Birds in an Oak Forest During a Gypsy Moth Outbreak in South-Slovakia

Abstract

In 1947 the writer observed a disastrous outbreak of the gypsy moth (Liparis dispar L.) in an oak forest near the village Cankov in South-Slovakia; by June most of the trees and shrubs were leafless. Further damage resulted from the oak mildew (Microsphaera quercina Burr.) which followed the defoliation and brought about necrosis of the young leaves of all the native oaks. A State Forest of about 320 hectares, 200 meters above sea-level, was studied during the first week in June. This soil is humus on a volcanic substratum with the nearest water two kilometers distant. Temperatures at noon tanged between 300 and 350 C.; the weather was dry and windless. The forest consists chiefly of Austrian oak (Quercus cerris) from 16 to 43 years old, with small amounts of English oak (Quercus robur) from 16 to 53 years old, Scotch pine (Pinus sylvestris) 40 to 60 years old, spruce (Picea) and European larch (Larix decidua) 40 to 55 years old. The composition of the shrubstratum is: hedge maple (Acer campestre), Tatarean maple (Acer tataricum), elm (Ulmus campestris), European privet (Ligustrum vulgare), bloodtwig dogwood (Cornus sanguinea), blackthorn (Prunus spinosa), English hawtlhorn (Crataegus oxycantha). and European evonymus (Evonymus europaeus), while on the edges grow black locust (Robinia pseudoacia), black elderberry (Sambucus nigra) and goat willow (Salix caprea). The undergrowth consists of grasses and bird vetch (Vicia cracca). Vast numbers of gypsy moth larvae were observed on the ground, on the undergrowth, bark of the trees and their branches. All of the woods and shrubs except the elderberry and common ash (Fraxinus excelsior) had been injured by the larvae. In Table 1 a list is given of the birds seen on the tract in descending order of their importance as predators of the larvae, as well as four counts on three different plots.