Influence of radar radiation on breeding biology of tits (Parus sp.).

The aim of the present study is to observe the influence of long-term exposure to radar radiation on breeding biology of tits (Parus sp.), living and building nests around a military radar station, emitting pulse-modulated microwave radiation of 1,200-3,000 MHz. Two series of 36 nest-boxes each were located on the radar station area. Measurements of exposure were performed separately for each nest-box. Average power density (P(av), W/m(2)) and dose of exposure (W/m(2) x h) were recorded for each nest-box during 45 days. Control nest-boxes (N = 42) were located in other part of the same forests, free from radar radiation. The assessment of effects of radar exposure on breeding biology of tits included number of inhabited nest-boxes, number of eggs, and nestlings in the nest (Why not chick mortality?). Experimental nest-boxes were either exposed to relatively high levels of radiation (2.0-5.0 W/m(2), mean 3.41 +/- 1.38 W/m(2)) or an intermediate level of radiation that ranged from 0.1-2.0 W/m(2) (mean 1.12 +/- 0.84 W/m(2)). For control nest-boxes the exposure ranged from 0.001-0.01 W/m(2) (mean 0.0062 +/- 0.0007 W/m(2)). Only blue or great tits occupied all nest-boxes, used in the experiment. The number of nesting blue tits was higher in nest-boxes located on the radar station area than in the control boxes. In contrast, control nest-boxes were inhabited mainly by great tits. On the radar station area, blue tits nested in high exposed nest-boxes (67,0%) and great tit occupied mainly these boxes, which were exposed to low-level radiation (62,5%), the difference being statistically significant (p < 0.01). No statistically significant differences in other parameters of breeding biology (number of eggs per box, number of nestling per box) were observed between tits occupying exposed and control nest boxes. Results of the present study show that radar radiation generally does not lead to decrease of number of nesting tits, but may cause shifts in tits species living around the radar station. (But is the microhabitat, apart from the radiation level, around each nest box more likely to attract one species of tit or another?).