Both the Guillemot Una aalge and the Razorbill Alca torda have an unusual breeding system in that the young leaves the breeding site when only partly grown and is taken to sea by the male parent; the female continues to visit the breeding site for up to several weeks before she too leaves the colony (Varoujean et al. 1979; Wanless & Harris 1986). Soon after their


Stay at the forefront of British birding by taking out a subscription to British Birds.

Subscribe Now