, spruce, and hemlock have been observed to be consumed by older caterpillars (later instars), most likely because all of their preferred food sources had already been consumed (McManus et al. 1979). Because of this, there aren’t many woody plants in Massachusetts forests during outbreak years whose leaves don’t turn into food for gypsy moth caterpillars.

It has also been observed that certain bird species consume adult gypsy moths. During outbreak years, for instance, blue jays have been seen to consume adult male moths with great vigor. Particularly, shortly after sunrise, blue jays on Cape Cod were observed gathering atop tree trunks and lower branches, specifically aiming for the moths’ resting place. The Blue Jays were seen feeding in the shrubs as the moths moved from the tree trunks to hide in the nearby shrub foliage throughout the day. They were even seen removing the male moths from the undersides of the leaves and even flying straight into the shrubs and flapping their wings to frighten and disturb the moths that were hiding (Odell 1977 cited in Smith and Lautenschlager 1981). Other bird species that consume adult gypsy moths include the Eastern Phoebe, Indigo Bunting, Ovenbird, and Common Yellowthroat. Nevertheless, it is unknown that any bird species consumes a sizable portion of adult moths.

One remarkable and fascinating fact is that the feathers shed their sheaths on day six or seven following hatching, and the nestlings grow their full set of feathers in just two hours. I’ll end by saying this: a group of cuckoos is referred to as a “asylum” of cuckoos!

The nest is a thin, twig-built saucer that is constructed in bushes or tiny saplings. One to five pale blue-green to yellow-green eggs laid by monogamous parents are incubated by both sexes. Cuckoos seldom lay their eggs in the nests of other bird species, but they do so occasionally in the nests of other cuckoos. They are not considered to be serious brood parasites.

When perching, the long tail’s white spots contrast with the gray-brown stripes. The less common black-billed cuckoo is distinguished by its smaller white tail spots, red eye ring, solid brown wings, and solid black bill. Their average length is 12 inches, their wingspan is 16 inches, and they weigh slightly less than 4 ounces. The song has a harsh, rattling “ka-ka-ka-ka-kow-kowp” and a repeated “coo” call that is completely unlike the clocks’ couplet rhythm.

You are welcome to get in touch with Blue Water Audubon if you would like to learn more about birds. Please visit and friend our “Blue Water Audubon Society” Facebook page for details on upcoming events and general information.

Seek for yellow-billed cuckoos in the Port Huron State Game area or anyplace nearby where forests and water combine in their unaltered state. They are widespread along a large portion of Mill Creek, the Black River, and other nearby wetland forests.