Warming Arctic summers unlikely to increase productivity of shorebirds through renesting

Abstract

Climate change in the Arctic is leading to earlier summers, creating a phenological mismatch between the hatching of insectivorous birds and the availability of their invertebrate prey. While phenological mismatch would presumably lower the survival of chicks, climate change is also leading to longer, warmer summers that may increase the annual productivity of birds by allowing adults to lay nests over a longer period of time, replace more nests that fail, and provide physiological relief to chicks (i.e., warmer temperatures that reduce thermoregulatory costs). However, there is little information on how these competing ecological processes will ultimately impact the demography of bird populations. In 2008 and 2009, we investigated the survival of chicks from initial and experimentally-induced replacement nests of arcticola Dunlin (Calidris alpina) breeding near Utqiaġvik, Alaska. We monitored survival of 66 broods from 41 initial and 25 replacement nests. Based on the average hatch date of each group, chick survival (up to age 15 days) from replacement nests (Ŝi = 0.10; 95% CI = 0.02–0.22) was substantially lower than initial nests (Ŝi = 0.67; 95% CI = 0.48–0.81). Daily survival rates were greater for older chicks, chicks from earlier-laid clutches, and during periods of greater invertebrate availability. As temperature was less important to daily survival rates of shorebird chicks than invertebrate availability, our results indicate that any physiological relief experienced by chicks will likely be overshadowed by the need for adequate food. Furthermore, the processes creating a phenological mismatch between hatching of shorebird young and invertebrate emergence ensures that warmer, longer breeding seasons will not translate into abundant food throughout the longer summers. Thus, despite having a greater opportunity to nest later (and potentially replace nests), young from these late-hatching broods will likely not have sufficient food to survive. Collectively, these results indicate that warmer, longer summers in the Arctic are unlikely to increase annual recruitment rates, and thus unable to compensate for low adult survival, which is typically limited by factors away from the Arctic-breeding grounds.

Mismatch‐induced growth reductions in a clade of Arctic‐breeding shorebirds are rarely mitigated by increasing temperatures

“…Although it remains unclear if trophic mismatches have population-level consequences (Franks et al, 2017;Miller-Rushing et al, 2010), reductions in growth rate, as we find in our study, may lead to reductions in chick survival (Sedinger et al, 1995), and lower chick survival has also been associated with a trophic mismatch (Lameris et al, 2018;Saalfeld et al, 2021). In addition, growth reductions may carry over to later life stages via smaller biometrics impacting foraging efficiency and survival in wintering areas (van Gils et al, 2016), or via reductions in survival and longevity as a consequence of compensatory growth with accompanying accumulation of cellular damage (Mangel & Munch, 2005).…”

“…Instead, it appears that for chicks of Red Knot ssp., islandica mitigation can take place between years, as in years in which the trophic mismatch is larger, temperatures during growth are also higher (Figure 7, Pearson's correlation between temperature and rescaled relative hatch = 0.93, p = .07). While for most populations, food availability will be a more important determinant of energetics and growth (Schekkerman et al, 2003; Schekkerman & Visser, 2001; Senner et al, 2017) as well as survival (Saalfeld et al, 2021), temperatures appear to have an important effect on condition for chicks growing up in the coldest conditions. This means that temperatures may compensate for growth reductions induced by a trophic mismatch only under specific conditions (see also McKinnon et al, 2013), but it is unlikely that this applies as a general rule.…”

“…Instead, it appears that for chicks of Red Knot ssp., islandica mitigation can take place between years, as in years in which the trophic mismatch is larger, temperatures during growth are also higher (Figure 7, Pearson's correlation between temperature and rescaled relative hatch = 0.93, p = .07). While for most populations, food availability will be a more important determinant of energetics and growth (Schekkerman et al, 2003;Schekkerman & Visser, 2001;Senner et al, 2017) as well as survival (Saalfeld et al, 2021), temperatures appear…”

“…In environments where food is limited outside a narrow period of peak occurrence (Visser et al, 2005), advancements of the food peak can effectively reduce the amount of food available to organisms during periods of high demand, for example, the offspring development stage (Drent & Daan, 1980). The resulting trophic mismatches can impact offspring growth (Doiron et al, 2015; Senner et al, 2017), survival (Lameris et al, 2018; Saalfeld et al, 2021) and recruitment (Reed et al, 2013). Such changes in species interactions due to a warming climate are considered an important threat to animal populations (Ockendon et al, 2014).…”

Life‐history attributes of Arctic‐breeding birds drive uneven responses to environmental variability across different phases of the reproductive cycle

“…In general, arthropod abundance was low at lower temperatures and increased at temperatures >5°C, but, importantly, we also documented periods of high temperature that coincided with low arthropod abundance during which we nonetheless observed high age‐specific chick masses. This suggests a thermogenic trade‐off for semipalmated sandpiper chicks at higher temperatures wherein the high cost of thermogenesis (Bakken et al, 2002 ; Schekkerman et al, 2003 ) may be minimized and growth maximized (McKinnon et al, 2013 ), permitting rapid chick growth even during periods of relatively low food abundance (but see Saalfeld et al, 2021 ).…”