Brood size, telomere length, and parent-offspring color signaling in barn swallows

Abstract

Trade-offs select for optimal allocation of resources among competing functions. Parents are selected to maximize production of viable offspring by balancing between progeny number and "quality." Telomeres are nucleoproteins, at the ends of eukaryotic chromosomes, that shorten when cells divide. Because shortening below a certain threshold depresses organismal functioning and rate of shortening depends on environmental conditions, telomeres are good candidates as mediators of trade-offs. We altered brood size of barn swallow Hirundo rustica and found that brood enlargement caused a reduction in relative telomere length (RTL). Reliable signals of offspring quality should evolve that mediate adaptive parental care allocation. Because nestlings with darker coloration receive more care, we analyzed the covariation between RTL and coloration and found that RTL increased with plumage darkness, both within and between broods. Hence, we provide unprecedented evidence that signals relevant to parent-offspring communication reflect telomere length and thus offspring reproductive value.

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

“…However, the causes of telomere attrition are likely to differ for the two extremes. The negative effect of increased brood size on telomere length is in line with previous studies (Boonekamp et al., ; Costanzo et al., ; Nettle et al., ), probably as a consequence of developmental stress caused by increased sibling competition and reduced access to food. By contrast, nestlings raised in reduced broods were not constrained by these factors and therefore maximized their growth rates.…”

The Odour of Sex: Sex-Related Differences in Volatile Compound Composition among Barn Swallow Eggs Carrying Embryos of Either Sex

“…It has also been demonstrated that nestling vocalizations [37] and gape colouration [38] varies between the sexes. Recent studies have also revealed significant differences in ventral colour between nestling of either sex [88,89] and differential variation in parental care allocation in relation to offspring plumage colouration among males as compared to female nestlings [90]. The existence of sex-related variation in offspring post-hatching phenotype and of differential allocation to either sex by parents suggests that sex-dependent egg odour might pave the way to pre-hatching differential allocation of care by parents.…”

Divergent patterns of telomere shortening in tropical compared to temperate stonechats

“…In addition, especially under high predation pressure, stonechats often skip a second clutch in favor of their fledglings (Scheuerlein et al, 2001). In addition, as environmental conditions and parental care during growth can influence telomere loss and maintenance (e.g., Costanzo et al, 2017), extended parental care may create more favorable conditions for tropical fledglings and juveniles that may allow them to maintain their telomeres better than temperate ones. A number of recent studies in temperate songbirds during the nestling period have shown that the rearing environment has an influence on telomere attrition rates in early life (e.g., Salmon et al, 2016;Soler et al, 2017).…”

“…A number of recent studies in temperate songbirds during the nestling period have shown that the rearing environment has an influence on telomere attrition rates in early life (e.g., Salmon et al, 2016;Soler et al, 2017). For example, growing up in large broods, high begging effort and low food availability hasten telomere loss in nestlings (Costanzo et al, 2017;Nettle et al, 2017;Young et al, 2017 , 2014;Salmon et al, 2017). The effect of extended parental care in tropical birds on telomere dynamics in fledglings should be further investigated, for example through brood size manipulation experiments.…”

“…For example, exposure to poor or stressful environments can lead to accelerated telomere loss in young birds (Costanzo et al, 2017;Haussmann, Longenecker, Marchetto, Juliano, & Bowden, 2012;Herborn et al, 2014;Nettle et al, 2017;Salmon, Nilsson, Nord, Bensch, & Isaksson, 2016;Soler et al, 2017;Young et al, 2017), which can be predictive of decreased survival as nestlings or fledglings (Boonekamp, Mulder, Salomons, Dijkstra, & Verhulst, 2014;Salmon, Nilsson, Watson, Bensch, & Isaksson, 2017;Watson, Bolton, & Monaghan, 2015). For example, exposure to poor or stressful environments can lead to accelerated telomere loss in young birds (Costanzo et al, 2017;Haussmann, Longenecker, Marchetto, Juliano, & Bowden, 2012;Herborn et al, 2014;Nettle et al, 2017;Salmon, Nilsson, Nord, Bensch, & Isaksson, 2016;Soler et al, 2017;Young et al, 2017), which can be predictive of decreased survival as nestlings or fledglings (Boonekamp, Mulder, Salomons, Dijkstra, & Verhulst, 2014;Salmon, Nilsson, Watson, Bensch, & Isaksson, 2017;Watson, Bolton, & Monaghan, 2015).…”