Satellite telemetry of Corncrake
Co-financed by the EU and European Regional Development Fund. Investing in your future. This project was financed by Cross-border Cooperation Operational Programme Objective 3 Czech Republic – Free State of Bavaria 2007–2013 1 Content
Study and protection of an enigmatic bird from agricultural landscapes . . . 3 Introducing the studied species ...... 3. What we know about Corncrakes ...... 4. What is satellite telemetry? ...... 6. Project objectives ...... 8. Monitoring and tagging methods ...... 8. How we used satellite transmitters to follow Corncrakes in the field . . . 10. Project results ...... 13. Behaviour in breeding areas ...... 13. Basic data for all tagged birds ...... 15. Experiences in Corncrake protection ...... 15. Migration ...... 19. Conclusions ...... 21 Animal species typical for biotopes of Corncrakes ...... 21. Final remarks ...... 22. Acknowledgements ...... 23.
Cryptic coloration and slow movements make Corncrakes almost invisible in vegetation. Study and protection of an enigmatic bird from agricultural landscapes
This joint Czech–German research project was launched with financial support from the European Regi- onal Development Fund: OBJECTIVE 3 “Investing in your future” 2007–2013. The project was administ- ered jointly by the Zoological and Botanical Garden of Pilsen and by LBV Cham, and it would not have been possible without the enthusiastic efforts of many ornithologists and other friends of nature. The study was carried out in the national protected landscape areas (NPLA) of Český les and Šumava in Pilsen Region, NPLA Slavkovský les in the Karlovy Vary Region (all in the Czech Republic), and also in the Cham District in Bavaria.
Introducing the studied species
The Corncrake (Crex crex) is a medium-sized member of the Rallidae family. Reminding one of a small par- tridge, Corncrakes typically weigh about 165 g. In total 15 species may be found in the Palearctic realm, while in the Czech Republic only 7 species have been documented, 2 of which are very rare. It is a typical species in wet meadows within agricultural areas. This exclusively migratory species has documented winter grounds in equatorial and southern parts of Africa.
The detailed biology of the Corncrake is still little known. It is protected in the European Union (EU) by Council Directive 79/409/EEC on the conservation of wild birds. This law was adopted by the Czech Republic in corresponding legislation for the protection of nature and Corncrakes are listed as a specially protected species in the category of extremely endangered species.
Protection of Corncrakes in the Czech Republic is supported, too, by other agricultural and environmental measures, and in particular by government directive 79/2007, which regulates husbandry of cultivated mea- dows and abandoned arable lands in areas where this species has been proven to occur.
Corncrake is a rather inconspicuous species, living mostly within dense grassland vegetation, and its pre- sence is often confirmed only by its stereotypic loud mating calls. Calling males defend their territories, and this facilitates their capture using playback recordings.
When escaping, corncrakes do not like to fly but rather disappear very discreetly by running in a crouched position with the head horizontally extended.
3 What we know about Corncrakes
The birds return from their African winter grounds to the Czech Republic around mid-May for breeding and migrate south again at the turn of August and September. Just after returning north, the males occupy their own previous territories or search for suitable new territories. Such areas are typified by damp mea- dow vegetation or fields with well grown cover, as is necessary for their safety. Their return from winter grounds is indicated by their characteristic monotonous “krekskreks” calls from which their scientific name is derived. From the second half of June, in suitable places one can hear these repeated calls throughout entire nights. Such places constitute so-called communal “leks,” where males effectively attract females from the larger area. During daylight hours, males call only sporadically, with the exception of the peak of the mating season. It is supposed that continuously calling males had not found females for mating. Due to the Corncrake’s extremely secretive lifestyle, the calling of males is the sole indicator of the species’ presence in an area. Suitable biotopes mainly include wet meadows, riparian lowlands around streams, old grown-up pastures, and, as may be necessary in some areas, agricultural fields with alfalfa or grain crops.
Females also can be heard in some cases, but their voices sound deeper. It is supposed that Corncrakes do not form (long-term) pairs. Females clutch twice a year, brooding about 6–10 mottled eggs in a nest usually hidden in dense meadow.
a b
c d
Chicks grow very rapidly and can fly after 2 weeks. Young chicks are black but soon turn brown: a) 3 days, b) 10 days, c) 13 days, and d) 17 days.
