Report on monitoring of th wind farm impact on birds in

Report on monitoring of th wind farm impact on birds in
the vicinity of Gnieżdżewo (gmina Puck, pomorskie
voivodeship)
Piotr Zieliński, Gerard Bela, Andrzej Marchlewski
Czerwiec, 2009
Piotr Zieliński
Ornithological Stadion
Museum and Institute of Zoology
Polish Academy of Sciences
Nadwiślańska 108, 80-680 Gdańsk
[email protected]
tel. 058 3080759
Gerard Bela
Os. Słoneczne 13/6
64-120 Garzyn
[email protected]
Andrzej Marchlewski
Wejherowska 15
84-100 Puck
[email protected]
Picture on the first page: ©Andrzej Marchlewski
2
Table of contents
1. Introduction ........................................................................................................................4
2. Methods..............................................................................................................................4
2. 1. Counting from an observation point ............................................................................4
2. 2. Searching of dead birds...............................................................................................5
3. Results................................................................................................................................5
3. 1. Brief characteristic of migration..................................................................................5
3. 2. Avoidance behaviour ..................................................................................................9
3. 3. Flight altitude............................................................................................................10
3. 4. Impact of weather conditions on migration................................................................12
3. 5. Penetration of farm area by predators ........................................................................13
3. 5. 1. Detectability of dead birds .....................................................................................13
3. 6. Mortality of birds caused by collisions with turbines.................................................13
4. Comparison of chosen migration parameters.....................................................................16
4. 1. Avoidance behaviour and habituation .......................................................................16
4. 2. Cranes migration in the years 2006-2009 ..................................................................17
4. 3. Mortality...................................................................................................................19
5. Discussion ........................................................................................................................19
6. Conclusions ......................................................................................................................21
7. References........................................................................................................................22
3
1. Introduction
The aim of the project was brief characteristic of the avifauna during spring migration within
the area of wind farm in the vicinity of Gnieżdżewo, gm. Puck, pomorskie voivodeship. The
report has been prepared upon the order of “DIPOL spółka z ograniczoną
odpowiedzialnością” company seated in Warsaw, Wiertnicza str. 169. In particular, the report
aims to describe:
• basic parameters of bird migration;
• the collision risk of birds.
2. Methods
Field surveys aimed to describe bird species composition and their numbers within the wind
farm area during spring migration. The monitoring was carried out only under the turbines of
DIPOL company.
Field surveys were based on:
• counting of birds from an observation point
- collected data enabled to describe using the airspace by birds;
- enabled to describe using the farm area as a foraging and resting place;
• searching of dead birds;
- obtained results will be used to estimate mortality of birds resulted from collisions
with turbines.
2. 1. Counting from an observation point
Field surveys – as in previous years – were carried out from the middle of March to the
middle of May (15.03.2009-15.05.2009). Because the basic assumption of monitoring is
collecting long-term data in the same way, methods were the same as in previous years. Bird
surveys ware carried out during a few-hour on-site sessions conducting in different weather
conditions. In March - 9 on-site visits were done, in April – 13, and 4 in May. In total, 26 days
were spent in a field , and on-average on-site visits were carried out every 2 days. In the peak
of migration fallen in April field surveys were carried out every 2-3 days. Bird surveys started
in early morning hours and lasted up to 8 hours. According to migration intensity and weather
conditions, the time of on-site visits were elongated or shortened.
To illustrate using the airspace by birds and estimate which bird species may be most
collision-prone with turbines, flight altitude has been classified into one of 3 categories: 0-40
m, 40-120 m and over 120 m. Flight direction has been also noticed. Weather conditions
having significant impact on flight direction and flight altitude of birds – have been obtained
from Internet (http://new.meteo.pl). Following meteorological data have been collected:
direction and velocity of wind, cloud cover, temperature and precipitation. Data were enriched
in own data collected in a field. Due to the farm location – the necking of Płutnica river valley
– neighbourhood of a forest and expected flight direction – observations were carried out
mostly from one point. Observation of birds behaviour in response to turbines located on their
migration route were also carried out (so called avoidance behaviour). Among other things
one noted: changes of flight direction resulted from a presence of turbines from 0º (no
change) to 180º (max. change of flight direction), flight altitude changes and other kinds of
behaviour, e.g. changes of a flock formation. Data on using the farm area by birds for resting
and foraging were collected during observation from a point, but also while walking between
4
particular turbines. Data on foraging places were also noticed and for all raptors that used
updrafts to increase altitude – a kind of flight. All more numerous bird flocks were mapped in
a scale of 1: 50 000 to show using the farm area as a foraging place.
The number of birds migrating in numerous flocks were estimated by enlarging the unit of
measure. According to this method, first 10 birds were counted preciously and then the count
was done by tens up to 50. The rest of flock was counted by 50s. Similar method has been
used to estimate the number of birds feeding and resting on fields.
Field surveys did not include birds migrating at night.
2. 2. Searching of dead birds
Searching of birds died due to collisions with turbines – were carried out during every field
visit, on average - every 2 days. The area in a radial up to 70 m around every turbine were
inspected. In a case when dead bird has been found, bird species, its age and sex, a distance to
a tower, a kind of injuries and an approximate time of collision were recorded. The
photographic documentation has been also taken.
