The effect of birds in reducing the numbers of the poplar borer (S. carcharias).
Investigations were made in five areas of Czechoslovakia in 1956-60 to determine the effect of birds on the population of Saperda carcharias (L.) boring in poplars. A total of 106 species of birds occurred in the areas studied, but most of them had little effect in reducing the numbers of the Lamiid, the larvae and pupae of which are situated deep in the wood, so that only birds that peck holes can provide control. These were primarily woodpeckers, the dominant one being Dendrocopos major. Since analysis of the digestive tracts of woodpeckers undertaken previously revealed scarcely any larval remains and examination of their nests is useless, as they feed on the insects mainly in the winter, a new method of assessment was devised. Selected trees were felled in each area, and 61 bolts showing holes made by the birds were cut from them and examined to determine whether the larvae and pupae had been extracted. The number of holes made by woodpeckers averaged 1.9 per trunk and ranged up to 10, and 98 per cent. of them were made by D. major, which destroyed 95.1 per cent. of the larvae and pupae of S. carcharias in the bolts. The adult beetles were destroyed by birds of several other species, but analysis of the contents of the digestive tracts revealed no eggs.