4 In years with usual weather conditions, the first clutch hatches around 15th June and the second at the beginning of August. Breeding is influenced by landscape elevation, however, and the number of chicks successfully raised depends on the timing of mowing. Females incubate their eggs alone for 17 days. Chicks grow quickly and their black colour turns to a spotted brown at the age of about 2 weeks, at which time they also can fly.
In mid-July the males mostly stop calling and begin moulting. Because the birds are synchronous moulters, they are unable to fly for 10 days and are very vulnerable at this time.
Direct observations of Corncrakes are very rare and discovery of their nests is quite exceptional. The- refore, all density figures are based only on “number of calling males”. As measured by this method, the total number of calling males in the Czech Republic is estimated (extrapolated) to be about 1,500–1,700.
In Pilsen Region, approximately 100 territories of males have been estimated to occur. This figure fluctuates from year to year according to vegetation development at the time of calling and also general weather conditions, but variation is probably also due to mortality during migration in some years.
Numbers of calling males in 2014 May June
Studied areas and locations of calling males in two monitoring periods (May and June) in 2014.
5 What is satellite telemetry?
Satellite telemetry (Argos system) is an automatic method for following the movements of tagged ani- mals. With their global coverage, the satellites can identify and locate the special transmitters even if birds are moving great distances over the sea or uninhabited areas, between continents, and the like.
The small airborne Argos-certified platform transmitter terminal (PTT) repeatedly sends short messages (0.2 seconds long, so-called “beeps”) in programmed periods every minute. Messages include a coded ID and other technical data (temperature, voltage, activity, etc.).
Messages from some larger PTTs may also include precise GPS locations as collected periodically according to the PTTs’ programming. However, such PTTs require more energy and are much heavier. The smallest PTTs are dependent only on the older, so-called “Doppler shift method”, which is less accurate because the geographic position is calculated according to the satellite position and very small changes in the received frequencies in subsequent “beeps”.
received frequency
received frequency > transmitted frequency
time
received frequency < transmitted frequency
Doppler curve satellite with polar orbit
leaving satellite approaching orbit
Transmitter (Argos PTT)
Chart illustrating how the Argos system calculates the Doppler shift from PTT messages.
6 Argos locations have highly variable accuracy. Even the very good-quality location of our bird provided by Argos (in the centre of the ellipse) may be off. The anisotropic nature of the error distribution means that the true position is theoretically expected to fall within the ellipse with 67% probability (i.e. 1 standard deviation). The real position of the bird was outside (red dot).
Dispersion of Argos locations (Kalman filter) of ID 115943 (June 17 – September 4, 2012) when the bird remained within a small home range area in the middle according to our field locations. All location classes in blue; best location classes (LC 1 to 3) depicted in red occur within an area of about 8 x 2.7 km.
The Argos commercial service, provided by French and American agencies, is not inexpensive. Today, it is the only functioning global system in the world for very small transmitters. It presently uses 6 active satellites with polar orbits, which means they are always passing over the poles. Thus, each satellite scans the entire globe in a belt about 5,000 km wide approximately every 1.5 hours. Con- sidering the size of Corncrakes, the only suitable tag available in 2012 was Microwave Telemetry’s PTT-100 solar-powered 5 gram tag. In fact, these tags weighed just 4.7 g and thus, given a bird wei- ghing about 167 g, they fall well within the rule of thumb that the extra weight should not exceed 3% of body mass.
At the beginning of our project it was not clear if the standard Teflon ribbon harnessing would be suitable for this species living in dense vegetation and whether the radiating power of the transmitter would be sufficiently strong for the satellites considering that the birds spend most of their time below wet vegetation where an antenna is not erect but rather is almost always touching the ground.
In the first year we verified that the system worked and that the satellites circling at a height of about 900 km above Earth and passing mostly many hundred kilometres to the side recorded at least one good quality location every transmission period. Before using it in the field, we conducted a few succe- ssful experiments with dummy tags at the Pilsen Zoo.
