What is this bizarre fuzzy little creature? It’s a Black coucal Centropus grillii chick, and what makes it particularly interesting is that it’s covered with simple, tubular, unbranched feathers (termed trichoptiles). If you know the literature on the evolutionary development of feathers you will have noticed that trichoptiles look suspiciously similar to the ‘stage 1 feathers’ hypothesised by Prum and Brush, and yet here they are in a neornithine. They rarely get a mention, despite being described by Shelford (1900), and despite being present elsewhere in cuculiforms and not restricted to the rather obscure and poorly known coucals: Kaiser (2005), for example, described them in roadrunner chicks.
Even without the trichoptiles of their nestlings, coucals are very neat birds. They are large, long-tailed terrestrial cuckoos of the Old World and Australasian tropics (c. 30 species) with enlarged hallux claws, rounded wings and high wing-loadings, and studies generally find them to be close to the base of the cuculiform radiation (Hughes 2000, Johnson et al. 2000, Sorenson & Payne 2005). Stalking through the undergrowth in search of arthropods and small vertebrates, they behave more like pheasants than cuckoos (an Australasian species is in fact called the Pheasant coucal C. phasianus), and it has often been noted that they have a superficially reptilian look about them. Indeed Feduccia and others have drawn attention to the fact that coucals strongly resemble archaeopterygids in size and proportions (this is not entirely accurate however, as the fossils show that archaeopterygids were substantially less neornithine-like than Feduccia says).
Coucals are communal breeders, the females are larger than the males, and in fact the males are often responsible for nest-building, incubation duties, and for care of the young (Andersson 1995, Maurer 2008). Males also routinely have one of their testes atrophied. Polyandry has evolved in C. grillii, and the reliance on males as the primary carers have uniquely made the Black coucal the only polyandrous bird known in which the nestlings are not precocial (Goymann et al. 2004, 2005, Goymann & Wingfield 2004).
The pictures were kindly provided by Greg Davies of Natal Museum, and Greg also provided a lot of helpful information and references on coucal trichoptiles and behaviour.
Refs – –
Andersson, M. 1995. Evolution of reversed sex roles, sexual size dimorphism, and mating system in coucals (Centropodidae, Aves). Biological Journal of the Linnean Society 54, 173-181.
Goymann, W., Kempenaers, B. & Wingfield, J. 2005. Breeding biology, sexually dimorphic development and nestling testosterone concentrations of the classically polyandrous African black coucal, Centropus grillii. Journal of Ornithology 146, 314-324.
– . & Wingfield, J. C. 2004. Competing females and caring males II. Sex steroids in African black coucals, Centropus grillii. Animal Behaviour 68, 733-740.
– ., Wittenzellner, A. & Wingfield, J. C. 2004. Competing females and caring males I. Polyandry and sex-role reversal in African black coucals, Centropus grillii. Ethology 110, 807-823.
Hughes, J. M. 2000. Monophyly and phylogeny of cuckoos (Aves, Cuculidae) inferred from osteological characters. Zoological Journal of the Linnean Society 130, 263-307.
Johnson, K. P., Goodman, S. M. & Lanyon, S. M. 2000. A phylogenetic study of the Malagasy couas with insights into cuckoo relationships. Molecular Phylogenetics and Evolution 14, 436-444.
Kaiser, M. 2005. Haltung und Zucht des Rennkuckucks, Geococcyx californianus (Lesson, 1829), im Tierpark Berlin. Milu 11, 448-461.
Maurer, G. 2008. Who cares? Males provide most parental care in a monogamous nesting cuckoo. Ethology 114, 540-547.
Shelford, R. 1900. On the pterylosis of the embryos and nestlings of Centropus sinensis. Ibis 1900, 654-667.
Sorenson, M. D. & Payne, R. B. 2005. Molecular systematics: cuckoo phylogeny inferred from mitochondrial DNA sequences. In Payne, R. B. (ed) Bird Families of the World: Cuckoos. Oxford University Press, pp. 68-94.