Cataracts in corvids

Author Dr David L Williams


Corvids (crows, rooks and jays) are anything but birdbrained, as Professor Nicky Clayton has shown in many research papers. But her group of scrub jays have, over several years, developed cataracts which influence their vision and hence may have welfare implications. Here is a recent paper investigating this problem and it’s associated welfare issues.

The development of cataracts in a colony of 55 Western scrub jays (Aphelocoma californica) kept in a colony is reported, etiopathology discussed and welfare implications debated. Birds were examined with direct and indirect ophthalmoscopy and slit lamp biomicroscopy. Intraocular pressures were measured with a rebound tonometer.

Thirty eight birds were diagnosed with some lens opacification, ranging from linear arrangements of small vacuoles to mature cataract. In some birds this lens pathology was seen concurrent with adnexal post-traumatic pathology or with substantial uveitic changes. Behaviour changes were only noted in birds with mature or near-mature cataracts. The lack of significant ultraviolet light and the provision of a suitable avian diet suggest that neither excess light nor inadequate nutrition could be factors in cataractogenesis.

While a genetic cause is difficult to exclude, the fact that these were wild caught birds from an outbred population without observed lens pathology in the wild renders this unlikely. We suggest that a post-traumatic aetiology is the likely causative factor in the genesis of lens opacities in these birds. The changes in behaviour and the impact on the welfare of birds with these ocular changes is discussed.

Cataracts in corvids: health and welfare implications of lens opacification in a colony of Western scrub-jays” is available for download here:

Published June 12, 2017 in the International Journal of Avian & Wildlife Biology, Volume 2 Issue 1. Authors: David L Williams and Nigel Slater, Department of Veterinary Medicine, University of Cambridge, UK.