To estimate how quickly birds died due to collisions with turbines are removed by predators,
on March 26th and April 1st, 7 dead birds were left, coming from the collection of
Ornithological Station Museum and Institute of Zoology PAS in Gdańsk: 2 Chaffinches
Fringilla coeleb, a Goldcrest Regulus regulus, a White Wagtail Motacilla alba, a Robin
Erithacus rubecula, a Great Tit Parus major, and a Starling Sturnus vulgaris. The birds were
left under the turbines no. 3 and 6 in habitats representative for the whole of farm area. During
each visit, one checked from a distance whether birds still lay under the turbines. One did not
approached them not to leave a smell trace which could lead predatory mammals to left birds.
One carried out the experiment based on checking the efficiency of dead birds detection by an
observer. On 26th of March 2009 and 1st of April were left dead birds under turbines. Two
observers have been tested under two different turbines. Birds were left on the same day or a
few days earlier. One person left dead birds for the other in a radial of 70 m. The second
observer could not see where the birds lay. For every observer have been left: one Goldcrest
Regulus regulus, one Chaffinch Fringilla coelebs, a Robin Erithacus rubecula and a Great Tit
Parus major. The time of searching was measured. The observer moved around a turbine
starting from a tower and making circles.
In field studies took part: Andrzej Marchlewski, Gerard Bela, Piotr Zieliński.
3. Results
3. 1. Brief characteristic of migration
In spring, 10449 migrating birds have been recorded on the study area – while flying in a
given direction or birds stopped foraging and resting, belonging to 57 species (Table 1). There
are – among them – species identified only to a genus: geese Anser sp. - 458 individuals,
Passerines Passeriformes – 442 individuals, gulls Larus sp. – 423 individuals. The
identification of these birds was impossible due to conditions: a distance to an observer, a
short time of observation, and difficulties in the identification of some species. To illustrate
the spring migration dynamics, birds number have been shown in 5-day periods.
5
Most intensively birds migrated from a half of March to first days of April (15th-20th 5-day
periods; 15.03-06.04). In this time the most numerous migrating flocks and high diversity of
species were recorded. The peak of migration – the time when migration is cumulated in a
short time - fell in 18th 5-day period (27.03.-1.03.) (Fig. 1). In this time migrated 88% of
Lapwings Vanellus vanellus, 81% of gulls Larus sp., 52% of Passerines Passeriformes (with
dominant Starlings Sturnus vulgaris), geese Anser sp. and 20% of Cranes Grus grus.
The great majority of records concerned flying birds - 72% of all recorded birds during spring
migration (N=7552). Intensity of using the airspace by birds was on average 133
individuals/60 minutes of observation for all species (in the range of 2-419 individuals/60
minutes) and fluctuated. At the beginning of migration (15th 5-day period) was poor (26-54
birds/hour). However, in the peak of migration (18th 5-day period) during one hour migrated
up to 419 birds. In the end of migration in some days was poorly noticeable (2 birds/60
minutes).
6000
Number of birds
5000
4000
3000
2000
1000
0
15
16
17
18
19
20
21
22
23
24
25
26
27
5-day periods
Fig. 1. Changes of the number of migrating birds in spring 2009 shown in 5-day periods.
The most numerous species during spring migration was the Starling Sturnus vulgaris
(N=3644 individuals; 34% of all recorded birds) that foraged mostly on fresh-plugged fields
(N=2153 individuals, 59% of all recorded Starlings). Starlings moved between feeding places
at low altitude (N= 840 individuals, 61% of all migrating Starlings), up to 40 m. Another 38%
of birds (N= 536 individuals) flew in the range of altitude 40-120 m. Starlings migrating over
120 m were not recorded. Another numerous bird species was the Chaffinch Fringilla coelebs
(N=940 individuals; 8% of all birds) that almost exclusively was observed during flight,
mostly up to 40 m over ground (N=838 individuals, 95% flying birds). Single individuals
were recorded higher – up to 120 m (N=42 individuals, 4% of flying birds). A bit more than
6% of Chaffinches (N=60 individuals) used the area for foraging and resting. Common was
also the Crane Grus grus (N=892 individuals; 8% of all birds) that reached exceptional
numbers. More than 99% of them were observed in flight (N=888 individuals). The majority
6
of Cranes flew at altitude > 120 m (N=504 individuals; 56% of all Cranes). There were birds
migrating in a given direction usually at high altitude, significantly making difficult to sight
them. Lower, at altitude 40-120 m were observed birds during direct migration as well as
moving between foraging and resting sites (N=300 individuals; 33% of all Cranes. Only 9%
of Cranes flew lower (up to 40 m) (N=84 individuals) moving on short distances. Only 4
Cranes foraged on fields between turbines.
During spring migration numerous were also gulls Larus sp. observed - almost exclusively –
while flying between feeding places. Their accessibility was related to farmed works.
In a total, 849 individuals belonging to three gull species have been recorded. The numerous
group of gulls were individuals not identified preciously to a species. It is much probably that
they were Herring Larus argentatus and Yellow-legged Gulls Larus cachinnans – species
numerously occurred on the coast. The great majority of gulls moved within the area of the
wind farm at low altitude up to 40 m (N=569 individuals; 67% of all gulls).
