Crows

You've no doubt seen the metal spikes that are placed on buildings to keep birds from roosting. Well, it has been discovered that magpies and crows are actually using those spikes in their nests – appropriately enough, to keep other birds away.

​Crows and their close relatives ravens are known to be quite intelligent. New research has now uncovered a previously unknown ability, with crows being observed building tools from multiple parts for the first time ever.

​​Crows are certainly clever creatures, so could we employ these brainy birds to help keep our streets clean? That's the basis of a project from Dutch startup Crowded Cities, which is looking to train crows to scoop up the butts in exchange for treats.