Do birds recycle their nests?
Most birds that build cup-nests do not reuse them. They rebuild a new nest each year and sometimes recycle the nesting material. One reason for this is that the nest, after one cycle of breeding, often has outlived its usefulness. The dried soft plant materials would have begun to rot. Another reason is that there would be the typical odour left by the birds and their nestlings after the latter have fledged. Such odour can attract predators. A third reason is that old nests often contain a large number of ectoparasites that are potentially harmful to the developing young. Among birds that build large platform nests of twigs that are more lasting, recycling of the nests may be common. These include large nests of ospreys, eagles, storks, hawks and kites (above).
Hole nesters, especially birds that are not able to excavate cavities for themselves, need to reuse nests previously occupied by other species. Sometimes they evict the current occupants in order to make use of the cavities for themselves. The case of the Long-tailed parakeet (Psittacula longicauda) trying to take over the nest cavity of a pair of Dollarbirds (Eurystomus orientalis) is a good example. Yellow-vented Bulbul (Pycnonotus goiavier) sometimes build over an old nest or partially completed nest (above). However, Lena Chow reported that the birds in her garden did use the same nest a few times, although she was not sure whether it was the same pair of birds or different pairs. But she observed recycling of nesting material year in and year out. Similarly, sunbirds rarely, if at all, reuse old nests (above). House Crow (Corvus splendens) does not reuse last season’s nest but recycle the nest material if the old nest is nearby (below). Baya Weaver (Ploceus philippinus) on the other hand sometimes repair an old nest as can be seen by the green material weaved over the older brown material.
Input by Lena Chow, YC; images by YC except top by Chan Yoke Meng.