Of all 10 raptor species recorded in spring on the study area the most numerous were
Buzzards Buteo buteo (N=128 individuals; 73% of all raptors), other raptors were rare.
Interestingly, there are two records of males of the Pallid Harrier Circus macrourus, which is
an irregular migrant in Poland. The breeding range of this species includes Russia between the
Black Sea, Yenisei River and Lake Baikal (Forsman 1999).
Using the study area by birds for feeding and resting was poor. Only 28% of birds were
recorded on a ground (N=2898 of individuals). Decidedly prevailed small passerine birds
(N=2834 individuals; 97% of all feeding) and among them - Starlings. Other foraging birds
were rare, e.g. raptors, mostly due to sparse migration recorded this spring. The breakdown of
all species recorded during field surveys and their number have been shown in the Table 1.
Table 1. Birds recorded during spring migration in the wind farm area near Gnieżdżewo in
2009.
Bird species
Spring
migration
flying foraging
Total
Sturnus vulgaris
Starling
1491
2153
3644
Fringilla coelebs
Chaffinch
880
60
940
Grus grus
Crane
888
4
892
703
150
853
141
492
Corvus frugilegus + Corvus monedula Rook + Jackdaw
Alauda arvensis
Skylark
351
Anser sp.
geese
458
Passeriformes sp.
Passerines
352
Larus sp.
gulls
423
Fringilla montifringilla
Brambling
369
Larus ridibundus
Black-headed Gull
369
Vanellus vanellus
Lapwing
271
458
90
442
423
50
419
369
6
277
7
Spring
migration
flying foraging
Bird species
Total
Columba palumbus
Woodpigeon
211
2
213
Miliaria calandra
Corn Bunting
129
5
134
Buteo buteo
Buzzard
103
25
128
Anthus pratensis
Meadow Pipit
54
58
112
Carduelis cannabina
Linnet
55
18
73
Emberiza citrinella
Yellowhammer
14
53
67
Carduelis flammea
Redpoll
60
60
Larus canus
Common Gull
50
50
Corvus corax
Raven
41
6
47
Anas platyrhynchos
Mallard
31
13
44
Motacilla alba
White Wagtail
20
24
44
Cygnus olor
Mute Swan
32
Columba oenas
Stock Dove
23
2
25
Turdus pilaris
Fieldfare
22
2
24
Emberiza schoeniclus
Reed Bunting
16
7
23
Pluvialis apricaria
Golden Plover
17
17
Phalacrocorax carbo
Cormorant
16
16
Ciconia ciconia
White Stork
13
13
Milvus milvus
Red Kite
13
13
Motacilla flava
Yellow Wagtail
7
Ardea cinerea
Grey Heron
9
Falco tinnunculus
Kestrel
5
Haliaeetus albicilla
White-tailed Eagle
8
8
Carduelis carduelis
Greenfinch
7
7
Larus argentatus/cachinnans
Herring/Yellow-legged Gull
7
7
Accipiter nisus
Sparrowhawk
5
5
Pica pica
Magpie
5
5
Hirundo rustica
Barn Swallow
4
4
Passer domesticus
House Sparrow
4
4
Perdix perdix
Grey Partridge
4
4
Anser anser
Greylag Goose
3
32
5
12
9
3
8
3
8
Spring
migration
flying foraging
Bird species
Total
Buteo lagopus
Rough-legged Buzzard
3
Circus aeruginosus
Marsh Harrier
1
Sylvia communis
Whitethroat
Aquila pomarina
Lesser Spotted Eagle
2
2
Circus macrourus
Pallid Harrier
2
2
Philomachus pugnax
Ruff
2
2
Turdus iliacus
Redwing
2
2
Charadrius dubius
Little Ringed Plover
2
2
Erithacus rubecula
Robin
2
2
Aquila sp.
unidentified eagle
1
1
Corvus corone
Hooded Crow
1
1
Circus cyaneus
Hen Harrier
1
1
Parus major
Great Tit
1
1
Sylvia curuca
Lesser Whitethroat
1
1
Phoenicurus ochruros
Black Redstart
1
1
Remiz pendulinus
Penduline Tit
1
1
Saxicola rubetra
Whinchat
1
1
2897
10449
7552
3
2
3
3
3
3. 2. Avoidance behaviour
Avoidance behaviour resulted from a presence of wind turbines on the migration route was
recorded in 92 individuals from 4 species (Table 2) and concerned only a bit more than 1% of
birds recorded in flight during the whole of spring migration. Changes of flight direction most
frequently were observed in Cranes Grus grus (N=87 ind., 94% of all birds showing
avoidance behaviour), in the Red Kite Milvus milvus (N=2 ind.), the Lapwing Vanellus
vanellus (N=2 ind.) and in the White-tailed Eagle Haliaetus albicilla (N=1 ind.). Avoidance
behaviour based especially on: changes of flight direction maximally by 90º, changes of
altitude or changes of flock formation (Picture 1). Some of birds showed also “nervous
behaviour” while flying between turbines based on a few or several dynamic changes of
direction lasting up to the moment when birds found the empty airspace. In most cases flight
direction was corrected in - so called - collision zone between 40 and 120 m and concerned 80
individuals (86% of birds). Above this zone (>120 m) avoidance behaviour were recorded in
12 individuals.
