This page is dedicated to other urban-natural-friends: the birds.
You can easily attract them offering food in many ways.
Here’s some experiments we’ve done for seeds-birdfeeders, they all work pretty well.
The COST: beside the material used, the main cost is having dirt in the area where the birdfeeder is located. The birds eat the seeds opening them with their beak and throwing away all the rest with other seeds that can invade your spot, and grow too.
The BENEFIT: the birdfeeder is another kind of biological bomb. Once the birds (mainly sparrows, but it depends on where you are located) know this spot, they’ll tweet the information to many others. It’s easy to have many of them daily and listen to them singing. If you like to mix the urban rumors with those natural sounds, these birdfeeders can really help!