Extended incubation recesses increase before nest abandonment in a high-arctic shorebird.

Parents can abandon their current clutch when reaching a physiological threshold to prioritise their survival and future breeding in the trade-off against current reproduction. Incubation is metabolically costly, and regular recesses are necessary to replenish energy reserves. Thus, an increase in the duration of these foraging trips may signal diminishing reserves and perhaps impending abandonment. Here, we tested the hypothesis that the probability of abandonment of uniparental nest is directly linked to the duration of extended recesses (i.e., recesses > 120 min). Analysing 13 years of breeding behaviour from Sanderlings (Calidris alba) using thermologgers placed in 120 nests, we found that both the frequency and duration of extended recesses were higher in nests that were ultimately abandoned. The probability of nest abandonment increased with time spent in extended recesses during incubation, with the final day before abandonment proving critical in the decision-making. In contrast, short recesses showed no relationship with abandonment probability, and neither recess type changed significantly as nests approached hatching, confirming the specificity of extended recesses as indicators of abandonment. With such results, parents likely remain at the nest until their reserves fall below a physiological threshold, when they have no choice but to leave the nest when the costs-benefits balance becomes unsustainable for the parent. Our study suggests the key link between extended recesses and nest abandonment; it paves the way for quantifying foraging success and variations in energy reserves of individuals to provide deeper insights into the mechanisms driving reproductive decisions and their impact on population dynamics.