7 Project objectives
The aims of this joint Czech–German project were to: study the little-known biological aspects of the Corncrake, and in particular territorial fidelity, seasonal interactions and dispersal of males, biotope preference, and migration strategy; apply innovative solar-powered satellite technology on a cryptic species that mates at night; systematically survey Corncrake behaviour by a combined telemetry method that includes using satellite-received transmitters to track birds via satellite and also directly on the ground; quantitatively monitor the population on standard plots in areas of Slavkovský les, Český les, Šumava, and Cham District; verify effectiveness of the agricultural subsidy programme for farmers in the Czech Republic and Bavaria; increase collaboration with farmers and propose new areas of management for the protection of this species within the next EU funding period; and raise public awareness of this species and increase its protection in the Czech Republic and Bavaria.
Monitoring and tagging methods
Monitoring of calling Corncrakes is possible only at night, primarily between 10 p.m. and 2 a.m. when their activity reaches its peak. Some birds may also call during daylight, but such calls represent only a fraction of the total and daylight evening counts would be incomplete. In suitable locations we used playback of the call. Wild males tend to approach the voice of a perceived intruder and can be captured using a mist net or dip net. This is a common method of capture used for ringing that can be conducted only by ringers having relevant permits. In our case, permission to carry out this activity in the protected landscape areas was also necessary. After ringing and collecting standard biometrical data (weight, bill, wing, tail and tarsus length), we selected the heaviest, most probably dominant males for tagging. We used a standard backpack installation for the PTTs.
Playback is a very effective method for luring and capturing corncrake males at night. Captured males were safely transported in cloth bags.
8 We always recorded the vegetation type at sites where the birds were identified or captured and the general management of neighbouring field plots was also later identified (timing of mowing, pasturing, anthropogenic changes, etc.). Prior to each night-time monitoring session, a detailed plan was prepared and the entire team split into several field groups with a carefully prepared itinerary for each.
Adverse spring weather sometimes undermined proper measuring of birds in the field and thus not only tag installation but also scientific documentation was carried out in our temporary field bases.
Ultra-small satellite transmitter with a solar cell on the upper part from Microwave Telemetry weighing only 4.7 g.
Proper backpack installation constitutes a very sensitive time and activity. Harnesses must be designed very carefully because corncrakes creep through very dense vegetation. Both harness and tag must fit perfectly into the plumage.
9 Each tagged corncrake was released the next morning in his own territory. This is “Jacob” being released near Srní in the Šumava Mountains. Local meadows form a very important refuge for this species.
How we used satellite transmitters to follow Corncrakes in the field
The transmitter signal is designed to fulfil the technical needs of the Argos system, but it can also be used as a source for direct monitoring in the field. We developed equipment and a methodology for field use that utilize the transmissions to acquire more precise information about tagged birds. In fact, the transmission cycle offers the opportunity to monitor tagged birds almost 20% of the time. The tran- smission periods (“ON”) deliberately progress through the day to provide useful sampling windows such that after a few days the aggregate sample covers the full 24-hour activity cycle. This innovative appro- ach also allows us to locate a bird in the field with extremely high accuracy by means of triangulation. It works especially well for sedentary species, but even moving birds spend some periods in restricted areas where they could be generally located according to Argos coordinates and subsequently studied by this approach.
A simple automatic activity recording system placed at a distance of about 1 km from the area used by a bird allows us to record the strength of all tag messages. As time passes and the tag transmits according to its cycle, transmissions occur at different times of the day. According to the existence and strength of the tag message, we therefore can effectively monitor the presence and activity of the tagged bird.
The activity monitoring system consisted of a simple whip antenna, a receiver (Icom R20, R10 or any other SSB with UHF range), connecting cables and jacks (including a 1:40 resistor attenuator), a voice recorder (Olympus, e.g. VN713PC) and supplementary batteries (6 AA NiMH and 6V lead acid gel battery, if nece- ssary, to support the receiver), all housed in a waterproof container so that it could be buried. The direc- tional system consisted of a rotating antenna with a battery on a tripod, receiver (Icom R20 or as above), laptop computer with a USB external sound card (i-tec) and Audacity/Audition software, specialized Alo- cator software for evaluating signal maxima, and a compass for zeroorientation of the rotating antenna.
