Invasive Waxbills Thrive in Spain’s Abandoned Farmlands
Study reveals how farmland abandonment and invasive plants fuel the spread of non-native birds.
A new study sheds light on the remarkable adaptability of the Common Waxbill (Estrilda astrild), an invasive bird species thriving in the eastern Iberian Peninsula. Researchers have found that the Waxbill, originally from sub-Saharan Africa, has established itself as a dominant species in degraded landscapes, particularly in areas where farmland abandonment and invasive plants have transformed the habitat.
The Rise of the Waxbill
The study, published in the Journal of Ornithology, investigated the distribution and ecological interactions of the Common Waxbill in two Mediterranean wetlands in eastern Spain. Through year-long bird surveys, researchers discovered that the Waxbill is not only abundant but forms a distinct avian community, reaching its highest numbers in autumn.
Unlike many native birds, the Common Waxbill shows a strong preference for human-modified habitats, particularly abandoned agricultural land overtaken by invasive plants such as Pampas Grass (Cortaderia selloana) and Giant Reed (Arundo donax). The study found a significant correlation between these invasive plants and Waxbill presence, suggesting that the spread of non-native flora is inadvertently providing the species with food and shelter.
A Bird That Thrives on Change
The adaptability of the Common Waxbill is key to its success. While many bird species are sensitive to environmental shifts, this small finch-like bird takes advantage of altered landscapes, feeding on a wide variety of seeds, including those from both native and non-native plants. Researchers recorded Waxbills consuming over 15 plant species, demonstrating their ecological plasticity.
Interestingly, the Waxbill did not show a strong preference for native or invasive plants in its diet, indicating that it is an opportunistic feeder rather than a specialist. This flexibility may help explain why the species has been able to colonize diverse environments, from tropical islands to Mediterranean wetlands.
Farmland Abandonment: A Double-Edged Sword
While the decline of traditional farming in Spain has allowed some native species to recover, it has also created opportunities for invasive species. As farmland reverts to shrubland dominated by aggressive non-native plants, it inadvertently favours species like the Common Waxbill.
“The Waxbill is not necessarily displacing native birds, but it is filling a niche that has been altered by human activity,” explains lead author Pau Lucio-Puig. “Understanding how invasive species interact with changing landscapes is crucial for biodiversity management.”
Implications for Conservation
The study highlights the complex ecological relationships between invasive birds, non-native plants, and land-use changes. While the Waxbill itself does not appear to outcompete native species directly, its success is a reminder of how human-driven environmental shifts can facilitate biological invasions.
With farmland abandonment expected to continue across southern Europe, conservationists may need to rethink land management strategies to balance habitat restoration with the control of invasive species. Monitoring the long-term impact of the Common Waxbill and its interactions with native fauna will be essential in shaping future conservation efforts.
For now, the Waxbill’s story serves as a testament to nature’s ability to exploit change—sometimes in unexpected ways.
28 Feb 2025
Read the full paper here.
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