In the natural breeding season stimuli from the nest which the female canary has constructed are instrumental in bringing nest-building to an end shortly before the first egg is laid, but active nest-building can be reduced at any time by substitution of an artificially constructed nest with a small internal diameter and grassy texture for the standard plastic canary nest-pan (Hinde, 1958). Conversely, if the material placed daily in the nest by the female is constantly removed nest-building continues for long periods at a high level (Hinde, 1965). Tactile stimuli from the nest are received by skin receptors in the ventral brood patch; this develops, under the influence of oestrogen and other hormones, during the pre-laying period and involves local defeathering, and an increase in vascularity and in sensitivity to tactile stimulation (Hinde, 1962; Hinde, Bell & Steel, 1963). The question arises whether, in an intact female, tactile stimulation reduces nest-building by lowering ovarian oestrogen production or by some other means such as an alteration in the responsiveness of central behaviour-controlling mechanisms to continuing high oestrogen levels.
Elizabeth Steel and R. A. Hinde
ELIZABETH STEEL and R. A. HINDE
Intact female canaries were either treated with pmsg and kept on long (20 hr light/4 hr dark) or short (about 10 hr light/14 hr dark) photoperiods from 1st March or were untreated and exposed to natural day lengths (Cambridge, England). Of the pmsg-treated birds, 65% laid after about 10 days, the latency being unaffected by the day length. Untreated birds laid over a month later.
Of the pmsg-treated birds which produced eggs, those kept on long photoperiods built nests much more on Days 5 to 2 before egg-laying than did those on short photoperiods. The difference is unlikely to be due merely to the longer time available for building, and suggests that the light regimen has a non-pmsg-mediated effect on building.
SUSAN GOSNEY and R. A. HINDE
M.R.C. Unit on the Development and Integration of Behaviour, University Sub-Department of Animal Behaviour, Madingley, Cambridge CB3 8AA
(Received 10th May 1975)
Budgerigar (Melopsittacus undulatus) reproductive development is affected by the photoperiod (Putman & Hinde, 1973), and nest-hole entry by the female is accelerated by oestrogen (Hutchison, 1971). In the canary, long photoperiods affect nest-building behaviour, not only by the classical hypothalamus—pituitary—gonad route, but also by influencing the effectiveness of exogenous oestrogen in ovariectomized birds (Steel & Hinde, 1972). The present experiments were designed to assess whether the latter effect occurs also in the budgerigar.
Ovariectomy was performed by suction and cautery under sodium pentobarbitone and ether anaesthesia. After the operation the birds were transferred singly to the experimental cages and kept on an 11 hr light:13 hr dark (11L : 13D) regimen for 2 days. The nest-box entrance was then opened and the birds tested for a further 7
Elizabeth Steel, Susan Gosney and R. A. Hinde
In the canary, the nest-building response of ovariectomized females to exogenous oestrogen is affected both by the length of the photoperiod (Steel & Hinde, 1972) and by male vocalizations (Hinde & Steel, 1976). Gosney & Hinde (1975) showed a similar effect of photoperiod on an analagous behaviour in the budgerigar; oestrogen-treated ovariectomized birds entered the nest-box sooner and spent longer periods within if kept in a long-day than in a short-day photoperiod. In view of the essential role of male vocalizations on reproductive development in the female budgerigar (review by Brockway, 1969) the present paper investigates the effect of male vocalizations on hormone-induced nest-box occupation by ovariectomized female budgerigars.
R. A. HINDE, ELIZABETH STEEL and B. K. FOLLETT
Nest building was induced in ovariectomized photosensitive canaries with a standard dose of oestradiol (0·05 mg thrice weekly) at various times of year. On a range of daylengths between 6 and 18 hr light/day, building behaviour tended to be more intense if the birds were exposed to long photoperiods. A similar result was found in photorefractory birds, both intact and ovariectomized.
Differences in building were unlikely to have been due solely to the amount of time available to birds on different photoperiods as hourly building rates still revealed a difference between groups. A marked difference in the latency of the response to oestrogen was found in the refractory birds.
Ovariectomy was not complete in many birds but the evidence from such birds and from the few which had been totally ovariectomized, as well as from those in the refractory period when long days did not result in ovarian growth, showed that endogenous oestrogen secretion was negligible.
The effect of long photoperiods in augmenting the induction of nestbuilding by oestrogen could not be reproduced by injections of either ovine or avian LH. This and other evidence suggests that a direct effect of gonadotrophins is not involved.