Sea buckthorn berries (Hippophae rhamnoides L.) predict size and composition of a great tit population (Parus major L.).

In seasonal environments variation in food abundance in the non-breeding season is thought to affect songbird population dynamics. In a unique tit-sea buckthorn berry system we can estimate the berry abundance and both the tit consumption and population dynamics. Six hundred nest boxes were available to great and blue tits (Cyanistes caeruleus) for breeding in spring and roosting in winter. We followed the dynamics including the recapture histories of individually marked great tits from 2008-2013. In each year we estimated 1) the winter sea buckthorn berry availability, 2) an index of berry consumption in December based on the colour of the faeces of roosting birds, 3) the number of breeding great and blue tits, 4) both recapture probability and the return rate of the great tits and 5) immigration rates. December berry abundance positively predicted the number of breeding pairs of both species in the subsequent season and great tit return rates in the second half of the winter. There wa...