Bird movement was studied at various ages in two flocks of 18,200 broiler chickens. 2. One-d-old chicks placed in corners of a 29 x 14 m brooding area dispersed evenly over the whole area in a period of 48 h. 3. At 15 d of age, when released from the brooding area, birds which were among the first to move to the far end of the house did not necessarily remain in that area of the house. 4. Starting at 4 and 5 weeks of age, birds marked individually were variable in their movement throughout the house during a 16- and 9-d period respectively. Even the least mobile individual covered an area of the house containing several thousand birds. 5. Closer scrutiny of movement by individual birds showed that some moved over areas of 20 m2 in an hour. Birds moved further than was necessary simply to reach food and water. No agonistic interactions were observed and there was no evidence that crowding was a physical restraint on bird movement. 6. Results indicated that birds were not generally attached to a particular site in the shed and that social factors did not restrict movement. Some implications of bird movement are discussed with regard to performance, welfare and leg abnormalities.
