lunes, 9 de febrero de 2009

January 2009: unprecedented 'white gull influx' [Enero de 2009: entrada sin precedentes de 'gaviotas blancas']

Larus hyperboreus 2w. Camariñas, A Coruña. 1.2.2009 © Ricard Gutiérrez

January 2009 has totalled a minimum of 28 Iceland Gulls (Larus glaucoides) and 33 Glaucous Gulls (Larus hyperboreus) in Spain (Rare Birds In Spain, January 2009 reports page). These numbers clearly are above the average of the period 2001-2008 in which data from the RBS website has been analyzed: 3,75 birds/January for glaucoides and 2,375 birds/January for hyperboreus, with a peak in 2005 before this extraordinary year 2009 results (figure 1). A late record from 31.1 of a Kumlien's Gull Larus glaucoides kumlieni is not included in this analysis.


Records of both species were concentrated along the NW coast, particularly around A Coruña province that collected 11 glaucoides and 11 hyperboreus, a 39,29% and 34,28% respectively of the individuals recorded per species. Records, however, reached the Canary Islands, indicating an Atlantic bias in the sightings, with Glaucous gull reaching three islands (only three previous accepted records for the islands) and one sole record for Iceland, the 2nd for the archipielago (read more in the Aves Canarias blog here), see figures below.

On 24.1.2009 a heavy storm, named Klaus, brought heavy winds to the Atlantic seaboard of Spain, even reaching the Mediterranean, where human casualties were unfortunately produced by severe winds. This storm brought hundreds of Kittiwakes Rissa trydactyla overland from the Atlantic to the Mediterranean and across inland Spain, being also frequent in the Atlantic harbours (read more in the Birdspain blog here or here for the Canary Islands situation).

Given this situation it is interesting to learn if the 'white gulls' above average arrived before or after the storm: Iceland gulls arrived clearly before (see figure below) at least to Galicia, later widespreading West and South (and further more even into the Mediterranean in February 2009). Glaucous gulls, however, showed higher numbers after the storm of 24.1 (see figure below).

gca: Gran Canaria; lzt: Lanzarote; fue: Fuerteventura; pon: Pontevedra; aco: A Coruña; lug: Lugo; ast: Asturies; can: Cantabria
compiled from data in Rarebirdspain.net (January 2009 bird news) © Ricard Gutiérrez


Movements in adults of Kittiwake towards their breeding grounds have been exposed as an explanation after the large proportion of adults involved in inland sightings. Unlike Icelands (only 2 adults reported out of 28 birds: 21.1 Pontevedra and 24.1 Fuerteventura), Glaucous gulls showed a larger proportion of adults (6 out of 32 birds). It may be the case, therefore that the storm could have also affected 'white gulls' populations on the move northwards to their breeding grounds besides mid-Atlantic birds. An Nearctic origin cannot be discarded since on 31.1.2009 one and another on 1.2 plus 3.2 Kumlien's Gulls, all adults, were noted.

It will be interested to follow the situation into February 2009 to see the spread of the arrival and to attempt a quantification of the episode, a difficult task though.

Larus glaucoides 1w. Cariño, A Coruña. 31.1.2009 © Ricard Gutiérrez


Resumen: Enero de 2009: entrada sin precedentes de 'gaviotas blancas'. Se recogieron datos de 28 gaviotas groenlandesas y 32 gaviones hiperbóreos en España en enero de 2009, muy por encima de la media de los años anteriores (ver figura). Las citas se concentraron en Enero en el NW, con la provincia de A Coruña con un tercio de las citas totales. También se citaron en Canarias, siendo de las primeras citas para las especies allí. La llegada de glaucoides se produjo antes de la tormenta 'Klaus' del 24.1.2009, mientras que la de hyperboreus es claramente posterior (gráficos). Sobre el origen de los ejemplares no se puede descartar cierto componente neártico como prueban las citas de tres Gaviotas de Kumlien entre el 31.1 y el 3.2.2009. El análisis de las citas de febrero 2009 podrá explicar la expansión de la llegada de gaviotas por el resto de España.