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Satellite Osprey Pete: Fishing area, summer 2007

Before the start of his autumn migration, i.e. during the period 14 July – 18 September, a total of 556 exact fixes for Pete were received. The fixes from the nest and its closest vicinity have been removed from the map to protect the birds. Based on this data, the total area of Pete’s home range was 235 km 2; 75% of the positions occurred within an area of 107 km 2. His longest fishing trips extended to the rainbow-trout basin 15 km away, maintained by the Pohtiolampi Osprey centre. There, Pete was immortalized by numerous photographers from home and abroad. Pohtiolampi is located at the concentration of dots in the north-east corner of the group of dots.

In July-August, the satellite picked up Pete’s position in the vicinity of Pohtiolampi every second day, though the transmitter was programmed to take only five fixes per day in August during daylight. During 1-17 Sept, we received at least one satellite reading from Pohtiolampi each day. It is likely that Pete has visited Pohtiolampi nearly every day, though it might seem to a human eye that there were more than enough good fishing waters for an Osprey closer to home. Apparently, it is a ‘good deal’ for an Osprey to fly a little further to a place where your prey is as easily available as at a supermarket.

The satellite monitoring during nesting season gave us accurate new information on the overnight sites of male Osprey. In total, 43 midnight fixes were received on Pete, 32 of which (75 %) were received from a one-hectare area near the nest, as expected. However, it is surprising that one fourth of Pete’s nights were spent over 5 km from the nest, in a small area on the west bank of the Roine lake.

As mentioned above, the first goal of the project is to test the aptitude of the 30-gram GPS transmitter for monitoring Ospreys

  1. at their home range in Finland,
  2. during migration, and
  3. at their winter range in Africa.

The first part of the test showed us beyond doubt that the transmitter worked excellently in Finland, at least during 14 July – 18 September. In theory, we could have gained 596 readings, so over 93 % of the positioning attempts were successful.

The second goal of the project was also a success. We gained a great deal of valuable information on their fishing range, roosting sites, and the importance of the exceptionally rich fishing ground some 15 km from the nest

Pete's autumn migration 2007 »