Seeing the Light on Welfare: UV as an Environmental Enrichment for Birds

Birds, including chickens, are commonly used in animal research. However, housing facilities are often optimized for mammals and contain no ultraviolet (UV) light. Unlike mammals, most birds are tetrachromatic, meaning that they can see in both the visible and ultraviolet (UV) spectrum. Facilities lacking UV light deprive birds of a range of colors that are a part of their natural visual repertoire. In our recent study, we examined the importance of UV lighting (specifically UV-A) as an environmental enrichment (EE) on the behavior and well-being of chickens. In addition to normal white light, some birds in the experiment received supplemental UV lighting for two hours each morning and again in the afternoon. Ultraviolet lighting provides an EE that may enhance the birds’ ability to visualize and interact with their environment.

Social cues in birds include feather movement and coloration, including UV reflectivity. Gentle feather pecking is a normal social and exploratory behavior in birds. Birds reared with UV lights engaged more in gentle feather pecking than those reared with white lights only. Birds reared with UV light also showed increased distress during short periods of social isolation from their pen mates. These findings suggest that the use of UV lights enhances birds’ social behaviors, and is useful in prompting their natural social repertoire.

Reducing fear response to human intrusion is especially important for birds handled regularly in research. Regular human interaction can be extremely stressful to birds fearful of humans. We investigated the impact of UV lighting on fear response to humans by using a flight distance test (measuring the distance a bird flees from a human intruder). Exposure to UV lights reduced the distance birds flew away from a person entering their pen. Similar to the use of other EEs, the presence of UV lighting in the pen reduces fear during common human-bird interactions.

Birds often forage unsuccessfully through their pen’s bedding, even though feed is continuously provided in a feeder. In turkeys, especially, young birds sometimes die of starvation, but are found with a gut full of bedding material. One potential explanation for these behaviors is that birds are unable to discriminate between feed and nonfeed (such as wood shavings). In our study, no birds died of starvation; however, we did see foraging in areas away from the feeder. This foraging behavior was reduced when the UV lights were on, suggesting that chickens use cues in the UV spectrum to help identify food. Proper lighting spectrum allows birds to fully and efficiently explore and interact with their environment.

Ultraviolet light is an important part of the environment of wild birds. Our findings indicate that this does not change for domestic species and that the use of UV lighting can be a vital addition to their housing environment. Our findings suggest that UV lighting can be used as an EE to enhance social behaviors and reduce fear of humans, and should be considered when developing avian research housing facilities to maintain the best welfare of laboratory animals.

By Dr. Rachel L. Dennis, Assistant Professor, Department of Animal and Avian Sciences, University of Maryland. This study was supported by an AWI Refinement Grant.