A classic system for studying trophic mismatch focuses on the timing of the spring caterpillar peak in relation to the breeding time and productivity of woodland passerine birds. Most work has been conducted in single-site oak woodlands and little is known about how insights generalise to other woodland types or across space. Here we present the results of a three-year study on the species composition and temporal distribution of the spring caterpillar peak on different tree taxa across 40 woodland sites spanning two degrees of latitude in Scotland. We used molecular barcoding to identify 62 caterpillar species, with winter moth (Operophtera brumata) the most abundant, comprising a third of the sample. Oak (Quercus sp.) and willow (Salix sp.) hosted significantly higher caterpillar abundances than other tree taxa, with winter moth exhibiting similar trends and invariantly proportionate across tree taxa. Caterpillar peak phenology was broadly similar between tree taxa. While latitude had little effect, increasing elevation increased the height of the caterpillar peak and retarded timing by 3.7 days/100m. These findings extend our understanding of how mismatch may play out spatially, with caterpillar peak date varying with elevation, and tree taxa varying in the caterpillar resource that they host.

JSMBAP_CaterpillarsDetails of all individual caterpillars collected (by branch beating) and identified along our Scottish transect of 40 woodland field sites 2014-16.JSMBAP_Branch_BeatingDetails on each branch beating and whether or not a caterpillar was captured. From our Scottish transect 2014-16.JSMBAP_HabitatHabitat data of each of the 40 field sites along our Scottish transect.JSMBAP_Nestbox_DetailsGeographic details of each bird nestbox (and site) on our 40-site Scottish transect 2014-16.JSMBAP_Tree_PhenologyTree phenology data for each focal tree studied along our Scottish transect of 40 field sites 2014-16.