This is a translation of a paper by the Faroese ornithologist Bergur Olsen
Ritan í minking
(Link to the original paper in Faroese with pictures and graphs. The paper is in PDF format (Acrobat Reader needed)).
The translation is here brought with permission from the author, December 2007
The most common gull specie
The situation in the northern hemisphere
No youngs the last two years
The population out of balance
Lack of nourishment
Shortage of sand-eel
Ridebestanden omkring Færøerne aftager, fordi der kommer for få unger på vingerne. De sidste fire år har været ualmindelig dårlige for riden. Årsagen er formentlig, at der for for lidt føde, specielt for lidt af tobis.
Kun 55 % af rideparrene plejer at få en unge i normale år og det er for lidt til at holde bestanden i balance. Men en del af de unger, der kom på vingerne i de gode år 1999 - 2002, er nu en del af ynglebestanden. Derfor er der mulighed for, at ridebestanden kan komme på fode igen.
The most common gull species
The population of kittiwakes around The Faroe Islands is decreasing, because too few youngs are fully-fledged. The last four years have been exceptional poor for the kittiwake. The reason why is probably shortage of food, especially to little of sand-eel.
Only 55 % of the pairs of kittiwakes normally succeed in raising one young every year and that is too little to keep the population i balance. A part of the youngs, which was a part of the good years 1999 - 2002, are now a part of the breeding population and therefore the kittiwakepopulation have a good chance of increasing again.
The kittiwake is a kind of gull and the most common gull in the world. Besides it is the kind of gull best fitted to breed in steep cliffs, where it builds a strong nest of soil, clay, grass and other things, which is "glued" to the rock. It returns to the same nest year after year, but build a new nest every year, because the nest usually has disappeared in the course of the winter. The kittiwake is also the kind of gull, which is best fitted to manage the open ocean. Although it can't dive, it finds all its food in the sea. It can only reach half a meter below the surface. It survives eating fish fry and other living creatures in the surface of the sea. Besides this, it feeds with the fishing vessels, both the food coming up along with the trawl and the waste of fish thrown overboard by the vessels.
The kittiwake populations are decreasing in most of the bird mountains on the northern hemisphere. And The Faroe Islands is no exception to that fact. To make a common evaluation, the group CBird, Circumpolar Seabird Group has begun to collect information about the kittiwakes, which is hold by counters of birds. Fiskirannsóknarstovan, Faroese Fisheries Laboratory, is the representative of The Faroe Islands in this group under the organisation CAFF, Conservation of Arctic Flora and Fauna.
In former time, it was common to catch kittiwake youngs as food around Ólai (the 29th of July), when the youngs were fully-fledged. But this catch has been very limited the last 50 years, among other reasons, because there have been so few youngs. Since 1988 it has been counted, how many youngs in average, which have been raised and fully-fledged in Høvdanum on Skúgvoy. There are also counts from 1982 and 1986. The result of these countings have shown very great difference in the breeding success from one year to the next.
The kittiwake often lay 2 eggs, so in the good years, there are more than one young in every nest. This has though seldom been the case since the countings began. On the other hand, there have been more years, where no youngs have been fully-fledged. And it looks like, that these years have become closer and closer. The first year with no youngs was in 1992, then 4 years passed, before it happened again in 1997 and 1998. It was the first time two years came in a row, but it happened already 4 years later, where 4 years came in a row, the years 2003 til 2007. The last two years no young have been fully-fledged.
The countings before 2001 were random samples. Since 2001the whole location has been counted and all youngs registered. This gives a more precise view of how the populations is decreasing. The number of fully-fledged kittiwakes has declined from around 6.700 to 0 in three years and the number of nests has declined to below the half. It is to be noted, that it is only in the very successful years 2001 and 2002, that the kittiwakes have managed to have two fully-fledged youngs. These later years, most of the pairs have got only one young as the second often died shortly after being hatched.
It is estimated, that 15 % of the kittiwake population dies every year and when no youngs comes to their wings more years in a row, the population quickly decline. To keep the population in balance, 70% of the pairs must have a fully-fledged young every year, because many of each years generation, dies before becoming sexually mature. In the 21 year, that we have counted, only 55 % of the pairs have had a fully-fledged young every year and that is too little to keep the population in balance. The kittiwake is 5 years old, before it lays it first egg, so a part of the good years 1999 - 2002, are now a part of the breeding population. It is there fore possible, that the population can increase again, if the circumstances are becoming better.
The total Faroese breeding populations was for the first time counted in 1987 and was at that time 230.000 nests. 10 years later the number had declined to 160.000. In the summer 2007 the count is repeated and we will then know, whether the situation is as critical, as the results from Skuoy evidently indicate.
The reason why so few kittiwake youngs are fully-fledged, is probably lack of food. This lack of food has been the case for a longer time, because when the kittiwakes have begun building their nest in May, these later years, there have been build fewer nests than expected. This decline in the number of nests indicate, that no youngs have entered the populations but hopefully, the situation is not that bad. More reasons can be. The food could go too deep in the sea, so it has been out of reach of the kittiwakes. Maybe the food has been too far away.
The most probably reason is lack of food, because it has not only been a problem for the kittiwakes, to get enough food. These later years have also been exceptionally bad for the artic terns, which have a way of feeding alike the kittiwakes and aren't able to dive. But also the puffins and guillemots have had difficulties in finding food, though they are able to dive as deep as 50 to 100 meters. For no known years before, the "fleyging", the catch by nets, have been so low as in 2006 (and 2007, translator's note).
Sand-eel is the most important food for all these birds, so the population of sand-eel must be in crisis. Sand-eel is also the main food for different species of fish, caught around The Faroes. It is therefore to be welcome, that money have been granted for counting especially sand-eel in the year 2007.