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Early Summer surveys at Grimsö

One of the 150 nest boxes checked for reproductive success of starling. Photo: Gunnar Jansson. One of the 150 nest boxes checked for reproductive success of starling. Photo: Gunnar Jansson.
Reproduction is the focus of much of the wildlife monitoring in spring and early summer at Grimsö Wildlife Research Station. Two of the species monitored are starlings and red fox.

Starling (Sturnus vulgaris) reproduction has been monitored annually at Grimsö since 1981. The survey is part of a national system which was initially started to detect potential effects of pesticides used in agriculture at the time. At Grimsö, 150 nest boxes, distributed in six separate areas, are checked several times during the reproductive season and the dates of egg laying, fledging etc. are noted. A slight but significant decrease in starling numbers, but not nesting success, has been observed over time. The factors behind the decrease is unclear, but it is at least partly thought to be related to a reduced use of grazing cattle.

Red fox (Vulpes vulpes) reproduction has been monitored in Grimsö wildlife research area since 1973. In this survey, ca. 190 dens are checked annually for signs of red fox and badger (Meles meles) reproduction. The local fox abundance, which may vary a lot between years, is an important factor and a classic topic in wildlife ecology since fox densities may strongly influence population fluctuations of many small game species like hares and grouse. The fox reproduction in turn, is strongly related to the seasonal abundance of voles which are an important food resource for foxes.
One of the dens checked for signs of reproduction of fox and badger. A trained dog could be very useful in this work when it comes to separate ongoing versus earlier use of a den. Photo: Gunnar Jansson.


Text: Gunnar Jansson.

Tags: grimsö

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