Crazy Over Cuckoos

by Steve Blight

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Some people are quite surprised to hear that we have cuckoos in the Land O’ Lakes region. They seem like an exotic bird that you might read about in stories set in far off lands. In fact in North America, there are six species belonging to the group of related birds that are collectively referred to as cuckoos – three species of cuckoos, two species of anis and the Roadrunner. Only two species are found in our area – the Yellow-billed Cuckoo and the Black-billed Cuckoo. The anis live in the southern United States and further south, and the Roadrunner is rumoured to be running away from an unlucky coyote somewhere in the American Southwest. Although the Black-billed Cuckoo is more common here, the Yellow-billed is a regular summer visitor as well. For example, this year I have only seen one cuckoo, and it was a Yellow-billed.

“Our” cuckoos are long, slender birds, about the overall length of a Blue Jay, but less stocky. Males and females look alike. They have solid light brown (taupe) backs, a clean white breast and under parts, and a thin, slightly down-curved bill. They have long tails with distinct spotting on the underside. The Yellow-billed Cuckoo has a mainly yellow bill, and the Black-billed has – you guessed it – a black bill.

Cuckoos have several unique behaviours and adaptations. Both cuckoos are known to be caterpillar specialists. The majority of their food is made up of spiny caterpillars like tent caterpillars, gypsy moths and fall webworms – caterpillars that few other birds will have anything to do with. They are most often observed moving furtively in dense younger forests or shrub lands seeking their caterpillar prey. Cuckoos are often noticed first by their call – a repeated soft “coo-coo-coo” for the Black-billed, and a more varied and guttural “kowp-kowp-kowp” for the Yellow-billed.

Although the Black-billed is the more common cuckoo in our area and is found much further north than the Yellow-billed, both species are usually found where there are significant outbreaks of spiny caterpillars. As a result, while they may seem quite common one year, they may be uncommon or even absent the next year in the same area if there are few caterpillars around.

Their preference for spiny caterpillars has led to a fascinating adaptation: the spines collect in the linings of their stomachs, and every so often, the entire lining and all the spines are shed and regurgitated by the bird as a compact pellet.

Another interesting behaviour is that both species occasionally lay their eggs in the nests of other cuckoos or even other species of birds – a behaviour known as brood parasitism. However, unlike the Common Cuckoo of Europe, which always lays its eggs in the nests of other species, the North American cuckoos only occasionally lay their eggs in other birds’ nests, especially when food resources are abundant.

Cuckoos arrive in our area fairly late in spring, but stay longer than most birds that winter in the southern United States, Central and South America. Peak arrivals are often noticed during the first week of June, and the birds stay until September or even October. Because of their nomadic search for caterpillar outbreaks, it has not been easy for scientists to figure out the conservation status of these birds. Most sources say that Ontario populations of cuckoos appear to be holding their own or declining slightly. On the other hand, sharper declines have been noted for both species on a North American-wide basis. Some sources suggest that the former widespread use of pesticides to control caterpillars has been an important factor underlying these declines.

While periodic outbreaks of Gypsy moths or tent caterpillars that eat every leaf from every tree may cause us concern, we can take some solace knowing that without these spiny vegetarians, there would be no cuckoos in the Land O’ Lakes!

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Please feel free to report any observations to Lorraine Julien at naturewatching@gmail.com  or Steve Blight at natureobservations@rogers.com