10 Automatic recording unit (scheme; alternatively with supporting parallel battery packs for recordings longer than one day).
Installation of the recording unit in the field with antenna and box detail.
Bird‘s wake-up time 5:36 while the sunrise at 5:56 on August 17, 2012
Activity monitoring chart (example): All movements produce signal fluctuations inasmuch as the PTT antenna is always at least slightly changing its orientation. As a result, we can easily identify periods of inactivity. In the recording set, the receiver is adjusted to a relatively low level of gain. Ideally, signals should be just slightly above background noise. The noise can be effectively reduced also by software programs.
11 The actual positions of tagged birds in the field are calculated from bearings detected by a system com- prised of a special rotating antenna, notebook computer, and some simple electronic circuitry. Locations calculated in this way are highly accurate.
A field installation of the rotating antenna set.
Set with rotating antenna (scheme) in the field. Bearings theoretically can be taken from any location (GPS defined) and with the rotator in varying positions, but our experience was that the best results were generated from recordings made repeatedly at fixed points around a bird’s permanent territory using a fixed wooden bracket or a tripod for the rotating antenna (zeroed-oriented to be pointing north), thereby facilitating easier post-processing of data.
ALOCATOR – special software that simplifies field work and post-processing: First screen shows recorded signal fluctuations and enables selecting a representative “round” (360°) for further analysis; the second evaluates graphically and numerically from where the strongest signal is coming.
12 In collaboration with S. Rerucha, special (Java-based) software ALOCATOR was developed that automa- tically indicates bearings from .wav files recorded during antenna rotations and saved by Audacity or another sound program. This software also stores all calculated results in .txt (column delimited) files, including file name (created as a necessary code for each bird/site/spot/repetition in field) and time when measured. A database can easily be assembled from these .txt files for input into triangulation software.
50 45 40 35 30 25 20 15 10 5 0 2012 2013 2014 2015
Numbers of calling males by areas and years: Český les, Slavkovský les, Šumava
Project results
During our 3-year project we tagged 8 Corncrake males in the Czech Republic and 4 males in Bavaria.
Tagged birds remained in the capture area until the time of migration as long as sufficient parts of mea- dows remained unmown until their departure. There was one exception to this in Bavaria, in which case the male probably did not find a female.
Behaviour in breeding areas
Repeated monitoring in the same locations enables the identification of changes from year to year. Num- bers of calling males are influenced by factors unique to the location and year like spring weather condi- tions but may also reflect long-term population dynamics connected with environmental changes that reduce suitable habitats. Management of meadows and urbanization seem to be the most important of these. In total, we documented 297 calling males in the Czech areas and only 16 in Bavaria. Bird identity was not recorded, however, and this count calculates each observation separately. Therefore, many birds may have been counted twice in a single year in both of the two monitoring visits.
During this period, a total of 156 males were ringed in the Czech Republic and only 10 males in Bavaria. Just 6 birds were retrapped already wearing rings. The most interesting case was that of a male coming from Unteres Odertal in Germany to Český les in the same spring. According to biometric data, heavier and thus probably dominant birds were found in the better biotopes. The general results led to revision
13 Males identified in Cham District: 2012, 2013, 2014.
Dr. Baumann and Markus Schmidberger Preparation before night-time monitoring and capturing in NPLA Český les at Přimda. near Cham monitoring “Heinrich”.
and a new design of “field blocks” important for special Corncrake subsidies within an agro-environ- mental programme. Good collaboration with local farmers resulted in more Corncrake-friendly meadow management characterized by delayed mowing and unharvested refugia.
One of this project’s most important discoveries was that tagged birds mostly stayed in very restricted areas until migration if at least some suitable habitat remained. They were silent, but present. Whether or not they were paired and breeding is unclear. However, some males (David, Heinrich, Lubo) moved from areas where the meadows were harvested very early. Activity records documented there to be a stan- dard behaviour of intensive movements during daylight and general night-time inactivity, although some birds continued to call.
