Impacts of ambient temperature and clutch size on incubation behaviour onset in a female‐only incubator songbird

Abstract

Ambient temperature is assumed to be the major cue used by passerines to synchronize their laying and hatching dates to the expected peak of prey availability. While laying eggs, females are still able to fine‐tune their hatching date following increasing or decreasing patterns of ambient temperature, mostly via changes in incubation onset. The onset of incubation behaviour in relation to the laying sequence could have later consequences for the duration of the incubation period and the extent of hatching asynchrony. Clutch size is also known to affect incubation patterns and might therefore condition potential responses to changing temperatures. In this study we assessed the association of ambient temperature and clutch size with the onset of four different incubation behaviours: partial and full nocturnal incubation, and partial and full diurnal incubation. We also evaluated how the onset and duration of each incubation behaviour might predict the duration of diurnal full incubation and the extent of hatching asynchrony. To achieve our aims, we monitored incubation behaviour using temperature data loggers during the egg‐laying period in three Mediterranean Great Tit Parus major populations in three consecutive years. Our results showed that increasing temperatures were related to an advance of diurnal partial incubation, but not its duration or the onset of full incubation behaviour. We did not find any effect of ambient temperatures on nocturnal incubation. However, females lengthened nocturnal partial incubation and delayed the onset of nocturnal full and diurnal partial incubation when laying larger clutches. Longer diurnal incubation before clutch completion was associated with greater hatching asynchrony. Moreover, longer diurnal partial incubation shortened the duration of the full incubation period. In conclusion, increasing ambient temperatures during the egg‐laying period advanced diurnal partial incubation, indirectly shortening the full incubation period and increasing hatching asynchrony.

Incubation before Clutch Completion Predicts Incubation Time and Hatching Asynchrony in the Blue Tit Cyanistes caeruleus

“…We found all of the females to be incubating already before or at clutch completion, which differs from findings by Stenning (2008) who showed, via nest checks, that incubation started at any time between six days before and eight days after clutch completion in a UK population. A similar but smaller spread was recorded for Great Tits via daily nest checks in a Spanish population (Álvarez & Barba 2014a, Diez-Méndez et al 2021. We also found more diurnal early incubation than previously recorded in other Blue Tit (e.g.…”

“…Wiebe et al 1998, for an overview see Wang & Beissinger 2011). Hatching asynchrony and early incubation as its main cause have been relatively well investigated in studies on nestbox-breeding tits (Paridae), in particular Great Tits Parus major (Gibb 1950, Kluijver 1950, Neub 1979, Haftorn 1981, Pendlebury & Bryant 2005, Lord et al 2011, Podlas & Richner 2013, Álvarez & Barba 2014a,b, Diez-Méndez et al 2020, 2021) and Blue Tits Cyanistes caeruleus (Gibb 1950, Neub 1979, Slagsvold et al 1995, Stenning 2008, Hadfield et al 2013, Vedder et al 2012), where only the females incubate the eggs (Haftorn & Reinertsen 1985).…”

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].…”

Reproductive fitness is associated with female chronotype in a songbird

“…Great tits are female-only intermittent incubators, who spend nights on their nest, but at daytime alternate between nest attendance (i.e., on-bouts) and foraging outings (i.e., off-bouts) (Diez-Méndez et al . 2021).…”

“…Great tits are female-only intermittent incubators, who spend nights on their nest, but at daytime alternate between nest attendance (i.e., on-bouts) and foraging outings (i.e., off-bouts) (Diez-Méndez et al 2021). From small temperature loggers (i.e., iButtons) inserted into nests of urban and forest-breeding great tits, we first infer incubation chronotype of females for both absolute and relative time, and assess consistency of chronotype across the breeding season.…”