Do domestic fowl form groups when resources are unlimited?

Abstract

We tried to determine the preferred group size of hens in single and mixed-sex flocks by allowing groups to form in a setting that we predicted would facilitate segregation. Two flocks of 50 medium hybrid hens and two flocks of 50 hens plus ten roosters were housed in large pens (5.5 m X 6.75 m) with litter floors from 1 day of age. Each pen was divided into three small ‘rooms’ ( 1.83 mX2.45 m), and two larger ‘rooms’ ( 1.85 m X 5.5 m and 2.45 m X 5.5 m). All five rooms were furnished with feeder(s), drinker(s), roost(s) and nestboxes so that birds could obtain all necessary resources in a single room, and could pass freely among rooms. Focal animal samples ( 1000) were collected from 14 to 25 weeks of age. Nearest-neighbour analyses indicated that individual hens associated with 26.6 f 0.4 other hens in their flock. Hens did not confine their movement within rooms: 21.5% of hens were sighted in all five rooms, 54.5% in four rooms and 19.5% in three. In hen-only flocks, the percentage of observations of birds in clusters of 1, 2-5, 6-9, and 10 or over were 16.68, 47.4%, 22.4% and 13.62, respectively, compared with 16.0%, 32.6%, 25.6% and 25.8% for flocks with roosters (x2 = 37.5, P < 0.001). These data indicate that hens did not form groups, and did not form attachments to specific locations. Roosters did not facilitate group formation but did influence the hens’ spatial distributions.