Finnish Museum of Natural History

The female pallid harrier Potku

Potku the Pallied Harrier In late June 2015 a female pallid harrier (Circus macrourus) breeding in Utajärvi, Northern Ostrobothnia was fitted with GPS/GSM transmitter. Being still a rare breeding species in our country, this marked the first occasion that a pallid harrier so tagged in Finland. The main breeding area of the pallid harrier covers the steppes of Russia and Kazakhstan. It is quite a mystery how and why the species has begun to breed in Finland.

By means of the transmitter we hope to shed light on female’s use of her breeding territory as well as, especially, her migration behaviour and overwintering areas. In recent years a growing number of pallid harriers have been observed in France and Spain between September and April. This leads one to guess whether some of the pallids breeding in Finland might opt for this migration route instead of the well-known route through the Middle East.

The transmitter was fitted by Ari-Pekka Auvinen and Julien Terraube, the latter of whom has studied pallid harriers in Kazakhstan. The transmitter is powered by a solar panel and weighs 17 grams. It was supplied by Beatriz Arroyo’s research group from the The Institute of Research in Game Resources, Madrid.

The female was named Potku which is Finnish for (a) kick. Potku is also the name of the remote village situated close to her breeding site in 2015.

Unlike in Kazakhstan, at least some of the pallid harriers breeding in Finland are philopatric (i.e. return to the same site to breed). We hope to know more about this issue when, if everything goes well, Potku returns to breed in Finland in 2016.

Joins us to follow Potku’s journey and gain an insight into the behaviour of this fascinating species!

Potku's nestlings One of Potku's fledglings in flight. Notice her bulging crop, which is full from a hazel grouse meal.

Autumn migration 2016

August 2 2016

Autumn is on its way

At this stage of summer it’s a little hard to believe that Potku’s autumn migration has been in full flight already for three weeks. When writing this, Potku is in eastern Ukraine.

Potku’s late spring and early summer (map) was rather eventful. She crossed the Gulf of Finland on April 28 and reached her breeding ground from previous summer on May 3. But then, contrary to our hopes and expectations, she continued to fly north into central Lapland. She finally stopped and seemed to settle down to breed in Kolari, western Lapland just off the border to Sweden. But after one week, on May 13, she suddenly flew even further north: another 150 km to Tarvantovaara wilderness area in Enontekiö, northern Lapland.

One can only guess if Potku had already found a partner in Kolari and flew together with him to Tarvantovaara. In any case, she seems to have started to lay eggs very soon after arriving there. Based on the GPS data Potku may have laid her first egg already around May 16. A couple of days after this she started to stay put. The incubation must have continued until June 5 or 6. Then something went wrong. Perhaps a fox ate Potku’s eggs?  Nest predation is a common threat to harriers that breed on the ground.

Everything related to Potku’s breeding is guesswork, however. Just like in Mauretania in the winter, Potku managed to find a quiet place on this planet for the summer too from where SMSes did not reach us. The Tarvantovaara wilderness area must be one of the least visited areas in Finland. During the most critical breeding period we did not receive any GPS data for more than one month. That’s why no one went to look for Potku’s nest either.

All in all, Potku’s summer was almost mystical. A GPS tagged, day active and relatively large sized bird of prey managed to stay in Finland from April 28 to July 19 without anyone getting a glimpse of her!

Potku’s autumn migration started on July 18 when she seems to have risen to her cruising altitude and taken a bearing southeast. Compared to last autumn, the pallid harrier has taken a more easterly course and flown much further south. This time she did not fly over the Gulf of Finland, but rather crossed the Karelian Isthmus, flew over Saint Petersburg and headed to the westernmost part of Russia.

So far she has not stopped for more than a day. Potku has flown some 2 300 km south and is now in eastern Ukraine north of Dnipro. On her way she checked such sights as the Chernobyl reactor which she practically flew over on July 28.

In total, the summer of 2016 was very bad for pallid harriers in Finland. There were almost no voles at all in the best known breeding area around Oulu and, accordingly, not a single successful breeding event. I managed to find one brood of four chicks in Kittilä, central Lapland, just 35 km away from the site where Potku stayed for a week in mid-May. So far, this has remained the only known brood in Finland this year.

