[Ecology of syngamosis in a large scale farming area].
Within recent 20 years, Czechoslovak agriculture has undergone considerable changes due to the introduction of largescale farming. Our contribution presents the results of studies on chickens (Gallus gallus f. dom.) reared traditionally on runs in an area contaminated with the eggs of Syngamus trachea distributed with pheasant faeces. In addition to postmortem examination of 336 chicken tracheae, their faeces collected for one year from the runs were examined, but syngamosis was not found. Studies on small stocks of fowl in gardens close to the fields visited regularly by roosting, Syngamus-infected pheasants disclosed an occasional incidence of syngamosis in the chickens, none in guinea fowl, but frequent infection in young and adult turkeys. Another observation was made on a chicken stock reared inside a pheasantry. Although the incidence of infection of the pheasants with syngamosis was high throughout most of the year, an occasional infection only of the chickens was observed in three months. Postmortem examination of 254 tracheae of free-living birds disclosed that the incidence of syngamosis was highest in the pheasant. - Due to the introduction of large-scale farming, numerous biotopes formerly covered with trees and shrubs, were changed into arrable land. A considerable reduction occurred in the former high stand of partridges (Perdix perdix), while the pheasant (Phasianus colchicus) became widely distributed in agricultural areas. We studied the ecology of the pheasant in various biotopes by means of regular coprological examination without disturbance of the pheasants under consideration. Throughout most of the year the pheasant roosts on trees often growing in moist biotopes. In the morning and evening, the pheasant feeds regularly off the ground close to the roosting trees. From the spring onwards, throughout the summer any autumn, we observed at several sites a marked distribution of pheasants from the trees into the field where they roosted on the ground. The incidence of infection decreased considerably in pheasants, roosting on the ground of dry field biotopes, while in pheasants roosting in moist field biotopes, the incidence of infection increased considerably during the spring and remained at these levels throughout the summer until the autumn. A decrease in the incidence of infection was observed in late autumn. The incidence of infection was low during the winter and the beginning of the spring, but was present in biotopes with trees on which the pheasants from the surrounding areas concentrated. Free-living pheasants in a moist forest surrounded by fields with intensive large-scale cultivation showed a higher incidence of infection with syngamosis than pheasants from a forest pheasantry, in which rearing had to be discontinued for reasons of the death of chicks due to syngamosis. The incidence of infection increases with decreasing altitudes. The partridge (Perdix perdix) suffers less from syngamosis than does the pheasant from the same area...