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Animals have been kept in captivity in the United Kingdom (UK) for centuries for ornamentation, as symbols of power, for conservation, and for education. However, captivity can be detrimental to animal welfare due to a variety of artificial conditions that they are not adapted to cope with. Birds are particularly susceptible to stress and reduced fitness in captivity due to restrictions in flight. In this review, a meta-analysis was undertaken to evaluate the effect of captivity on haematocrit, corticosterone levels, hippocampus size, body temperature, body mass, blood nutrient levels, survival, fecundity, and basal metabolic rate in many wild bird species. It was found that captivity led to an increase in haematocrit levels while there was a decrease in both survival and fecundity. There was also an increase in CORT and blood nutrient levels and a decrease in hippocampus size but those studies indicated publication bias. I demonstrated that, even when living in legislatively acceptable conditions, captive birds still suffer from chronic stress and reduced capacity to survive when released into the wild. Animal welfare legislation and enforcement were evaluated and it was concluded that they are insufficient to maintain the welfare of birds and more attention needs to be paid to bird welfare in captivity. To my knowledge, this is the first meta-analysis conducted to evaluate the effect of captivity on birds.
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