Look at this tiny little fighter pilot. This is the pygmy falcon, (Polihierax semitorquatus), Africa’s smallest raptor bird. Native to several regions in Africa, including southern Ethiopia, Somalia, Uganda, Kenya and Tanzania, this compact killer only grows to about 20 centimeters long (a bit less than 8 inches), which makes it only slightly larger than a house sparrow. But don’t let this guy’s small stature and extreme fluff fool you – it doesn’t just hunt insects, lizards, snakes and mice, it also hunts other birds, striking them down in mid-air and ripping them from their nests.
And speaking of nests, the pygmy falcon sure knows how to live in style. They’re too busy dive-bombing the shit out of their prey to worry about domestic matters like building a nest, so they move into other species’ nests instead. In southern Africa, the pygmy falcon population lives and breeds in the enormous homes of the sociable weaver bird (Philetairus socius), the largest and arguably most elaborate structures built by any bird on the planet. Sometimes these nests will stretch 7 meters across and can easily weigh more than a ton. They basically look like someone threw a big, golden-brown haystack in a tree and it stuck. Sometimes they’re so big, they snap the branches and collapse all over the place.
Built like the bird equivalent of an apartment block, the sociable weaver’s nest can house hundreds of pairs of birds from several generations. They’re sectioned off like honeycomb with over 100 little chambers connected by a complex system of tunnels and entrances, and lined with plant matter, fur and cotton. They even have their own heating and cooling systems, with internal chambers retaining the heat to keep everyone warm at night, and the cooler rooms arranged around the edge of the structure to be used as a shady refuge during the day. These nests can be occupied for over a century before they start to decay.
Inside, the pygmy falcons can be quite sweet for the miniature assassins that they are, occasionally living in what’s known as polyandrous relationships, which means the chicks are cared for by three, sometimes four adults, including both parents. The reason for this congregation of babysitters could be for added defense, or maybe they just enjoy the warmth of all that collective fluff.
The pygmy falcons aren’t the only ones who take advantage of the hospitality of the aptly named sociable weavers – Kalahari tree skinks (Trachylepis spilogaster) also gather around their colossal nests, feeding, nesting, and basking in the sun. And a study conducted by Australian researchers earlier this year found that although lizards are one of the pygmy falcon’s absolute favorite foods, they appear to have absolutely no effect on the tree skinks’ population near the weaver nests. None. In fact, they report that, “We observed skinks on all trees with active pygmy falcon nests, while we observed no skinks on three trees without pygmy falcon nests.” WTF are you doing, lizards?
While it’s not clear why the pygmy falcons aren’t eating the Kalahari tree skinks to oblivion, it could be because they’re hunting and eating everything else, including the skinks’ other predators, so are inadvertently protecting them. If you’re going to be protected by something, it might as well be a communal-living puffball of death.
—Bec Crew / @BecCrew