THE INFLUENCE OF PHOTOPERIOD ON NEST BUILDING, OVARIAN DEVELOPMENT AND LUTEINIZING HORMONE SECRETION IN CANARIES (SERINUS CANARIUS)

Abstract

SUMMARY Female canaries were exposed to various lighting schedules in January—February to assess the photoperiod necessary for reproductive development. Nest building was not increased with lighting schedules of 8 h light: 16 h darkness per day (8L: 16D) and 10L: 14D but was increased after 4 weeks of 12L: 12D or 14L: 10D. Placing of nest material was greatest with a lighting schedule of 14L: 10D. Plasma and pituitary luteinizing hormone (LH) levels were low when 8L: 16D was used and the ovaries and oviducts remained undeveloped. There was a significant rise in the weights of the ovaries and oviducts with 10L: 14D per day. This change was not reflected in the plasma LH level but the amount of LH in the pituitary was increased. Exposure to 12L: 12D or 14L: 10D caused substantial development of ovaries and oviduct growth, and significantly increased levels of plasma and pituitary LH. These two groups were indistinguishable in all these parameters. Oestrogen treatment of a group exposed to 8L: 16D decreased plasma and pituitary LH in four out of six birds. Behaviourally, some of these birds showed an increase in gathering and placing of nest material. In an oestrogen-treated group exposed to 14L: 10D no effect was seen on plasma LH concentration, but the group showed significantly more gathering and placing behaviour than untreated birds. Oviduct weight was increased in both oestrogen-treated groups.