Climate change is driving a sharp decline in bird populations, with barn swallows (Hirundo rustica) among the most visible casualties. SEO/BirdLife estimates that a million specimens vanish from Spain every year, a figure that underscores a troubling trend felt across much of Europe. The situation in other regions of Europe appears even more severe.
The shrinking barn swallow population is alarming: a loss of 41 percent occurred between 1998 and 2012, and a further 33 percent in the last decade. A report from the NGO cites a ten percent probability of extinction for the Iberian Peninsula within the next century. Despite these declines, the swallow remains listed as a threatened species in only four autonomous communities: Andalusia, the Balearic Islands, Castilla-La Mancha, and Extremadura.
Rapid population decline is a key criterion used by the International Union for Conservation of Nature to classify species into threat categories. This metric is one of the values detected through data gathered by the Sacre common bird tracking program run by SEO/BirdLife.
Swallow population trends and responses are often featured in ecological reports. For example, the Sacre program highlights that species such as the shrike, quail, western jackdaw, barn swallow, little owl, little lark, and Dartford warbler show declines that could warrant a vulnerable status since their numbers have fallen by more than 30 percent over about fourteen years. The group emphasizes that some of these species, including the gray shrike, are already recognized as endangered in Spain, while others remain unevaluated.
One factor behind the barn swallow decline is rural depopulation, which leads to abandoned breeding sites in agricultural landscapes. This trend helped SEO/BirdLife name the swallow Bird of the Year in 2014. In urban areas, the loss is compounded by modern buildings lacking proper holes and crevices for nesting, removing essential nesting opportunities for these and other birds.
Additionally, the heavy use of insecticides and other chemical products reduces the insects swallows feed on and harms breeding success. A single swallow consumes roughly 850 flies and mosquitoes, a substantial portion of the urban insect population each year.
After traveling about 5,000 kilometers, swallows reach human homes. A swallow freshly arrived from the Sahel can cross the Sahara and complete the journey with astonishing resilience, as noted by a Conservation technician and SEO/BirdLife delegate who highlights the importance of protecting nests and nesting sites. People are encouraged to keep an eye on eaves and other nooks where birds traditionally build their homes, and to consider ways to support nesting by offering safe nesting options.
Efforts for swallows include practical actions such as installing artificial nests or providing accessible nesting materials like mud or straw. SEO/BirdLife acknowledges recent scientific work on climate change impacts on birds, including a 2017 study by Carlos Cano Barbacil and Javier Cano Sánchez that warned of behavioral shifts, migratory phenology changes, geographic distribution shifts, and, in the most serious scenario, the risk of extinction for some species.
Researchers describe climate warming as a major threat to ecosystems, while also noting that birds can serve as early indicators of climate change. In light of this, swallows are seen as indicators that reveal how warming temperatures reshape migration and life cycles.
Because climate change has driven earlier migration for swallows, they now arrive in Spain about a month sooner than in the mid-twentieth century. An additional consequence is that more Sub-Saharan birds winter in Spain, including barn swallows, a trend that has grown over the last ten years. SEO/BirdLife notes that migratory species can adapt their cycles through earlier departures, faster migration, and shorter distances traveled, but adaptation takes time. Some scientists fear that European birds that fail to adjust their life cycles may continue to decline, and swallows might be among them.
Birds and Weather Program
The systematic recording of phenological observations is crucial for species like the barn swallow. SEO/BirdLife’s Birds and Climate program collaborates with researchers to map the effects of climate change on fauna and flora and provides tools for volunteers to contribute data that help mitigate this planetary challenge. The Birds and Climate initiative uses mobile apps that enable observers to log arrivals of swallows, the bloom of almond trees, or the first bee flights. These data sets offer invaluable insights into how climate change affects living systems. A general Sacre report and associated materials continue to guide these efforts, emphasizing transparency and ongoing monitoring.
Ongoing monitoring and collaboration with climate researchers help build a clearer picture of how the barn swallow and other species respond to changing conditions. The goal is to inform conservation strategies that support nesting, feeding, and migration, reducing the risk of local extinctions and helping populations recover where possible.
The program also points to future directions in research and policy, stressing practical steps communities can take to protect nesting sites and to minimize disturbances during critical breeding periods. By combining field observations with climate data, scientists aim to forecast how migratory birds will fare under different scenarios and to guide conservation actions accordingly.
As climate dynamics continue to unfold, the work of the Birds and Climate program remains essential for understanding and mitigating the effects on barn swallows and other species. The collaboration between field biologists, citizen scientists, and policy makers helps translate data into actions that safeguard bird populations for years to come.
Further information and data from the Sacre program and related assessments can be explored in public reports produced by SEO/BirdLife. These materials contribute to a broader understanding of how climate variability interacts with land use and biodiversity across the Iberian Peninsula and beyond.
Environment division inquiries should be directed to the appropriate program channels for guidance and updates on ongoing conservation initiatives.