The birds (around 10,000 living species) are the most numerous tetrapod vertebrates classified as Neorinthes(Kan et al. 2010). Columbiformes is amongst the most easily recognized avian orders worldwide. The Rock pigeon (Columba livia), also known as Rock dove, is a member of the family Columbidae, which include some 310 species. This species includes the feral pigeon, the wild rock pigeon, and the domestic pigeon. Mostly wild Rock pigeons are pale grey in colour with two black bars on each wing; although domestic and feral pigeons are different in colour and pattern. Pigeons are stout bodied birds with short necks and short slender bills with a fleshy cere. The largest species are crowned pigeons which are nearly size of turkey whereas smallest are New World ground-doves of the genus Columbina, which are quite similar in size as a House sparrow(Murton and Westwood 1966).
Pigeons and doves have wide range of distribution on Earth, except for driest areas of the Antarctica, Sahara Desert and its surrounding islands. The family has adapted to most of habitats. A large numbers of species are present in tropical forests and woodlands; some inhabit savannas, grasslands, deserts, temperate woodlands and even the barren sands(Falc 2013). Rock pigeon is the largest species which had a large natural distribution from Britianand Ireland to Arabia, Northern Africa,Europe, Central Asia, India, up into China(Baptista et al. 1997).
Pigeons live in diverse environment which is so complex ranging from hot, rainy, cold that can be potentially harmful for them. However they adjust themselves by generating stress responses(Harvey et al. 1984). These stress responses are integrated neuroendocrine responses that cause activation of hypothalamus-pituitary-adrenal (HPA) axis and secretion of Corticosterone and experiences basic emotion of fear. Although it can be difficult to measure stress, results from some species demonstrate that Cortisol responses and fear behaviour responses in individual birds are related(Cockrem 2007). Stress is induced when any animal/ bird experiences variations in its environment that may have an effect on body responses that have the purpose to maintain the homeostatic condition. A good knowledge about health status related to the handling of caged birds and the struggle to improve their veterinary care, have important role in deciding the success of these caged birds (Villegas et al. 2004).
Pigeon’s behavioural comparison between captive and wild populations is a useful tool as it is commonly believed that birds suffer if they are unable to perform a full repertoire of natural behaviours. Two main behaviours commonly displayed in captivity include stereotypical behaviour and abnormal behaviour(Guyon 2009).
While the trend of keeping pigeons in captivity is ever increasing, the major challenge while keeping them in captivity is their inability to survive. The reason seems to be change in environmental conditions or to subclinical infections in wild becomes aggravated in confinement. The poor ability of birds to survive may cause derangements in blood and biochemical parameters as a result of stress due to confinement (Azeez et al. 2013). The related stress values are generally not reported and data is scarce.
Blood is an important medium to determine the health state of a bird. Blood analysis is helpful in assessing both the physiological and pathological conditions of a bird. Haematology and blood biochemical profiles are very helpful integral tools to diagnose and treat the diseases in birds and to provide information about bird’s nutritional status and physical condition. These two factors also help scientists understanding the multiple contributing functions of blood corpuscles. The variations in haematological ratios depend on various factors like age, species, the phase of sexual maturity, environmental and health condition (Rey Vázquez and Guerrero 2007). Haematological ratios are closely associated with response of an animal to its environment, an aspect that birds live in the environment that might exert some impact on haematological parameters. Besides, all possible facilities and care are provided; the birds kept in captivity are under continuous stress and are more likely to be infected. The caged stress may have an effect on haematopoietic system in the body of human, animals and birds. Haematopoietic marrow values decrease in caged environment. This results in low levels of red blood cells (RBCs), haemoglobin (Hb), white blood cells (WBCs). The values of RBCs count, Hb, MCH, WBCs count were lower in Nigerian laughing dove in caged environment (Azeez et al. 2013). Biochemical indices may also be influenced by caged stress. ALT, AST and CK levels were known to be higher in captive puna ibis. This was may be due to injury during capture (Coke et al. 2004). In caged layers, the calcium, phosphorus and bone geometry were investigated. In caged eagles, glucose levels were higher than in free-living eagles. These changes could be closely associated with the differences in nutritional level and metabolism of birds (Ferrer and Dobado-Berrios 1998)