this Sunday have been watching two different species of Redshank in the center of interpretation of Raco de L'Olla. Along with avocets, stilts, jars, terns, ducks and gulls have appeared two figures is not very common sight in these places and more at this time, there are two species of Redshank, the clear Redshank (Tringa nebularia) and Spotted Redshank (Tringa erythropus .)
is a pleasant surprise to find two specimens of these species feeding on the lagoon, first by the lack of sightings of both species throughout the Mediterranean and, secondly, because due to the dates on which we , individuals of these species should be in their breeding areas far from the gaps in the Albufera Natural Park.
Both dark-clear Redshank are ivernantes species in very small numbers and specific points of the English coast.
For Tringa erythropus is a species that breeds in the open forest tundra in northern Europe and Asia and is distributed throughout the year so widely dispersed throughout Europe and can reach points of equatorial Africa remain a long-distance migratory in Spain can be seen during pre-and post-nuptial migration.
This species has a winter in Spain is scarce and highly concentrated in the marshlands of the Guadalquivir and Ebro Delta (85% of sightings).
Tringa
nebularia has many aspects of their ecology similar to T. erythropus as breeding sites overlap and dispersal strategy and migration follows similar patterns, however T. nebularia tolerates salinity ranges in the wetlands which is located this species (euryhaline), found in saline wetlands, brackish and fresh water and therefore the alternatives on the species when the winter. Thus we find both in the Mediterranean wetlands and the Ebro delta and the Salinas de San Pedro del Pinatar (Murcia), as in the wetlands of North and West English as Villaviciosa and the estuaries of Arosa or estuary the Umia in Galicia.
Therefore, if both should now be breeding in the tundra of northern Europe and Asia for thousands of miles from the Albufera ... they are doing these two guys here? Three options are being considered for the moment, in the first place could be that these individuals had been disoriented during migration due to bad weather and have ended up lost on our shores. This option is not new for every year individuals of species listed what is known as the Nearctic (provinientes of America). Last year was sighted up to 5 Pectoral Sandpiper, Calidris melanotos in marshes of the lagoon or Northeast Asia as two years ago with the Agujeta escolopacea ( Limnodromus scolopaceus ) appeared in the Albufera proviniente of the North Eastern shores of Russia.
Another option being considered is to try juveniles as there are cases of waders in which nuptial migration not perform all individuals but only those who can ensure reproductive success. So young individuals do not perform the migration at least in its first year of life, for the Curlew Sandpiper (Calidris ferruginea ).
The third option is an intermediate solution to the first two ie, that individuals found in the lagoon are individuals who have begun the migration and who have exhausted energy reserves during the same so have had to stop halfway to regain strength and feeding. It is known that migration is an activity that consumes an enormous amount of energy and also the long distance migratory birds, as in the case before us, obvious geographical references used for guidance in your trip, so the migration routes birds usually pass through the Mediterranean and Atlantic coasts is so easy that due to the weakening of individuals have finished their journey into the lagoon. This stop dates that are being caused these individuals we see in the Raco de L'Olla have not been replicated this year.