9
Picture 1. Migrating Cranes Grus grus and
a Buzzard Buteo buteo changing the flock
formation over the wind farm in spring
2009. Avoidance behaviour was observed
frequently in bird flying in a given
direction in spite of high altitude of
migration (photo P. Zieliński)
Table 2. Avoidance behaviour of particular bird species recorded in spring 2009.
Avoidance behaviour
Change of direction other
90o
Total
increase of altitude
„nervous” behaviour
Species
Crane, White-tailed Eagle,
Red Kite
Crane
Lapwing
Number
of birds
65
25
2
92
3. 3. Flight altitude
The main migration took place at low altitude (Fig. 3). Most intensive using the airspace took
place up to 40 m over ground. In this zone migrated over 60% of birds (N=4256 individuals).
In two other zones migration had similar intensity. Together with change of particular altitude
zones, bird species composition also changed. The highest diversity of species was observed
low, up to 40 m (N=35 bird species). In the range of 40-120 m – 21 bird species, and 17
species above 120 m. In the lowest zone were recorded small bird species as well as large little maneuverable. In the next two altitude zones prevailed large-size birds. Such differences
probably results from difficulties in noticing small Passerines migrating higher especially
during sunny days with high pressure. In the lowest zone prevailed small Passerines (N=3172
individuals; 69% of all Passerines). Common, in this zone, were also raptors, thought the most
preferred altitude for migration was altitude >120 m. Generally, together with increase of
altitude of raptors migration, increased also the size of migrating flocks. In the lowest altitude
zone only single individuals were observed (1-2 birds, 29 records), higher migrated small
groups of maximum 3 individuals (1-3 birds, 36 records). However, at high altitude (> 120 m)
migrated single individuals as well as groups of maximum 8 birds. Only at high altitude were
10
recorded flocks of 4-8 birds (6 records). The migration of wildfowl – mostly geese Anser sp.
took place as usual at high (considerably over rotor-level) altitude, making difficult to identify
bird species. Lower, moved single ducks that foraged on small water ponds within the farm
area. Using the airspace by Cranes Grus grus was significant especially at the rotor-level.
Some birds at this altitude migrated toward eastern direction (N=115 individuals), but other
(N=185 individuals) formed flocks (V-shaped) and increased altitude after starting from
foraging place located in the Płutnica river valley. Cranes moved over the farm area toward
all directions and more than 1/3 of them directed toward Bielawskie Błota [nature reserve]
where was located the night roosting place. At rotor-level the most often were recorded group
up to 10 individuals. Rarely flew flocks of 20-60 birds, and exceptionally up to 80 birds.
Long-range migration taking place at high altitude (> 120 m) concerned small flocks (up to 10
individuals) as well as flocks up to 80 birds (Fig. 2).
In spite of intensive using the collision zone by Cranes, the number of migrating birds grew
together with altitude (Fig. 2). For all bird species the zone of working rotors (40-120 m) –
where most frequently collisions take place – was used by less than 20 % of birds.
flight altitude (m): 0-40
flight altitude (m): 40-120
26
24
22
20
18
16
14
12
10
8
6
4
2
0
flight altitude (m): >120
Number of cases
Crane Grus grus
26
24
22
20
18
16
14
12
10
8
6
4
2
0
26
24
22
20
18
16
14
12
10
8
6
4
2
0
N _0
N _(10 )
N_( 10;20)
N _( 20;3 0)
N _(3 0;40)
N_(40;50)
N_(50;60)
N_( 60;70)
N_( 70;80)
N_ >80
Ranges of number
Fig. 2. Categorized histogram of using the airspace by Cranes during spring migration in
relation to flock size and flight altitude in 2009.
11
Passerines
Cranes
[m]
[m]
> 120
> 120
40-120
40-120
0-40
0-40
0
1000
2000
3000
4000
0
Number of birds
200
400
600
Number of birds
Raptors
Wildfowl
[m]
[m]
> 120
> 120
40-120
40-120
0-40
0-40
0
20
40
60
80
Number of birds
0
200
400
600
Number of birds
All bird species
[m]
> 120
40-120
0-40
0%
50%
100%
Fig. 3. Approximate flight altitude of Passerines, Cranes, raptors, wildfowl and all bird
species in spring 2009.
3. 4. Impact of weather conditions on migration
Spring migration intensity irrespective of wind velocity was similar. At weak wind 0-10 km/h
2720 migrating birds have been recorded (36 %). At middle wind velocity blowing in the
range of 11-20 km/h birds migrated a bit less numerously – 1898 ind. (25%). Together with
increase of wind velocity > 20 km/h migration was again more numerous - 2916 individuals –
38% of migrating birds. Up to 40 m migration was very similar irrespective of wind velocity.
Birds flying higher (40-120m) preferred for migration stronger wind blowing with velocity >
20 km/h. However, direct migration at higher altitude > 120 m took place at weak wind (0-10
km/h) or at strong (> 20 km/h).
