Lesser Black-backed Gull (graellsii & intermedius)

(last update: May 17 2015)

Lesser Black-backed Gull 1cy J8PL July 31 2011, Troms, Norway. Picture: Morten Helberg.

Ringed pullus, Larus fuscus ssp. At least one bird from this ringing section, J7PU already has a life history within 2 months, as it was observed on 26 September 2011 in Dumpiai near Klaipeda, the Lihuanian coastline and no doubt this individual will turn out to be nominate fuscus.

Juvenile nominate fuscus from the breeding grounds in N Europe can be found in the sections August & September. Below, we describe migration to the wintering grounds from north Norwegian ring recoveries. Five Norwegian authors, Morten Helberg, Geir Systad, Ingve Birkeland, Nils Lorentzen & Jan Bustnes published an article with this title in Ardea 97, 2009. The complete PDF can be found HERE. In this section, we only describe in short the findings regarding juveniles.

Northern Norway: breeding ground for dark-mantled and pale-mantled LBBG

Traditionally, two subspecies of LBBG could be found in Norway: dark-mantled nominate fuscus in the north and pale-mantled intermedius in the south. Last decades, nominate fuscus breeding figures have dropped dramatically, while those figures for pale-mantled birds have increased. Nowadays (but already from the late 1980's) pale-mantled birds, either with origins in graellsii-land or colonisers from south Norwegian intermedius-land can be found way up in northern Norway.
Extensive ringing programmes in southern Norway show that juvenile intermedius follow the 'western flyway': from S Norway, through the North Sea bassin down along the Atlantic coast to the Iberian Peninsular and the west African coasts of Morocco and Mauritania. For north Norwegian populations, such migration research was unknown.
The three northernmost counties (Nordland, Troms and Finnmark) were visited from year 2000 onwards, to supply darvic rings to adults (June) and juveniles with body mass >300 gr (July). Darvic rings were used in 12 colonies, with varying numbers of breeding pairs (two pairs to 400 pairs). Three of these colonies held 'pure fuscus' while the other nine colonies held both fuscus and intermedius/graellsii in about equal portions (see Table 1).

All resights up to May 2008 are included in this research. When pulli were ringed in mixed colonies, they could not be determined to subspecies. Between 2000-2007, 1284 juveniles were colour-ringed. 83 birds (6.5%) were resighted in 20 countries. There was a slightly higher probability of resighting juveniles from mixed colonies (7.5%, n=749) than from pure fuscus colonies (4.9%, n=535).
30% were classified as eastern migrants (eastern flyway through Finland, Black Sea, Israel to the Rift Valley) and 70% were western migrants (see figure 2, click on image for enlargement). The direction of migration was irrespective of the colony type (70% and 74% of the juveniles were western migrants in mixed and fuscus colonies respectively).

42 juveniles were seen in winter (1 November - 31 March). 29 from mixed colonies, 13 from fuscus colonies, in 12 countries. 83% of the birds were seen along the western migration route, and there was no difference between colony type. 23 juveniles (79%) from mixed colonies were seen in an area between England/France and Mauritania, 2 in Italy, 2 in Israel and 1 in Cameroon. From pure fuscus colonies, 11 were found between England and Senegal, 1 in Israel and 1 in Kenya. If birds were seen in consecutive years, it was often from the same wintering location again. Winter site fidelity appears to be high.

The probability of resightings from birds following a western route is much higher than from birds following an eastern route, as there are less observers along the eastern route. Hence, the actual proportion of juvenile birds following an eastern route will be much higher. Nevertheless, it is surprising that most of the juveniles from pure fuscus colonies (74%) had a western migration.

Table: