In the search for stereopsis
- University of California, Davis, Department of Ophthalmology, Sacramento, CA, USA and Vision Touch and Hearing Research Centre, University of Queensland, Queensland, Australia
- Correspondence to: I R Schwab, University of California, Davis, Department of Ophthalmology, Sacramento, CA, USA; irschwab{at}ucdavis.edu
Owls were probably not the first nocturnal avian denizens. After all, they had to evolve from a diurnal species, and this probably required some bridge families. The bridge between the sister taxa of swifts and hummingbirds to the nocturnal owls was probably the order Caprimulgiformes with good cladistic and systematic evidence of this intermediacy. The strange birds in this order are not household names and include the nightjars, oil birds, potoos, owlet-nightjars, and frogmouths. All of these birds are characterised by enormous gaping mouths, tiny feet, crepuscular and/or nocturnal activity. The nightjars, oil birds (with perhaps one rare exception), potoos, and swifts are wing feeders and do not take food off the substrate. Only the frogmouths and the owlet-nightjars can utilise substrate food sources, and appear to be close to the owls themselves in several ways. The Papuan frogmouth on this month’s cover is a good example of this predominately insectivorous order, and will illustrate the evolution from swifts to owls.
The frogmouth family (Podargidae) comprises 12 species and is probably a relic family close to owls. As can be seen, the Papuan …
