Volunteers wanted to help count Barn Owls in Portugal | Biodiversity

The community is being challenged to participate in the first Barn Owl census to quantify this species which is decreasing in Portugal and which is a “partner” in the investigation of small mammals or in the protection of heritage.

“We need all eyes and ears attentive in as many places as possible to get as much information about the species”, said this Friday, March 10th, to the Lusa agency Inês Roque, researcher at the University of Évora and volunteer at the Portuguese Society for the Study of Birds (SPEA), entities promoting the national census.

The objective is to know the distribution and abundance of the barn owl, whose population has been decreasing in Portugal.

This nocturnal bird lives close to people and often nests in buildings, so promoters challenge the community to participate in the census. Between this Friday and Sunday, the second “barn owl weekend” will take place, in which volunteers from all over the country are invited to spend at least ten minutes in the street, after dark, and to report barn owls they have seen or heard.

Audible contacts or sightings of the bird and nests can be reported at any time.

The researcher said that schools are also being involved in the initiative, with, so far, 1621 students enrolled in 40 schools in 29 municipalities, from Braga to Vila do Bispo (Algarve). Face-to-face actions were also carried out with more than 500 students.

“Everybody, regardless of experience level, can participate”, said Inês Roque.

The first results collected in this census may be released during the month of April.

Barn owls have been decreasing

Despite being present from north to south of the country, the population of the barn owl has been decreasing and there are several threats that the species faces: roadkill, alteration and destruction of habitats, the increase in extensive agriculture, the bioaccumulation of some pesticides in their adipose tissue, the looting of nests and even the “negative image” due to their association with death.

The barn owl is a medium-sized nocturnal bird of prey (about 35 centimeters long), with white plumage on the heart-shaped face and gray and orange dorsal plumage. When seen in flight at night, it may appear as a white lump and may be identified by the sound which, in adults in flight, is shrill and “scratched”, resembling that of a stiff pulley.

On Saturday, in Tarouca, district of Viseu, the project “Placement of nest boxes in the monastery” will be presented.

The monastery is that of Santa Maria de Salzedas, where three nest boxes were installed with the aim of encouraging the owls to return to the building and “restoring the environmental and ecological balance”.

This is an initiative of the Northern Regional Directorate of Culture (DRCN), in collaboration with the Parish Council of Salzedas.

In a statement, the DRCN said that the presence of barn owls in Salzedas Monastery “is not new”, but that the species seems to have “abandoned” the historic building a few years ago.

Now, he added, the expectation is to restore the population of owls in this habitat, as their presence is a deterrent to pigeons, considered one of the greatest threats to built heritage.

Investigating the Barn Owl since 2006, the University of Trás-os-Montes and Alto Douro (UTAD), in Vila Real, has already collected 6500 regurgitations of this bird, from which it removed about 23,000 prey.

“By analyzing the regurgitations in the laboratory, we were able to understand what kind of rats we have in that region. It is a time-consuming methodology in the laboratory, but in terms of results it is quite enriching because it brings a lot of information about the presence of small mammal species”, he said. to Lusa Hélia Gonçalves, researcher at the Laboratory of Fluvial and Terrestrial Ecology at the Center for Research and Agro-Environmental and Biological Technologies at UTAD.

Barn Owl Regurgitations
Rui Gaudêncio

An excellent bioindicator

The nocturnal bird is considered a partner in the investigation and was also a source of information for the construction of the new Red Book of Mammals of Mainland Portugal, which should be launched in April and which had the collaboration of UTAD.

Hélia Gonçalves explained that the barn owl essentially feeds on mice, but can also catch birds or bats. Swallows prey whole, absorbs soft tissues; the bony structures, feathers or fur are in a cavity of the predator’s digestive system which is then regurgitated.

“The most I’ve identified so far in a regurgitation was ten rats”, pointed out the researcher, who mentioned that the average number of prey found is four.

But studies of barn owls, namely their feathers, also help to monitor environmental contaminants (mercury and pesticides).

“This owl hunts where we produce our food. It is an excellent candidate for a bioindicator of agricultural source contamination”, stated, in turn, Inês Roque.

The researcher from the University of Évora said that nests are monitored annually, which starts in April at Companhia das Lezírias, monitoring the development of juveniles and scientific ringing.

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