Dataset: Thermoregulation of understory birds in lowland Amazonia

Understanding the capacity for thermoregulation is critical for predicting
organismal vulnerability to climate change, especially in lowland tropical
rainforests, where warming conditions combine with high humidity and
limited elevational or latitudinal refugia. Here, I focused on nine
species of ground-foraging insectivorous birds in the genus Myrmoderus,
Myrmornis, Hylopezus, Myrmothera, Formicarius, and Sclerurus—sensitive
forest specialists characterized by recently documented population
declines in both disturbed and undisturbed forests. Using high-resolution
data from loggers deployed on birds and their environment, I examined
whether and how birds used thermoregulation and whether ambient water
provided cooling opportunities. Variation in the rate of temperature
change over the diel cycle suggested that all species employed behavioral
and physiological thermoregulation, but some patterns differed by species’
phylogenetic relatedness. All species warmed hours before their
environment at sunrise, then experienced lower temperature increases at
midday relative to the ambient thermal flux. These morning warming periods
peaked around sunrise for all but Sclerurus rufigularis and constituted
the diel temperature change maxima for five of the nine species. Six
species exhibited pronounced oscillations in temperature change consistent
with regular bathing around sunset, possibly for thermoregulatory or other
purposes. This oscillation was the most prominent feature in the diel
thermal flux for all three Sclerurus species and, to a lesser extent, for
Myrmoderus ferrugineus, Myrmornis torquata, and Myrmothera campanisona.
Local rainfall reduced ambient temperatures, and birds experienced
stronger cooling in the wet season and with higher rainfall intensity.
However, rain-induced cooling events were markedly absent in all three
Sclerurus spp. These results highlight the fundamental role of water in
avian thermoregulation and suggest that terrestrial insectivores attempt
to maintain thermal homeostasis throughout the diel cycle. The observed
thermoregulatory behaviors highlight a potentially critical aspect of
their vulnerability—thermal regimes are profoundly altered by forest
disturbance, climate change, and their combination.