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Cuckoos

by Mike Scully

This article first appeared in the September 2003 issue of the San Antonio Audubon News.

There are few places on earth where the distinctive calls of some sort of cuckoo do not form a prominent part of the outdoor chorus. Most all of Eurasia, Africa and Australia ring at some season with the loud musical mating calls of the famously parasitic members of this order, the repetitive cadence of the Common Cuckoo (Cuculus canorus) in particular giving the family its common name and inspiring a timeless genre of Bavarian clocks.

The cuckoos (Culiciformes) comprise one of the more distinctive orders of birds; apparently they are a very old group with no close relatives except perhaps for the odd South American Hoatzin (sometimes included in the order). As a group, cuckoos have slender builds and long tails, all have zygodactyl feet (like a parrot), most are insectivorous and/or carnivorous, many species having the unique ability to feed upon hairy or otherwise noxious caterpillars. About half of this order are highly specialized brood parasites, most such parasites being native to the Old World.

A peculiarity common to many cuckoos is an unusually accelerated rate of development of the young. Despite the fact that the duration of incubation may be much less than most other birds (as little as four days in some), the altricial young hatch in a surprisingly advanced state of development, these traits being particularly advantageous to the brood parasites in the group. In addition, the young of some species, though not yet able to fly, may leave the nest in as little as five days. In those species that raise their own young, the nest is often a simple platform of twigs with both parents sharing parental duties. Hatching is generally asynchronous, the survival of the smallest young being doubtful in times of hardship.

Here in Texas, the diversity of this order is well represented by our three locally breeding species. The odd Groove-billed Ani (Crotophaga sulcinostris) reaches the northern edge of its extensive range in our area. Anis often brood cooperatively, up to eight birds tending their eggs and young in the same nest. The familiar Greater Roadrunner (Geococcyx californianis) is the most northern representative of a group of terrestrial Central and South American cuckoos, three of which are obligate brood parasites. Roadrunners rear their own young and, as in many raptors, the smallest members of the brood are occasionally killed and eaten by their siblings or parents.

Most accounts mention that the Yellow-billed Cuckoo (Coccyzus americanus) will occasionally lay its eggs in the nests of other birds, particularly in times of food abundance. The success of such attempts is open to question; this species does not normally produce copious numbers of eggs after the manner of a cowbird, nor do the large blue eggs necessarily mimic those of the intended host as is common with Old World cuckoos.

Interestingly, the Yellow-bill has been observed laying eggs in and attempting to cohabit active songbird nests, sharing incubation and feeding duties with the original inhabitants. Again, the success of such ventures is open to question but might shed light on a possible behavioral origin of brood parasitism.

The familial traits of rapid growth and an ability to devour noxious caterpillars allow the Yellow-billed Cuckoo to efficiently exploit the ephemeral food abundance associated with insect population outbreaks, particularly those of tent caterpillars and cicadas. Although a single brood of two to five young is the norm, in times of abundance broods of as many as eight young have been recorded and up to three broods may be reared in rapid succession, the female initiating a new nest while the male tends the fledged young.

 

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