Experimental manipulation of incubation period reveals no apparent costs of incubation in house wrens

Sakaluk, Scott K.; Thompson, Charles F.; Bowers, E. Keith

doi:10.1016/j.anbehav.2018.01.006

Cited by 17 publications

(12 citation statements)

References 40 publications

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“…Support for the incubation inefficiency explanation is equivocal. An experimental study of house wrens Troglodytes aedon that used cross-fostering of eggs to extend or reduce the length of time females had to incubate a clutch had no effect on hatching success (Sakaluk et al, 2018), suggesting that the inefficient incubation hypothesis is unlikely. However, females in lower body condition incubate for longer and have reduced hatching success due to lower incubation temperatures (Hepp et al, 2006) and increased incubation recesses (Bueno-Enciso et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

Incubation in a Temperate Passerine: Do Environmental Conditions Affect Incubation Period Duration and Hatching Success?

2020

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The timing of breeding often has a profound influence on the reproductive success of birds living in seasonal environments with rapidly changing nestling food availability. Timing is typically investigated with reference to lay dates, but it is the time of hatching that determines the ambient conditions and food availability that nestlings experience. Thus, in addition to lay date, phenological studies may also have to take account of variation in the length of the incubation period, which is likely to depend on both environmental conditions and parental traits. The primary aim of this study was to use a 24-year dataset to investigate the abiotic and biotic factors influencing variation in incubation duration in long-tailed tits (Aegithalos caudatus), a species in which incubation duration varies substantially (range: 12-26 days). We found support for our predictions that drier conditions, later breeding attempts and larger clutches were associated with shorter incubation periods. Larger clutches were also more resilient to increases in incubation duration associated with wet conditions. Surprisingly, warmer ambient conditions were associated with longer incubation periods. Secondly, we assessed the consequences of variation in the length of incubation periods for the risk of nest predation and the hatching success of surviving clutches. We show that longer incubation periods are likely to be costly due to increased exposure to nest predators. In contrast, we found only marginal effects of environmental conditions or incubation duration on hatching success, implying that wet conditions cause slower embryo growth and hence longer incubation periods, rather than causing embryo fatality. We suggest that long-tailed tits' nests and parental behavior protect eggs from mortality arising directly from adverse weather conditions.

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Section: Discussionmentioning

confidence: 99%

Incubation in a Temperate Passerine: Do Environmental Conditions Affect Incubation Period Duration and Hatching Success?

2020

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“…We predicted that if there were a relationship between CORT and reproductive investment and success, it would most likely emerge post-hatch, given the higher maternal energy expenditure required during chick rearing than during incubation ( Nilsson and Råberg, 2001 ; Humphreys et al, 2006 ; Sakaluk et al, 2018 ; but see Williams, 2018 ). However, female CORT levels during chick rearing were unrelated to any measure of reproductive investment (nest box visits and nestling growth rate) nor any measure of reproductive success (nestling mass at day 14 and fledging success).…”

Section: Discussionmentioning

confidence: 99%

“…For example, a lack of relationship could be due to different functions of CORT; when resources are plentiful, elevated CORT could stimulate energy mobilization and parental provisioning; however, CORT could also be elevated in parents experiencing stressors ( Vitousek et al, 2014 ). Even within a breeding season, different stages can have differing parental energetic requirements presumably requiring different levels of GC-mediated energy mobilization ( Humphreys et al, 2006 ; Nager, 2006 ; Tulp et al, 2009 ; Sakaluk et al, 2018 ).…”

Section: Introductionmentioning

confidence: 99%

Maternal glucocorticoid levels during incubation predict breeding success, but not reproductive investment, in a free-ranging bird

et al. 2020

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The hormone corticosterone (CORT) has been hypothesized to be linked with fitness, but the directionality of the relationship is unclear. The ‘CORT-fitness hypothesis’ proposes that high levels of CORT arise from challenging environmental conditions, resulting in lower reproductive success (a negative relationship). In contrast, the CORT-adaptation hypothesis suggests that, during energetically demanding periods, CORT will mediate physiological or behavioral changes that result in increased reproductive investment and success (a positive relationship). During two breeding seasons, we experimentally manipulated circulating CORT levels in female tree swallows (Tachycineta bicolor) prior to egg laying, and measured subsequent reproductive effort, breeding success, and maternal survival. When females were recaptured during egg incubation and again during the nestling stage, the CORT levels were similar among individuals in each treatment group, and maternal treatment had no effect on indices of fitness. By considering variation among females, we found support for the CORT-adaptation hypothesis; there was a significant positive relationship between CORT levels during incubation and hatching and fledging success. During the nestling stage CORT levels were unrelated to any measure of investment or success. Within the environmental context of our study, relationships between maternal glucocorticoid levels and indices of fitness vary across reproductive stages.

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“…At the time of banding, we weighed nestlings and measured their tarsus length to assess size-adjusted body mass (García-Berthou 2001). When measured prior to fledging, this size-adjusted mass positively predicts offspring recruitment and their reproductive success in the population as adults (Bowers et al 2014a, 2015c), and, when measured in adulthood during breeding, maternal lifetime allelic fitness (Sakaluk et al 2018). We checked nests daily beginning on day 13 to check for fledging.…”

Section: Methodsmentioning

confidence: 99%

Condition-Dependent Begging Elicits Increased Parental Investment in a Wild Bird Population

Bowers

Jenkins

Mueller

et al. 2019

The American Naturalist

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The coevolution of parental supply and offspring demand has long been thought to involve offspring need driving begging and parental care, leaving other hypotheses underexplored. In a population of wild birds, we tested experimentally whether begging serves as a negatively condition-dependent signal of need or a positively condition-dependent signal of quality. Across multiple years, we food-supplemented nestling house wrens shortly after hatching, and simultaneously manipulated corticosterone levels to simulate the hunger-induced increase in glucocorticoids thought to mediate begging. This allowed us also to test whether begging is simply a proximate signal of hunger. Days after supplementation ended, food-supplemented nestlings were in better condition than non-supplemented nestlings and begged for food at an increased rate; their parents, in turn, increased provisioning to a greater extent than parents of non-supplemented young, as begging positively predicted provisioning. Food-supplemented nestlings, therefore, attained above-average condition, which predicted their recruitment as breeding adults in the local population. Glucocorticoids increased begging in the short-term, but this transient effect depended on satiety. Thus, glucocorticoids promoted begging as a proximate response to hunger, whereas the longer-term changes in nestling condition, begging, and food provisioning suggest that begging ultimately signals offspring quality to elicit increased investment, thereby enhancing offspring survival.

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Experimental manipulation of incubation period reveals no apparent costs of incubation in house wrens

Cited by 17 publications

References 40 publications

Incubation in a Temperate Passerine: Do Environmental Conditions Affect Incubation Period Duration and Hatching Success?

Incubation in a Temperate Passerine: Do Environmental Conditions Affect Incubation Period Duration and Hatching Success?

Maternal glucocorticoid levels during incubation predict breeding success, but not reproductive investment, in a free-ranging bird

Condition-Dependent Begging Elicits Increased Parental Investment in a Wild Bird Population

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