Aves, p�le ornithologique de Natagora

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Aves, 40/1-4 | 2003 | 69-70

  Longevity of Black Stork (Ciconia nigra) nests and nest site protection in Latvia.
Strazds, M.

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Article summary

We have analysed Black Stork nests that are regularly controlled since 1978. The nests found before 1980 (n=17) had an average age of 22 years (16-40); nests found during 1981-1990 (n=16) were on average 16.1 (11-20) years old. All nests were of unknown age when found. THe longest un-interrupted successful breeding in one nest so far lasted 11 years (as long that nest has been known). Nest changes are predicted mostly by either collapse of nest site or disturbance. Collapses are often caused by nest size -old nests can reach 170 x 155 x 115 cm dimensions and are estimated to exceed one ton in weight; average nest size are 115 x 111 x 49 cm (n=139). Of these, only 13 nests have an age known with precision. Disturbed birds tend to move further away, on average 993 m (n=25; 60 - 2350 m), than undisturbed ones, only 99 m (n=39;0 - 960 m) to build new nest. Main causes for disturbance are human origin, however predator disturbed birds (n=2 2,150 and 2,350 m) move also far away; more than 10 predated nests are followed, only two have been reoccupied after some years. Based on these data a micro reserve size was suggested for the Black Stork - 250 m radius around the nest site or on average 20 ha. These would include 84 % of non-disturbed natural movments. Considering that the micro reserves should not be limited to a fixed radius but by the shape of old-grouwth forests, they would include 89 % of natural movements. The government has accepted our proposal and according to new regulations (accepted on 30 January 2001) around each long-living stork nest a micro reserve 10-30 ha wide shall be designated. A seasonal buffer zone (up to 30 ha in total) is required too.

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