Going to sleep with a full belly: Thermal substitution by specific dynamic action in shorebirds

Behavioural and physiological responses to experimental temperature changes in a long-billed and long-legged bird: a role for relative appendage size?

“…This result is analogous to that found by Ryeland et al (2017), in which shorebirds reduced their back rest behaviour at high T a values to favour heat flux into the environment. At hot conditions, but below their T b (39-40 °C; see also González-Medina et al 2020), we also found that the proportion of time spent resting on back rest, and to lesser extent on unipedal, was related to the relative size of bill and legs, respectively. Dunlins with the largest relative bill sizes clearly spent more time with their bills exposed compared to dunlins with the smallest relative bills, supporting dunlins adjusted their bill postures to increase dry heat transfer into the environment at high temperatures.…”

“…Following the acclimation period, the RMR and EWL were measured at 10 °C, 25 °C and 35 °C during the "high tide" simulation period after 4 h of fasting to ensure that the birds were in a postabsorptive state (see González-Medina et al 2020). The dunlins were weighed (± 0.1 g) before and after the metabolic measurements, and the mean body mass (M b ) was used in the analyses.…”

“…Oxygen consumption (VO 2 ) and EWL were measured using an open flow-through respirometry system (Sable Systems) following González-Medina et al (2020). Briefly, each post-absorptive individual was placed in a polypropylene metabolic chamber (effective volume = 3.9 L) inside a compressor-cooled incubator (Memmerts GmbH, Germany).…”

“…Maintaining a high body temperature (T b ) within a very narrow range may be a major challenge for endothermic vertebrates when they are confronted with environmental Communicated by K. van Oers temperatures beyond their thermoneutral zone, i.e., range of ambient temperatures within which endotherms are able to maintain their T b without increasing metabolic rate and water loss (Boyles et al 2011;McKechnie et al 2017). Many birds live in open landscapes where they are regularly exposed to acute external cold and heat loads and as a result, these have evolved specific behavioural and physiological responses to cope with these thermal challenges (Luskick et al 1978;Brodsky and Weatherhead 1984;Tieleman et al 2002;Amat and Masero 2004;Gutiérrez et al 2015;González-Medina et al 2020). Groups such as shorebirds, waterfowl and gulls rely on exposed intertidal areas for foraging.…”

Heat tolerance limits of Mediterranean songbirds and their current and future vulnerabilities to temperature extremes

“…overlooking the effect of solar radiation or activity). In the wild, these rates could be substantially higher owing to locomotor activity, heat increment of feeding ( González-Medina et al, 2020 ), or higher environmental heat loads. This, combined with the predicted increase in heavy droughts along the Mediterranean Basin ( IPCC, 2021 ), could lead to shorter times to lethal dehydration than predicted among Mediterranean songbirds.…”