LIKE A DECORATION Twenty or more other species of birds have been recorded as using snakeskins more or less commonly, or occasionally perhaps on the basis of availability or of chance. But with the above they're an essential part of the nest. In some of the species the snakeskins are arranged as a rim around the edge of the nest almost as a decoration; sometimes the snakeskins may make up most of the nest. Now as to possible correlations. The species are not closely related. Except for the two flycatchers the other five represent five different families. The distribution over the world is wide, too: America, Asia, Madagascar, Australia. Various explanations for the behavior have been advanced. It has been suggested that it's correlated with hole nesting, but three of the seven do not nest in holes. The most common theory is that it's to frighten away possible predators by making them think there is a snake in the nest. However, this is not very likely, and, too, one wonders why the birds that use the snakeskins are not frightened themselves. Indeed, one writer, surely not seriously, has suggested that the fright in early life of crested flycatchers at finding a snakeskin in the nest accounts for the upstanding crest in this species! "BURGLAR ALARM" THEORY Another suggestion is that the snakeskin, by the rustling noise it makes when touched, acts as an alarm bell or a burglar alarm to warn the rightful occupants of the nest when an intruder approaches. This also seems a rather weak explanation. We are left, then, with the fact that this curious habit has been developed in a few birds, not closely related, that live in various parts of the world and that have very different habits. It is usual with them. A number of others occasionally have this habit. My first clue as to the proper background against which to solve this habit came when, unpacking a bird collection made in Borneo by curator of anatomy D. Dwight Davis, I took out a bulbul's nest. In its outer edge were flat, weathered leaves that resembled snakeskins. Later, when we received a bird collection from Dr. D. S. Rabor of the Philippines there was a nest of another species of bulbul and this too had flat, dead, weathered leaves in it that looked like snakeskin. When I was in Madagascar, in 1929-31, I had found three nests of the Madagascar bulbul with a snakeskin used in each. Here was a clue. I decided to investigate the nests of the other species of bulbuls of southern Asia and Africa where the family is represented by many species. By considering the snakeskin-using species against the background of the nesting of the other species some correlation might appear.