Abstract
The ecological consequences of climate change have been recognized in numerous species, with perhaps phenology being the most well‐documented change. Phenological changes may have negative consequences when organisms within different trophic levels respond to environmental changes at different rates, potentially leading to phenological mismatches between predators and their prey. This may be especially apparent in the Arctic, which has been affected more by climate change than other regions, resulting in earlier, warmer, and longer summers. During a 7‐year study near Utqiaġvik (formerly Barrow), Alaska, we estimated phenological mismatch in relation to food availability and chick growth in a community of Arctic‐breeding shorebirds experiencing advancement of environmental conditions (i.e., snowmelt). Our results indicate that Arctic‐breeding shorebirds have experienced increased phenological mismatch with earlier snowmelt conditions. However, the degree of phenological mismatch was not a good predictor of food availability, as weather conditions after snowmelt made invertebrate availability highly unpredictable. As a result, the food available to shorebird chicks that were 2–10 days old was highly variable among years (ranging from 6.2 to 28.8 mg trap−1 day−1 among years in eight species), and was often inadequate for average growth (only 20%–54% of Dunlin and Pectoral Sandpiper broods on average had adequate food across a 4‐year period). Although weather conditions vary among years, shorebirds that nested earlier in relation to snowmelt generally had more food available during brood rearing, and thus, greater chick growth rates. Despite the strong selective pressure to nest early, advancement of nesting is likely limited by the amount of plasticity in the start and progression of migration. Therefore, long‐term climatic changes resulting in earlier snowmelt have the potential to greatly affect shorebird populations, especially if shorebirds are unable to advance nest initiation sufficiently to keep pace with seasonal advancement of their invertebrate prey.
Highlights
For Dunlin and Pectoral Sandpipers, where our top‐ranked model predicting chick growth indices included food availability, we found that the percentage of broods 2–10 days old that had sufficient food for average growth was highly variable among years, ranging from 0% to 100% in both species, but was unrelated to the degree of phenological mismatch (Figure 6)
Our results indicate that Arctic‐breeding shorebirds have experienced increased phenological mismatch under earlier snowmelt conditions, with shorebirds tending to hatch after peak insect emergence in early snowmelt years, but before peak insect emergence in late snowmelt years
Previous studies have noted high, but variable levels of phenological mismatch within shorebird species breeding throughout the Arctic (Kwon et al, 2019; McKinnon et al, 2012; Reneerkens et al, 2016; Senner et al, 2017)
Summary
The ecological consequences of climate change have been recognized in numerous species, with documented changes occurring to morphology (Gardner, Peters, Kearney, Joseph, & Heinsohn, 2011; Millien et al, 2006; Sheridan & Bickford, 2011; Teplitsky & Millien, 2014; van Gils et al, 2016), distributions (Austin & Rehfisch, 2005; Parmesan & Yohe, 2003; Thomas & Lennon, 1999), and phenology (Crick, Dudley, Glue, & Thomson, 1997; Forchhammer, Post, & Stenseth, 1998; Hovel, Carlson, & Quinn, 2017; McDermott & DeGroote, 2017; Parmesan & Yohe, 2003; Post, Forchhammer, Stenseth, & Callaghan, 2001; Stenseth et al, 2002; Walther et al, 2002). Relying on the timing of peak insect emergence as it relates to the date of shorebird egg hatching when defining phenological mismatch ignores the fact that having a sufficient amount of food for adequate growth during development is likely more important for an individual's fitness than is timing of hatch in relation to peak insect emergence. To address this shortcoming, we estimated phenological mismatch over a 7‐year period in relation to food availability and chick growth rates in a community of Arctic‐breeding shorebirds experiencing advancement of environmental conditions (i.e., snowmelt; Saalfeld & Lanctot, 2017). We (a) describe the inter‐ and intra‐annual variation in available invertebrate biomass in relation to snowmelt and seasonal weather conditions, (b) estimate phenological mismatch between timing of peak insect emergence and shorebird hatch relative to timing of snowmelt, (c) determine how the degree of phenological mismatch relates to food availability and growth rates of chicks, and (d) determine how timing of hatch with respect to snowmelt influences food availability of chicks for eight shorebird species
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