05.15.2026 | Discoveries, News, Places, Wild Life
In Spain, as around the world, solar energy is a booming industry. Last year, the solar farms that dot the nation produced more than a fifth of its electricity. This is obviously good news for a planet working to wean itself off fossil fuels. But in their haste to get in on the solar rush, Spanish companies—which must offset their impacts on local wildlife—are making choices that may threaten birds.
That dire outlook is the result of recent scientific research, led by Jesús M. Avilés, an avian ecologist with the Spanish National Research Council. In a recent paper focusing on the nest boxes erected by solar companies, Avilés and his colleagues argue that they’re probably not helping many birds—and if they are, it’s the wrong ones.
In Spain, the law requires that industry mitigates the harm it does to natural habitats. On solar farms, this often means that managers install bird nesting boxes alongside the solar panels. But in their paper, which analyzed 130 environmental impact assessments published by solar developers as part of their planning applications, Avilés and his colleagues found that, more often than not, these shelters are attracting the wrong clientele. 
Worse still, many of the nest boxes are poorly designed. As a result, they threaten to kill juvenile birds and warp local food webs.
The problems Avilés and his colleagues have with the nest boxes run the gamut. In many cases, Avilés says, solar developers are installing nest boxes designed for cavity-nesting species, like little owls and European rollers, in areas bereft of trees where those birds would never normally be found. When they do target a specific bird, the company usually buys generic boxes, which are untested in the environmental conditions of the sites where they’re installed.
The material used to build a nest box matters, Avilés says. Tree swallows, for example, suffer less from pesky blowfly larvae if they’re inside a box made of aspen instead of plywood. Great tits and blue tits face less nest predation if their home is made of pine instead of woodcrete.
Yet of the 130 solar farms that the scientists studied, 94 percent did not specify what materials their nest boxes were made out of. Those that did specify typically listed wood, concrete, or cork, with no ecological rationale given.
Nest boxes also have to be well-built and well insulated. And in the scorching Spanish heat, where temperatures peak around 45 degrees Celsius (113 degrees Fahrenheit), they should be placed away from the sun’s unrelenting glare—not right alongside solar panels designed to catch as many rays as possible. Without shade, “nestlings could simply be fried during the summertime,” Avilés says.
The potential for dead nestlings aside, inappropriately placed nest boxes also threaten to upset the delicate steppe ecosystems in which many of Spain’s solar farms are situated.
Many nest boxes, for instance, appear to be installed to boost populations of cavity-nesting birds of prey like the endangered lesser kestrel. While boosting raptor populations isn’t necessarily a bad thing, any nest boxes they leave unoccupied are likely to be filled by jackdaws and starlings, colonial species that nest in huge numbers, putting yet more pressure on threatened and endemic species. 
Not that solar plant developers are exactly curious about which birds are occupying their nest boxes. Of the 130 operations analyzed by Avilés and his colleagues, only three had plans to monitor their nest boxes after installation. All of these factors taken together indicate that the industry is bypassing any possible alternatives to nest boxes, and is therefore suggestive of a widespread “greenwashing” strategy that masks “the true ecological consequences of [solar] infrastructure,” the researchers write in their paper.
Peter Korsten, an ecologist at Aberystwyth University in the United Kingdom who was not involved in the research, agrees that might be the case, though he adds that ignorance might also be playing a big part.
Korsten says the Spanish researchers’ study is thorough and illuminating, and it raises valid questions about the effectiveness of nest boxes as offset measures. Fundamentally, Korsten says, the research demonstrates that developers need a more nuanced understanding of an area’s local ecosystem. With that, they could “use available resources for offsetting environmental impact in better ways.”
Korsten also says it’s worth investigating where else developers are using—or perhaps misusing—nest boxes as a form of environmental compensation. 
At least in some places, the installation of nest boxes in solar plants may not be as disorganized as Avilés and his colleagues describe. A recent study of several installations in Spain’s Extremadura region found thoughtfully placed shelters that are boosting the reproductive success of European rollers.
Even so, Angel Sánchez García, the sustainable development coordinator at Spain’s Cornalvo Natural Park and the report’s author, agrees that more work needs to be done to educate developers on which nest boxes are appropriate to install, and why. That’s why Sánchez García recently organized a workshop on nest-box installation for technicians, developers, and consultants involved in writing environmental impact assessments at the National Environmental Impact Assessment Congress, a meeting he hails as a “great success.”
Reform, then, might be in the offing. Right now, though, Avilés remains concerned that too many nest boxes are going up in the wrong places. In recent years, he’s seen them popping up all over, including dangling high above some of the country’s newest motorways. These shelters, perched high above the flow of traffic, fit the very definition of a bad home in a bad neighborhood.
Greg Noone
Greg Noone is a writer and editor at NS Media Group, and lives in Cambridge in England. His work has also appeared in The Atlantic, New York magazine, and The Guardian.
bioGraphic is powered by the California Academy of Sciences, a renowned scientific and educational institution dedicated to regenerating the natural world through science, learning, and collaboration.

source