The impact of social factors on nesting in laying hens (Gallus gallus domesticus)

in the wild, a hen usually moves away from her flockmates and finds a secluded place in which to nest. Several factors influence the hen's decision of where to lay her egg. In addition to the quality and safety of the nest, she may also consider social factors. Under commercial conditions, there are usually more potential nest sites than in the wild, but hens have no opportunity to move away from flockmates and social factors might therefore be more important. The aim of this experiment was to study the effects of competition and disturbances on nest-site selection in commercial laying hens. Hens were housed in 16-litter floor pens (15, 30, 60 and 120 hens per group X 4 replicates) and the levels of aggression and disturbances were compared between nest boxes and pen corners. The number of hens per nest box area was the same for all group sizes but, since all pens were rectangular, there were more hens per corner area in the larger groups. Despite the higher number of birds passing through the corners (movements per minute and unit area: corners 25.0 +/- 2.9; nest boxes 2.4 +/- 0.3, P < 0.001) and a higher level of aggression directed towards nesting birds (nesting birds in corners received 4.8 +/- 1.8 pecks per minute and non-nesting birds 0.02 +/- 0.004 pecks per min, P = 0.010), most hens laid their egg in the corners (18.1 + 3.3 eggs per corner area and 3.5 + 0.8 eggs per nest box area, P < 0.001). However, the time a hen stayed at the nesting site correlated to the level of aggression: the more pecks a hen received the shorter the time she stayed (P = 0.0013), while the more pecks she gave the longer she stayed(P < 0.001). Therefore, social factors had a greater effect on the time spent at the nest site than on the selection of the nest site. (C) 1999 Elsevier Science B.V. All rights reserved.