CONSTRUCTION OF ARTIFICIAL NESTS

Construction of artificial nests was undertaken mainly to provide new nest-sites (nest platforms) for the Osprey. This task involved also reconstruction of those nests of the Osprey, White-tailed Eagle, Golden Eagle and Lesser Spotted Eagle which had sustained damage. Jointly in 1993-2000, 175 nests were built or reconstructed. Ca 70% of the artificial nests were constructed thanks to the financial support obtained for the project from the EcoFund Foundation, the remaining part being financed by the Nature Conservation Office in Szczecin, Provincial Departments of Piła and Katowice, Drawieński National Park and several Forestry Divisions in north-western Poland. The nests for the Golden Eagle and Lesser Spotted Eagle were built owing to voluntary activity of the Eagle Conservation Committee members.

The highest number of artificial nests (151) were constructed for the Osprey. In Poland this species builds nests in medium-aged trees, i.e. about 150 years old, whereas the felling age of stands ranges from 80 to 120 years depending on the region. And thus one of the main reasons behind the low number of this species in Poland is the scarcity of old pines having a suitably shaped crown, which would enable the birds to build a nest in.

Making use of the experience gained in Finland, where currently over 40% of the Osprey population, estimated at ca 1 000 breeding pairs, occupy artificial nests, the Committee set about constructing artificial nests in order to improve the situation of Ospreys in Poland. The nests were built in the place of the destroyed natural ones in the territories already occupied by birds, or in tree stands representing potential breeding site of the species.

In 1995-2000 Ospreys occupied almost 30 artificial nests, which means that now ca 50% of the Polish population of this species breed in artificial nests. This is a very good result, ensuring longer durability of nests of a large part of the Polish population, and hence reducing brood losses due to nest fall.

Figure 5. Number of artificial nests constructed for the Osprey in Poland in 1993-2000 (green bars) and the number of nests occupied by the birds (red bars).

In 1993-2000, 20 artificial nests were built for the White-tailed Eagle. Over a half of them got occupied each year (in 2000 White-tailed Eagles used as many as 14 artificial nests).

In 1999 an artificial nest was constructed for the Golden Eagle in the Bieszczady Mts, close to the place where a natural one used to be. This nest was occupied in the next year. In the same region, another nest for this species was built to replace the natural one which had dropped from the tree in the autumn of 2000.

Besides, two artificial nests were constructed for the Lesser Spotted Eagle (one in Western Pomerania and the other in the Carpathian Mts. These nests were occupied by the birds and used for breeding.