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

Abstract

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.

High nest failure but better nestling quality for early breeders in an alpine population of Northern Wheatear (Oenanthe oenanthe)

“…However, for the Wheatears breeding in our high-elevation study site, early breeding also carries the risk of low temperatures and severe weather conditions, which may indirectly lead to high failure probability in early springs and early in the season through increased predation risk (e.g. Rauter et al 2002, Kluen et al 2011, Higgot et al 2020, Marcelino et al 2020. This seems to be especially the case for the higher elevation nests within our study site that were subject to lower temperatures early in the season and which had higher failure rates at this time, in common with Horned Larks in British Columbia (MacDonald et al 2016).…”

Early Breeding Conditions Followed by Reduced Breeding Success Despite Timely Arrival in an Alpine Migratory Songbird

“…We observed a generally higher variability in breeding phenology in the early spring of 2020, which was found also in McGuire et al (2020), and a delayed hatching. Clutches experiencing a rainy season or severe weather events, such as snow storms, have a prolonged incubation period, exposing the nest to predators for a longer period at the same time, and generally higher failure rates (due to abandonment, hatch failure and predation) than clutches in a dry season (Rauter et al, 2002;Kluen et al, 2011;Higgot et al, 2020;Marcelino et al, 2020). Further explanations for variations in breeding success in alpine birds include annual variations in temperature, where success is lower in years with lower mean temperatures (Mingozzi et al, 2021), but also variations in weather-dependent resources (Barras et al, 2021) and local predation risk (Rauter et al, 2002).…”

Intraspecific variation in incubation behaviours along a latitudinal gradient is driven by nest microclimate and selection on neonate quality

“…Two closely coupled incubation behaviours that are important life‐history traits have prompted recent debates—incubation period duration and nest attentiveness. Sibling competition and time‐dependent sources of clutch mortality (nest predation and weather‐related failure) should impose strong directional selection to minimize incubation period duration (Case, 1978; Conway & Martin, 2000a; Higgott et al., 2020; Remeš & Martin, 2002; Ricklefs, 1993). Incubation period duration could also be subject to phylogenetic (Deeming et al, 2006) and allometric constraints imposed by body size or egg size (Case, 1978; Ricklefs & Starck, 1998).…”