Sitting in the open: How nest microclimate influences incubation behavior in an open-cup nesting passerine

Submitted by Michi on 5 March 2025.

Picture above: female hooded warbler sitting on her nest in a screen capture from one of the videos taken during the study (photo: Kelly Williams).

In their recent paper, Kelly Williams and co-authors demonstrated how the microclimate within and around the nest affected both the incubation behaviour of the female and hatching success of the eggs.

Their study focused on an open-cup nesting passerine, the hooded warbler (Setophaga citrina) in a population in southern Ohio, USA. Kelly and her co-workers used iButtons to measure nest microclimate and in-nest temperatures for incubating hooded warblers, using the in-nest temperatures to estimate incubation behavior.

                                                                              The author watching an incubating female on her nest (photo: Kelly Williams).

The team found that clutch size, year, and females’ experience influence female management of incubation behavior and in-nest temperatures.

                                                       Female hooded warbler in hand (photo: Kelly Williams).

With respect to climate, when ambient conditions were relatively warm females incubated for longer periods of time, with fewer (but longer) off-bouts, resulting in a higher proportion of time spent incubating. When conditions were cooler females leave the nest more to forage for themselves. However, as the variability of ambient temperatures increased, females were found to take more off-bouts and on-bouts.

Not surprisingly, incubation behaviors directly influenced the realized in-nest temperatures: longer on-bouts and more incubation time overall generated higher and more stable in-nest temperatures. In contrast, longer off-bouts resulted in lower mean in-nest temperatures and less stable nest temperatures resulting in lower hatching success.

The study by Williams et al thus demonstrates the links between ambient temperatures and female incubation behaviour and the study provides important insights into the way that birds are likely to respond to current and future climates.

Read the full article here. 

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