Effects of “acid rain” on a population of Great Tit(Parus major) in the higher regions of the Harz Mountains | Auswirkungen des „Sauren Regens“ (Waldsterben) auf eine Kohlmeisen-(Parus major-) Population in den Hochlagen des Harzes
1998
Zang, Herwig
The damage to forests through “acid rain” is patently obvious in the higher regions of the Harz Mountains. This disturbance in the forest's ecological system has also affected the frequently found and otherwise robust Great Tit. In two study areas with nest boxes (together covering 25 hectars at a height of 800–920 m a.s.l.) the population has been halved in the period between 1969 and 1997. The clutch-size has declined by 8%, the breeding results of successful pairs by 18% and the nesting success when unsuccessful pairs are included by 30%. The total nesting success of the whole area has declined by 50%. The number of birds “breeding on empty nests” is higher than in other regions. Between 1971 and 1987, the average minimum age of nesting females was constant 2.2–2.4 years. Between 1993 and 1997, however, the average minimum age was only 1.15 years. The changes in the chemistry of the soil due to “acid rain” with its consequences for the trees (forest damage “Waldsterben”), the fauna (reduction in food abundancy, particulary in winter due to a decrease in the number of spiders) and the physiology of the birds (lack of calcium) are discussed as the main reasons for this development.
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