This is truly strange. A new report (subscription/pay-per-view) in todays Science has found that birds are using pieces of platic bags to their benefit. In this study, the birds (black kites, a European raptor) were found to use the pieces to decorate their nests, which by itself, it not novel. Such decorations are common, and have been ignored. But this new study concluded that the decorations actually serve a purpose, in that fitter birds used more decorative materials than less fit birds.
So are other animals doing the same or similar thing - using pieces of plastics for their gain? And what are the longer term, evolutionary issues with this? What would happen if in the extreme all plastic bags were banned world wide? I have no answers, but am just fascinated by all of this.
The article is also discussed at Wired.com