Data from: Free‐moving artificial eggs containing temperature loggers reveal remarkable within‐clutch variance in incubation temperature

Incubation is a crucial aspect of avian parental care and measuring incubation temperature in the wild can improve our understanding of life history tradeoffs and inform conservation efforts. However, there are challenges associated with measuring the temperature of eggs in natural nests. Most studies to date have measured incubation temperature by using a single, stationary logger in each nest. However, real eggs are rotated and moved throughout the nest by the parent during the incubation period, and thus, a stationary logger may not accurately represent the temperature experienced by individual eggs within the entire clutch. We recorded incubation temperature in nests by using multiple, mobile artificial egg temperature loggers. We installed six mobile loggers and one stationary logger in wood duck (Aix sponsa) nests to compare the two logger types in the field. We found that at a given ambient temperature, mobile loggers recorded lower average and more variable temperatures than stationary loggers. Further, temperatures recorded by stationary loggers showed no relationship with clutch size, while mobile loggers captured temperatures that were lower and more variable as clutch size increased. Also, the multiple mobile loggers revealed that eggs within a nest experienced a substantial range of temperatures throughout the incubation period. We discuss potential limitations of this method, but believe that it is a promising way to collect biologically‐relevant incubation temperature data and provides an opportunity to advance our understanding of incubation temperature as a parental effect.Incubation temperature in wood ducksData were collected from incubating wood duck hens nesting in nest boxes at the Savannah River Site in Aiken, SC, USA in Spring-Summer 2014. Two types of temperature loggers (6 mobile and 1 stationary) were installed into nest boxes to record egg temperature when hens were incubating. Both logger types were modified and inserted into artificial eggs filled with wire-pulling lubricant to mimic the thermal properties of real eggs. We also recorded ambient temperature within the nest box, and measured hen body mass and tarsus length. Averages and standard deviations in temperature were calculated for each nest from the entire incubation period (~30 d). Averages and standard deviations for the mobile loggers are averages of the 6 loggers in each nest. Logger type: M = mobile; ST = stationary. Clutch size includes all fake eggs (i.e., temperature loggers). All average incubation temperatures and standard deviations in temperature reflect a correction for slight differences between temperature recording devices. In three nests, one or two mobile loggers were pushed to the side of the nest either in the middle or end of incubation. 'Excluding pushed loggers' indicates that these pushed eggs were removed from the mean and standard deviation in temperature calculations for their respective nests.Hope_et_al_data.xls