Birds threatened and not threatened by collisions

Birds threatened and not threatened by collisions

posted on March 26, 2019

Let’s identify, which birds species die as result of collision with wind turbines. In European database there are already information about 14 418 victims found, which belonged to 257 species (Dürr 2019). However, these are only incomplete data, and what’s more we don’t know the methods of obtaining them. But they can say something. You can see that number of carcasses of particular species in this database is very diverse – from 1 individual (e.g. siskin) to 1901 individuals (griffon vulture). You can then compare number of victims in Germany and Spain with numbers of particular species in these countries (vast majority of records in this database come from these countries). This comparison leads to preliminary conclusion that relatively highest collision rate show diurnal raptors, as well as large gulls, white stork, raven, or eagle owl (see: Tab. 1), while collisions of other species constitute only a negligible percentage of their country populations (breeding, passage and wintering).

Table 1. Species showing the relatively highest collision rate with wind turbines in Germany and Spain. N – number of founded victims in 2002-2015 in Germany or Spain (Dürr 2015; in case of these species, most of victims are probably birds belonging to breeding populations of a given country). For comparison there are also examples of four species showing relatively low collision rate. DE – Germany; ES – Spain; * – source of data: Südbeck et al.2007; ** – source of data: Mebs & Schmidt 2014.

Species	Country	N	% of national breeding population	National breeding population size (individuals)
white-tailed eagle Haliaeetus albicilla	DE	119	7,8	ca 1 520**
griffon vulture Gyps fulvus	ES	1892	3,8	ca 50 000**
booted eagle Hieraaetus pennatus	ES	44	1,4	ca 3 100**
osprey Pandion halietus	DE	17	1,4	1 254**
red kite Milvus milvus	DE	301	1,2	ca 25 800**
white stork Ciconia ciconia	DE	53	0,6	8 400 – 8 600*
eagle owl Bubo bubo	DE	16	0,5-0,6	2 800 – 3000*
peregrine Falco peregrinus	DE	13	0,5	ca 2 400**
black kite Milvus migrans	DE	36	0,3	ca 12 800**
lesser kestrel Falco naumanni	ES	62	0,2	ca 28 600**
common gull Larus canus	DE	45	0,2	22 000 – 23 000*
buzzard Buteo buteo	DE	373	0,2	ca 210 000**
marsh harrier Circus aeruginosus	DE	22	0,1	ca 17 600**
raven Corvus corax	DE	24	0,1	20 000 – 24 000*
hobby Falco subbuteo	DE	12	0,1	ca 10 800**
herring gull Larus argentatus	DE	95	0,1	88 000 – 90 000*
for comparison (species with relatively low collision rate):
skylark Alauda arvensis	DE	87	0,001-0,002	4 200 000 – 6 400 000*
swallow Hirundo rustica	DE	22	0,001	2 000 000 – 2 800 000*
house sparrow Passer domesticus	DE	3	0,00001-0,00003	11 200 000 – 22 000 000*
quail Coturnix coturnix	DE	1	0,001-0,003	36 000 – 76 000*

What have these species in common and what distinguishes them from the others?

First of all: behaviour. These are species almost every day, entire year, soaring highly (> 50 m), and therefore often being at the height of the rotor (20 – 250 m). They clearly do not avoid turbines, therefore they often collide with them. The highest risk of their collision occurs not during migrations, but in their breeding, wintering and feeding grounds. Species which flying usually very low, and flying higher only during migrations are much less vulnerable to collisions. Moreover, one of the reasons of low collision rate is also that they are passing then mainly on the level much exceeding the height of wind turbines. For example the probability of collision of quail is negligible. The quail is passing highly and only twice per year: during fall migration to wintering ground and spring migration to breeding ground. What’s more, from my observations I conclude that migrating flocks of bigger species, such as geese and lapwings, clearly avoid turbines – just like other obstacles. Therefore, they rarely succumb to collision with them (see: Dürr 2019). Flocks of migrating waterflow can avoid turbines both at day and at night, also in poor visibility (Kühn et al. 2005).
Second: number. They are uncommon species (occurs at relatively low densities on a scale of country). The number of collisions alone can indicate at the most on vulnerable to collisions of given species, but not on his threat by collisions. Only the comparison of the number of victims with the number of species can be a measure of the threat of given species by collisions. The same number of collisions has a relatively more negative impact on the populations of uncommon species than common ones. For example death of 5 rare white-tailed eagles or griffon vultures has a much more negative effect on their populations than death of 5 common skylarks or swallows.

