Desirable residences? Or death traps for birds?

Do birds fight fires? Do they go on holidays by the seaside?
No, I didn't think so. But apparently these kinds of elaborate nest-boxes are fashionable and can be found in many a garden up and down the country, providing nesting accommodation for garden birds.
And while they might look good hanging from a tree in the garden or tucked in a safe place away from neighbourhood cats, the RSPB believes these kinds of boxes are unsuitable. Why?
According to a recent press release:  "In some cases, unsuitable nest-boxes made with the wrong material or a poor design could lead to injury and even death." 
Ian Hayward, RSPB wildlife advisor, told The Telegraph: "There are so many elaborate nest-boxes on sale that look the part but are really quite dangerous to nesting birds. Don't be tempted to go for the unusual shapes and colours -- traditional, wooden nest-boxes really are the best -- and often the most cost effective too."
You can find out how to make your own simple nest-box on the National Nest-Box Week website or try the BBC Science & Nature page.