Branta Issues > Issue №19 (2016)

Factors of bird mortality on overhead medium voltage power lines (35-110 kV) in the northern part of the Azov Sea region

O. I. Bronskov, G. G. Mosin, M. O. Bronskova

The article considers the influence, providing on birds by medium voltage power lines (35-110 kV). The study was conducted from October 2012 to December 2015 (with interruptions) in the northern part of the Azov Sea region, the administrative region of Donetsk (Fig. 1). The main attention was focused on migratory and wintering birds, and therefore summer studies were not carried out. Multiple examinations were done in 6 control sites comprising power lines of different designs. The control sites were located both on the mainland and on Bilosaraiska and Kryva spits. Additional pedestrian surveys along power lines throughout the entire region were also taken. A total of 67 fieldtrips were made, and the covered distance amounted to 394.3 km. 
During the research a total of 12,998 individuals (103 species and 13 orders) were recorded in the entire studied area. Most of birds (n= 59 or 45%) were registered in autumn. The Starling (Sturnus vulgaris), Rook (Corvus frugilegus), and Chaffinch (Fringilla coelebs) were main dominants (in decreasing order).  Almost all of the 20 dominant species belonged to passerines, except for the Yellow-legged Gull (Larus cachinnans). In winter, we counted 33% of the total number of the recorded birds, whereas their species diversity in the season decreased to 36 species. The Calandra Lark (Melanocorypha calandra), Goldfinch (Carduelis carduelis), and Yellow-legged Gull dominated. In spring, the species diversity was the highest and included 83 species. The Wigeon (Anas penelope), Grey Plover (Pluvialis squatarola), and Starling prevailed. Twenty dominant non-passerines species were added by the Garganey (Anas querquedula), Little Gull (Larus minutus), and Shelduck (Tadorna tadorna). Any seasonal dependence for the number of dead birds against their total recorded number was not found.
To identify how birds cross power lines and use the area under poles their location in regard to poles and wires were registered (Table 1). Most of birds (48.3%) used the area to search for food or to rest, 37.9% of individuals crossed the lines above the wires, 3.3% - below the wires, and 2.1% - between the wires that in certain conditions could cause collisions and injuries or death of birds.
The density of bird deaths on power lines in coastal salt marshes (0.19‑0.25 ind./ km of the route) was substantial, irrespectively of a construction type of the power line. This fact can be explained by availability of those bird species in the area, which are more subject to collision with wires (gulls, ducks). (Andryushchenko et al. 2014, our data).
In steppe areas and agrocenoses we examined five construction types of medium voltage power lines (35-110 kV). The highest death density was recorded in site 1, consisting of 12 chains of 110 kV (chain is a set of several wires, usually 3, required for electric energy supply) on 6 rows of poles with different designs (Fig. 2.1). The death density on 2-chain 110 kV power lines on concrete poles was lower (Fig. 2.5), and the lowest on 1-chain lines of the same voltage (Fig. 2.2). There were no dead birds under a 110 kV line with horizontal wires (Fig. 2.3) and under a 1-chain 35 kV line on concrete poles (Fig. 2.4).
During the whole period of the research we have found remains of 29 birds (17 species of 6 orders) perished because of collisions with wires of medium voltage power lines. According to death probability the bird groups rank as follows: Great Bustard (Otis tarda); ducks (Cygnus sp., Anas platyrhynchos, Tadorna tadorna); birds of prey (Buteo buteo, Circus cyaneus, Falco sp., Asio otus); Charadriiformes (Larus cachinnans, Philomachus pugnax); passerines (Fringilla montifringilla, Turdus merula, Anthus campestris, Garrulus glandarius, Pica pica, Larus cachinnans). It was found out that the peculiarities of bird eyesight, maneuverability and specific behavioral reactions can influence the probability of collisions with power line constructions. 
During the whole period of the research we did not found any birds died from electrocution on medium voltage power lines.

We have concluded that medium voltage power lines represent the greatest threat to birds in places of their local concentrations, i.e. those with good forage or protection capacities on agricultural lands or natural systems (coastal salt marshes, steppe areas). In addition, cases of bird deaths are observed on power lines that traversed bird migration routes.
Power lines with two chains and vertical wires (Fig. 2.5) appear to be the greatest threat to birds. The negative effect is enhanced when there are several lines located close to each other.
As usual, birds cross power lines freely and without any harm for themselves, but under the coincidence of above-mentioned factors added by limited visibility due to weather conditions (rain, fog, snow, etc.) the probability of bird deaths because of collisions with wires considerably increases.
To prevent these situations, we propose to make an ornithological expertise over a period of one year before building new power lines to ensure them do not cross the protected areas, sites of large bird concentrations and bird migration routes as well. In potentially dangerous places the wires should be equipped with devices making them more visible to birds especially during bad light conditions. These devices should be contrast in colour to their environment and have, if possible, moving and light-reflective parts. The prevalence should be given to power lines with a lesser number of wires and horizontal configuration of them. The lines already existing  should be inspected to reveal the most dangerous sections for birds and to be further equipped with the above-mentioned devices to scare birds away. The sections of power lines where the mortality of birds from the IUCN list is regularly recorded should be placed underground.