14 Basic data for all tagged birds (Note: Due to the transmission period’s being 2 days + 10 hours and insufficient solar charging in some cases, dates may have been inaccurate by as many as several days. Ivan and Lubo returned to Europe next spring.) ADAM BOHUMIL CHRIS FRITZ DAVID EDA PTT ID 115943 115942 115941 128725 128723 128726 Ring No H 140293 H 136889 FL 17577 H 140985 H 144562 H 140984 Tagging place Vranov N. Kramolín Cham Nösswartling Sítiny Zhůří Region Domažlice Mar. Lázně Cham, D Cham, D Mar. Lázně Kašperské Hory Tagging date 17. 6. 2012 2. 7. 2012 24. 5. 2013 24. 6. 2013 24. 6. 2013 23. 6. 2013 Vegetation type mesophile cultivated wetland and cultivated cultivated meadows mesophile cultivated uncultivated natural meadows cultivated meadows meadows meadows meadows Meadow mamagement not mowed totally mowed mowed mowed except totally mowed pasture a small plot Timing of mowing not mowed mowed before mowed before ? mowed before tagging pasture from August tagging tagging Behaviour at home settled - - settled deserted settled Note medows left intact hay harvest, mortality data failure depart to Baltic and longtime settled electric fences return to Broumov area despite cold Departure date 4. 9. 2012 - - end of August 1. 7. 2013 1. 9. 2013 Migration behaviour direct - - monitored till 20.8. - stop-overs Last PTT location 18. 9. 2012 21. 7. 2012 5. 6. 2013 20. 8. 2013 17. 7. 2013 7. 4. 2014 Tracking period (days) 89 20 13 56 23 288 Last location site Eritrea identical identical identical Broumov area, CR Kenya Direct distance (km) 4215 - - - 255 (Balt 500) 6260 Wintering area - - - - - Kenya GOLI HEINRICH IVAN JAKUB KAREL LUBO PTT ID 128724 115941 128727 128729 128728 128730 Ring No H 144580 FL 17586 H 143662 H 148323 H 148325 – Tagging place Srní Cham Žebráky Srní Srní Cham Region Sušice Cham, D Přimda Sušice Sušice Cham, D Tagging date 23. 6. 2013 25. 5. 2014 20. 6. 2014 5. 7. 2014 5. 7. 2014 3. 6. 2015 Vegetation type cultivated meadows cultivated mesophile cultivated meadows cultivated meadows totally and abandoned meadows cultivated meadows and abandoned and abandoned arable mowed arable lands arable lands lands Meadow mamagement mowed later totally mowed mowed later mowed later mowed later mowed later Timing of mowing mowed on 26. 7. mowed after 1. 6. mowed after 20. 8. mowed 10. 8. mowed 10. 8. mowed June Behaviour at home settled deserted settled settled settled deserted Note short move to numerous stop- small wetland and corner left not corner left not stop-overs: Czechia, nearby valley overs after depart edges not mowed mowed mowed, later PTT Serbia, Croatia on 22. 6. failure Departure date 2. 9. 2013 7. 9. 2014 5. 9. 2014 4. 9. 2014 20. 8. 2014 28.–31. 8. 2015 Migration behaviour direct stop-overs direct direct stop-overs direct Last PTT location 9. 11. 2013 23. 9. 2014 22. 10. 2015 4. 12. 2014 28. 10. 2014 5. 5. 2016 Tracking period (days) 139 121 489 152 115 337 Last location site South Sudan Hungary Italy Zambia Sudan Serbia Direct distance (km) 4830 580 7200 6830 4620 7500 Wintering area - - Zambia Zambia - Tanzania
Experiences in Corncrake protection
Systematic protection of suitable biotopes for corncrake breeding is the only way that we can protect these birds. Although it is difficult to combine maximized agricultural production and the breeding bio- logy of this species, at least some compromises can be found, such as delayed mowing, leaving patches
15 of meadow uncut, and modified mowing methods (slow speed, cutting from the centre of the field or meadow outward). There also are several modern practices that reduce the chances for successful bre- eding of Corncrakes, such as farming monocultures (which greatly reduce environmental diversity) and intensive pasturing of wet or moist lands. Our study proved that males (and most probably also females) remain in their original territories at least until migration, and possibly later, when their presence cannot be proven by calling. Some farmers may qualify for subsidies if they accept some level of modified man- agement in order to provide breeding sites for Corncrakes.
