Incubation is an important component of avian parental care and slight changes in incubation temperature can aff ect off spring phenotype. Although many extrinsic and intrinsic factors may generate variation in incubation temperature, they remain underexplored under natural conditions. Using a robust data set encompassing 55 nests, 22 816 behavioral observations, and Ͼ 1 million paired ambient and egg temperatures, we describe the relationships among abiotic factors, female incubation behavior, incubation temperature, and incubation period for tree swallows Tachycineta bicolor . We report a large amount of individual variation in incubation behaviors and average incubation temperatures for our study population. Th e average on-bout incubation temperature was 34.1 ° C, with daily egg temperatures ranging from 18.0 -39.2 ° C. Females modulated the number of times they left the nest and the amount of time they stayed off the nest according to interactions between precipitation and temperature patterns. Models generated from our observations predicted that the number of female off -bouts was the lowest under warm and dry conditions while more off -bouts were taken under cold and dry or warm and wet conditions. During cold and dry conditions, females stayed off their nest ∼ 4 times longer than under warm and dry conditions. However, this pattern was reversed under periods of rainfall; females tended to take shorter off -bouts when it was rainy and cold compared to longer off -bouts during warmer rain events. Furthermore, variation in female behavior was associated with diff erences in overall incubation temperature such that females that maintained greater incubation constancy produced higher incubation temperatures at a given ambient temperature than those that displayed lower incubation constancy. Our results provide perspective on the timing of breeding, as some of the advantages of breeding early may be countered by cooler, early season temperatures and precipitation that cause reproducing females to favor self-maintenance at a potential cost to optimal incubation temperatures for off spring development.

Disease is among the leading causes of global amphibian population declines, and may contribute to declines of the giant hellbender salamander (Cryptobranchus alleganiensis). We provide some of the first information about how hellbenders physiologically respond to end- and ecto- parasites, insights that could be critical to their conservation.

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In an analysis of avian and mammalian thermal tolerances recently published in this journal, Khaliq et al. () reported that endotherm thermal niches are phylogenetically conserved in tropical, but not temperate, regions. However, closer examination of the data upon which this analysis was based reveals that many of the upper critical temperature (UCT) data are not valid. Approximately 55% and 42% of avian and mammalian UCT data, respectively, originated from studies in which animals were not exposed to air temperatures high enough to elicit an increase in metabolic rate above minimum levels; the cited UCT values are merely the highest air temperatures at which measurements took place. An additional 18% and 25% of avian and mammalian UCT data, respectively, represent values based on just one individual per species and/or measurements at too few air temperatures above the thermoneutral zone (TNZ) to reliably estimate the UCT.

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