Summer 2016


Spring migration 2016

NB! The times shown on the map are always in GMT. Its difference to e.g. Finnish time is -2 hours and summer time -3 hours. The times may be given as local time in the text. If so, the text will mention it.

April 25 2016

Potku is coming!

Finally. There’s a weather front rising from the Baltics towards the north. It’s going to bring Potku home.

One week ago Potku was flying swiftly near the coast of the Baltic Sea, but the presumably bad weather stopped her journey near the border between Lithuania and Belarus. Now the current blowing from the Baltics towards Finland seems to bring her finally home.

Potku’s spring migration across Europe took a more coastal route than in the autumn. On April 14, flying between Antwerp and Brussels, the bird crossed Belgium in a day. The next night she rested at a field west of the city of Nijmegen. From there Potku’s journey continued to northern Germany with the aid of a brisk tailwind. At one point her flight direction seemed to be taking her across the Baltic Sea by the longest possible crossing. However, at the border between Germany and Poland, at the shore of the Szczecin Lagoon, she changed her course more towards the east. Northern Poland was crossed in two days on April 17 and 18. Her last field hunting period took place in western Belarus near the village of Kaziany on April 20 to 24.

With some luck Potku will the hit coastline of the Gulf of Finland today!

April 13 2016

Stuck near Paris

On the first days of April I was hoping that I could soon go and meet Potku in Utajärvi where she bred last summer. At the end of the last update, early in morning of March 29 Potku was approaching Gibraltar in northern Morocco. That day became a true wayfaring day.  The female pallid harrier flew 1 200 km nonstop in 24 hours! She had passed the whole of the Iberian Peninsula before the sun rose again. Her average speed was exactly 50 km/h.

Potku didn’t stop flying even after she had crossed the Pyrenees. The bird flew until the next evening , March 31, when she finally settled for the night at a patch of woodland northeast of Poitiers in western France. Her continuous flight had been more than 1 500 km long.

Half way through France she slowed down. During the three first days of April Potku flew another 400 km to northern France until she stopped altogether. On April 4 she suddenly turned back south! Potku flew approximately  100 km towards Paris and stayed there hunting on the fields for nearly a whole week. A friend of mine already joked about her staying there to breed…

Luckily, on April 12, she must have recalled her northern breeding grounds when she started to head for the northeast again.

1 April 2016

Spring is happening for real!

Potku’s transmitter fell quiet again for nearly three months. Sure that made me worried. The pallid harriers that Julien tagged in Kazakhstan started their spring migration on average on the 23rd of March (± 6 days). Now that the transmitter finally downloaded its data we can say that Potku started her journey back north on the 26th. Today, on the last day of March, Potku may well be already in Europe in southern Spain.

Potku’s New Year’s trip to Senegal was finally quite short. The pallid harrier passed over the Senegal River on the 5th of January, but was back in Mauretania already three days later. Judging from a map, there she hid again in the most remote of places. Locations from January are a bit to the east of those from December. Google Maps even has a name for this area: E-n-Tatrat. I presume it’s some kind of a wadi? There’s not much you can find out about E-n-Tatrat on the Internet. Mainly just some automatically generated weather data. And then there is this one site that guarantees to find you the cheapest hotel in E-n-Tatrat!

At the turn of January/February Potku moved a little less than 100 km north and fixed herself at a relatively small patch of land north of the small city of Magta Lahjar. There she stayed for the whole of February until she started move further north during the first days of March. I believe it’s not right to call this migration yet although she did fly some 900 km by 23rd of Mach. Potku stopped frequently on the way and eventually stayed for ten days east of the desert city of Bir Moghrein that we already came to know from her autumn migration.

One detail of Potku’s March journey begs to be mentioned. This time she seems to have flown right above the remarkable Richat Structure, also known as the Eye of Sahara. If you are not familiar with this wonder yet, I suggest you make a picture search of Richat Structure and spend a moment in awe of this peculiar geological formation.

