Body Condition in the Eurasian Woodcock Wintering in the West of France: Practical Study for Wildlife Management during Cold Spells

摘要

The Eurasian woodcock (Scolopax rusticola) is one of the most widespread species of the Scolopax genus in temperate regions. However, population levels can be greatly affected by harsh cold spells that led woodcocks to starve by exhaustion of their body fuels. To better understand the vulnerability of woodcocks to such climatic conditions it is of a major importance to determine the amount of their body reserves (both lipids and proteins) throughout the wintering season. This was performed on 55 individuals collected by hunters in the western part of France during two consecutive winters under mild weather conditions. Body reserves, that can be mobilised, were determined as the difference between the total amount of lipids and proteins minus the values obtained on starved individuals found dead during previous cold spells. Overall, body reserves did not significantly change over both winters (p 0.40), the maximal mean value (1539 ± 117 kJ) being however reached in January. Storing body fuels would not adversely affect wing and power loading, suggesting that the amount of body reserves would agree with the "starvation-predation trade-off". If woodcocks sit through a cold spell, their mean survival time (or fasting endurance) would be 6.5 ± 0.5 days; 25 to 40% of the birds would have a life expectancy of 7-9 days, and about 8 to17% less than 5 days. On the contrary, if woodcocks immediately leave their wintering quarter, they would be able to perform a trip of 740 ± 50 km, 20 to 40% of the woodcocks being able to fly over 750 km. Body mass explains only 47 to 57% of the fasting endurance and flight autonomy variations, and therefore we recommend a further carcass analysis to accurately estimate body condition. These results underscore the suitability of determining the state of body reserves for practical cases of population management and hunting policy during cold spells.