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.
IntroductionThe cognitive capacity of avian species has long been underrated; the very phrase 'bird-brained' suggests a pretty minimal executive function in these animals. Yet studies from a small number of investigators -one might particularly highlight Pepperberg's work with African grey parrots [1] or Clayton's studies with scrub-jays [2] -suggest that at least in psittaciformes and corvidae we see species with considerable cognitive abilities. Indeed Emery, working with Clayton, has termed her birds 'feathered apes' because of their superlative decision-making abilities [3]. Such suggestions may have significant implications for keeping these birds in an experimental setting. Here we report the development of cataracts in a majority of scrub jays kept in an experimental colony and discuss the possible etiologies for lens opacification in these birds.Professor Clayton first noted interesting behavioral characteristics of the Western scrub jay (Aphelocoma californica) while undertaking her doctoral studies in the University of California, Davis two decades ago. These birds hide or 'cache' food items for retrieval later but other scrub jays often steal the items after viewing the caching behaviour of one of their compatriots. Clayton recognized that some birds, noting a second bird observing them while caching, then re-hid the food item when the observing bird was no longer present. She realized that such behaviour suggests a 'theory of mind' in the caching bird which can in some way comprehend what the observing bird is thinking and planning to do. Research on a colony of Western scrub-jays brought back to the UK to evaluate their cognitive function has resulted in a large number of scientific research publications, of which a few recent ones are [4][5][6]. ...