Fig1: Balearic Shearwater (Puffinus mauretanicus)*

The Balearic Shearwater Puffinus mauretanicus is Europe’s only Critically Endangered seabird with a population thought to be around 3200 breeding pairs (18000-25000 individuals). The breeding population is mostly restricted to the Balearic archipelago but the seas around Cornwall are very important foraging areas especially for young birds.

On their island homes, colonies of Balearic shearwaters are at risk of predation from introduced mammals and they are prone to fisheries bycatch which combined are reducing adult and chick survival. Research by various organisations and individuals is ongoing including satellite tagging which will help target mitigation for bycatch and to highlight areas that are important feeding grounds to afford them better protection.

There has been a northwards shift in at-sea distribution from Biscay to southwest UK in recent years, increasing the numbers in UK waters. This is possibly related to an increase in sea surface temperature although other factors and increased survey effort could also be significant. Climate change could see the importance of the UK increasing further for this critically endangered seabird.

Fig2: Balearic Shearwater (Puffinus mauretanicus)*

August and September are good months for spotting Balearic shearwaters around Cornwall’s coast. They often come quite close to shore but care is needed to not confuse them with the closely related Manx shearwater. The Balearic is slightly larger than the Manx brown above and quite pale and ‘dull’ below (unlike the Manx which is black above and sparkling white below), this can be tricky in poor/light/glare when Manxies look browner. It flies with rapid, shallow wingbeats on stiffly held wings. It will rest on the water, and also plunge-dive for food.
It is hoped that a planned coordinated land/sea survey around the coast from Dorset to Lundy on one day in mid August by RSPB and MARINElife volunteers and staff will give a snapshot of how many birds are using our seas and where, helping build the evidence to save this beautiful seabird from extinction.

Published: Aug 2015
Claire Mucklow (RSPB Cornwall Projects Manager)

Photos:
*Fig1: Skua 20100427 161943 (12560085194)" by Marcabrera - Skua_20100427_161943. Licensed under CC BY-SA 2.0 via Commons - https://commons.wikimedia.org/wiki/File:Skua_20100427_161943_(12560085194).jpg#/media/File:Skua_20100427_161943_(12560085194).jpg

*Fig2: http://www.marine-life.org.uk/seabirds/balearic-shearwater