|Razorbill showing bill
with white line and two grooves |
beyond it of an adult
During the seabird wreck of February 2014 I looked sufficiently closely at over 50 of the Razorbills washed up in Anglesey to have seen if they had white lines on their bills. As all did, none would have been first or second winter birds. This fits with ringing recovery data from British and Irish colonies, showing the young birds mainly disperse further to the south than the adults. Moreover, on fine winter mornings adult Guillemots and Razorbills sometimes come ashore at the breeding colonies for just a few hours. To do this it must be assumed that they would have been at sea within a few hours flying time of the colonies.
|Peter Hope Jones
surveying for Razorbills |
and Guillemots accompanied by dependant
young in the Irish Sea, August 1981
As information on bill grooves might be of further interest in determining which segments of the Razorbill population succumbed off different parts of NE Atlantic coasts, photos were taken showing the bills of 25 birds on Anglesey beaches. Of these, 14 had the white line plus two grooves (W+2). Five more would be classified as W + 1.5 and five had W + 1. Only one bird was W + 0.5 and was thus probably over age 2 but still immature.
Whether In a few weeks time it may or may not be possible to detect if there are fewer Razorbills ashore in any of the South Irish Sea colonies remains to be seen. Guillemots stand on open ledges where sample sections of whole colonies can be monitored to determine breeding success. This is somewhat more difficult with Razorbills as most lay in crevices or partly hidden under boulders, so estimates of productivity variability are less reliable in this species. Individual long-lived seabirds are known to sometimes skip a year in attempting to breed. Whether more Razorbills will enter this breeding season in poor condition and skip a year is possible and worth looking out for. The proportion of adult Razorbills accompanied by chicks at sea during the immediate post-breeding period in July-August might be an alternative indicator of productivity. The chicks leave the cliffs when half grown and are looked after at sea for about another 6+ weeks by one parent. At sea each small juvenile stays close to the parent, while making frequent high pitched contact calls. Experience from seabird at sea surveys in the 1980s showed that Ad+juv couples are relatively easy to distinguish. They were not scattered thinly all over the whole Irish Sea, but the young had been shepherded to a few favourable areas. Would this be another way to gather supporting evidence for relative breeding success?
This blogpost was written by Ivor Rees, a regular contributor to the Natur Cymru magazine.