Attractive Spring-food for willow grouse (Lagopus lagopus subsp. lagopus L.) studied using plant macrofossils and pollen in faeces: a methodological discussion

Abstract

While macrofossil remains of herbs and flowers have disintegrated beyond identification, pollen survives the digestive process and can be identified, sometimes to species level, and is hence an important tool in determining and reconstructing animal diets.

This study compares macroscopic plant parts and pollen remains in faeces from grouse. While macroscopic remains reflect the quantity of bark, twigs, berries and leaves in the birds' food, the pollen also reflects other food, such as catkins, flower buds with developed pollen, flowers and pollen attached to leaves.

Both techniques reflect that Betula and Salix are the most important food for grouse in early Spring. Pollen analysis shows that later in Spring, after snow-melt, the birds are attracted to different plants, firstly, it is taxa within the Ericales and their fruits from the previous year. The nutrient value of food in periods with more or less snow cover is based on the environmental conditions of the previous year. Later on, different herbs, including insect-pollinated plants rich in nectar/sugar, are recorded in the pollen but are not reflected in the macro study, and are therefore lost in most calculations and not discussed. Nutrient content calculations based on Spring and Summer flowers need to be compared with the environmental and climate conditions of the current year.

Keywords:

• Catkins
• nectar
• plant macro remains
• pollen
• nutrient content
• grouse

Acknowledgements

We would like to thank Yngvar Hagen and Odd Jacobsen for allowing us to use unpublished data and material, Eldar Gaare, NINA for help with literature, Karl-Dag Vorren, Ingvar Byrkjedal, Vigdis Vandvik for valuable data, discussion and comments to the manuscript, and James Greig and John Birks for improving the language. Special thanks are due to Prof. Sigmar Bortenschlager of the Institut für Botanik der Universität Innsbruck for making working facilities available for DM. We are grateful to the two anonymous reviewers and Richard Bradshaw for their helpful comments. This is publication No. A227 from the Bjerknes Centre for Climate Research.