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Research Training Scholarships

Emma Smith

“Influences of the light environment on avian behaviour and welfare”

In 1999 Emma Smith, under the supervision of Prof. Innes Cuthill, Dr. Arthur Goldsmith and Dr. Andy Bennett at the University of Bristol, was awarded a UFAW Research Training Scholarship to investigate avian vision. Bird vision is significantly different from that of humans - birds can perceive a wider spectrum of light than we can, and they can see into the ultraviolet (UV; 315-400 nm). Commercial light sources are typically UV deficient, and may make the UV reflecting aspects of the environments that they illuminate appear to be an unusual colour to birds (ie. they may give abnormal 'colour rendering'). This lack of UV wavelengths may also 'hide' visual information that the birds could potentially benefit from. For example, if birds normally use UV reflective patches on the plumage of other birds to assess social status, the absence of UV in the illuminant may increase the probability of aggressive interactions and fights occurring, as the birds would be less able to assess the dominance of other individuals.

Apart from the spectral composition of the light, there are other aspects of the captive visual environment that may be suboptimal for birds. Most fluorescent lights 'flicker' on and off at 100 times per second (100 Hz). This rate of flicker is too fast for most adult humans to perceive consciously. However, as birds may have better motion perception than humans, they may perceive 100 Hz lighting to be stroboscopic. Furthermore, most captive birds are kept in cages, the bars of which form a highly repetitive pattern over space. Evidence from the human literature suggests that repetitive visual stimulation, both from viewing temporally repetitive flickering lighting and the spatially repetitive striped pattern of cage bars, may engender stress in birds. Certain rates of repetition ('frequencies') are predicted to be more aversive then others, as some frequencies cause a stronger response in the nervous system than others. Consequently, Emma’s research systematically investigated the effect of UV wavelengths, flicker rate and spatial frequency on avian welfare.

Firstly, Emma investigated the impact of the absence of UV, specifically the effect the lack of UV would have on birds' perception of their environment by giving poultry and passerines UV 'colour blindness' tests. Emma found that UV sensitivity appeared to form part of normal colour vision in both poultry (Japanese quail, Coturnix coturnix japonica) and passerines (European starlings, Sturnus vulgaris). This showed that UV deficient lights would give abnormal colour rendering of the environment as far as the birds are concerned (see Smith et al. 2002). In some animals, certain aspects of visual development are impaired if their visual systems are not appropriately stimulated whilst they are young. However, Emma found that rearing Japanese quail without UV did not prevent them from perceiving UV later in life, which showed that supplemental UV could be a potential environmental enrichment, even for birds that have never previously experienced it. However, although UV sensitivity forms part of the birds' colour vision, it seems that birds may not have a strong specific preference for UV wavelengths.

Emma found that although groups of European starlings generally prefer supplemental UV light, this preference may be simply for the higher overall light intensity it provides (see Greenwood et al. 2002). Furthermore, the provision of UV wavelengths during rearing did not measurably affect the physical development, behaviour or plasma corticosterone of quail. Corticosterone is the major 'stress hormone' in birds, which rises when the bird is under stressful conditions. UV deficient lighting did not cause even minor rises in the level of this hormone. Therefore, UV deficient artificial lighting does not appear to harm the welfare of birds outside of the context of social signalling or other major choice involving assessment of UV reflecting surfaces.

Emma did find some tentative evidence that both the flicker rate of the lighting and the spatial frequency of the visual surround have some effect on avian welfare. Starlings generally prefer high frequency (>30 kHz) to conventional (l00 Hz) fluorescent lamps although this preference may be modified by the spatial frequency of the environment. The frequency of the lighting does not appear to be a major factor in the welfare of recently caught wild starlings relative to the stress of adjusting to captivity. However, there is some evidence that both the frequency of the lighting and the spatial frequency of the visual surround affect the preferences, behaviour and physiology of starlings once they are acclimatised to indoor housing. These effects did not match predictions from the human literature, indicating that first, birds may perceive particular ranges of spatial and temporal frequency differently from humans, and second, that further research is needed into how these factors affect their welfare.

Emma, successfully completed her PhD during 2003. As a result of this, Emma published several papers in the scientific press on her work on avian vision. Furthermore, as a direct result of her work, some practical changes were made to the way that animal husbandry is conducted in zoos in the USA. Several US zoos agreed to change the artificial light environments and make them more natural: non-flickering lighting, natural photoperiods and ultraviolet-containing lights were provided. Emma says that “whilst we might not have solid evidence that this change will promote a significant increase in welfare, it certainly will do no harm, and the provision of UV will form an environmental enrichment in terms of providing a greater range of visible colours to the birds”.

Published papers arising from Emma’s project supported by UFAW:

Smith, E.L, Greenwood, V.J., Goldsmith, A.R., and Cuthill, I.C. 2005. Effect of supplementary ultraviolet lighting on the behaviour and corticosterone levels of Japanese quail chicks. Animal Welfare. 14: 103-109 ISSN 0962-7286

Smith, E.L., Cuthill, I.C., Griffiths, R., Greenwood, V.J., Goldsmith A.R and Evans J.E. Sexing Starlings Sturnus vulgaris using iris colour. 2005. Ringing & Migration, 22. Pp 193-197

Greenwood, V.J., Smith, E.L., Goldsmith, A.R., Cuthill, I.C., Crisp, L.H., Walter-Swan, M.B., and Bennett, A.T.D. 2004. Does the flicker frequency of fluorescent lighting affect the welfare of captive European starlings? Applied Animal Behaviour Science. 86: 145-159.

Greenwood, V.J., Smith, E.L., Cuthill, I.C., Bennett, A.T.D., Goldsmith, A.R., and Griffiths, R. 2003. Do European starlings prefer light environments containing UV? Animal Behaviour. 64: 923-928.

Greenwood, V.J., Smith, E.L, Church, S.C., and Partridge, J.C. 2003. Behavioural investigation of polarisation sensitivity in the Japanese quail (Coturnix coturnix japonica) and the European starling (Sturnus vulgaris). Journal of Experimental Biology. 206: 3201-3210.

Greenwood, V.J., Smith, E.L, Church, S.C., and Partridge, J.C. 2002. No evidence of polarisation sensitivity in the Japanese quail (Coturnix coturnix japonica). Perception, 31. Supplement. Pp48a.

Smith, E.L., Greenwood, V.J., Bennett, A.T.D. 2002. Ultraviolet colour vision in birds: inferring physiology and perception from behaviour. Perception, 31. Supplement. Pp 66c.

Smith, E.L., Greenwood, V.J., Bennett, A.T.D. 2002. Ultraviolet colour perception in European starlings and Japanese quail. Journal of Experimental Biology. 205: 3299-3306.

Smith, E.L, Greenwood, V.J., Goldsmith, A.R., Cuthill, I.C. and Bennett, A.T.D. 2001. Can unnatural visual scenes cause stress in captive birds? Perception, 30. Supplement. Pp73a.