• Energy-saving hypothermia reduces flight ability in mourning doves.

      Lima, Steven L;; Carr Jennie (2012-05-21)
      Overwintering birds are frequently exposed to thermal challenges that can quickly decrease energy reserves, thus leading to an increase in the risk of starvation. During these periods of energetic hardship, many avian species use nocturnal hypothermia to conserve energy that would otherwise be lost remaining warm throughout the night (McKechnie & Lovegrove 2002). However, a cool body temperature (Tb) may limit a bird’s ability to monitor the environment and may slow their response to a potential threat. Thus, birds likely trade-off between the benefits of energy-saving hypothermia and the potential costs of reduced behavioral responsiveness to predators (Welton et al. 2002). Our study organism, the mourning dove (Zenaida macroura), is frequently exposed to energetic challenges and high predation during winter (Roth & Lima 2003), making them an ideal species for such a study. Our preliminary work has also demonstrated that doves routinely use nocturnal hypothermia when energetically stressed during food deprivation; doves typically drop their Tb by 2 °C on control nights with food available ad libitum with an approximate 4 °C and 7 °C drop in Tb following one and two days of food deprivation, respectively (Carr & Lima, unpublished data). These drops in body temperature can lead to significant energy savings during periods of energetic stress. However, the flight muscles also cool significantly, potentially leading to slower muscle contractions and reduced flight ability. In this study, we tested the flight ability of hypothermic mourning doves to examine how these energy-saving drops in nighttime Tb influence a bird’s ability to escape from a potential threat. The behavior of hypothermic birds has not been examined in detail (but see Laurila & Hohtola 2005) and testing flight ability while hypothermic will provide valuable insights into potential trade-offs between energy-conservation and predation risk. This research will also provide the ground-work for future tests of hypothermia under different levels of perceived risk to further examine potential mechanisms behind these behavioral responses.