ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1982.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1982.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1982.tb00011.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractMany ecologists have argued that predation is of little consequence in the regulation of gamebird numbers and that predator control in game management is a waste of time. Their case has included two lines of evidence; firstly, gamekeepers do not appear to be reducing predator numbers significantly; secondly, mortality by predation appears to be compensatory and therefore has little impact on gamebird populations as a whole. However, a closer examination of the activities of gamekeepers indicates that they do reduce predation pressure either by reducing or completely removing some predator species, or by temporarily reducing their number on a local basis. Recent research including an investigation of partridge population processes explored with a computer simulation model indicates that predation does regulate both autumn and spring densities. Other factors play an important role only when predators are removed.

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1982.tb00012.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractIn a short but intense field investigation, surface activity of common voles in a cropped lucerne field was assayed by live‐trapping while, simultaneously, hunting activity and yield of three species of raptors were recorded by continuous observation. Pronounced short‐term rhythms in trappability of the vole population ran parallel with fluctuations in yield per hour of flight‐hunt of hen harriers and kestrels. These raptors, as well as Rough‐legged buzzards, hunted more at times of increased vole surface activity; hen harriers savedc.15 hours of flight‐hunt per day by such temporal adjustment, corresponding to about 12% of their daily energy intake. Voles suffered a predation rate of an estimated 02%per day; under such heavy predation and temporal concentration of raptor hunting at times of increased vole activity, surface feeding in synchrony with the vole majority was associated with increased risk of

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1982.tb00013.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1982.tb00014.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract(1) Seabird‐cetacean associations involve many genera.(2) Some seabirds/cetaceans associate with more species than others, e.g. minke and pilot whales, Common dolphins and porpoises amongst cetaceans, and gannet&kittiwake amongst seabirds. Killer whale, sperm whale, shag and cormorant have not been recorded in associations, in the N.E. Atlantic.(3) All observed associations would be predicted on the basis of the diets of the associated species.(4) Most associations are probably opportunistic or incidental, as a result of concentration of shared prey.(5) Some species, however, may associate more regularly, e.g. minke&pilot whales, Common dolphin and porpoise amongst cetaceans and gannet amongst seabirds. It is not possible to say which derives benefit from the association, but on theoretical grounds it is most likely to be the seabird.(6) Minke and pilot whales may drive towards the surface food normally out of reach of seabirds, particularly Procellariformes. Common dolphins feed by herding fast‐moving fish shoals into tight groups which will be a more concentrated food source for diving sea‐birds, such as gannets, and make food more accessible to other species. Porpoises may achieve the same result with inshore shoals of sprats and sand eels, particularly for auks and kittiwakes, and

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1982.tb00015.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY