The Effects of Nestbox Thermal Environment on Fledging Success and Haematocrit in Tree Swallows

Ardia, Daniel R.

doi:10.3184/175815513x13609528031394

Cited by 43 publications

(44 citation statements)

References 50 publications

(50 reference statements)

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“…In a given year, ca. 25-50% of clutches in the population hatch asynchronously, with eggs within a clutch hatching over two to three or, occasionally, 4 days; the remainder of clutches hatch synchronously, with all eggs of the clutch hatching within a day (Bowers, Sakaluk & Thompson 2011, 2013. The length of the nestling period is typically 15-17 days (Bowers, Sakaluk & Thompson 2013); the oldest, largest nestlings usually leave the nest first, with the rest of the brood following within a few hours.…”

Section: Study Area and Speciesmentioning

confidence: 99%

“…Blood samples were stored in microcapillary tubes on ice while in the field and processed in the laboratory later the same day. After centrifuging blood samples and measuring haematocrit, a widely used measure of condition and health (Richner, Oppliger & Christe 1993;Ots, Muruma¨gi & Hõrak 1998;Norte et al 2008;Morrison, Ardia & Clotfelter 2009;Williams 2012;Ardia 2013), we stored red blood cells for later use in molecular sex identification of nestlings (for details of these procedures, see Forsman et al 2010;Bowers, Sakaluk & Thompson 2011).…”

Section: General Field Proceduresmentioning

confidence: 99%

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Persistent sex‐by‐environment effects on offspring fitness and sex‐ratio adjustment in a wild bird population

Bowers

Thompson

Sakaluk

2014

Journal of Animal Ecology

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Summary A major component of sex-allocation theory, the Trivers-Willard Model (TWM), posits that sons and daughters are differentially affected by variation in the rearing environment. In many species, the amount of parental care received is expected to have differing effects on the fitness of males and females. When this occurs, the TWM predicts that selection should favour adjustment of the offspring sex ratio in relation to the expected fitness return from offspring. However, evidence for sex-by-environment effects is mixed and little is known about the adaptive significance of producing either sex. Here, we test whether offspring sex ratios vary according to predictions of the TWM in the house wren (Troglodytes aedon, Vieillot). We also test the assumption of a sex-by-environment effect on offspring using two experiments, one in which we manipulated age-differences among nestlings within broods, and another in which we held nestling age constant but manipulated brood size. As predicted, females with high investment ability over-produced sons relative to those with lower ability. Males were also over-produced early within breeding seasons. In our experiments, the body mass of sons was more strongly affected by the sibling-competitive environment and resource availability than that of daughters: males grew heavier than females when reared in good conditions but were lighter than females when in poor conditions. Parents rearing broods with 1:1 sex ratios were more productive than parents rearing broods biased more strongly towards sons or daughters, suggesting that selection favours the production of mixed-sex broods. However, differences in the condition of offspring as neonates persisted to adulthood, and their reproductive success as adults varied with the body mass of sons, but not daughters, prior to independence from parental care. Thus, selection should favour slight but predictable variations in the sex ratio in relation to the quality of offspring that parents are able to produce. Offspring sex interacts with the neonatal environment to influence offspring fitness, thus favouring sex-ratio adjustment by parents. However, increased sensitivity of males to environmental conditions, such as sibling rivalry and resource availability, reduces the fitness returns from highly male-biased broods.

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Section: Study Area and Speciesmentioning

confidence: 99%

Section: General Field Proceduresmentioning

confidence: 99%

Persistent sex‐by‐environment effects on offspring fitness and sex‐ratio adjustment in a wild bird population

Bowers

Thompson

Sakaluk

2014

Journal of Animal Ecology

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“…Birds are therefore under strong selection pressures to select a nest site and construct nests that provide suitable thermal conditions for embryonic development. Parental brooding behaviors can regulate nest microclimates, but such behaviors are energetically costly and parents can mitigate these demands by altering the design of nests in relation to predictable variation in environmental conditions (Mertens, 1977;Møller, 1984;Lombardo, 1994;Hilton et al, 2004;Dawson et al, 2011;Heenan and Seymour, 2012;Ardia, 2013;Heenan, 2013;Windsor et al, 2013;Cruz et al, 2016).…”

Section: Environmental Adjustmentmentioning

confidence: 99%

Causes and Consequences of Intraspecific Variation in Nesting Behaviors: Insights from Blue Tits and Great Tits

Mainwaring

2017

Front. Ecol. Evol.