Spring migration took place toward all directions with similar intensity (Fig. 4), though
slightly more were recorded during migration toward south. Clearly marked migration toward
12
north and west concerned birds moving on relatively small distances in relation to wind
direction.
N
NW
NE
W
E
SW
SE
S
Fig. 4. Directions of bird migration over study area in spring 2009.
3. 5. Penetration of farm area by predators
According to carried out experiment with dead birds left under turbines one may conclude
that penetration of farm area by predators was not significant. An average time of exposition
was a bit more than 6 days. A Robin lay shortest (3 days), and a Starling – longest (9 days).
3. 5. 1. Detectability of dead birds
Left Goldrest was found by one of observers after 2 minutes, and a Chaffinch after 12
minutes. The Robin has been found after 15 minutes, the Great Tit after 17 minutes. The other
observer after searching lasting 33 minutes did not find any left bird.
3. 6. Mortality of birds caused by collisions with turbines
In spring 2 dead birds that collided with turbines were found - a Starling Sturnus vulgaris and
a Yellowhammer Emberiza citrinella (Picture 2, 3). The Yellowhammer is a common
breeding species in Poland, widespread in the whole of the country, usually sedental with a
stable population. The Starling is also common and during migration locally may occur in
large numbers. The breeding population of this species shows small decline or fluctuates in
succeeding years. The number of the Starling in Europe significantly decreased in last years
mostly due to changes of farmland using (Tomiałojć, Stawarczyk 2003, Chylarecki, Jawińska,
Kuczyński 2006, Sikora et al. 2007). The birds have been found in the second half of March
and in April under different turbines (Fig. 5). Their sex and age were identified according to
manual for bird identification in hand - Svensson (1992). Found birds were adult, a Starling
was a male, and a Yellowhammer – a female. The inspection of birds showed that the
Yellowhammer collided minimum 10 days earlier. However, the collision of the Starling took
place 1-2 days before finding.
13
study area
• wind turbine
dead bird
Fig. 5. Location of dead birds found under turbines near Gnieżdżewo in spring 2009. Digits –
numbers of wind turbines assumed for the purposes of this report.
14
Mortality of birds due to collisions with turbines was 0.1 birds/turbine during 2 months of
studies (15th March-15th May) and stayed on a low level.
Dead birds found within the wind farm area near Gnieżdżewo are:
• protected under art. 33 par. 1 of Act on Nature Protection;
• are not listed in Annex 1 of Birds Directive (EU Directive 79/409/EWG on protection
of wild birds);
• are not listed in Polish Red Data Book of Animals (Głowaciński 2001).
Table 3. Dead birds found under turbines near Gnieżdżewo in spring 2009.
Species
Number
of ind.
No. of
turbine
Distance to tower
(m)
Date
1
11
1
13.04.2009
8
4
20.03.2009
Sturnus vulgaris
Starling
Emberiza citrinella
Yellowhammer 1
Picture 2. Dead Starling Sturnus vulgaris found under the turbine no. 11 on 13th of April
2009 on the wind farm area near Gnieżdżewo (photo A. Marchlewski).
Picture 3. Dead Yellowhammer Emberiza citrinella found under the turbine no. 8 on 20th of
March 2009 on the wind farm area near Gnieżdżewo (photo A. Marchlewski).
15
4. Comparison of chosen migration parameters
4. 1. Avoidance behaviour and habituation
Wind farms and other kinds of constructions existing on the birds migration route obligate
them to work out some kinds of behaviour enabling farther migration and in extreme cases
contribute to avoid collisions. There are three the most important kinds of behaviour observed
in migrating and breeding birds: avoidance behaviour – all changes of flight direction resulted
from a presence of a barrier. In an extreme case the migration route can be changed by birds
due to deterring effect of a barrier. Habituation – gradual accustoming to a barrier and
physical habitat loss resulted from building of turbines in feeding area. The majority of these
kinds of behaviour is positive (habituation, changes of flight direction) and significantly
decreases the collision risk. This concerns especially common bird species on the area that use
intensively the airspace - poorly maneuverable, large-size species and small passerine birds
migrating in numerous flocks. In the years 2007-2009 during spring migration avoidance
behaviour of 10 birds species has been recorded. This concerned very small birds – Passerines
and large ones – raptors, Cranes, in a total of 229 individuals (Table 4). Nearly half of
avoidance behaviour cases were recorded in a collision zone (N=99 individuals; 43%).
Interestingly, over zone of a working rotor (> 120 m) cases of avoidance behaviour were more
frequent (N=121 individuals; 52%). The least correction of flight direction was noticed in
small birds that changed a direction by maximally 45º. Large-size birds, e.g. Cranes, Whitetailed Eagles corrected flight direction much more, changing chosen direction completely
even by 180º and bypassing the barrier.
Other kinds of avoidance behaviour recorded during spring migration were changes of
altitude taking place usually out of wind farm area, disrupting of migrating flock (flocks of
geese and Cormorants) and “nervous” behaviour of birds flying through farm area. Less
frequently were observed birds turning back. Such change of direction resulted from a
presence of a wind farm were caused by so called barrier effect - birds flying in spring at first
toward east changed flight direction toward south or north.
