Geographic variation in incubation behavior of a widely distributed passerine bird

Abstract

Incubating birds must trade-off leaving the nest to forage with staying on the nest to maintain optimal temperatures for developing embryos. This trade-off is expressed through incubation behavior, which can be heavily influenced by climate, food availability, attentiveness of their mates, and nest predation risk. Comparative studies across species have shown that incubation behavior varies across latitude, but few studies have explored how incubation behavior varies across sites within species. We might expect incubation behavior to be flexible and respond to local environmental challenges; alternatively, behavior may be relatively fixed and vary little across a species’ range. We explored four incubation behaviors (male feeding rate, female off-bout duration, female off-bout frequency, and the proportion of time incubating females spent on the nest) in a widespread songbird, the yellow warbler ( Setophaga petechia ), breeding at a temperate and subarctic site. As temperatures warmed at both sites, males fed females less often, and as male feeding rates decreased, off-bout durations and frequencies increased causing the proportion of time on the nest to decrease. While incubation behaviors changed in similar ways between sites, off-bout durations shortened with increasing male feeding rates most strongly at the temperate site. Overall, these results show flexibility in incubation behaviors in response to different environmental cues, which likely minimize costs associated with provisioning incubating parents and maintaining warm nest temperatures, and suggests that male feeding may be especially important for breeding in cold regions.

Genetic and Social Transmission of Parental Sex Roles in Zebra Finch Families

“…In contrast, male nest attendance time was not related to the behaviour of the genetic father, however, it was influenced negatively by humidity, suggesting a more flexible response and compensation to changes in the non-social environment by males than by females during incubation. Our results are in line with previous studies reporting male and female parents to react differently to environmental changes in various bird species (Magrath et al, 2005;Charmantier et al, 2008;Kosztolányi et al, 2009;Vincze et al, 2017;Rohwer and Purcell, 2019;Sharpe et al, 2021;Ton et al, 2021). In zebra finches, a recent study also corroborates our finding suggesting sexually different flexibility and reactions to changing environmental conditions, however, with a sexually contrasting effect of ambient temperature (Ton et al, 2021).…”

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

“…Daily nest attentiveness was positively correlated with latitude in burrowing owls, and nest microclimate explained a significant proportion of that variation, largely corroborating previous studies. Diurnal nest attentiveness was higher at high‐latitude sites than at low‐latitude sites in two species of warblers (Rohwer & Purcell, 2019; Sofaer et al., 2020). However, 24‐hr nest attentiveness was similar between sites for one of the species (Sofaer et al., 2020) and the difference in nest attentiveness between the two study sites for the other warbler species was fully accounted for by variation in ambient temperatures and male feeding rates.…”

“…However, 24‐hr nest attentiveness was similar between sites for one of the species (Sofaer et al., 2020) and the difference in nest attentiveness between the two study sites for the other warbler species was fully accounted for by variation in ambient temperatures and male feeding rates. Under cooler ambient conditions, females increased their attentiveness, and males increased their rate of provisioning food to the female (Rohwer & Purcell, 2019). Comparative studies have also suggested that nest attentiveness is higher among temperate species than among tropical species (Chalfoun & Martin, 2007; Martin, 2002; Martin et al., 2007).…”

The importance of nighttime length to latitudinal variation in avian incubation attentiveness

“…Four nest videos from the population in California were missing daytime activity of between 20 min and 3 h of the focal 24‐h period; these nests were excluded from analyses of the total time spent on the nest but contributed data to other summary metrics and analyses. Although incubation feeding of females by males has been shown to influence attentiveness (Martin and Ghalambor , Rohwer and Purcell ), this behavior was rarely observed in our study populations and therefore was not included in our analyses.…”

“…In contrast, embryonic development occurs over the entire 24‐h period, and 24‐h attentiveness is likely to better capture the temperature regimes experienced by the young (Martin et al ). Latitudinal comparisons have focused on daytime attentiveness, but daytime patterns can exaggerate variation in attentiveness over the entire 24‐h period (Ricklefs and Brawn , Álvarez and Barba , Shaw and Cresswell , Rohwer and Purcell ). This potential bias is because birds typically show an uninterrupted nightly rest period, and lower latitude populations (with typically lower daytime attentiveness) experience longer nights during the breeding season compared to high latitude populations.…”