Statistics say that, after altering the landscape, flying into and impacting against glass surfaces is the second most common cause of premature death amongst birds. This not only includes sizeable sound-proofing walls, but also the windows and glazed doors of flats, houses and company headquarters.
In addition, birds are also put in jeopardy by a lack of nesting areas due to changes in the landscape and large-scale farming or forestry. There is an incredible scarcity of trees with nesting cavities in the wild and urban areas. The tendency to insulate facades from heat loss and cold results in birds losing an ever greater number of crevices and niches that are suitable for nesting.
Some birds are also at risk from various outbreaks which often spread rapidly between individuals and amongst flocks. Trichomoniasis (greenfinches) and the usutu virus (blackbirds) are the examples of this.
The figure shows that birds die prematurely through electric shock, hunting (by humans and predators such as cats) and risks arising from things including collisions with motor vehicles and pesticides in the environment.