All described above, abnormal kinds of behaviour, resulting from a presence of a barrier had
different intensity in relation to birds number. In a case of the Crane – a species most
frequently correcting flight direction, the number of migration birds in the years 2007-2009
were adequately 623 individuals, 254 individuals and 888 individuals. In all of the years the
percentage of birds correcting direction were not higher than 10% (9%-2007, 4% - 2008, 9% 2009). In a way small correction of direction or altitude are desired. Together with growing
number of cases, the probability of the collision with turbines decreases. The lack of dead
victims among large-size collision-prone species confirms such predictions.
16
Table 4. Avoidance behaviour observed in the years 2007-2009 during spring migration.
Bird species
Year
Number of birds
Buteo buteo
Miliaria calandra
Cygnus olor
Columba palumbus
Grus grus
Accipiter nisus
Milvus milvus
Columba oenas
Buzzard
Corn Bunting
Mute Swan
Wood Pigeon
Crane
Sparrowhawk
Red Kite
Stock Dove
2007
2007
2007
2007
2007
2007
2007
2007
23
2
4
31
61
1
1
3
Grus grus
Crane
2008
11
Haliaeetus albicilla
Grus grus
Milvus milvus
Vanellus vanellus
White-tailed Eagle
Crane
Red Kite
Lapwing
2009
2009
2009
2009
1
87
2
2
Total
229
4. 2. Cranes migration in the years 2006-2009
During spring migration taking place from the end of February to the half of May the Crane is
regularly recorded in the whole of country area, however, more numerous migration takes
place - among other things - in northern Poland, especially on the coast (Tomiałojć and
Stawarczyk 2004). In the vicinity of the Gdańsk Bay a key resting-site on the migration route
of the species and while breeding season are Bielawa marshes [Bielawskie Błota nature
reserve]. Intensive research in this area enabled to describe dynamics of Cranes migration and
using this site and the vicinity in a year cycle (Sikora et al. 2004). The research carried out on
the wind farm area near Gnieżdżewo in the years 2006-2009 during spring migration showed
fluctuating intensity of Cranes migration in succeeding years (Fig. 6, 7). The earliest peak of
migration were recorded in 2007 – in the second half of March. The maximum number in a 5day period was - 183 birds. Generally, migration of Cranes is double-peaked and the second
one is usually lower than the first one. In 2009 migration of Cranes was unusually numerous.
Frequently flocks of 100 to nearly 200 birds were recorded. The peak of numbers in this
spring fell in the end of migration of the species. In the first half of may were recorded the
biggest flocks with maximum up to 350 birds in one 5-day period.
17
Crane
Crane
400
350
800
Number of birds
Number of birds
1000
600
400
200
300
2006
250
2007
200
2008
150
2009
100
50
0
0
2006
2007
2008
2009
Years
Fig. 6. Changes of the number of Cranes
during spring migration in the years 20062009. The trend line has been shown.
14 15 16 17 18 19 20 21 22 23 24 25 26 27
5-day periods
Fig. 7. Changes of the number of Cranes
during spring migration shown in 5-day
periods.
Using the airspace by Cranes in spring in the years 2006-2009 fluctuated (Fig. 8). Data
collected in pre-investment and post-investment period showed that the main migration takes
place at high altitude - above 120 m. Univocally, it indicates that the investment does not
obligate to change flight direction – there is not so called “barrier effect”. Intensity of the
airspace using by birds at a working rotor level (40-120 m) also depends on the number of
birds. The potential collision risk could take place in 2007 year when in spring in this zone
were recorded nearly 200 Cranes, and also in 2009 – when in a collision zone moved nearly
300 Cranes during spring. The lack of collisions with turbines probably results from adequate
adaptation of these birds to relatively new element of landscape, which is a wind farm.
Doubtless, avoidance behaviour is a kind of adaptation, most frequently observed just in
Cranes (N=159 individuals; 69% of all birds showing avoidance behaviour). Moreover,
Cranes due to their long life may accustom and remember wind farm locations and
successfully avoid them. All these positive kinds of behaviour give good results during
permitting weather and when birds do not reach maximum numbers. It is worth to emphasize
that in future may come to collisions of Cranes with turbines due of gradually increasing
number of individuals. During 4 springs one noted that the number increased between years
2006 and 2009 more than twice (Fig. 8). Generally, the number of migrating birds still grows.
Interestingly, in last years has been observed higher increase of the airspace using by Cranes
at rotor level (40-120 m) and in the lowest zone (0-40 m) than above 120 m. In spite of the
growing number of Cranes in particular years, their number as compared with all species is
still lesser than 3%. The above analysis showed that the attractiveness of adjacent feeding
sites grows what means that using the airspaces over the farm area also may increase.
18
altitude 40-120 m
Crane
400
Number of birds
Number of birds
1000
800
600
400
200
0
300
200
100
0
2006
2007
2008
2009
2006
2007
Years
Number of birds
Number of birds
80
60
40
20
0
2008
Years
2008
2009
altitude >120 m
100
2007
2009
Years
altitude 0-40 m
2006
2008
2009
600
500
400
300
200
100
0
2006
2007
Years
Fig. 8. Changes of the number of migrating Cranes Grus grus in the years 2006-2009 in
particular altitude zones. The trend line has been shown.
