Seasonal variation in food supply and breeding success in European Coots

Chick survival in the European Coot typically shows a convex seasonal pattern. Previous experiments revealed that this pattern is directly linked to hatching date and that food supply within the first ten days after hatching is a causal factor in this relationship. However, the precise mechanism through which food affects survival seasonally under natural conditions remained so far unclear. The present study therefore investigates the natural seasonal variation in food abundance during brood care, and compares this variation in food supply with the seasonal variation in chick survival for different years. Annual and seasonal variation in chick survival was explained by variation in the insect biomass delivered to the brood within the first ten days after hatching. The variation in insect supply to the chicks was not due to differences in the time spent by early and late pairs in feeding young, but directly related to seasonal variation in the insect biomass available. Seasonal variation in insect abundance was thereby identified as the critical factor in the causal relationship between hatching date, food supply and chick survival.

Brinkhof M.W.G., ARDEA 85 (1): 51-65