Cultural meadow in NPLA Český les where corncrake “Adam” spent the entire breeding period from tagging (18 June 2012) until migration (4 September 2012). This meadow block is subsidized under the programme for corncrake support.
a b
c d
Other examples of corncrake biotopes: a) complex of mountain natural meadow near abandoned village of Zhůří in Šumava; b) meadow in NPLA Český les – home of corncrake “Ivan” (after postponed mowing, he continued to occupy the remaining wetland area and later moved to the bordering unmown plot edge); c) remaining unmown meadow near Cham – home range of “Chris”; d) thanks to LBV’s actions, part of the meadow remained unmown and the tagged “Fritz” was able to stay a few weeks longer there.
16 1a 1b
Early mowing of a meadow is the standard approach for farmers but it hinders the successful breeding of corncrakes and therefore they mostly escape to more suitable areas (e.g. higher altitudes). Corncrake “Heinrich” subsequently visited a few places in Bavaria and finally found a suitable meadow near Mariánské Lázně (1a) where he stayed 1 month (July 8 – August 1, 2014). He later moved to near Pilsen (Vodní Újezd, 1b), where he remained even after the mowing in a few vegetation strips along ditches until his departure (September 7, 2014).
2a Corncrake David was captured on harvested meadows near Mariánské Lázně (Sítiny) and not surprisingly he moved north up During migration, the corncrakes stop often near urbanized to the Baltic coast but later returned to the Czech border area near areas. “Karel” made his first stopover near Lake Balaton (2 a,b). Broumov. This behaviour seems to document the common fate of He stayed in a small plot with the highest coverage of reeds and many birds trying to breed in a modern agricultural landscape. reed grasses (2c).
2b 2c
17 Migration stopover of “Heinrich” in Hungary was situated in Abandoned orchard and slope among dispersed houses and a clearing among black locust and with wild cannabis growth. buildings near Novi Sad (Serbia). “Eda” stopped over here for 17 days (31 August–16 September 2013).
To spot a flying corncrake is a very rare event and to take a photo of it is really unique, but to do so for a bird with a transmitter in flight? Our “Jakub”!
The first tagged corncrake “Adam” after his release in a meadow near Vranov.
18 Migration
Migration normally occurs from approximately 20th August to 5th September. Birds migrate in almost a straight line and mostly at night, passing over the Mediterranean and the Red Sea. Six of our corncrakes reached Africa. Two different migration strategies were observed: continuous migration and migration with a few longer stopovers. Some corncrakes migrated very quickly, covering about 1,600 km in 48 hours, but the others did so rather more slowly and with long stopovers. Very important stops are situa- ted in southern Sudan, where new agricultural areas have emerged in irrigated areas between the Blue and White Nile. Four birds reached their typical winter grounds in Kenya and Tanzania and two in Zambia.
We also documented two cases of the return migration to Europe. “Ivan” (ID 128727) returned to the Dolomites from Zambia on 24/25 June. The distance between the previous (in the Czech Republic) and later (in Italy) territories was 350 km. Sometime during 26th or 27th August 2015 this bird started the next stage of migration but signals soon disappeared in the Po River lowlands. The second bird ended in
Map showing movements in Europe. While non-breeders “David” and “Heinrich” from Bavaria escaped to the Baltic Sea or found a place in the Czech Republic, respectively, other birds stayed in their small spring home ranges until migration. At the beginning of migration, two birds (“Karel” and “Heinrich”) stopped near Lake Balaton and two others (“Eda” and “Jakub”) in Serbia. Other tagged birds continued their migration without stopping: Eda, Ivan, Karel, Goli, Jakub, Bob, David, Heinrich, Adam, Lubo.
19 Map showing migration over the Mediterranean Sea and Africa. Birds generally follow a southeasterly migratory route to the coast, but from Turkey they fly either directly to Egypt or to Saudi Arabia. From there, they turn to Africa, often flying directly to new agricultural areas in southern Sudan: Eda, Ivan, Karel, Goli, Jakub, Bob, David, Heinrich, Adam, Lubo.
