Kirsty H. Macphie, Jelmer Menno Samplonius, Jarrod Hadfield, James Pearce-Higgins, Albert Phillimore 

1. Climate warming is causing many spring biological events to advance in timing and where the phenology of resource and consumer advance at different rates this can result in trophic asynchrony. While the temperate study system of deciduous tree – caterpillar – insectivorous passerine has been widely studied, little work has examined whether phenological distribution of caterpillars differ among tree taxa and habitats. If such differences exist they have the potential to underpin spatial variation in the trophic asynchrony in this food web.
2. Our first aim was to identify the effects of host tree versus local woodland composition on caterpillar abundance. Following this, the main aim was to examine the effects of tree taxon on the phenological distribution of caterpillar abundance and the trend in mass of individuals, with guild biomass the product of these two metrics.
3. We collected data on caterpillar abundance and mass throughout spring from 44 sites with varied woodland compositions across seven years. First, we analysed differences in caterpillar abundance among tree taxa and identified any additional effect of local woodland composition. Second, we explored differences in the phenological distribution of caterpillars among tree taxa, focusing on caterpillar i) abundance, ii) mass and iii) biomass.
4. We found substantial variation in the caterpillar abundance supported among tree taxa, including evidence that the density of oak foliage within a woodland can increase the abundance of caterpillars found on other trees. Some aspects of the phenological distribution of caterpillars differed among tree taxa, in particular the height of the peak, highest on oak. We show minimal, but significant, variation in timing and duration, whereas we did not find much evidence for variation in the shape of the phenological distribution or mass gain of caterpillars.
5. We show that the abundance and phenological distribution of caterpillars does differ between deciduous trees and that oak is distinct from most other common taxa. Woodland composition is likely to influence the site-level trend in caterpillar abundance and biomass; contributing to spatial variation in an important component of the woodland ecosystem and an ephemeral resource relied upon by many consumers species.