April 1932 – vol. 25, issue 11–313 THE incubation-period of the British Lesser Black-backed Gull (Larusf. graellsii) is not known. In the Practical Handbook is the statement under this species : " Period said to be 21 days (Paynter), but estimate appears low". On the island of Skokholm, Pembrokeshire, I was able to obtain the following nine records in 1931.BRITISH LESSER BLACK-BACKED GULL. Dates of Laying est Jo. 1st egg. 2nd egg. 3r... This article is only available to registered users.To read more, please log in or purchase a subscription.