The Guernsey population has seen a steady increase over the past 25 years. It is difficult to say whether this has been because of increase in the local resident population or an increase in the number of migrants.
Migrants start to arrive in August and moult here and there is a very small increase in November, presumably of birds that have moulted elsewhere. Birds begin to return to the breeding areas in March leaving 100-200 mostly non-breeding birds on the island's beaches.
Although widespread at low tide, birds tend to roost in a small number of large flocks, the largest being on Lihou. Other smaller flocks roost opposite the Fish Factory (Rocquaine), at Portinfer and on Omptolle, an island off the north-east coast of Guernsey.