 The soft, chittering sound of young blue tits calling for food can be heard in the trees. This is another event in nature that is distinctly early this year. Like the flowering of the wild roses, which are already rampaging in the hedges, it is something one expects to notice in the first week of June. It is not easy to see these fledgelings, who lurk deep in the foliage, but if one gets a glimpse one finds that their cheeks are yellow, unlike their parents' cheeks, which are white. Young tits depend considerably for food on the tiny moth caterpillars that feed on oak leaves, or hang on silken threads from the twigs. It has been feared that if global warming brought forward the nesting of the tits, the caterpillars would not yet be available for the young when they needed them. However the caterpillars too are out early, munching away, so it seems that the warm spring has had the same effect on them as it has on the birds. a hopeful sign.  Derwent May