The photoperiodic control of concentrations of luteinizing hormone in male migratory chaffinches Fringilla coelebs L.

Abstract

Plasma luteinizing hormone (LH) levels in migratory male chaffinches exposed to natural lighting in northern Italy were seasonally high during May and June. In birds held on a fixed short day length of 8 hr light: 16 hr darkness from February to July, plasma LH levels increased slowly reaching a low plateau in July. The seasonal fall in plasma LH levels in June was not reversed by transferring the birds to continuous light in October and February: the larger increase was observed in February. It was concluded that the initiation of breeding may involve an underlying Autonomous increase in reproductive function, and that breeding is terminated by the development of absolute as opposed to relative long day refractoriness.

Key words:

• Luteinizing hormone
• Daylight effect
• Breeding
• Migratory bird
• Fringilla