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Lemming, Arctic Fox and Climate

During the course of our analyses, we examined if climatic factors such as thickness of snow pack, rapidity of snowmelt (snow thickness on 1 June, snow-free area on 5 June) and air temperature (during previous winter and current spring and summer) had an effect on lemming abundance and fox breeding activity.


After analyses, no relationship between climatic factors and ecological variables could be identified. This may be explained by the fact that fox reproduction and lemming abundance are both influenced by one another in a complex cycle (see Lemming). The effects of this cycle are so strong that they may overshadow other weaker influences.

Lapland Longspur and Climate

The potential relationships between climatic factors and Lapland Longspur egg laying date, egg hatching date and clutch size (number of eggs in the nest) were investigated. Our analyses revealed that laying and hatching dates are strongly associated with climatic conditions such as snow thickness on 1 June, snow-free area on 5 June, air temperature and number of days with average temperature above 0°C. As for clutch size, it is influenced by air temperature and number of days above 0°C.

Our results show that both laying and hatching dates are later in years with later snowmelt (thicker snow pack on 1 June and less snow-free area on 5 June). This relation may easily be explained by the fact that Lapland longspurs, which are nesting on the ground, cannot built their nests before nesting sites are snow-free. It is also noteworthy that the same relationships are observed for laying and hatching dates. This may be explained by the fact that incubation has a set time length in birds, and for Lapland Longspurs, hatching always occurs 12 to 13 days after the last egg has been laid. Hatching dates are therefore following the same trends as laying dates.

 

Laying and hatching dates are also associated with the number of days above 0°C. Indeed, our analyses demonstrate that Lapland Longspurs lay and hatch earlier in years with more days above 0°C. Similarly, laying and hatching dates are related to annual and summer air temperature, with earlier dates in warmer years.

 

For the clutch size, our results show that females lay more eggs when summer temperatures are higher. Similarly, clutch sizes are larger when, in a year, there is a higher number of days above 0°C.