ORIGINAL ARTICLE Short restraint time does not influence markers of serum oxidative stress in homing pigeons (Columba livia) D. Costantini 1,2 and H.-P. Lipp 1 1 Division of Neuroanatomy and Behaviour, Institute of Anatomy, University of Zurich, Zurich, Switzerland, and 2 Dipartimento di Biologia Animale e dell’Uomo, University La Sapienza, Roma, Italy Introduction Organisms are continually challenged with several stressors of different nature (e.g. biochemical, physi- ological, environmental). On one hand, stress response is per se of adaptive nature as it allows the organism to cope with stressful challenges, no matter of what nature and to maintain or restore body homeostasis. On the other hand, stress response may be inadequate, resulting in deleterious consequences for the health and for the biological fitness of the organism (Korte et al., 2005). Free-living animals may cope with stressful stimuli by using different behavioural strategies. For exam- ple, they can move away from a stressor or seek a place that better fits their ecological needs. In captiv- ity, however, the situation may be very different. Indeed, captive animals have little or no control over the timing, duration or magnitude of a stressor to which they are exposed. For example, there is a gen- eral agreement that one important stressor in captiv- ity would be restricted movement because of a small cage (Morgan and Tromborg, 2007). Indeed, restraint is a common means to induce a stress response (Glavin et al., 1994). Capture and restraint stress (acute stressor) have become widely used by ecophysiologists to examine how vertebrates respond to unpredictable environmental stressful challenges (i.e. labile perturbation factors; Wingfield et al., 1998). It is also suggested that housing animals under crowded conditions may cause adverse effects on their well-being. For example, the physiological response of an individual, placed in a confined space might be intensified by the presence of additional individuals in the same space. Crowding has been Keywords free radicals, antioxidants, oxidative stress, birds, flight, stress response Correspondence David Costantini, Dipartimento di Biologia Animale e dell’Uomo, University La Sapienza, Viale dell’Universita ` 32, I-00185 Roma, Italy. Tel: +39 06 49914780; Fax: +39 06 4958259; E-mail: david.costantini@uniroma1.it Received: 2 May 2008; accepted 29 August 2008 First published online: 8 December 2008 Summary Restraint in a confined space, such as a cage or a box, may be perceived by birds as a stressful condition. Some concern has been expressed about restraining homing pigeons (Columba livia) in transport crates for sport or for scientific research. Therefore, this study sought to test whether short restraint time in a transport crate for 1, 2 or 18 (overnight) h causes oxidative stress in homing pigeons and whether it is more stress- ful than flying. To isolate the effect of crowding from that of transport per se, the pigeons were kept in an immobile crate, that is, without any movement. To quantify oxidative stress, we measured serum levels of oxidative damage (ROMs) and of antioxidant capacity (OXY). We found that pigeons restrained in transport crates showed no significant varia- tion for both markers of oxidative stress, regardless of the duration of restraint. Conversely, pigeons which had flown around 200 km had increased levels of oxidative damage and decreased levels of serum OXY, both clear manifestations of oxidative stress. These results suggest that maintaining homing pigeons in transport crates for a short time (i.e. 1–18 h) does not cause oxidative stress. DOI: 10.1111/j.1439-0396.2008.00880.x 24 Journal of Animal Physiology and Animal Nutrition 94 (2010) 24–28 ª 2008 The Authors. Journal compilation ª 2008 Blackwell Verlag GmbH