The word kleptomania is from the Greek words κλέπτω (klepto) “to steal” and μανία (mania) “mad desire, compulsion”, meaning a compulsion to steal. In birdy news lately is the term kleptotrichia, referring to the behavior of birds stealing hair from mammals to line their avian nests. But some birds steal feathers from other birds in an unusual behavior called kleptoptilia.
The Neotropical Palm Swift or Fork-tailed Palm Swift (Tachornis squamata) is native to tropical South America and Trinidad in the Caribbean. The bird is a slender and narrow-winged with a long, forked tail, found in marshy habitats, or sometimes open forest, usually near Moriche Palms (Mauritia flexuosa) in which it nests.
When birds of any species build nests, they use an amazing variety of materials – leaves, twigs, spider webs, animal fur, grass, mud, lichens, stones, and artificial material like string, cellophane, aluminum foil and dryer lint. Many species use feathers in the nest lining for insulation. The Fork-tailed Palm Swift uses fresh body feathers of medium-sized birds, especially pigeons, not just to line the nest, but construct the nest. The nest is then glued with the bird’s saliva to the inside of a dead leaf of a Moriche Palm.
Being airborne for most of its life, landing on palm leaves only to roost and nest, it would seem a challenge to gather feathers for nest-building material. Turns out that the swift attack other species of bird, ripping feathers from their backs. Whether in level or undulating flight, the swifts circle high above and swoop down on pigeons, woodpeckers, flycatchers, thrushes and dozens of other species.
It takes one to three months for Fork-tailed Palm Swifts to build their nest, probably because kleptoptilia is not all that efficient a process to obtain nesting material. Why feathers for nest construction? Well, good insulative materials are required as the nests are built high in palm trees exposed to wind and weather; the feathers are both strong and waterproof as well.
There is also kleptoparasitism, parasitism by theft, exhibited by perhaps 200 species of birds. A classic example is that of frigatebirds that chase other sea birds to force them to drop their food. Bald Eagles will harass Ospreys to force them to drop their fish and gulls will harass pelicans.
Penguins are kleptos too, but instead of stealing food, Gentoo Penguins, for example, steal stones from other penguins’ nests to add to their own. And then there is a phenomenon known as kleptothermy during which birds huddle together to share body heat. In the cold Antarctic, Emperor Penguins do it in masses of thousands of birds. In the more temperate areas Pygmy Nuthatches of North America and Mousebirds of Africa huddle in groups of a few to a dozen to keep warm. But in this case, “klepto” is not really appropriate because the birds are sharing heat, not stealing it. It’s really a case of mutualism, a kind of symbiosis.