Young female Osprey M47387 ”Justiina”

The young female Osprey, ”Justiina”, was caught at her nest in Loppi on 22 Aug 2003, when she had been able to fly for nearly a month, and she weighed 1660 g. Justiina was fitted with a 35 g satellite transmitter that runs on solar power (manufacturer Microwave). Justiina was the youngest of three. The eldest, another female, was moved to Spain, where she was set free with a satellite transmitter on her back.

Autumn migration 2003

Justiina started her autumn migration surprisingly early for her age. She spent the night 24–25 Aug in the vicinity of her nest. On the following night, the reading came from Latvia, on the shore of the Riga bay, 12 km south of the Estonian border. After that Justiina gradually proceeded southwards through Latvia (27 Aug–3 Sept) and northern Lithuania until she reached an area that is dotted with small rivers and lakes, c. 40 km west of Vilna. Justiina stayed in this area for as long as five week (5 Sept–11 Oct) before continuing through Belorussia (13 Oct) and the Ukraine (14 Oct) to the valley of the Siret river in Romania (15 Oct).

For six days (18–23 Oct), the readings came from the river Trotus, which rises from the Eastern slopes of the Carpathians and runs to the valley of Siret. As late as 24 Oct, Justiina was still in Romania, 200 km due West of the Danube delta, but on 26 Oct, she had gone over the border to Bulgaria, to the shores of a small river that flows into the Danube. The satellite registered Justiina for the last time on 27 Oct, when she was on the Northern side of the Balkan mountains, near the Rusenski Lom national park. It will remain a mystery what happened to Justiina or her transmitter – unless a possible ring recovery or recapture tells us the truth sometime in the future.

The satellite monitored Justiina’s migration for 63 days, in which time she progressed 2041 km, averaging 32 km/day. If we do not include the long stopovers in the calculations, her average speed on the actual travelling days was 97 km/day. If Justiina had flown from Loppi to Bulgaria ”as the crow flies”, the trip would have been 1898 km long, i.e. she made the extra distance of 143 km (7 %).