Nest-site attendance and foraging ecology of the Northern Fulmar (Fulmarus glacialis) on the Faroe Islands. Is the Northern Fulmar a useful indicator of ecosystem productivity and pollution?

Detta är en avhandling från Department of Biology, Lund University

Sammanfattning: Popular Abstract in English As far as we know the Northern Fulmar (just referred to as Fulmar from her on), did not start breeding on the Faroe Islands before about 150 years ago. But it has been known by the Faroese for a long time. Mainly as a bad omen and according to folklore fishermen would return home if they encountered Fulmars when out at sea, since they believed it was the bringer of storms. The Fulmar has increased in numbers fast since it started breeding on the Faroe Islands, and is today the most common seabird species on the Faroe Islands, with an roughly estimated population of about 600,000 pairs. Although it is a "new bird" on the Faroe Islands, no other seabird species is today used to such extend for human consumption. After the Fulmars started breeding on the Faroe Islands they were used for bait by fishermen, but it is said that at some point an old man did not have the strength to go out fishing anymore so he started eating the "the bait" Fulmars instead, and thus started the tradition of eating Fulmars on the Faroe Islands. The Fulmar only feeds out at sea and because of its abundance it is considered a significant consumer of resources from the Faroese marine ecosystem. Despite this, remarkably little is known about the life-history of this gracious souring bird since no study has been done about the Fulmar on the Faroe Islands. Although it has been mentioned in various scientific work up until the 1950's, and even got some pages in James Fisher´s seminar work on this species in 1952, no study has focused solemnly on the Fulmars ecology on the Faroe Islands. Because of its importance from mainly a scientific, but also from a cultural point of view I decided to study the ecology of this bird species on the Faroe Islands. The focus of my work was: -a detailed study about how much time the birds spend at the colony and when they are visiting the colony or the "nest-site attendance patterns" and what physical and biological factors determined the observed patterns -a diet study to see what the Fulmars eat and thus where it "belonged" in the Faroese marine ecosystem. This was also done to try to study the Fulmars´ reliance on commercial fisheries, since there is a lot of so called "offal" from ships (e.g. intestines from gutted fish, bait etc) that the birds might eat -since the Fulmar is a surface feeder, i.e. not a diving seabird, it takes all its food at the surface and is known to come in contact with marine litter this way, probably because it reminds the birds about some of the planktonic food they eat out at sea. In order to investigate to what extent Fulmars get polluted by ingesting plastic I cooperated with the international working group on marine litter Save the North Sea. In order to study the nest-site attendance two colonies were used, one located on a cliff by the sea while the other was a so called "inland colony" located about 1 km from the sea. At the colony by the sea, nest-site observations were done from 2004 to 2007 with binoculars and surveillance cameras with infrared leds. These cameras were able to "see" during the night making it possible to observe the birds day and night all year long. This was necessary in order to study in greater detail individual nest-site patterns and breeding ecology. At the inland colony observations were done with binoculars only and number of birds counted at the end of each month from 1995 to 2009. This was done in order to study the effect wind, temperature and marine ecosystem productivity had on nest-site attendance. In both colonies most birds were seen in April, when pairs are strengthening the pair bonds and copulating. This was followed by an abandonment of the nests until late May, when the eggs are laid. This abandonment of the colony has sometimes been called the "honeymoon" but nowadays its more commonly called the "pre-laying exodus". Interestingly the cameras revelled that the birds only stayed at the colony during daylight and that there decision regarding when to arrive to, and depart from the colony was totally dependant on when the sun was rising or setting, respectively. Furthermore the amount of time they stayed at the colony each day was determined by the length of the day. This I interpreted as a strong indication that the birds were out at sea looking for food during the night. The colony by the sea was more or less abandoned in September with birds returning in December, while at the inland colony, which was bigger, the birds were present all year except in October. It is unclear why there was a difference between how long the birds stayed at the two colonies, but one explanation could be that the birds in the smaller colony left earlier and returned later then usual because that colony was also used for other studies (not included here), that might have disturbed the birds. During the so called non-breeding season (from December to March) the number of birds attending the colony seemed to be regulated by wind, or rather by wind speed. This is not so strange considering the energy a soaring bird like the Fulmar can save when using the wind. But interestingly, during the breeding season (from April to August) the number of birds attending the colony was determined by how productive the marine ecosystem close to land was. This was probably because the birds are restricted in how far away they can go in search for food during the breeding season since the chick needs to be fed on a regular basis, especially when it is young. Although the Fulmar is not a picky bird when it comes to food, and will eat almost anything it can swallow it had a preference for fish which was the major food source. But they also ate squid, polychaetes, crustaceans and various scavenged prey, even small birds unlucky enough to end up in the water. What was really surprising and very interesting was that the mesopelagic Glacier Lanterfish (Benthosema glaciale) which lives at around 400 meter depth dominated in the diet. The obvious question is how did the Fulmar, who can barely dive to 2 m depth eat a fish that lives at 400 m depth? As it turns out this fish species comes all the way up to the surface looking for food (zooplankton) during the night, where the Fulmar might get hold of it if it was able to forage out at sea during the night. This strengthen the earlier mentioned idea that the Fulmars are indeed out looking for food during the night. Because of what is know about the Fulmars feeding habits and how exposed it is to marine litter, the international Fulmar study group Save the North Sea (SNS) uses the Fulmar for their studies on how polluted the North Sea is with plastics. The Faroe Islands were used as a reference area to the North Sea since it was deemed to be relatively clean. The policy target is that less then 10% of the Fulmars have more then 0.1g of plastics in the stomach. But shockingly 58% (varying between 46% and 78% between different places) of the birds had more then this amount of plastic in the stomach.