Getting to Know: Ontario’s Cuckoos

A cuckoo isn't just a noisy bird that pops out of that antique clock hanging in your kitchen. Cuckoos exist, and we have two species of them right here in Ontario: the Black-billed Cuckoo and the Yellow-billed Cuckoo. Their distinct guttural croaks and soft repetitive coos can be heard throughout the night, but these elusive birds often remain unseen, hidden away amongst the dense foliage of the forest. Let's get to know the faces behind the mysterious calls in the night.

Black-billed Cuckoo (Coccyzus erythropthalmus)

Identification & Sounds

Black-billed Cuckoos are slender-bodied birds with an often hunchbacked appearance when perched. Similar in size to a Mourning Dove, but with a very long tail, and fairly long, partly-curved black bill. Their white underparts contrast their patternless, brown upper half, and sport a striking red ring around the eyes. The less common Yellow-billed Cuckoos are similar in both size and appearance, but have - as their name suggests - a yellow bill and matching yellow eye ring. Their calls are distinct, and hard to mistake for another bird when heard. Black-billed Cuckoos have a song of 3-5 toots, all the same pitch. They repeat this in sets for several minutes and can be heard singing at all hours. Their call is a guttural croak that is used by both males and females. Click here to hear the sounds of the Black-billed Cuckoo. Yellow-billed Cuckoos have a softer song that sounds like a repeated cooing noise. Males sing to attract females, and females coo back during courtship. Their call is a series of hollow-sounding syllables in the sound of "ka-ka-ka-ka-ka-kow-kow-kowlp-kowlp-kowlp-kowlp". Click here to hear the sounds of the Yellow-billed Cuckoo. Listen for them calling overhead throughout the night upon arrival during spring migration.

Habitat & Nesting

Cuckoos are long-distance migrants, flying to South America for the winter months. As with many bird
species, migration takes place at night. During the spring and summer months, both Black and Yellow-billed Cuckoos spend much of their time in habitat with dense cover and a healthy insect population including mature woodlands, overgrown orchards, and marshes. Black-billed Cuckoos typically nest in shrubs, no higher than 7' from the ground, but may choose a location as high as 50'. Yellow-billed Cuckoos are less choosy when it comes to height for their nesting site, constructing their nest anywhere from 3'-90' above ground. Both species lay one or two broods of 1-5 eggs each. Chicks hatch naked and reliant on their parents, but grow at an exceptional rate with a nestling period of only one week. Once fledged, the young remain unable to fly for nearly two weeks. Interestingly, cuckoos have been known to occasionally partake in brood parasitism, meaning that they will lay their eggs in other birds' nests to care for and raise. Chosen hosts are usually other cuckoos, but may also be Chipping Sparrows, American Robins, Gray Catbirds, and others. 

Diet & Foraging Habits

Black-billed Cuckoo (Coccyzus erythropthalmus)
eyeing tent caterpillars

Cuckoos are omnivorous, feeding on a variety of foods depending on season and availability. On their wintering grounds, they feed mostly on berries and small fruits. While here in North American during the spring & summer, cuckoos primarily feed on insects such as grasshoppers and beetles, with a large portion of their diet consisting of caterpillars. Rather than actively hunting for their prey, cuckoos prefer to lie in wait, hidden amongst branches for long periods of time waiting for insects to crawl past them. When they are within range, the cuckoo will lurch forward or dive to snatch them up. Cuckoos specialize in eating hairy caterpillars like forest tent caterpillars, fall webworm, and invasive gypsy moth caterpillars, consuming up to 100 in a single sitting. Most birds are uninterested or unable to eat these types of caterpillars due to their irritating hairs, but cuckoos have developed a unique way of handling them. Once a cuckoo has caught a hairy caterpillar, it shakes it furiously to expel as many hairs as possible. Sometimes they will also rub the caterpillar on a surface such as a branch in an attempt to remove even more of the prickly hairs. Because the hairs are indigestible, they wind up sticking to the bird's stomach lining which can cause issues in the digestive system if the hairs were to remain there. To get rid of the spines, cuckoos are able to shed the entire lining of their stomach and dislodge it by regurgitating it in the form of a pellet (what's a pellet? Read all about them here).

Conservation & How You Can Help

As with the state of many North American bird species, cuckoo populations are in decline. Black-billed Cuckoos have seen a 68% decline, and Yellow-billed Cuckoos a 52% decline since 1970. These troubling losses are largely due to habitat loss, pesticide use, and climate change. Because cuckoos migrate at night, they are highly vulnerable to collisions with buildings and other human-made structures, and many of these collisions are fatal. Studies have shown particularly with Black-billed Cuckoos, that if the rate of decline continues as it is, we will lose over half of the remaining population by 2055. To help our struggling cuckoo populations (and all wildlife), Cornell Lab of Ornithology has put together a list of actions we can take at home. This actions include: make windows bird-safe, keep cats indoors, reduce lawn space and plant native plants, avoid pesticide use, buy bird-friendly coffee, avoid plastic use where possible, and participate in community science efforts. Click here to learn more about the Seven Simple Actions to Help Birds. 

Black-billed Cuckoo (Coccyzus erythropthalmus)

How to Spot Them
There is no real way to guarantee tracking one of these secretive birds down, but here are a couple tips that may help in the search:

• Become familiar with their sounds and listen for them at night. Listening for cuckoos calling at night can help you determine their location and help with scouting the area the next morning. An interesting note; in folklore, cuckoos have been referred to as "rain crows" because it is said that they call just before rain falls. While this is not a scientific finding, it may be worth listening as a storm approaches to test the theory.
• Look twice. Cuckoos have an odd shape when perched, which can sometimes give them the appearance of a twisted branch. Scan the lower to mid section of a tree or shrub slowly, then scan again.
• Watch out for tent caterpillars, webworm, and gypsy moth caterpillars. As mentioned above, these are a favourite of both black and yellow-billed cuckoos and are relatively easy to find. This year in particular there is a large boom in gypsy moths, with many forests in the area being infested. While this is an issue for our native tree species, it may provide a unique opportunity to see a cuckoo. Tent caterpillars and webworms create large nests and congregate inside of them, cuckoos take advantage of this and will often sit and pick the caterpillars out one by one until they've had their fill.

If you've seen or heard a cuckoo in your area, we want to hear about it! Tell us your experience in our Facebook group, Ontario Birds by WBU Barrie and WBU Newmarket.

Happy trails!

- Shayna Hartley