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Nest building is an important and yet under-studied stage of the reproductive cycle in many taxa, including birds, and whilst we have a decent understanding of interspecific variation in avian nesting behaviors, our understanding of intraspecific variation in nesting behaviors is much less developed. This is largely because an insufficient number of studies have been performed on any one species to draw robust conclusions. Fortunately, though, the amount of research on the nesting behaviors of nestbox-breeding blue tits (Cyanistes caeruleus) and great tits (Parus major) has increased dramatically in recent years and their nesting behaviors are now sufficiently well-studied to offer useful insights into intraspecific variation in avian nesting behaviors. Studies show that individuals of both species select nest sites based on the presence and/or absence of conspecifics and heterospecifics and whilst neighbors were assumed to adversely affect focal individuals by competing for resources, they are now considered beneficial as they provide information about habitat quality and contribute to anti-predator defenses. Nest-building females accurately gauge local weather conditions and respond to predictable variation in environmental conditions by building nests with variable amounts of cup lining material to create suitable nest microclimates for nestlings. Meanwhile, both species vary the amount of aromatic plant materials in their nests in relation to the abundance of nest-dwelling parasites and pathogens and as aromatic plant materials also play a role in sexual selection then nest materials can have multiple functions. The height of nests is negatively correlated with the local risk of predation but whilst predator avoidance favors lower nests, sexual selection favors taller nests. In fact, higher quality females build taller nests that contain more green plant material which in turn influences the amount of care provided by males. This suggests there is considerable intraspecific variation in nesting behaviors in blue and great tits, and in birds generally, and highlights that birds are adept at adaptively varying their nesting behaviors in response to multiple factors. There is, however, a paucity of evidence directly linking such variation in nest building behaviors to reproductive success or fitness more broadly and so further studies could usefully examine such links because trade-offs between competing selection pressures may constrain adaptive nesting behaviors.

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“…Perhaps a direct effect of treatment was only seen in 2012 because nestlings in 2013 and 2014 responded to the doubled parasite load by increasing haematopoiesis at a rate faster than ectoparasites were capable of removing blood cells (Dawson & Bortolotti 1997a), whereas nestlings in 2012 were not energetically stressed enough for such a response to occur. Also, haematocrit is often lower at warmer ambient temperatures, due to dehydration (Ardia 2013), and ambient temperatures were warmer in 2014 than in 2013 (see above), which may explain why overall haematocrit levels were less in 2014 than in 2013.…”

Section: Haematocritmentioning

confidence: 99%

“…This, along with the fact that it can be affected by many different factors, is why haematocrit has been criticized as not being a robust indicator of nutritional status or condition (Dawson & Bortolotti 1997c;O' Brien et al 2001 ;Fair et al 2007 and references therein). Haematocrit is a fairly reliable indicator of water balance (Ardia 2013), but using it as an indicator of oxygen-carrying capacity should be done with caution.…”

Section: Haematocritmentioning

confidence: 99%

Trade-offs in the early development of tree swallows (Tachycineta bicolor): offspring characteristics, offspring quality, and parental care

Unger¹

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Life-history theory predicts that because organisms have limited resources available to them, they must make decisions to prudently allocate resources in a way that maximizes fitness.Therefore, there is expected to be a trade-off between current reproductive effort and future survival and reproduction, with those individuals investing in a current breeding attempt doing so at a cost to their own survival and/or future fecundity. Altricial birds rearing young are consequently expected to be prudent in their allocation of resources between broodmaintenance and self-maintenance, and their allocation choices may be influenced by numerous offspring characteristics that potentially indicate offspring "quality" or condition.My thesis had three main goals: 1) to understand if the smallest nestling tree swallows in a nest are of inherent poor "quality", or if they are the smallest simply due to being outcompeted by their older and larger siblings; 2) to investigate whether, in an environment with parasites, it is the parents or their offspring who bear the costs associated with parasitism; and 3) to better understand the function of gape and flange colouration in nestling tree swallows. Overall, I wanted to understand how each of these nestling characteristics affect, and are affected by, parental life-history trade-offs. By pairing observational data with a cross-fostering experiment, I determined that both total egg mass and yolk mass increased with order of laying. N estlings that hatched earlier in the hatching sequence and were manipulated to be smaller within the size hierarchies in nests performed in a similar fashion as if they had retained their size advantage, but had lower immune responses, which may be because these earlier-hatched nestlings hatched from earlier-laid eggs with smaller yolks. By manipulating parasite levels in nests and then comparing nestling immune function and growth, and parental provisioning rates with control nests in a three-year study, I observed no 11 significant effects of larval blow flies parasitizing nestlings, except parasitized nestlings showed slightly lower haematocrit levels in one year. Deleterious effects of parasitism may have been compensated for by parents, as the parents of parasitized nestlings fed their young at marginally higher rates than the parents of parasite-free nestlings. By manipulating either gape redness or flange colouration (both within ultraviolet and human-visible wavelengths) of nestling tree swallows and carrying out feeding trials, I determined that parents did not preferentially feed nestlings with redder gapes. Instead, they fed nestlings with flanges that reflect in the ultraviolet more than nestlings with non-ultraviolet-reflective flanges, although only when nestlings were older. Parents also appeared to feed nestlings with blackened flanges less throughout the nestling period. Overall, my studies indicate that 1) tree swallows may allocate extra nutrients to later-laid eggs to alleviate detrimental effects of within-brood size hierarchi...

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The Effects of Nestbox Thermal Environment on Fledging Success and Haematocrit in Tree Swallows

Cited by 43 publications

References 50 publications

Persistent sex‐by‐environment effects on offspring fitness and sex‐ratio adjustment in a wild bird population

Persistent sex‐by‐environment effects on offspring fitness and sex‐ratio adjustment in a wild bird population

Causes and Consequences of Intraspecific Variation in Nesting Behaviors: Insights from Blue Tits and Great Tits

Trade-offs in the early development of tree swallows (Tachycineta bicolor): offspring characteristics, offspring quality, and parental care

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