Drivers of fatal bird collisions in an urban center

Millions of nocturnally migrating birds die each year from collisions with built structures, especially brightly illuminated buildings and communication towers. Reducing this source of mortality requires knowledge of important behavioral, meteorological, and anthropogenic factors, yet we lack an understanding of the interacting roles of migration, artificial lighting, and weather conditions in causing fatal bird collisions. Using two decades of collision surveys and concurrent weather and migration measures, we model numbers of collisions occurring at a large urban building in Chicago. We find that the magnitude of nocturnal bird migration, building light output, and wind conditions are the most important predictors of fatal collisions. The greatest mortality occurred when the building was brightly lit during large nocturnal migration events and when winds concentrated birds along the Chicago lakeshore. We estimate that halving lighted window area decreases collision counts by 11× in spring and 6× in fall. Bird mortality could be reduced by ∼60% at this site by decreasing lighted window area to minimum levels historically recorded. Our study provides strong support for a relationship between nocturnal migration magnitude and urban bird mortality, mediated by light pollution and local atmospheric conditions. Although our research focuses on a single site, our findings have global implications for reducing or eliminating a critically important cause of bird mortality.

Forecasting of the number of bird collisions with turbines in the territory of Pre-Azov region wind park using the route census method

The information system has been designed to ensure the analysis of information on the monitoring results of the wind power plant (WPP) territory using the route census method. The database contains 48 fields, reflecting the monitoring results of birds’ behavior in the territory of WPP and processing the initial data: year, month and day of observation, a number of birds of this species, flight altitude, flight speed, direction of flight, coordinates of the bird registration point on the Google-map, average number of birds flying over the territory of the wind park at a given time, coordinates of the points of intersection of the bird flight path with the perimeter of the wind park or observation site, the length of bird flight path over the observation site, and other parameters. The analysis of distribution of birds in the territory of the “Primorsk-1” WPP according to the types of migration (forage, transit, nesting, and ground), direction of flight and altitude characteristics has been carried out. The total number of registered birds was 8927 specimens of 72 species, of which 802 specimens of 11 species were referred to the transit type, 2511 specimens of 32 species – to the forage type, 5614 specimens of 60 species were on the ground (ground type). Most birds (63%) belong to the ground type. 28% of birds were registered in the forage group, 9.0% of birds were flying in transit. The greatest activity of birds is manifested in the autumn migration season, when the transit group accounts for 77% of all annual transit flights. The proportion of birds of forage and ground types, registered in autumn, is 68% and 74%, respectively, of the total number of birds registered in autumn. In the group of ground birds, the overwhelming majority of specimens belong to the period of autumn migration (4141 birds or 74%). The least number was observed in the winter season (317 birds or 5.6%). The author proposes a mathematical model for analyzing birds’ interaction with turbines using the results of monitoring the territory of wind power plants by means of route census method. The model makes it possible to obtain information on the probability of different species of bird collisions with wind wheels and the number of collisions with turbines, depending on the flight characteristics of birds, parameters of wind parks and observation conditions in different seasons. In the risk zone of birds’ interaction with turbines, only specimens of one species, Buteo buteo, were observed. The calculated probability of one bird collision when passing through the wind wheel is 0.19. The anticipated number of bird collisions with turbines during one year of the “Primorsk-1” wind park functioning is in the range of 5.6÷6.7 specimens.

Birds crossing over roads: species, flight heights and infrastructure use

How high do birds fly above roads, and how do they use the road infrastructure (bridges, lampposts etc.)? These questions are rarely explored in ecological studies but were addressed by us during research in 2016–2018 in southern Poland. In total, 1665 individual birds belonging to 24 species were recorded. Species differed significantly in the height at which they crossed over roads, but about 30% of all crossings were at heights below 12 m, hence at potential collision heights. The proportion of birds perching on lampposts in the central reservation between carriageways also differed significantly between species. The surrounding landscape and road infrastructure, especially lampposts, modified the species composition associated with roads. This knowledge has practical importance, not only in regard to collisions, but also to much less studied aspects such as plant seed dispersal and/or corrosion of the infrastructure. Lampposts, as a taller component of the infrastructure, may not directly affect vehicle-bird collisions, but a flight to them may be a risky business, and we recommended higher lampposts to discourage low-level flights. This information may need to be incorporated into future studies on road ecology, as well as in mitigation programs.