Ringed Greater Black-backed Gull in Izaro island observed in Ondarroa

During the last century the European population of Greater black-backed gulls Larus marinus was stable or with a slight decrease in their most important breeding areas, in Scandinavia, Great Britain and Iceland. However, in recent years their breeding range has expanded to the French Atlantic coast. This population has reached the Bay of Arcachon in the Gironde.

Greater Black-backed Gull seen in Ondarroa (Photo: Asier Aldalur)

Vídeo made in Izaro spring 2014

In the Basque Country the first observation of a pair of Greater black-backed gull exhibiting territorial behavior happened in 2012. All of them took place in colonies of yellow-legged gulls. Moreover, a couple built their nest in the colony of gulls in Punta Lucero (Zierbena) and other showed reproductive behavior on the island of San Nicolas (Lekeitio), this one also in the midst of a colony of yellow-legged gulls. Furthermore, it was confirmed that a third couple built the nest and laid two eggs that failed to hatch on the island of Izaro (Bermeo). The couple returned to the nest of Izaro island in 2013, where they pulled out a single calf, and, last year, they breed successfully three chickens.

A pair of Black-backed Gulls in the coast. 

With the aim of monitoring the population of this new bird specie of breeding in the Basque Country, volunteers from the Society of Sciences Aranzadi captured and banded the two members of the couple, as well as the four chicks hatched so far. As a result we can know details of the biology of reproduction of this couple, as well as collect data of survival and dispersal. For example, a fisherman from Bermeo found the body of one of the chickens about 3 miles off the coast of Urdaibai, while another has been observed recently in the port of Bermeo. Asier Aldalur, profesional bird bander of Aranzadi, send us kindly a recent photo of the adult female from Izaro in the port of Ondarroa, one of his favorite places during the winter.

Photo Greater Black-backed Gull in Ondarroa (Photo: Asier Aldalur)

If you want to know more about Gulls: http://laruseus.blogspot.com.es/