Skulkers of the avian world, yellow- and black-billed cuckoos are often heard but rarely seen. Their guttural “cu-cu-cu” fills the air where furry caterpillars abound. Cuckoos’ favorite foods include some hirsute pests: gypsy moth larvae and tent caterpillars in spring; fall webworms in summer.
Caterpillar hairs do not bother cuckoos the way they bother other birds because cuckoos vomit up the hairs, stomach lining and all. Cuckoos are the lucky recipients of a special adaptation that enables them to periodically shed the lining of their esophagus and stomach, removing the accumulated mat of hairs. Then they grow a new stomach lining.
To encourage cuckoos and their pest-control efforts, plant trees to give them the forest-edge habitat they prefer.