Deconstructing incubation behaviour in response to ambient temperature over different timescales

Abstract

Avian embryos need a stable thermal environment to develop optimally, while incubating females need to allocate time to self‐maintenance off the nest. In species with female‐only incubation, eggs are exposed to ambient temperatures that usually cool them down during female absences. The lower the ambient temperature the sooner females should return to re‐warm the eggs. When incubation constraints ease at increasing ambient temperatures, females respond by increasing either incubation effort or self‐maintenance time. These responses are population‐dependent even within the same species; but it is uncertain whether they are caused by local environmental conditions or they are an artefact from limited datasets, different methodological approaches or the timescale over which incubation behaviour is measured. In this study, we collected incubation data from three Mediterranean great tit Parus major populations during three consecutive years. We measured the duration of each off‐ and on‐bout event, used these variables to compute nest attentiveness at three different timescales (full incubation, daily and hourly periods) and assessed the impact of ambient temperature on bout duration and nest attentiveness. We found that females maximized on‐bout duration at different local temperatures, ranging from 10 to 20°C; but lengthened off‐bouts linearly across a range of 0–38°C in all three populations. These local differences translated into opposite linear nest attentiveness patterns at the full incubation scale: Females increased either incubation effort, longest on‐bouts between 15 and 20°C or self‐maintenance time, longest on‐bouts at 10°C. It was at daily and hourly periods when we detected non‐linear nest attentiveness patterns, as expected from on‐bout duration, peaking at different local ambient temperatures. Females first increased incubation effort up to a certain temperature value and then increased self‐maintenance time at the highest ambient temperatures. Further research is needed to understand which factors are behind the turning points from one behaviour to the other.

Gut microbiome disturbances of altricial Blue and Great tit nestlings are countered by continuous microbial inoculations from parental microbiomes

“…However, despite bi-parental care, we observed a stronger effect of maternal than paternal microbiomes on chick gut microbiomes (see also [27]). Females spend more time than males during nest building [42, 76], egg laying [77–79], incubation [80–82], and brooding [42, 83, 84], which could lead to a maternally biased shedding of microbes that can be acquired by the chicks. Indirect transfer of maternal microbes via nest environment has also been shown in Zebra finch chicks ( Taeniopygia guttata ) [15].…”

Indirect maternal effects via nest microbiome composition drive gut colonization in altricial chicks

“…Chick gut microbiome convergence towards nest microbiome suggests that the nest environment plays an important role in gut microbiome colonization and the structuring of the microbiome community, likely leading to the brood effect observed in altricial birds. Female tits spend longer time than males in the nest‐box during nest building (Mainwaring, 2017; Perrins, 1979), egg laying (Diez‐Méndez, Sanz, & Barba, 2021; Lord et al, 2011; Pendlebury & Bryant, 2005), incubation (Bambini et al, 2019; Diez‐Méndez, Cooper, et al, 2021; Nilsson, 2000) and brooding periods (Andreasson et al, 2016; Perrins, 1979; Rodríguez & Barba, 2016). These behaviours would further result in indirect maternal‐biased transfer of microbes due to increased amount of female contact with nest material.…”

“…Female tits spend longer time than males in the nest-box during nest building (Mainwaring, 2017;Perrins, 1979), egg laying Lord et al, 2011;Pendlebury & Bryant, 2005), incubation (Bambini et al, 2019;Diez-Méndez, Cooper, et al, 2021;Nilsson, 2000) and brooding periods (Andreasson et al, 2016;Perrins, 1979;Rodríguez & Barba, 2016). These behaviours would further result in indirect maternal-biased transfer of microbes due to increased amount of female contact with nest material.…”

Reproductive fitness is associated with female chronotype in a songbird

“…Our study results come with some caveats. Because we report correlative data from wild birds, we cannot assess whether chronotype was affected by the local microenvironment, either directly or via differences in individual quality (Diez-Méndez, Cooper, et al, 2021;Maury et al, 2020). We have recorded female chronotype only during one life-cycle stage, incubation, similar to earlier studies on males that considered only courtship (Murphy et al, 2008).…”