Effects of temperature and nest heat exposure on nestling growth, dehydration and survival in a Mediterranean hole‐nesting passerine

Abstract

Variable environments impose constraints on adaptation by modifying selection gradients unpredictably. Optimal bird development requires an adequate thermal range, outside which temperatures can alter nestling physiology, condition and survival. We studied the effect of temperature and nest heat exposure on the reproductive success of a population of double‐brooded Spotless Starlings Sturnus unicolor breeding in a nestbox colony in central Spain with a marked intra‐seasonal variation in temperature. We assessed whether the effect of temperature differed between first and second broods, thus constraining optimal nest‐site choice. Ambient temperature changed greatly during the chick‐rearing period and had a strong influence on nestling mass and all body size measures we recorded, although patterns of clutch size or nestling mortality were not influenced. This effect differed between first and second broods: nestlings were found to have longer wings and bills with increasing temperature in first broods, whereas the effect was the opposite in second broods. Ambient temperature was not related to nestling body mass or tarsus‐length in first broods, but in second broods, nestlings were lighter and had smaller tarsi with higher ambient temperatures. The exposure of nestboxes to heat influenced nestling morphology: heat exposure index was negatively related to nestling body mass and wing‐length in second broods, but not in first broods. Furthermore, there was a positive relationship between nest heat exposure and nestling dehydration. Our results suggest that optimal nest choice is constrained by varying environmental conditions in birds breeding over prolonged periods, and that there should be selection for parents to switch from sun‐exposed to sun‐protected nest‐sites as the season progresses. However, nest‐site availability and competition for sites are likely to impose constraints on this choice.

Harsh conditions during early development influence telomere length in an altricial passerine: Links with oxidative stress and corticosteroids

“…In addition to the effect of treatment, we found that nestlings raised in second broods had larger telomeres than those raised in first broods. This was unexpected, because first broods are typically characterized by higher growth rates and less mortality than second broods in our population, due to higher food availability and milder weather (Muriel et al., ; Salaberria, Celis, López‐Rull, & Gil, ). However, given the particularly harsh weather conditions during first broods in the year of study (see above), it is likely that developmental stress levels were higher for first broods, as shown by the higher levels of corticosterone and MDA found in these broods.…”

An integrated analysis of micro- and macro-habitat features as a tool to detect weather-driven constraints: A case study with cavity nesters

“…They can also trigger a detrimental cascade where parents first spend shorter time in attending nests, the absence of incubating parents then both increases the risk of egg microbial infections and predation, and decreases hatching synchrony potentially resulting in higher mortality of the youngest nestlings [54]. Accordingly, previous findings showed a decreased hatching and fledging success as temperature increased [15, 16]. …”

Context‐dependent effects of yolk androgens on nestling growth and immune function in a multibrooded passerine

“…We investigated how the effects of yolk androgens on developmental and immunological traits in spotless starling chicks changed depending on the breeding attempt, as the environmental conditions become harsher (Salaberria et al ., ) and parental energetic reserves are gradually reduced (Stouffer, ; Verhulst & Tinbergen, ; Wiggins et al ., ; Styrsky et al ., ; Reed & Clark, ). Our results supported context‐dependent effects of yolk androgens on early development, survival and cell‐mediated adaptive immunity.…”

“…Based on the context dependence of early maternal effects (Krist et al ., ), we predicted that androgen treatment (compared to control treatment) would have a positive effect on chick growth and less immunosuppressive side effects during the first brood, because of more suitable breeding conditions that would balance energy requirements (Monaghan, ; Ilyina et al ., ). In contrast, during the second brood, characterized in our study site by low precipitations that dramatically reduce prey abundance (Turner, ), increased nest ectoparasite abundance (López‐Rull et al ., ) and high thermal stress for nestlings (Salaberria et al ., ), we would expect that the costs of increased yolk androgens would overcome their benefits for nestlings.…”