It seems that Potku started itch for breeding on the 23rd of March. Three days later she passed over a 200 km stretch of West Africa in just seven hours. From there she has flown across Morocco so that on the morning of the 29th Potku was approaching Gibraltar 75 km northeast of Rabat.

On the whole, Potku’s spring migration has first taken a slightly more eastern route than her autumn migration – now she even visited Algeria very shortly. Now, for the past two days, she has been flying more directly towards Gibraltar.  

Autumn migration 2015 and winter 2015/2016

NB! The times shown on the map are always in GMT. Its difference to e.g. Finnish time is -2 hours and summer time -3 hours. The times may be given as local time in the text. If so, the text will mention it.

13 January 2016

The perfect hideaway

The contrast could not have been much stronger. I had lost all my hope – or rather I hoped for one thing only: that the transmitter would have perished and not the bird. There was minus 22 degrees in Oulu. I was checking up on two injured whooper swans that I had been involved in rescuing. They swam in a stretch of river that the warm process waters from a nearby factory kept from freezing. A brisk northern wind was moving the vapour that hung over the zero degrees water.

I looked at my phone: Tuomo calling. I didn’t want to interrupt the conversation I was having with a sympathetic Saturday stroller so I switched off the sound. Soon there was a message on the screen: Call me! Uh, what now – another injured swan freezing to death somewhere?

When I finally called back a burst of hot West African fell on my face and all snow melted around me. The news was unexpected and totally exhilarating. Tuomo had half accidentally visited Potku’s monitoring page in the morning. As it happens, we suddenly had three months of data at our disposal!

It is hard to say where Potku had been hiding. There’s very little anything on the map. When we lost contact at the beginning of October Potku was flying southwest towards Nouakchott, the capital of Mauretania. From there the pallid harrier changed her course due south and visited the border region between Senegal and Mauretania near Lake Bkiz. Then she turned east and flew another 200 km inland. Potku arrived at the semi desert area south the small town of Aleg on October 6 and did not leave there until January 5. Anyone can have a look at satellite pictures from that area. It’s mostly sand, but also some scattered small tree or bushes? Maybe a touch greener during the rainy season?

Just after New Year Potku left her perfect hideaway and flew over the Senegal River into the golden land of Youssou N’Dour, Orhestra Baobab and all the other amazing musicians that Senegal has produced. I know, it’s only a silly long distance affair. I have never even been to Senegal yet I have learned the basic of Wolof at the University of Helsinki.

Let’s hope we hear soon from Potku again. Tey am naa baaneex – today I have happiness!

5 October 2015 onwards


No news to tell about Potku. I check the transmitter data daily, but there are no new messages. Maybe Potku has flown into the Sahel region where the GSM network is patchy to say the least? Or maybe there’s something wrong with the transmitter? Last time there was a five day hole in the data which cannot be explained by poor GSM network since GPS works everywhere.

A French colleague who monitored African black harriers with similar tags advised us to be patient. It may sometimes take weeks to get the locations. Let’s hope so.

September 24 - October 4 2015

Lost and found in Western Sahara

Apologies for the delayed update – Potku kept us holding our breaths for a whole week. The bird crossed the border between Morocco and Western Sahara in the evening of September 27. After this two more locations were received until the transmitter fell quiet east of the city of Smara. Potku had flown into the desert. The next message was not received until a week after. In principle the GPS should have tracked her location even without a telephone network, but still a gap of five days and 600 kilometres remains in her route.

The GPS had located Potku in the morning of September 29 when she got up from her roost in the middle of prefect emptiness 130 km southeast of the desert village of Bir Moghrein. The next data point is from the western part of Mauritania from Sunday morning October 4 when Potku was flying towards the capital city of Nouakchott some 200 kilometres northeast of it. Judging by satellite images nothing but sand connects these two points.

The way in which Potku crossed Morocco is interesting. Whereas she flew around the Pyrenees along a route that allowed her to avoid all the highest peaks, she did just the opposite with the Atlas Mountains. The pallid harrier crossed the highest mountain range of northern Africa at its highest point. She flew over 3 600 metre high terrain just a couple of kilometres off the highest peak of the Atlas Mountains, Toubkal, which stands at 4 167 metres. The whole trek over Morocco, over 1 200 kilometres, took Potku just four days.