The combination of these two factors (behaviour that vulnerable given species to collisions and relatively low number of given species) make a given species threatened by collisions with wind turbines. There is no data on the mortality of birds on the offshore turbines, but according to the above onshore-turbines conclusions, it can be presumed that seabirds often soaring highly throughout the whole year also belong to the most collisional species.

Therefore can tentatively conclude that the most threatened by collisions are (In B-finder Team we call it: category 1.) uncommon bird species throughout the whole year often soaring highly. To such species belong:

– diurnal raptors,

– storks,

– ravens,

– some large and medium size owls,

– flying seabirds (such as gulls, shearwaters, fulmars, jaegers, sulids, pelicans, petrels, albatrosses, tropicbirds, frigatebirds and some terns).

Fig. 1. The griffon vulture soaring near Ciudad Rodrigo phtographed by Michał, B-fnder Team, during his holidays in Spain, 2005.

The category 2. are species potentially much less threatened by collisions with wind turbines. These are:

common bird species throughout the whole year often flying high (at the height of wind turbine rotors i.e. 20 – 250 m),
bird species (both common and uncommon) often flying highly only on breeding grounds during their breeding period (mainly performing display flights).

To this category belong: larks, crows, choughs, bee-aeters, swifts, swallows, goatsuckers, pigeons, some owls, hummingbirds, majority of pipits, majority of terns, majority of sandpipers, oystercatchers, practincoles, lapwings, some plovers, rollers, longspurs and snow buntings, snowfinches, serins, some american sparrows. For common species from this group (e.g. skylark or swallow) collisions are not a significant threat due to the large numbers of these species (see above). Whereas in the case of uncommon species from this group large risk of collisions occurs only in their breeding grounds during the breeding periods. Taking into account numbers of these species and the distribution of wind turbines, it can be concluded that this category of species is currently not significantly threatened by collisions with wind turbines.

Other bird species due to their behaviour and numbers are quite not threatened by collisions with wind turbines. This is category 3.

So, only species belonging to category 1 are significantly threatened by collisions with wind turbines. I checked how many bird species regularly occurring in Europe and North America (Canada and USA) belong to this category. As it happens, both in Europe and in North America to category 1 belongs only 15 % of species (Fig. 2).

Fig. 2. Numbers of European and North American bird species significantly threatened by collisions with wind turbines (red), and not significantly threatened (green).

I noticed that all species significantly threatened by collisions are the big birds. Their body length (without a tail that is poorly visible or invisible in the thermal sensors) is at least 15 cm (6 in). This is the length of the smallest birds in this group: lesser kestrel Falco naumanni (in Europe) and american kestrel Falco sparverius (in North America). All B-finder models are sufficient for automatic mortality monitoring of these species – big birds.

When bird mortality monitoring are conducting, one should take into account that serious ecological problem constitute only collisions of species significantly threatened by collisions. Therefore it should not lump all birds together.

Paweł
B-finder Chief Scientific

References:

Dürr T. 2015. Vogelverluste an Windenergieanlagen in Deutschland. Daten aus der zentralen Fundkartei der Staatlichen Vogelschutzwarte im Landesamt für Umwelt Brandenburg. Retrieved April 1, 2016 from http://www.mugv.brandenburg.de/cms/detail.php/bb2.c.451792.de
Dürr T. 2019. Vogelverluste an Windenergieanlagen in Deutschland. Daten aus der zentralen Fundkartei der Staatlichen Vogelschutzwarte im Landesamt für Umwelt Brandenburg. Retrieved February 4, 2019 from http://www.lugv.brandenburg.de/cms/detail.php/bb1.c.312579.de
Kühn M., Cheng P.W., Bergström H., Dahlberg J.-Å, Duffy J., Jacquemin J., Thiringer T., Passon P., Pettersson J. 2005. Utgrunden Offshore Wind Farm: Results of 5 Years of Operation and Research. Copenhagen Offshore Wind.
Mebs T., Schmidt D. 2014. Die Greifvögel Europas, Nordafrikas und Vorderasiens. Biologie, Kennzeichen, Bestände. Kosmos, Stuttgart.
Südbeck P., Bauer H.-G., Boschert M., Boye P., Knief W. 2007. Rote Liste der Brutvögel Deutschlands. Fassung, 30. November 2007. Ber. Vogelschutz 44: 23-81. (fehlerkorrigierter Text vom 6.11.2008).