Decrease of Swallows in post-breeding migration

Urdaibai Bird Center has been doing a monitoring of swallow's roosts that are in the reeds of Gautegiz Arteaga during migrations as in years before.

During pre-breeding migration, the monitoring campaign was carried out from March to late May. The first specimens coming from Africa were seen in mid-March. During April could be confirmed that some Swallows had already occupied their nesting places in the farms of Urdaibai, although the great majority of the groups that came every evening, carried on with their trip to the north after have spent the night in the refuge of the reed.

Swallows and Sand Martins resting in the reed

Due to the bad weather we had during almost all the spring, a lot of Swallows lost their first egg-laying, and we also confirmed that Swallow's population have decreased in relation to years before.

During post-breeding migration (the campaign began in August), groups of juveniles who have born in the surroundings, began to gather around the marsh to start their long trip to Africa. More entered in August, the big groups (above all juveniles coming from the north) began to gather, being able to gather in the roost from a few hundred or even thousands of them.

How reed looks while is used as a roost

In this month, we could see that the number of Swallows that have used the roost has decreased significantly comparing with years before, either because of the bad year for reproduction, or the migration has been delayed for other reasons and they are still coming. Although in the last days we have seen an increase in the number of specimens that come to use the reed, it has nothing to do with the population that could be expected in the roost for these days.

Swallows and Sand Martins resting during the day while they are migrating