September 15–23 2015

Goodbye Europe

Now we know one big thing about Potku’s overwintering: she did not stay in Europe.

The female pallid harrier spent eight days in the Eure-et-Loir department southwest of Paris after which, on the morning of September 19, she started to fly resolutely towards Africa. The first night she spent east of the city of Poitiers in western France. The next night remains a slight mystery since Potku was still flying around midnight local time somewhere near Zaragoza in northern Spain. A few hours earlier she had crossed the Pyrenees near the Bay of Biscay between Biarritz and Pamplona. The highest mountains on her route were about 1 000 metres high – flying this way she avoided having to climb over the highest peaks of the Pyrenees.

Potku didn’t spend a lot of time in Spain. The second one of her nights in the country she spent on a field 70 km inland of Alicante, the third already close to the Alboran Sea east of the port town of Almeria. On Wednesday morning September 23 the pallid harrier headed to the western end of Mediterranean and made the 200 km sea flight in seven hours. In Morocco she flew another 150 km inland and settled for the night on a hill that, in satellite image, looks quite dry and barren.

September 10–14 2015

Over Paris

The fields of Picardy didn’t hold Potku for longer than an hour after all. Just before noon on Thursday September 10 she continued her journey southwest. After five pm local time the bird was already in the western airspace of Paris. Potku crossed the city of love across the large Bois de Boulogne park, not far from the Roland Garros stadium well-known for hosting the French Open tennis tournament. Soon after this the pallid harrier must have looking at the symmetrical gardens of Versailles as she flew by two kilometres east of them.  The next night she spent at a woodland patch a good 50 km southwest of Paris. The next morning, Friday 11th, Potku flew another 20 kilometres to reach her next stopover destination near the village of Voise in the Loire valley.  There she’s been hunting until now, Monday evening September 14.

September 7–10 2015

Hitting the Gallic roosters*

On the morning of September 8 Potku must have had enough of commuting between the beech forests of Huy and the wetlands of Großes Bruch in Central Germany when she got on her flight gear again. The first day’s leg was a moderate 60 km flight towards southwest to the city of Göttingen where she spent another night in a forest patch surrounded by arable fields. After this the bird embarked on her longest day flight to date: 400 km  in 12 hours to the border between Belgium and France. When writing this, Potku has already moved well into France:  she seems to be hunting on the fields south of the village of Burelles in the region of Picardy in Northern France.

* Yes, I believe she could hit a small rooster, or at least a chicken, if need be. I recently showed the remnants of a prey item from last summer’s nest site to an expert: the bones and feathers had belonged to a female black grouse, which weighs on average (1 kg) twice as much as Potku.
August 31 – September 6 2015

In the middle of Germany

What happened during the first week of September can be told in a few words: Potku got stuck in the middle of Germany. On the last day of August the female pallid harrier flew 110 km in six hours from Bad Belzig to the border between Saxony-Anhalt and Lower Saxony. Here, on the fields west of Neuwegersleben, Potku has spent a whole week. In addition to regular cultivated lands, the Neuwegersleben district boasts also the protected wetlands of Großes Bruch where Potku hunted for three days. The two last nights she has slept at another protected area, the hills of Huy, in one of the largest almost pure beech forests of central Europe.

August 24–30 2015

Back to Poland

Did she forget something? After having spent two nights in eastern Germany Potku turned back to the direction she came from. Well, in the end, she didn’t go too far back: Flying 50 km northeast to Poland seems to have sufficed. Potku spent the next six days on the fields between the small villages of Kowalów and Lubiechnia Mała*. On August 30 she seems to have resumed her travelling mode and continued in the western direction she was heading before. When writing this, Potku is situated near Bad Belzig 70 km southwest of Berlin.

* The poetry of the places she visits continues. Could there a much more beautiful name for a village than Lubiechnia Mała? As far as I know and have been told, Lubiechnia does not really mean anything.  Yet the name sounds, to me at least, like it could be based on the Slavic word for love (lubit/любить in Russian, lubowac in old Polish). Mała, for its part, is Polish for little (one).   
August 22–23 2015

Then she takes Berlin.

