Jannie Fries Linnebjerg

Sympatric Breeding Auks Shift between Dietary and Spatial Resource Partitioning across the Annual Cycle

When species competing for the same resources coexist, some segregation in the way they utilize those resources is expected. However, little is known about how closely related sympatric breeding species segregate outside the breeding season. We investigated the annual segregation of three closely related seabirds (razorbill Alca torda , common guillemot Uria aalge and Brünnich’s guillemot U . lomvia ) breeding at the same colony in Southwest Greenland. By combining GPS and geolocation (GLS) tracking with dive depth and stable isotope analyses, we compared spatial and dietary resource partitioning. During the breeding season, we found the three species to segregate in diet and/or dive depth, but less in foraging area. During both the post-breeding and pre-breeding periods, the three species had an increased overlap in diet, but were dispersed over a larger spatial scale. Dive depths were similar across the annual cycle, suggesting morphological adaptations fixed by evolution. Prey choice, on the other hand, seemed much more flexible and therefore more likely to be affected by the immediate presence of potential competitors.

Foraging Ecology of Three Sympatric Breeding Alcids in a Declining Colony in Southwest Greenland

Abstract. Sympatric nesting seabird species are often found to differ in one or more aspects of their foraging ecology. This is usually interpreted as resource partitioning, potentially due to current or past competition, but other explanations have been proposed. Three closely related species of alcids breeding together in subarctic southwest Greenland differed in several aspects of their foraging ecology during chick rearing. Thick-billed Murres (Uria lomvia) and Common Murres (U. aalge) did not differ in their diving behavior but both species differed markedly with Razorbills (Alca torda). Thick-billed Murres foraged mainly close to the colony, whereas Common Murres and Razorbills also made foraging trips to the mainland coast. Common Murres made significantly more bouts (series of dives) per trip than Thick-billed Murres, but significantly fewer dives per bout than Razorbills. Median dive depth of Thick-billed and Common murres was twice that of Razorbills. Thick-billed Murres nested on open ledges and spent most of their non-foraging time on the ledge attending the chick. Common Murres and Razorbills nested under boulders and in crevices and often left their chicks alone (particularly at night) and rested on the water. One interpretation of this pattern is that the risk of predation from Glaucous Gulls (Larus hyperboreus) was much higher on open ledges, and that Thick-billed Murres therefore had to guard their chicks at all times.

Effects of oil and oil burn residues on seabird feathers.

It is well known, that in case of oil spill, seabirds are among the groups of animals most vulnerable. Even small amounts of oil can have lethal effects by destroying the waterproofing of their plumage, leading to loss of insulation and buoyancy. In the Arctic these impacts are intensified. To protect seabirds, a rapid removal of oil is crucial and in situ burning could be an efficient method. In the present work exposure effects of oil and burn residue in different doses was studied on seabird feathers from legally hunted Common eider (Somateria mollissima) by examining changes in total weight of the feather and damages on the microstructure (Amalgamation Index) of the feathers before and after exposure. The results of the experiments indicate that burn residues from in situ burning of an oil spill have similar or larger fouling and damaging effects on seabird feathers, as compared to fresh oil.

Breeding biology of Fluttering Shearwaters (Puffinus gavia) on Burgess Island in northern New Zealand

ABSTRACT The Fluttering Shearwater (Puffinus gavia) is an abundant seabird endemic to breeding colonies in northern and central New Zealand. The species remains poorly studied, and here we present the first study to examine its breeding biology in detail. Fluttering Shearwater nests were monitored from laying in September to fledging in January 2016 on Burgess Island in the outer Hauraki Gulf, northern New Zealand. Nine (22%) of forty-one natural nests were located under dense vegetation on the ground. Eggs were laid over a period of 39 days with laying peaking on 12 September. Incubation length was 50.0 ± 3.7 days and chicks fledged after an average of 74.2 ± 4.3 days, from late December to the end of January. Chick growth corresponds to the pattern observed for other Procellariiformes, gaining body mass rapidly to a maximum of 115% of adult mass, and then losing mass until fledging. Chicks were fed most nights throughout chick-rearing. Breeding success was 63.8% and similar to other Puffinus species breeding in pest-free colonies. This study provides baseline biological data for a poorly studied, yet common, New Zealand endemic seabird. The obtained new information will allow for further ecological investigations and improved conservation management.