Influence of incubation recess patterns on incubation period and hatchling traits in wood ducks Aix sponsa

Abstract

Parental eff ects are infl uential sources of phenotypic variation in off spring. Incubation temperature in birds, which is largely driven by parental behavior and physiology, aff ects a suite of phenotypic traits in off spring including growth, immune function, stress endocrinology, and sex ratios. Th e importance of average incubation temperature on off spring phenotype has recently been described in birds, but parental incubation behaviors like the duration and frequency of recesses from the nest can be variable. Th ere are few studies describing how or if thermal variation as a result of variable incubation aff ects off spring phenotype. We incubated wood duck Aix sponsa eggs under three diff erent incubation regimes, based on patterns that occur in nature, which varied in off -bout duration and/or temperature. We measured incubation period, morphometrics at hatching, and monitored growth and body condition for nine days post hatch. When average incubation temperature was allowed to drop from 35.9 ° C to 35.5 ° C as a result of doubled off -bout duration, we found a signifi cant 2 d extension in incubation period, but no eff ects on duckling hatch mass, or growth and body condition up to nine days post hatch. However, when average incubation temperatures were equivalent (35.9 ° C), doubling the duration of the simulated off -bouts did not infl uence incubation period or any post hatch parameters. Our results suggest that if incubating parents can maintain favorable thermal environments in the nest via altered behavior (e.g. manipulating nest insulation) and/or physiology (e.g. heat production), parents may be able to avoid the costs of longer incubation periods resulting from increased off -bout duration.

Do extended incubation recesses carry fitness costs in two cavity-nesting birds?

“…2 longer. Carter et al (2014) reported similar results for Wood Ducks (Aix sponsa), and these longer incubation periods could be related to the suboptimal thermal conditions experienced by the embryos due to the extended recesses. Longer incubation periods may have fitness costs associated with an increase in the risk of predation (Martin 2002) and with increased energy expenditure by embryos during development, which could have a negative impact on nestlings (Hepp et al 2006, Eiby and Booth 2009, DuRant et al 2013.…”

“…Carter et al. () reported similar results for Wood Ducks ( Aix sponsa ), and these longer incubation periods could be related to the suboptimal thermal conditions experienced by the embryos due to the extended recesses. Longer incubation periods may have fitness costs associated with an increase in the risk of predation (Martin , Martin et al.…”

“…Our result could be due to the conservative nature of our classification system, or to females with at least one extended recess subsequently compensating by providing optimal conditions during the remainder of the incubation period (Carter et al. ). Other investigators have also reported no effect of prolonged periods of hypothermia on hatching success (Haftorn , Wang and Beissinger ).…”

Diverse incubation rhythms in a facultatively uniparental shorebird – the Northern Lapwing

“…Perhaps breeding in a temperate climate does not require continuous incubation attendance (but see temperate species in Bulla et al 2016b). Essentially, the between nest variability in nest attendance – which can be as much as a 6.5 hours difference per day – seems huge and is much larger than nest attendance fluctuations known to influence embryo development (Hepp et al 2006; Carter et al 2014; Bueno-Enciso et al 2017), or length of the incubation period (Grønstøl 2003; Martin et al 2007; Carter et al 2014; Bueno-Enciso et al 2017).…”

Hatching date vs laying date: what should we look at to study avian optimal timing of reproduction?

“…4) Intensity of incubation . This is certainly another neglected aspect of avian reproduction, though it seems clear that birds may adjust incubation effort, including duration of incubation bouts, proportion of daytime spent incubating, and even temperature, in a deliberate way (Haftorn , Cresswell and McCleery , Martin and Briskie , Hill et al ), and this can advance or delay egg hatching (Hepp et al , Martin et al , Thierry et al , Carter et al ). To some extent, onset of incubation and intensity of incubation may be difficult to separate, because onset of incubation usually is not a sharp turning point but a gradual increase in nest attentiveness (Haftorn , Cresswell and McCleery ).…”