Serbia at the same place where he had had a long stopover the year before. Its tag unfortunately stopped there. New agricultural areas in southern Sudan, created in recent decades as the result of large irrigation projects, provide good feeding grounds and birds often change their migration routes to access them.
20 Conclusions
A special combined method of telemetry was developed which uses satellite-received transmitter sig- nals to locate the general area being used by birds and then uses the same signals to track them more precisely and monitor them using a ground-based tracking methodology. This method proved to be very efficient for this kind of ultra-small PTTs which use the standard, inaccurate Argos method.
Collaboration with farmers is an important factor in preserving the breeding ranges of corncrakes.
Mowing at slow speed starting from the centre of the plot is less dangerous for corncrakes as well as other species.
During this 3 year project we tagged 8 corncrake males in the Czech Republic, and 3 males in Bavaria. Tagged birds stayed in the capture area until the time of migration, as long as sufficient parts of meadows remained unmown until their departure. Migration normally occurs from the end of August to the beginning of September (20. 8. to 5. 9.). Birds migrate in almost a straight line and mostly at night, passing over the Mediterranean and the Red Seas. Two different migration strate- gies were observed: continuous migration and migration with a few longer stop-overs. Some corn- crakes migrated fast covering about 1600 km in 48 hours but the others slowly with long stop-overs. We documented also a case of the return migration to Europe. The distance between the former and latter territories was 350 km. New agricultural areas in southern Sudan, created in recent decades as the result of large irrigation projects, provide good feeding grounds, and birds often change their migration routes to access them. A special combined method of telemetry was developed, which uses satellite-received transmitter signals to locate the general area being used by birds, and the same signals to track them more precisely and monitor them using a ground-based tracking methodology.
21 Animal species typical for biotopes of Corncrakes
a b c
d e f
g h i
a) Grasshopper warbler, b) Quail, c) River warbler, d) Common snipe , e) Tawny owl, f) Reed warbler, g) European tree frog, h) Whinchat, i) Red-backed shrike
Final remarks
Work to evaluate all collected data will continue. We can conclude that this project fulfilled its stated goals and the methods and tools developed proved their functionality. Our results determined for the first time the migration routes of Corncrakes to their winter grounds and also provided an example of the annual round-trip of an individual Corncrake. Large movements caused by hay harvesting as opposed to very sedentary behaviour in the case of postponed mowing confirmed the importance of agricultural measures. In general, our results push recognition of the Corncrake, a very secretively living species, to the next level and increase practical knowledge towards conservation of the species in the Czech Repub- lic and Bavaria. Successful completion of this 3-year project does not conclude our efforts. Its results have in fact raised many additional questions. A positive conclusion is that the protection of these birds as well as other animals inhabiting the agricultural landscape is urgent but achievable. On behalf of the researchers working on this project: Lubomír Peške, Jiří Vlček, Tomáš Peš, Jiřina Pešová, and Markus Schmidberger
22 Acknowledgements
District Government of Upper Palatinate, in particular Dr. Heinrich Baumann, Dr. Wolfgang Nerb; Pilsen Region; LBV Cham – all co-workers; Administration of Český les PLA – Dr. Milena Prokopová and all co-workers; Administration of Slavkovský les PLA – Pavla and Přemysl Tájkovi and others; Administration of Šumava NP and PLA; Zoological and Botanical Garden Pilsen; Václav Strolený, Richard Viduna, Marie Kolářová, Carmen Hradilová, Jaroslav Vogeltanz; farmers Josef Hlavsa and Frederick van Everdingen.
Objective 3 – Co-financed by the EU and European Regional Development Fund. Investing in your future.
© In 2017 published by Zoological and Botanical Garden of the City of Pilsen, contributory organization Text: Lubomír Peške and Jiří Vlček Basic maps: Google Earth Photos, schematic drawings and maps: Lubomír Peške, Jiří Vlček, Richard Viduna, Tomáš Peš, Jaroslav Vogeltanz, Jiřina Pešová, Alena Skálová, Karel Brož and Panoramio Graphic design: Jan Kubeš (www.kubesdesign.cz) Print: AVALON – reklamní studio Kolín ISBN 978-80-270-2687-6 24