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The fishing range of Osprey Jukka in summer 2009

In the period 31 July – 24 September, we received a total of 430 GPS-level readings on Jukka. In theory, we could have had 437 readings, so a total of 98.4% of the readings were successful! Two years earlier, the success rate of the same transmitter was 93% in Finland. One of the readings was completely incomprehensible. According to this reading, at 6 o'clock on 8 July, Jukka had been flying due east, 50 km east-northeast of his nest, above the Alho village in Padasjoki, at an elevation of 470 metres and a speed of 42 km/h! This reading has been deemed faulty at this stage and we have omitted it from the map and the calculations on Jukka's home range.

During the period 31 July – 24 September, his home range covered a total of 487 km². The range was calculated on the basis of the smallest possible polygon drawn around all the readings on the map. If we only include 90% or 75% of the readings, the ranges will only be 27 km² and 11 km², respectively. The 100% and 75% ranges of Pete were 235 km² and 107 km². This means that Jukka's range is twice as large as Pete's was; this was caused by Jukka making a few longer fishing trips in different directions, while Pete mainly flew east and northeast, i.e. towards Pohtiolampi. However, most (75%) of Jukka's readings are concentrated to a smaller area than Pete's.

The satellite only caught Jukka in Pohtiolampi on six days; the 4th, 5th, 7th, 10th, 12th and 13th of September. The difference compared to Pete, who was nesting five kilometres nearer Pohtiolampi, was evident: he had availed himself of the rainbow trout every two days in August and nearly every day in September. Based on this data, the answer to the question above – did it make sense for Jukka to fly all the way to Pohtiolampi for fish – seems to be: 'Hardly.'

In addition to Pohtiolampi and Roine, Jukka made longer fishing trips in other directions, such as 20 km southwest to the shoreline in Toijala, and 15 km southeast to the shores of Hauhonselkä.

For conservation reasons, the readings near the nest have been omitted from the map. However, they were included in the home-range calculations.

Jukka's autumn migration 2009 »