Hot and dry conditions predict shorter nestling telomeres in an endangered songbird: Implications for population persistence

Abstract

Climate warming is increasingly exposing wildlife to sublethal high temperatures, which may lead to chronic impacts and reduced fitness. Telomere length (TL) may link heat exposure to fitness, particularly at early-life stages, because developing organisms are especially vulnerable to adverse conditions, adversity can shorten telomeres, and TL predicts fitness. Here, we quantify how climatic and environmental conditions during early life are associated with TL in nestlings of wild purple-crowned fairy-wrens ( Malurus coronatus ), endangered songbirds of the monsoonal tropics. We found that higher average maximum air temperature (range 31 to 45 °C) during the nestling period was associated with shorter early-life TL. This effect was mitigated by water availability (i.e., during the wet season, with rainfall), but independent of other pertinent environmental conditions, implicating a direct effect of heat exposure. Models incorporating existing information that shorter early-life TL predicts shorter lifespan and reduced fitness showed that shorter TL under projected warming scenarios could lead to population decline across plausible future water availability scenarios. However, if TL is assumed to be an adaptive trait, population viability could be maintained through evolution. These results are concerning because the capacity to change breeding phenology to coincide with increased water availability appears limited, and the evolutionary potential of TL is unknown. Thus, sublethal climate warming effects early in life may have repercussions beyond individual fitness, extending to population persistence. Incorporating the delayed reproductive costs associated with sublethal heat exposure early in life is necessary for understanding future population dynamics with climate change.

Causes and consequences of variation in early‐life telomere length in a bird metapopulation

“…In black‐tailed gulls ( Larus crassirostris ), telomeres were even elongated during an El Niño year, in which weather was generally milder and sea surface temperatures lower, resulting in improved foraging conditions (Mizutani et al, 2013 ). Similarly, the change in TL in greater‐eared bats ( Myotis , Foley et al, 2020 ), early‐life TL in European badgers ( Meles , van Lieshout et al, 2021 ) and purple‐crowned fairy‐wrens ( Malurus coronatus , Eastwood et al, 2022 ) was positively associated with generally good weather conditions (favorable temperatures and rainfall). Furthermore, in other Norwegian populations of house sparrows, nestling TL was positively associated with the NAO index averaged across approximately 2 weeks before and after hatching, which locally reflected higher temperatures, lower rainfall, and lower wind speed (Pepke, Kvalnes, et al, 2022 ).…”

Temperature, size and developmental plasticity in birds

“…When the environmental cues that drive developmental plasticity are unreliable indicators of trait optima, plasticity can lead to population declines [ 108 ]. Further, changes in the thermal environment can impact aspects of the phenotype beyond size, including thermoregulatory control, which can be constrained or enhanced by variation in developmental temperatures [ 98 ], and warmer temperatures can have direct deleterious effects on the physiology of developing individuals [ 109 ]. Even when plasticity might be adaptive, it may be insufficient to prevent long-term fitness declines [ 110 ], and there is little evidence of selection for plasticity in response to thermal conditions [ 111 ].…”

Thermoregulatory strategies of songbird nestlings reveal limited capacity for cooling and high risk of dehydration

“…This trade-off may have immediate impacts on nestling body condition and important consequences in adulthood (Monaghan 2008). Indeed, long-term 3 studies have associated increased ambient temperatures during the nestling stage to reduced breeding success and shorter lifespans as adults (Schoech et al 2011;Dupont et al 2019;Kraft et al 2019;Eastwood et al 2022).…”