Nest location selection in laying hens

Nesting behaviour in feral fowl consists of a sequence of behaviours: 1) selection of a nest location (based on e.g. suitable habitat), 2) selection of a specific nest site (based on e.g. available nesting materials), and 3) nest building (Duncan et al. 1978, McBride et al. 1969). Most of the research on nesting behaviour in chickens has focussed on step 2 (e.g. Huber et al. 1985, Appleby & McRae 1986, Duncan & Kite 1989, Hughes 1993, Petherick et al. 1993, Struelens et al. 2005), but much less is known about step 1 and 3.

Ethologists often claim that the preferences of our farm animal species and those of their wild ancestors are the same. There are however examples of the opposite, e.g. nest location selection in the domestic hen. Domestic hens kept under semi-natural conditions choose a location for their nests some distance away from the flock (McBride et al. 1969, Duncan et al. 1978), but the same birds kept under commercial conditions will not only refrain from isolating themselves but even actively choose the same nest as other birds have used or indeed are still using (Appleby et al. 1984). There are a number of possible explanations for why hens should have a propensity to lay their eggs in the nests of other hens, including intra-species nest parasitism and risk of predation. Although nest location selection has been studied in feral hens, little is known about whether they also lay some of their eggs in the nests of other birds.

Many hens in modern production systems show symptoms of severe frustration during the pre-laying period, when the housing conditions, for one or another reason, restrict the hens in their nesting behaviour (Duncan 1970, Wood-Gush 1972, 1975). This results in pacing and increased aggression, and thus should be avoided. Apart from constituting a welfare problem to the animals, unsatisfactory conditions for nesting behaviour have considerable economical implications since this can interfere with the collection of eggs produced. Unattractive nesting conditions may result in floor eggs, i.e. eggs laid outside nest boxes (Cooper & Appleby 1996). Floor eggs require a manual effort in order to be collected and there is a risk that the eggs will be contaminated, resulting in reduced value of the eggs. In addition, the loss of eggs may be increased, as floor eggs are often broken (Guesdon & Faure 2004). The welfare of the laying hens and the profitability of the system thus greatly depend on the nesting behaviour that the hens are allowed to express. Due to the high number of eggs produced during a hen’s lifetime (>320), the potential of improving both welfare and economical aspects by optimising the conditions for nesting behaviour is huge.