Green facades provide animals with shelter and thus promotes ecological diversity: insects, butterflies, birds, etc... Whoever doesn't like spiders, mice (yes, they too ...) and sparrows coming too close to the window, may limit this with wisely arranged trellises.
A facade greening can even temporarily tempt birds and insects to stay, but also comprehensively serve as a wildlife habitat. The importance of such refuges is real today in our highly built-up urban environment! Some birds such as blackbirds like to build their nests here, but also beetles and other creepers can also settle here. Spiders, for example, like to stay in the habitat and prey on other insects. The correct placement of trellisis can hinder any creatures at the windows.
Wall gardens are also good for the protection of birds: Insects in the garden serve as food for birds which like to look around and grab a snack! Often they even build their nests in the trellis! But many climbing plants themselves are food for animals, for example Ivy berries are popular with birds, those of Firethorn serve as winter food. Virginia Creeper and ivy serve as a bee pasture, and blooming honeysuckle attracts revelers with their beguiling smell.
Some mice and raccoons can climb greened up walls! If fruits are on a trellis, wasps and bees can be troublesome. Also sparrows in the ivy can be disruptive...Ahhh nature.