Leeftijd, geslacht, conditie en voedsel van Zeekoeten Uria aalge betrokken bij de massastranding op de Hollandse kust, november 1990

In November 1990, heavily oiled Guillemots washed ashore in The Netherlands following a massive spill of Venezuelan Bachaquero crude’ off the coast. Around 1000 Guillemots were received at rehabilitation centres and an estimated 2000 individuals beached dead. Moderate to high densities of Guillemots were recorded at sea during ship-based surveys in the weeks preceding the stranding (figure I). A sample of 40 Guillemots was dissected, in order to obtain information on age, sex, condition and diet. Most Guillemots were mature (no bursa Fabricii; table 3) and biometrics matched those of Scottish breeding populations (table 1). The diet comprised mainly clupeids (Sprat and Herring), with small quantities of Whiting, Bib, Stickleback, Dragonet and unidentified squid (table 4, figure 2). The results were compared with Guillemots stranded in February 1992 and May 1985 and it was shown that the age composition was significantly different from the later strandings (more adults), while sex-ratio and biometrics were similar. Birds stranded in May took mainly sandeel.