They weigh about 20 grams and look incredibly delicate. Yet they return to the Iberian Peninsula each year after traveling more than 5,000 kilometers, from the Gulf of Guinea in Africa where they spend the winter. They fly nearly nonstop across the Sahara and the Mediterranean, braving rain and sand storms. A single couple feeding their young can remove up to 1,700 flies and mosquitoes a day. There is no more effective and ecological insect control. Swallows signal spring as they come back to Europe to breed.
The barn swallow (Hirundo rustica) is one of the best known and most studied birds. This species has helped scientists understand migration, sexual selection, and reproduction in birds. Its close association with humans through history makes it a familiar part of culture, and climate change has made its earlier arrival a visible sign of changing seasons. The species is often seen as an omen of better weather.
Despite its abundance, the barn swallow is declining in many areas due to shifts in rural landscapes and agricultural policies and practices. SEO/BirdLife, the organization that named the bird Bird of the Year in 2014, has highlighted these concerns.
Although not officially threatened, the species faces serious issues for decades, such as widespread pesticide use reducing insect prey, deliberate removal of nesting sites under the pretext of pollution, the challenge of nesting in new rural buildings, and the loss of countryside with many barns and other structures demolished, according to SEO/BirdLife.
Types of “special interest”
In the National Endangered Species Catalogue, the barn swallow is listed as a species of special interest. It is the most common swallow, breeding across much of North America and Eurasia outside polar regions and deserts. In winter it migrates through South America, Africa, southern Asia, and northern Australia. Eight subspecies are recognized, though some may represent distinct species, especially among American forms.
According to the SEO/BirdLife Bird Guide, the Rustica subspecies is the one most frequently found in Spain. Some reddish-bellied birds may belong to subspecies from the Middle East or may simply be local variants.
Swallows are widely distributed during the breeding season and in transit across the Iberian Peninsula, the Balearic Islands, Ceuta and Melilla. They winter sparingly in the south, particularly along the lower Guadalquivir. In the Canary Islands, they are common in the gorges and have recently started breeding in Gran Canaria.
Spaniards winter in the Gulf of Guinea and gradually return to breeding grounds with a delay of up to three months between northern and southern regions. In Andalusia and Extremadura, individuals typically arrive in January and become numerous from February; they reach the center and east of the peninsula after a month and are common only by April on the northern Meseta and Cantabrian coasts. By then, they are present across mainland Spain.
They usually leave southern breeding grounds from July to early September, with transitional individuals following the Mediterranean coast during September and October. From June onward, roosting gatherings form, mainly composed of juveniles.
A million couples in Spain
While exact numbers in Spain are hard to pin down, the population includes well over a million pairs, with roosts hosting more than 100,000 birds. Across Europe, estimates range from 16 to 36 million couples. Between 1980 and 2003, the species experienced a notable decline across the continent, with an estimated 27 percent population loss.
This small bird is highly social and monogamous. Nests are usually built in rural and urban structures such as barns, porches, and terraces; in the southern part of the peninsula some swallows inhabit rocky desert valleys. Their main prey consists of flies and mosquitoes, and they also catch flying ants, wasps, beetles, and other small insects.
The breeding season runs from May to August, during which two broods may occur, each lasting about 14 to 16 days. The female lays three to six eggs. Adults can eat, drink, and feed the young without stopping to fly. Chicks remain in the nest for 20 to 22 days and the species can breed up to 1,600 meters in elevation. Only the female incubates the eggs.
When the breeding season ends, swallows, both juveniles and adults, often gather to sleep in suitable places such as reed beds before starting their migration, which may see other related species moving as well. Predators include gulls, owls, hawks, and domestic cats.
Destroying nests of any swallow species can carry penalties up to 200,000 euros. Both Spanish and European laws regard damage to these birds and their nests, whether occupied or not, as a serious crime.
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