A paper published by researchers at The University of Edinburgh shows that birds rely on experience when building nests. It had long been thought that proper nest-building was passed down genetically, but this new research shows that birds have physical cognition of materials. The group tested zebra finches by giving them two types of string to build nests with. From the paper, "after building a complete nest with either [stiff or flexible] string type, however, all birds increased their preference for stiff string."

Source: Bailey, ID, Morgan, KV, Bertin, M, Meddle, SL & Healy, SD 2014. 'Physical cognition: birds learn the structural efficacy of nest material' Proceedings of the Royal Society B-Biological Sciences, vol 281, no. 1784, pp. 20133225., 10.1098/rspb.2013.3225.

Photo of Marsh Wren feeding chicks by Alan Vernon.