Male Osprey M-38139 ”Laho”

The male Osprey ”Laho” was caught near his nest in Tuulos on 4 Aug 2003, when he was fitted with a battery-powered satellite transmitter (weight 30 g, manufacturer Microwave) and the id ring W1. Laho weighed 1480 g when he was caught. Pertti Saurola ringed Laho with a normal aluminium ring in 1995, when he was a nestling at Loppi 45 km from his nesting place of year 2003. One of Laho’s fledglings of 2003 was moved to Spain, where it was fitted with a satellite transmitter.

Autumn migration 2003

Laho’s transmitter was originally programmed for the Osprey project in Lapland. This is why the transmitter was in its slow ’rest cycle’ at the beginning of his migration, i.e. it sent signals only every five days. Thus, such events as the beginning of the migration are known only within a five-day period: on the evening of 25 Aug, Laho was still on his territory, but on the night between 30 and 31 Aug he was in Estonia, 13 km southeast of Rapla, 277 km from his nest. His migration most probably started on 29 or 30 August.

The following reading came from Poland on 5 Sept, 121 km south of Warsaw, and the reading from 10 Sept shows that Laho was flying from Poland, southeast of Krakow, and crossing Slovakia, to northern Hungary. In the early morning of 16 Sept, Laho was still in Hungary, 26 km south of Kecskemét, but on the morning of 21 Sept, he was already in Tunisia, flying over the Atlas mountains , 213 km from the shores of the Mediterranean. Measured as the crow flies, Laho progressed 1608 km during these five days, making an average of 321 km per day. He had covered twice as much, 3214 km, from his nest by now. If we assume that he set out on the morning of 30 Aug, his average speed will total 189 km per day.

The following satellite reading was a surprise. It showed us that Laho had turned back in his tracks, and spent at least the time 26–30 Sept by the Ichkeul National Park at the northern tip of Tunisia, on the isthmus between two renowned bird lakes (the Quarat al Ashkal and Banzart). From here his flight continued near or possibly even along the eastern coast southwards, since on 2 Oct Laho was at the shore of the bay of Gabes, 62 km southwest of Sfax.

Laho crossed the Sahara near its broadest point. The desert voyage of over 2000 km went from the bay of Gabes to the shared boundary between Tunisia, Algeria and Libya (3 Oct), from whence he continued over Algeria and over the Tinghert plateau (5 Oct), and then on along the western side of the Ahaggar mountains 15 km westwards from the peak of the 3003 metre high Tahat (7 Oct). He left the Tropic of Cancer behind at noon on 7 Oct. In the morning of 9 Oct, we had a reading from Tidjedal in Mali, 150 km south of the Mali border. Laho crossed the Sahara desert in a week or so (2–9 Oct), flying an average of 300 km per day.

On the 11th of October, Laho had progressed to the west of the zero meridian, into Burkina Faso 155 km from Ouagadougou. The following reading (12 Oct) was still received from Burkina Faso, but on 14 Oct, Laho was fishing in the 125 km long lake Kossou of the Ivory Coast, and from 16 Oct at the Lac de Buyo. Both ’lakes’ have formed as a result of the damming of large rivers.

If we assume that Laho started his migration early in the morning on 30 Sept, the trip of 7574 km to the Lac de Buyo took 47 days in all, so his average speed was ‘only’ 161 km/day. Due to the slow cycle of the transmitter at the beginning of his voyage, we cannot estimate the exact number of flight and resting days for Laho. As the crow flies, the distance from Tuulos to Lac de Buyo is 6647 km, so as much as 927 km, i.e. 12% of Laho’s migration journey was ‘superfluous’. When we consider Laho’s surprising to-ing and fro-ing in Tunisia on 21-30 Sept, we can understand why his progress was slow and where the extra kilometres accumulated.

Winter 2003-2004

For a month, i.e. until 17 November, we received good readings on Laho from a small area around Lac de Buyo. After that, the transmitter has been working very poorly; there were no readings at all for three months! Finally, the consistent though very imprecise readings received on 20 Feb, 26 Feb, 7 Mar and 13 Mar showed that Laho had spent the whole winter at the Lac de Buyo.

Spring 2004

The monitoring of Laho’s spring migration had to rely on only two indefinite readings due to the malfunction of the transmitter. The first reading from outside his wintering place came on 23 mar from the north of the Ivory Coast, only 78 kilometres from the border to Burkina Faso. A week later, Laho was crossing the Sahara. The last reading came on 29 Mar from a point 60 km north of the Tropic of Cancer, 375 km due west from the reading on 7 Oct during his autumn migration, and c. 2,200 km from his wintering place.

Summer 2004

A pair of ospreys was observed at Laho’s nest as early as the end of April. Three eggs were laid in the nest, and two nestlings were hatched. Since the male had a transmitter on his back, we can be certain that Laho had returned safely to his nest, and that the observation of the spring migration failed due to the malfunction of the transmitter. It was our goal to recapture Laho and remove the faulty transmitter. However, during this year, Laho had grown more cautious and was able to avoid the traps set by the researchers. This means that Laho will not be rid of his transmitter until the cotton thread fastening it disintegrates or we manage to catch him next year.