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

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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.

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