USE OF A BEHAVIOUR PATTERN IN THE STUDY OF OVARIAN ACTIVITY IN THE DOMESTIC FOWL

Cole & Hutt (1953) reported nesting in non-laying ovulating hens and Wood\x=req-\ Gush (1963) showed that nesting behaviour occurs in birds in which the functional oviduct had been removed and also in birds which had been turned into obligatory internal layers by ligating the infundibulum. Wood-Gush & Gilbert (1964) later found that the ruptured follicle was important for nesting behaviour to occur, for in twenty-five birds out of thirty-four in which this follicle was removed or ligated nesting behaviour was affected, while no signi- ficant effect was apparent in the sixty-two control birds which underwent one of three other treatments to the ovary, showing that nesting is highly correlated with the occurrence of ovulation. A striking feature of the behaviour of the original experimental internal layers studies was the high nesting rate. The data suggested that, if nesting behaviour is related to ovulation, the ovulation rate of the birds had been increased. The object of this work was to investigate the nesting rate of a larger number of obligatory internal layers, as a means to studying ovarian function. Brown Leghorns which had completed one laying year were paired for pro- duction and genotype and one of each pair was made into an internal layer. The experiment was repeated using twelve pullets of like genotype which had been in production for only a few weeks. They were randomly divided into two groups of six birds each, and those of one group were made into internal layers. The first experiment was run for 10 months and the replication for five. (The birds were housed in pens containing more trap nests than birds, so reducing competition for nests.) Laporotomy was performed under general anaesthesia and the infundibulum ligated with a coarse silk suture at about the point where it joined the magnum. The wound healed rapidly. Food and water were available in the pens at all times and extra light ensured a minimum day-length of 12 hr. In both experiments the birds were fully experienced with the trap nests used and a bird was classified as nesting only if it had been found in a firm sitting position; i.e. it pecked the investigator on being disturbed or when picked up kept the legs pressed up to the body. The birds were closely observed to ensure that false nesting, resulting from peck-order interactions or other causes, would not confuse the data. It is clear in Table 1 that the nesting rate of each internal layer was greater than the egg production of its paired control. It was also greater than the nesting