4. 3. Mortality
During spring migration in the years 2007-2009 mortality of birds resulted from collisions
with turbines stayed on a low level. In all 3 seasons 2-3 birds collided with turbines annually
(most in 2007). Victims of collision were always small passerine birds Passeriformes: the
Goldcrest Regulus regulus, the Skylark Alauda arvensis, the Snow Bunting Plectrophenax
nivalis, the Starling Sturnus vulgaris and the Yellowhammer Emberiza citrinella. All the
species are protected under art. 33 par. 1. of Act of Nature Protection and not listed in Annex
1 of Birds Directive EU Directive 79/409/EWG on protection of wild birds. Species of birds
found under turbines are common. During breeding season they reach in adequate habitats
high densities. During migration are also numerous, exceptionally even invasive. Mortality
observed in the farm area near Gnieżdżewo is not important for breeding and migrating
population of mentioned species.
5. Discussion
In the years 2006-2009 basic parameters of spring migration – the number of birds and
species composition - varied significantly. The first year of studies showed the potential of
this site located on the migration route of birds breeding in Eastern Europe and in Asia. The
large-scale character of migration observed at that time (nearly 30 thousands of birds in 2006)
has not been recorded in succeeding years. In 2007 year – 8011 birds were recorded, in 2008
– 7073 birds and in 2009 - 10449 birds. Lesser number of birds in succeeding years does not
19
indicate the decline of the number of migrants or change of the migration route. It probably
results from fluctuations of the number, weather conditions during fields survey - direction
and velocity of wind, temperature, cloud cover, and a pressure (Langston, Pullan 2003). The
most permitting weather to take up long-distance migration is at that time when prevail
systems of high pressure with weak wind blowing from a direction, which birds fly toward
(front wind). At that time main migration takes place considerably higher over ground and
small birds – as observation showed – prevailing in this site - are not sighted by an observer.
However, in spring 2006 prevailed low pressure obligating birds to fly on a low level and
enabling to count them. Among migrants prevailed small passerines Passeriformes. They
were 28% - 77% of all recorded birds in different years. Numerous were also gulls Lari and
wildfowl Anseriformes - mostly migrating geese. Decrease of the number of raptors
Falconiformes observed in the vicinity of Gnieżdżewo has been noting since 2008.
In a way it is a positive phenomenon due to the significant collision risk of raptors, however,
from the other hand one can see a negative deterring effect of wind farms that contribute to
significant impoverishment of migrating avifauna of this site. One recorded that the species
number decreases in similar fast rate. In 2006 - 16 species of raptors have been recorded. e.g.
the Golden Eagle Aquila chrysaetos, the Lesser Spotted Eagle Aquila pomarina, the Whitetailed Eagle Haliaeetus albicilla, the Osprey Pandion haliaetus listed in Annex 1 of Birds
Directive. In the next years 2007-2009 accordingly - 12 species, 11 species and 10 species.
Interestingly, significant increase of Cranes Grus grus number was recorded in this site last
year that flew at low altitude (up to 120 m) more frequently than during pre-investment
period.
Changes of the number observed while lasting of monitoring on the wind farm area may have
different grounds. Most frequently they resulted from annual fluctuations of birds number due
to e.g. low breeding success or survival rate on wintering sites. Changes of the migration
route may have also been caused by a wind farm being a barrier for birds. However, a barrier
effect has the most significant impact on breeding birds that regularly move between feeding
area and their nests or on birds that frequently and numerously fly through farm area, e.g.
from night roosting site toward feeding area. In a case of birds nesting in colonies, a barrier
which is a wind farm and which birds must fly through may cause the increase of the collision
number (Everaert and Stienen 2007, Stienen et al. 2008). However, change of the migration
route is most frequently caused by many wind farms covering large area (Drewitt and
Langston 2006).
To the group of most collision-prone birds species belong large-size and poorly maneuverable
species and birds using the airspace in high density and intensity, e.g. birds breeding in
colonies, raptors (Kingsley and Whittman 2005, de Lucas et al. 2007, Everaert and Stienen
2007, Stienen et al. 2008). According to Barrios and Rodriquez (2004), Everaert and Stienen
(2007), higher collision factor has been recorded in sites with high density of breeding pairs,
in neighbourhood of breeding colonies or in the vicinity of communal roosting sites where
birds many times during breeding season move in big flocks between roosting and foraging
places, e.g. Starlings.
In addition, the collision risk may be forced by other factors, e.g. field topography, the
location of farm, species composition and density of birds flying through the wind farm area
(Langston and Pullan 2003). Studies carried out near Gnieżdżewo showed relatively small
number of collision-prone species. The number of raptors between the years 2006-2009
decreased by a half. The number of birds species also decreases. Main migration of other
collision-prone species (Cranes, geese) takes place mostly at high altitude. Long-term studies
carried out on the farm area as well as and in the vicinity show how much changeable are
basic parameters of migration. Some systematic groups – recently relatively numerous and
20
represented by many species (raptors) – now are recorded less frequently what is – in a way –
positive. However, other species, e.g. Cranes are recorded more frequently in this area, which
is used not only for migration but also for resting in the vicinity of wind farm (the Płutnica
river valley).
