摘要:

Infections withAscaris lumbricoideswere found in approximately 75% of 1090 pigs in Advanced Registry Test Stations. Most of these infections were acquired by the pigs during the preweaning period. The infections recorded were not definitely harmful to the animals. Studies on factors influencing ascariasis are in progress.

ISSN:1923-4287    

DOI:10.1139/cjr44d-005

出版商:NRC Research Press    

年代:1944

数据来源: NRC

摘要:

Dafila acutais an abundant transient through British Columbia following routes along the outer coast, the inner coast, and the main north and south river systems of the interior. The spring migration takes place during March and April and is not protracted but the autumn migration is one of successive movements from mid-August to early December. The largest flight sometimes appears on the mainland coast in late October. Both northbound and southbound flocks concentrate on the Coastal Plain. The chief wintering grounds are in western Oregon and in California, the most densely populated nesting grounds in Alaska. Recoveries of banded birds have verified observational migration data and have shown also that many individuals use the same route in successive years, some arriving at a given point on approximately the same date. In British Columbia the principal nesting ground is the parklands of the Cariboo region and the peak of the spring migration is in late March or early April. Following its conclusion the residual population is scattered over a wide area characterized by grassland and many types of ponds and sloughs. Courtship is at its height in April and laying commences in May. Nest sites usually are dry and may be several hundred yards from the nearest water. The majority of young appear in June and are led by the females to meadows and marshes provided with adequate cover. The females remain with the brood and actively defend them during adolescence. Males leave the females when incubation begins and gather in small bands on water adjacent to the nesting grounds. Many migrate in advance of the flightless period. Downy young feed largely on the larvae of aquatic insects. The most important item in the diet of adults during autumn and winter is seeds of various meadow and aquatic plants. On the coast this element is characterized by Polygonaceae andScirpus americanus, in the interior by Potamogetons andScirpus acutus. Insects and animal matter generally constitute a less important food. The pintail is second to the mallard,Anas platyrhynchos, in economic importance and like it is a source of revenue to the Province. On the debit side the pintail causes some loss to agriculture by eating forage crops but this is not extensive and is amenable to control.

ISSN:1923-4287    

DOI:10.1139/cjr44d-006

出版商:NRC Research Press    

年代:1944

数据来源: NRC