Secrets of the Cuckoo

The discovery of a Black-billed Cuckoo calling from a brushy gully along Beaver Lake Road east of Winfield in early July, 2014 by Mike Force and Doug Kragh caused a minor gold rush of birders hoping to add the bird to their lists. But I don't want to tell the usual story of how birders flocked from far and near for a rarity; instead, I want to give some background information about the Black-billed Cuckoo as a species, for, as I quickly found out while browsing through a couple of sources of information, Coccyzus erythropthalmus is a fascinating bird.

The Beaver Lake Road Black-billed Cuckoo photographed by Mike Force, 4 July 2014. 

Here, in no particular order are some of my favourite facts. Unless I have noted otherwise, I found these in the 2001 Birds of North America account (No. 587) compiled by Canadian ornithologist, Janice M. Hughes.

1. Probably everyone knows that both Black-billed and Yellow-billed Cuckoos eat insects, and that the Black-bill, in particular, eats caterpillars, including spiny ones. But did you know that once such spines accumulate heavily in the Black-bill's stomach, it sheds its stomach lining, coughing it up as a pellet?

2. Again just about everyone knows that nestlings of most species can be divided roughly into precocial or altricial types. Precocial chicks hatch downy and ready to go. California Quail chicks are a good example. So are Killdeer chicks. In a few hours the precocial young of both species are running around, following one or both of their parents, learning what's good to eat and what's not.On the other hand altricial young are born naked and helpless. The chicks of swallows, sparrows, and American Robins are good examples. Usually their eyes are sealed shot for the first day or two, they have to develop strength to raise their heads and they are restricted to living in a nest, instead of running around like those baby Killdeers we find so adorable along the shores of our favourite wetlands.

Black-billed Cuckoos have altricial chicks, and since adult cuckoos are so slow moving and slightly reptilian, I had assumed that their chicks would take forever to develop. Not so. In fact, Black-billed Cuckoo chicks are among the most rapidly developing chicks in the altricial world. After an eleven day incubation period (1-3 days shorter than many more highly evolved passerines), the cuckoo chick can raise himself up, using his feet and his bill. By day 6 stiff looking feathers are beginning to burst out of sheaths. On day 7 the chick becomes fully feathered, the sheaths having completely burst open. Your average American Robin is still pretty obviously a glum looking, tailless helpless nestling at the same age. Also on day 7 the cuckoo chicks leave the nest to clamber about the shrubbery. They can hop as well as climb.

3. The Black-billed Cuckoo chick has a couple of interesting defence techniques. When another creature appears to threaten the chick it will assume a motionless sky-pointing posture, like an American Bittern. It may also bark and "voids brown, sticky excretion from cloaca, if handled." Charming. If all else fails, and the chick is handled, it will play dead.

The same bird. Photo by Mike Force, 4 July 2014. 

4. Parent Black-billed Cuckoos will fly at nest disturbers especially if they hear their young barking. They open their bills, spread their tails, droop their wings and call loudly while hopping around at the ends of branches.

5. The Black-billed Cuckoo is distantly related to the much more famous European Cuckoo which is an A-lister among the world's parasitic birds. The European Cuckoo lays its eggs in the nests of a wide variety of other birds. Once the young E. Cuckoo hatches and feels an egg pressing against its back it has the automatic response to push whatever out of the nest. Thus the cuckoo kicks out its potential step brothers and step sisters and becomes the only nestling that its foster parents have to feed. The Black-billed Cuckoo generally raises its own young, but sometimes a Black-billed Cuckoo will lay and egg or two in another Black-billed Cuckoo's nest (intraspecific brood parasite). Some individuals may also lay eggs in at least 11 other bird's nests (interspecific brood parasite) including the nests of Yellow-billed Cuckoos, Chipping Sparrow, American Robin, Gray Catbird, and Wood Thrush.

6. Black-billed and Yellow-billed cuckoos are nocturnal migrants, a fact sadly revealed by the birds' fatal collisions with television towers in the United States and Canada. Black-bills winter in northern and western South America.

For more information about the Black-billed Cuckoo and 715 other species of birds that breed in North America check The Birds of North America Online http://bna.birds.cornell.edu/bna/