Mortality of birds within the area of wind farm near Gnieżdżewo was 0.1 birds/turbine during
2 months and stays on a low level. Moreover, during last three springs (2007-2009) the
number of birds that collided with turbines is almost constant. Such little number according to
some authors (de Lucas et al. 2007) may result from short-term using this area for migration
and from relatively low intensity of migration – additionally - fluctuating in particular years.
Mortality of birds due to collisions with turbines fluctuates, sometimes is very low – 0.03
bird/turbine/year (de Lucas et al. 2007), 0.19 bird/turbine/year (Barrios, Rodriguez 2004), and
sometimes very high – up to 345 dead birds during 2 years (Lekuona and Ursula 2007).
6. Conclusions
1. during spring migration 10449 birds were recorded belonging to 57
species; the most numerous species was the Starling Sturnus vulgaris,
the Chaffinch Fringilla coelebs and the Crane Grus grus;
2. the farm area in Gnieżdżewo is used by birds for long-range migration,
local movements, for feeding and resting; migration took place toward
all directions, however, the most frequently toward the south with a
peak in the end of March (18th 5-day period; 27.03.-31.03.2009);
3. 72% of birds migrated through or over the farm, and 28% of birds
rested or foraged on the farm area;
4. avoidance behaviour was recorded in 92 individuals - 1% of birds
recorded in a flight and mostly concerned large-size species, in
particular Cranes Grus grus (N=87 individuals);
• in the years 2007-2009 avoidance behaviour of 10 bird species
(N=229 individuals) was recorded; most frequently the
correction of flight direction was observed in Cranes Grus grus;
5. migration took place mainly at low altitude - up to 40 m over ground
(60% of all birds), on average 20% of birds migrated at a rotor level
(40-120 m) and the same number in the zone > 120 m;
6. in spring 2009 were recorded 2 birds died due to collision with
turbines: one Starling Sturnus vulgaris and one Yellowhammer
Emberiza citrinella, found under the turbines no. 11 and 8;
7. mortality of birds died due to collision with turbines near Gnieżdżewo
stays on a low level – 0.1 bird/turbine during 2 months of studies.
21
7. References
Barrios L., Rodriguez A. 2007. Spatiotemporal patterns of birds mortality at two wind farms
of southern Spain. In: de Lucas M., Janss G. F. E., Ferrer M. (eds.) Birds and wind farms.
Risk Assessment and mitigation. Quercus, Madrid.
Chylarecki P., Jawińska D. & Kuczyński L. (2006). Monitoring Pospolitych Ptaków
Lęgowych – Raport z lat 2003-2004. Warszawa: OTOP
Drewitt A. L., Langston R. H. W. 2006. Assessing the impacts of wind farms on birds. Ibis
148: 29-42.
Everaert J, Stienen E. W. M. 2007. Impact of wind turbines on birds in Zeebrugge (Belgium):
Significant effect on breeding tern colony due to collision. Biodiversity and Conservation 16:
3345-3359
Forsman D. 1999. The raptors of Europe and the Middle East. A handbook of field
identification. T&AD POYSER. London
Głowaciński Z. (red.) 2001. Polska czerwona księga zwierząt - kręgowce. PWRiL, Warszawa.
Kingsley A., Whittman B. 2005. Wind turbines and birds. A background review for
environmental assessment. Environment Canada/Canadian Wildlife Service.
Langston R. H. W., Pullan J. D. 2003. Wind farms and birds: an analysis of the effects of
wind farms on birds, and guidance on environmental assessment criteria and site selection
issues. Strasbourg, Council of Europe, Directorate of Culture and Natural Heritage.
Leukona J. M., Ursula C. 2007. Avian mortality in wind Power plants of Navarra (Northern
Spain). In: de Lucas M., Janss G. F. E., Ferrer M. (eds) Birds and wind farms. Risk
Assessment and mitigation. Quercus, Madrid.
de Lucas M., Janss G. F. E., Ferrer M. (eds) 2007. Birds and wind farms. Risk Assessment
and mitigation. Quercus, Madrid.
Sikora A, Półtorak W. 2004. Bielawskie Błota. Ss. 137-141 w: Sidło P.O., Błaszkowska B. &
Chylarecki P. (red) Ostoje ptaków o randze europejskiej w Polsce. OTOP: Warszawa
Sikora A., Rohde Z., Gromadzki M., Neubauer G., Chylarecki P. (red.) 2007. Atlas
rozmieszczenia ptaków lęgowych Polski 1985-2004. Bogucki Wyd. Nauk., Poznań.
Stienen E. W. M., Courtens W., Everaert J. 2008. Sex-biased mortality of common terns in
wind farm collisions. The Condor 110(1): 154-157.
Svensson L. 1992. Identification guide to European passerines. Stockholm
Tomiałojć L. & Stawarczyk T. 2003. Awifauna Polski: rozmieszczenie, liczebność i zmiany.
PTPP "pro Natura", Wrocław.
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