Most birds of prey are loners. They might form huge flocks during migration, but for the rest of the year, they stick to themselves. The red-footed falcon is different. This kestrel-size bird frequently travels and roosts in large groups across Eastern Europe and Central Asia. It even nests in colonies, with hundreds of pairs of slate gray males and buffy-red females all living together in what Hungarian ornithologist Péter Palatitz calls “super-busy cities.” Within these avian metropolises, the falcons fight for nests, steal from each other, mate outside their partnerships, and leave eggs for others to raise. For scientists interested in how birds behave, “this system is a heaven,” says Palatitz, who has studied the falcons for 20 years.
These raptors don’t build their own cities. Instead, they occupy the abandoned nests of the rook, a relative of crows. But rooks have long been seen as agricultural pests and were so thoroughly persecuted in the 1980s and ’90s that their population crashed. The red-footed falcons, with nowhere to nest, plummeted to a quarter of their former numbers. In 2006, Palatitz launched a plan to reverse that decline by placing thousands of nest boxes throughout Hungary. The falcons responded enthusiastically. Over the next decade, their numbers doubled.
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As the falcons rebounded, Palatitz took the opportunity to answer some long-standing questions about these little-studied creatures. For example, he knew that they winter in Africa but not their route or specific destination—key information for understanding how the species spends half its life. So, between 2009 and 2015, Palatitz and his team fitted 28 individuals with satellite transmitters. The devices revealed that the birds, which weigh just four to seven ounces, can cross the Mediterranean and the Sahara in a nonstop five-day flight. A week later, they end their 6,000-mile trek in southern Africa, where they stay for months.
But in resolving one mystery, Palatitz unearthed another. The tracking data hinted that in March, before returning north, the red-footed falcons all pass through the same small stretch of central Angola. Why? Some of the team thought this was a coincidence, but Palatitz argued that the birds were gathering at a huge roosting site. He bet a beer that he was right, and began making plans to visit Angola.
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The team came across a site where falcons streamed in from all directions, blackening the sky. Some darted around at eye level. Others wheeled overhead. They perched shoulder to shoulder on every available branch. As he watched them, Palatitz started crying. It was like being “in a new dimension,” he says, “like I’m not part of the Earth but I’m more part of the sky.”
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Palatitz knew the falcons were sociable, but he had completely underestimated just how sociable they could be. In the summer, the birds are spread across thousands of miles from Hungary to Kazakhstan. But for six weeks in February and March, every last one passes through this tiny, 1.5-square-mile region of central Angola, which the team now calls “Falcopolis.”
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No one knows exactly how many red-footed falcons congregate at Falcopolis. “Estimating them in the sky is impossible,” Palatitz says. Instead, his team is trying to count the birds by measuring the area over which they roost and the carrying capacity of those trees. If successful, the team will have an unprecedented way of counting a species that, in the summer, is scattered over a vast and largely unmonitored area. The red-footed falcon population has been estimated at up to 400,000 individuals. At Falcopolis, “I think I’ve seen one million birds in the air,” Palatitz says.
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What compels these falcons to gather in such preposterous numbers? And why do they come to that particular part of Angola? “We don’t know,” Palatitz says. But he has some guesses. Falcopolis is on a peninsula surrounded by rivers and is easy to find from the air, he explains. Its climate is temperate and agreeable. It’s got plenty of large roosting trees. Human presence may have helped the falcons by suppressing mammalian competitors and predators. And since agriculture isn’t practiced intensively, there are still plenty of insects around. In particular, every March winged termites burst from the ground, swarming so densely that they look like static on an old television set.
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Meanwhile, news of Falcopolis is spreading quickly. At a recent conference, Angola’s president described it as a national treasure. The Ministry of the Environment went to the site, marking the first high-level governmental visit to the area in decades. A six-foot-tall falcon statue now stands in the main square of the nearest municipality, Mungo. And Palatitz’s team has started bringing international volunteers to Falcopolis, where Agostinho is training locals to guide future tourists.
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