Impact Type: Deposition of pollutant
It has been demonstrated that anthropogenic acid deposition can significantly reduce levels of available calcium in soil and the abundance of calcareous items such as snail shells. Recent research in areas adversely affected by acid deposition in continental Europe suggests that reduced calcium availability has resulted in an increased incidence of eggshell defects in small birds (Pyatt et al. 1998, Drent & Woldendorp 1989). Green (1998) suggested that acid deposition can affect eggshell thickness in thrushes (Turdus spp.).
Chamberlin et al. (2000) suggest that a reduction in acid deposition will have a beneficial effect on a number of bird species including: Dipper, Great Tit, Song Thrush and Ringed Ouzel. While Logie et al. (1996) showed th at acidification can have a significant impact on the reproductive success of Dippers.
However, research by Ramsay & Houston (1999) in the UK failed to find evidence that reduced calcium availability was causing egg shell defects in Blue Tits (Parus caeruleus). The significance of acid deposition effects will depend on the soil type supporting the vegetation on which the birds feed.
Birds that are most dependent on foliage-dwelling invertebrates are more likely to affected by acid deposition. Birds which feed mostly on aquatic or terrestrial invertebrates are less likely to be affected by acid deposition, as these species are buffered against acidification in areas of high critical loads (Chamberlin et al. 2000). The distribution of piscivorous birds may be influenced by the effects of acidification on their prey (Muniz 1990).
|Critical Load/ Level|
No estimate available