A Spatial Perspective on the Phenological Distribution of the Spring Woodland Caterpillar Peak

Abstract

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 generalize to other woodland types or across space. Here we present the results of a 3-year study on the species composition and temporal distribution of the spring caterpillar peak on different tree taxa across 40 woodland sites spanning 27 of latitude in Scotland. We used molecular barcoding to identify 62 caterpillar species, with winter moth (Operophtera brumata) being the most abundant, comprising one-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 per 100 m. 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.

Best environmental predictors of breeding phenology differ with elevation in a common woodland bird species

“…In addition, our results concur with other studies on woodland passerines indicating that air temperature has a strong causal effect on egg‐laying dates (Pereyra, 2011; Phillimore, Leech, Pearce‐Higgins, & Hadfield, 2016; Shutt, Burgess, et al, 2019; Shutt, Cabello, et al, 2019; Simmonds, Cole, & Sheldon, 2019; Visser, Holleman, & Caro, 2009). Our study improves the understanding of mechanisms involved in the determining factors of bird breeding phenology by showing that air temperature has a negative indirect effect through plant phenology or snow melt‐out date, depending on the elevation.…”

“…There is evidence that difference in tree phenological responses may affect bird phenology (Veen et al., 2010), but in our case using larch phenology was the most relevant as it occurred just before egg‐laying while spruce (the other dominant tree species) occurred more than a month later (Pellerin, Delestrade, Mathieu, Rigault, & Yoccoz, 2012, Asse et al., 2018; Bison et al, 2019), spruce buds have a lower frost resistance than larch buds (reviewed in Bigler & Vitasse, 2019). Moreover, there is evidence that invertebrate phenology may be similar between tree taxa (Shutt, Burgess & Phillimore, 2019), at least when considering between‐year variability. The same larches were surveyed every year since 2007.…”

Gradients in richness and turnover of a forest passerine's diet prior to breeding: A mixed model approach applied to faecal metabarcoding data

“…One surprise in our data was the prevalence of winter moth early in the spring. The larvae of this species are one of the main foods provisioned to nestling tits (Betts, 1955; Perrins, 1991) and whilst they are the most common spring Lepidopteran larvae on our transect, their availability peaks in late May/early June (Shutt, Burgess, et al, 2019), and so we did not anticipate finding them in the diet in March/April. A post hoc analysis (GLMM with threshold response, site and nestbox effects as random and year effects as fixed) revealed that the probability of occurrence in a sample increases significantly in the days running up to the site‐average first egg laying date (b = 0.039, CI = 0.023–0.055), from around a 2% chance at 30 days prior to laying to 17% at the average site‐level blue tit first egg date.…”

“…Species richness—or α‐diversity—of temperate invertebrate taxa generally decreases with increasing latitude (Baselga, 2008) and peaks at mid‐elevations (Beck et al, 2017) and in the summer months (Thomsen et al, 2016). Within forests, invertebrate richness can vary among tree taxa by more than an order of magnitude, and in the UK has been found to be highest on Salix , Quercus and Betula (Kennedy & Southwood, 1984; Shutt, Burgess, & Phillimore, 2019). In addition to changes in species richness, species composition may change from one community to the next, which is quantified as β‐diversity (Baselga, 2010; Whittaker, 1972).…”

Among tree and habitat differences in the timing and abundance of spring caterpillars

“…For instance, in Great Britain, although oak trees are the second most common broadleaf tree taxon, they make up just 16% of the area covered by broadleaf woodlands (Stagg & Ward, 2019), and many lepidopteran and passerine species in this system will feed, forage and nest in a variety of woodland habitats (Allan, 1979;Hagemeijer & Blair, 1997;Perrins, 1979;Skinner, 2009). The extent to which inferences about the caterpillar phenological distribution made in relation to oak can be generalised to other habitats is largely unknown (Shutt, Burgess, et al, 2019). Therefore, it is important to consider how the caterpillar peak varies among woodlands with different habitat compositions when aiming to understand the potential for trophic asynchrony across heterogenous temperate deciduous woodlands (Burger et al, 2012).…”