Bird density and mortality at windows

Shooting is still a main threat for raptors inhabiting urban and suburban areas of Rome, Italy

“…This could be easily explained by the high density of structures potentially dangerous for birds within the city, such as vehicles and windows. The hard impact of birds on windows is well documented (Hager et al 2008) and collisions with cars is considered the current main cause of mortality for birds (Pons 2000), with millions of individuals killed every year (Erritzoe et al 2003). Our findings comply with most other studies which have analysed admission causes for raptors at wildlife rehabilitation centres by determining that collision with human-made structures is the main admission cause for raptors inhabiting urban and suburban habitats (Wendell et al 2002;Rodríguez & Rodríguez 2010;Molina-López et al 2011).…”

Landscape, Legal, and Biodiversity Threats that Windows Pose to Birds: A Review of an Important Conservation Issue

“…Various landscape features can influence the density of birds near windows, such as location of a dwelling, the amount of glass exposed to the environment, the immediate and surrounding vegetation, the presence of water as an attractant, and artificial lighting conditions. All species may be potentially vulnerable to window strikes, but past and current studies clearly reveal that not all species have been documented as window strike casualties [6][7][8][9][10][11][12]. Ruffed grouse (Bonasa umbellus, American woodcock (Scolopax minor), Accipiter hawks, hummingbirds, Catharus and Hylocichla thrushes, and ovenbird (Seiurus aurocapilla) are suspected to be deceived by clear and reflective panes more often because of their habits of swiftly flying through restricted passageways through dense vegetation [8,9,13,14].…”

“…American robin (Turdus migratorius) and cedar waxwing (Bombycilla cedrorum) are suspected to be more vulnerable to flying into windows after becoming intoxicated on fermented fruits [8,9,18]; accounts indicate that birds behave similar to humans when under the influence of alcohol and as such those that "drink" and fly are apt to be more vulnerable than those that do not. Addressing differential species vulnerability to windows, recent detailed studies have found North American and Neotropical migrants, those flying long distances or at night, to be killed more often than diurnal migrants or non-migratory residents [6,7,[10][11][12]. Those species known to occur in large numbers around buildings, especially in urban areas, such as rock pigeon (Columba livia), European starling (Sturnus vulgaris), and house sparrow (Passer domesticus) are known collision casualties [3,8], but at most study sites they have been recorded infrequently or not at all as window fatalities [6][7][8][9][10][11][12].…”

“…Addressing differential species vulnerability to windows, recent detailed studies have found North American and Neotropical migrants, those flying long distances or at night, to be killed more often than diurnal migrants or non-migratory residents [6,7,[10][11][12]. Those species known to occur in large numbers around buildings, especially in urban areas, such as rock pigeon (Columba livia), European starling (Sturnus vulgaris), and house sparrow (Passer domesticus) are known collision casualties [3,8], but at most study sites they have been recorded infrequently or not at all as window fatalities [6][7][8][9][10][11][12]. This seeming immunity to windows is likely the result of their behavior flying to perches such as sills and ivy or other vegetation that are near glass surfaces where, like feeders close to windows, if they strike the glass they do so with a force below which is needed to injure or kill themselves, but enough to learn to avoid the space thereafter [3,19].…”

“…This seeming immunity to windows is likely the result of their behavior flying to perches such as sills and ivy or other vegetation that are near glass surfaces where, like feeders close to windows, if they strike the glass they do so with a force below which is needed to injure or kill themselves, but enough to learn to avoid the space thereafter [3,19]. Resident northern cardinals (Cardinalis cardinalis) may similarly gain protection when discovering their reflected image and responding to it as a rival in their territory [3,8,11,12]. Hager and his colleagues reported little or no support for bird density near windows explaining the species and number of fatal strikes at the buildings they studied [11,12].…”