Potku spent two nights in Poland. First, after resting the night approximately 100 km northwest of Warsaw, she flew 270 km west-southwest. Her route was dead straight and apparently she flew quite high: The GPS-tag does not measure altitude yet there was a sharp ten degree drop in temperature when she took off. After flying over the historic city of Poznan she settled for the night at a woodland patch near the small village of Wasowo. However, something must have happened during the night. During the hours when her tag was offline (24–06 Polish time) she had moved another 30 km towards Germany.

On Saturday August 22 Potku crossed the border between Poland and Germany a little south of Frankfurt an der Oder. Form there she had only a short flight to her next stop at the east bank of Lake Scharmützelsee.

Here Potku rested here for a little longer. Maybe she wanted to feel the vibes of a European capital: the distance between her two consecutive roosts and the Brandenburg Gate is only 55 km.

August 17–21 2015

Potku turned west.
For Potku Latvia was only a one night affair. On Monday 17 she flew some 160 km southeast to northeastern Lithuania where she stayed the night at fields north of the town of Utena.  Next morning at 11 o’clock it was time for her to carry on again and change countries. This time Potku decided to leave western democracies and try her luck in Belarus.  There she spent two nights: from Tuesday to Wednesday near the city of Lida and from Wednesday to Thursday at the outskirts of Shchuchyn.  Come Thursday morning she must have felt to urge for travel and freedom again when she turned west-southwest towards Poland. At the time of writing this, on Friday 21, Potku is waking up to the morning well into the heartland of Poland. She sure didn’t fly straight south!
During the past couple of days, a read ringed young female pallid harrier has been seen south of Stavanger in western Norway. The code of the ring is not quite clear yet, but practically there are only two options left: either a nestling ringed in Sievi on June 29 or one of the daughters of Potku!

August 13–16 2015

A lot can happen over one weekend: Potku is now in Latvia!

After having spent a couple of days on the southern banks of Lake Oulujärvi and near the towns of Lapinlahti and Siilinjärvi in Northern Savonia the female pallid harrier started to fly briskly in a south-southwestern direction. At 9 in the morning on Friday 15 she was flying above the city of Kuopio. Only seven hours later she was some 250 km away in Virolahti by the northern coast of the Gulf of Finland heading oversea to Russia! 

After crossing the Gulf of Finland in two hours she settled for the night in a forest 20 km southeast of the town Ust-Luga near the Estonia–Russia border. In the morning Potku resumed her south-southwestern direction and flew by the eastern shore of Lake Peipus towards Latvia. The next night she would spent near Latvia’s biggest lake, Lake Lubāns.

If Potku continued to fly in this direction she would eventually fly through Belarus, Ukraine and Romania and end up in Greece before facing the Mediterranean.   Is she really flying straight over to Africa already or will her course change anytime soon?

August 7–12 2015

The first sings of Potku ’s fledglings having become independent were received on August 7 when she moved permanently a few kilometres north of her breeding territory. Here she stayed a couple of days until, at noon on August 10, she took a bearing south. Potku flew approximately 50 kilometres to the southern edge of lake Oulujärvi – and to where exactly!

The Finnish basic map is dotted with poetic, funny as well as downright rude names of places. One of my favorites is Pahamaailma, Bad World, is Suomussalmi near the border to Russia. I haven’t been there yet, but some day… On one of the unlucky days this summer, after having spent hours in vain searching for pallids, I decided to fulfil one dream and visited Hevonvitunsuo, Horse Cunt’s Mire, in Kiiminki. However, it is the mire that Potku chose for her first night’s resting place that is at the top of my list: Iso-Onneton, The Big Unhappy, the most poetic of them all!

On Tuesday August 12 Potku seems to be moving gradually south east towards the village of Ojanperä in Kajaani where searched for the nest of another pallid harrier couple earlier this summer with no luck.

Person in charge of the page: 
Text: Ari-Pekka Auvinen, photos: Ari-Pekka Auvinen, Web management: Markus Piha