Miniaturized temperature loggers placed in Red-necked Grebe (Podiceps grisegina) nests revealed that 16 of the 32 monitored pairs abandoned their nests for extended periods lasting 3-9 h during at least two of the three nights that they were monitored. When incubating pairs left their nests unattended, temperatures of the thermistored egg usually dropped precipitously to below 30°C within 15-25 min. Duration of a pair’s incubation period was positively associated with the number of minutes that the thermistored egg was below 30°C in our 3-day samples, yet nesting success remained high. Embryos appeared to be tolerant of this cooling; 26 of the 32 monitored nests hatched young, and there was no detectable increase in the failure of eggs to hatch for pairs neglecting their clutches more than 3 h per night. We suggest Red-necked Grebes preemptively leave their nests at night to avoid predation on their eggs or themselves.