The Regional Director for Sea Affairs revealed that the 2020 Common Tern Census, which were conducted during the month of June, concluded that there are currently around 7,950 breeding birds in the archipelago of the Azores.
According to Filipe Porteiro, there were an estimated 3,347 common tern couples (Sterna hirundo), spread over 167 colonies across the archipelago, 630 roseate tern couples (Sterna dougallii), spread over 20 colonies on all islands, except São Miguel, and one sooty tern couple (Onychoprion fuscatus) nesting on Praia Islet, Graciosa Island.
The Regional Director pointed out that, compared to the census conducted in 2019, this year's figures “are much more encouraging” for the common tern, since there were 1,061 more couples, although there were about one hundred fewer roseate tern couples.
“The trend regarding the tern nesting numbers in the Azores is considered stable,” the Regional Director said, noting that “it has been verified that these figures vary considerably from year to year in both species."
Praia Islet on the island of Graciosa, yet no offspring or egg was sighted in the nest."
The Regional Director also highlighted the fact that, on the island of Flores, where more than seven hundred common tern couples were registered, the census team found a common tern that “had been ringed 15 years ago in Capelinhos, Faial Island.”
In this regard, he highlighted the efforts to ring seabirds for the study of the species and the assessment as to whether they return to the Azores and migrate between islands. As he further noted, “the ringing of seabirds allows us to know more about the life cycle of these birds and understand the dynamics related to the migrations they make every year, in addition to the choices they make regarding the islands where they nest."
The 2020 Tern Census was coordinated by the Regional Directorate for Sea Affairs in partnership with the Island Natural Parks and the Environmental Services, involving eight senior technicians, 30 Nature Watchers and four volunteers from SPEA (Portuguese Society for the Study of Birds) and IOMA (Asas do Mar Association - Azores Ornithology Institute).
This census intends to quantify the populations of the two main tern species that nest in the Region: common tern and roseate tern. Both species are classified internationally and very sensitive to disturbances and pressures resulting from human activities and non-native predatory species.
The Regional Director pointed out that “most” tern colonies are located “on cliffs, isolated pebble beaches and inaccessible coastal islets, and only a few can be observed from a distance, from land, through binoculars and telescope.”
This census, carried out across the archipelago, involves sea campaigns, through boat trips around the coast of all islands, “with the number of birds living in each colony estimated with the use of a horn that causes them to fly, allowing them to be counted."
In colonies where visitation is possible, the nesting and egg laying of each species is counted. This monitoring allows to estimate the breeding population of common and pink terns in the Azores and to map the distribution of multiple colonies established on all the islands.
As part of the Marine Strategy Framework Directive, the Tern Census is carried out annually within the scope of the monitoring programme for seabird populations in the Azores, MONIAVES.
This census began in 1989, taking place on an annual basis since 1993 in the main colonies, at the initiative of seabird researchers from the Department of Oceanography and Fisheries at the University of the Azores and IMAR. In the last decade there has been a growing effort to fully monitor colonies across the archipelago.
Since 2016, the Regional Government has been responsible for the coordination of the census. The monitoring and collection of population data on seabirds with regional, community and international protection status, such as the common and roseate tern, is a legal obligation, not only under the scope of the Marine Strategy Framework Directive but also under the Birds Directive (Natura 2000 Network) and the OSPAR Convention.