Bird abundance in England was studied on and around green walls versus bare control walls to determine habitat value. Birds used the upper half of green walls for nesting, food, and shelter, but were never found on bare walls. Birds in both areas used nearby vegetation and the roofs of buildings, but more birds were found near the green walls.
Chiquet, Caroline, John W. Dover, and Paul Mitchell. (2013). Birds and the urban environment: the value of green walls. Urban Ecosystems, 16(3), 453-462.
