Nest decorated with plentiful silk/floss

Tan Teo Seng recently sent me an old nest from his garden in Singapore. The nest looks very much like that of the Yellow-vented Bulbul (Pycnonotus goiavier) (above).

It is a neat cup 10 cm diameter and 5 cm deep with a 5 cm diameter nest cavity, very much like any other bulbul’s nest (1, 2).

There is one major difference in this nest. The rim of this nest is embellished thickly with whitish silk. The strands are tough and do not break easily, suggesting that it is not spider silk. Can it be spider cocoon silk? Or can it be of plant origin?

UPDATE: Wang Luan Keng, our field ornithologist, just told me that the white silk is styrofoam, used as a fine packing material. 7th Sept.2008