Studies of pre-breeding Fulmars (Fulmarus glacialis), their recruitment to breeding populations and intermittent breeding
The aim of the study was to attempt to identify prebreeding Fulmars and study their behaviour and look at their recruitment and intermittent breeding in general. Over 300 unringed Fulmars of unknown breeding status were caught and ringed during the study but it was not possible to positively identify a prebreeder from breeders. By looking at attendance at colonies throughout the year at confirmed nest-sites and potential nest-sites it was concluded that non-breeding birds were present throughout the prebreeding period although confirmed nest-sites were occupied more often and for longer. Also by looking at individually marked birds and comparing Fulmars of unknown breeding status with birds known to have bred, it was concluded that the latter category arrived earlier in the year in general. Fulmars not known to have bred before were more mobile within the colonies than breeding birds but little was established about dispersal to other colonies except one bird of unknown breeding status ringed on Eynhallow, Orkney, which was recovered at a colony in the Faeroes. The number of unringed Fulmars associated with Eynhallow but not breeding there was estimated about 1400-3100 birds. Intermittent breeding of Fulmars was found to fluctuate considerably between years as did index of recruitment and these two were negatively correlated. On average 28-29&'37 of fulmars which have bred before do not breed each year and that proportion correlated negatively with proportion of eggs hatching. Gaps in the breeding history lasting more than one year were often followed by a change in mate and/or nest-site. An attempt was made to experimentally prevent ten established pairs from breeding by blocking their sites. Time of loss of site was found to be important and the effects of losing the site could last more than one breeding season.