Evidence of Small Changes in Daytime Body Temperature in Active Black‐Capped Chickadees in Response to Supplemental Food Availability
Source: PubMed Central Open Access, NCBI / U.S. National Library of Medicine
ABSTRACT In winter, small birds may be able to reduce their energy expenditure by decreasing daytime body temperature (). While the use of reducedduring the active‐phase is not well understood, one factor predicted to shapeand heterothermy is food availability. We experimentally manipulated the presence of supplemental food at a bird feeder and monitored subcutaneous temperature () in 15 overwintering black‐capped chickadees () during feeder visits to investigate whether food availability shapes daytime. Chickadees had lowerwhen the ambient temperature was lower, and this effect was strongest when the feeder was empty. Diurnal patterns inalso varied as a function of food treatment; on days when the feeder was full, chickadees exhibited a mid‐afternoon peak in, while on days when the feeder was empty, chickadees exhibited a mid‐morning minimum in. Treatment‐related differences in diurnalpatterns and ambient temperature effects align with effects reported in earlier studies, though they are notably smaller in magnitude. We attribute the differences in effect sizes to the fact that our manipulations involved removal of supplemental food, rather than complete food deprivation, and that we measuredin active individuals. Although the observed effect sizes forwere small, this study is an important step toward understanding how access to a reliable food source during winter may shape energy management in small wintering birds. Future studies that obtain measures ofoutside of when ind
Abstract
ABSTRACT In winter, small birds may be able to reduce their energy expenditure by decreasing daytime body temperature (). While the use of reducedduring the active‐phase is not well understood, one factor predicted to shapeand heterothermy is food availability. We experimentally manipulated the presence of supplemental food at a bird feeder and monitored subcutaneous temperature () in 15 overwintering black‐capped chickadees () during feeder visits to investigate whether food availability shapes daytime. Chickadees had lowerwhen the ambient temperature was lower, and this effect was strongest when the feeder was empty. Diurnal patterns inalso varied as a function of food treatment; on days when the feeder was full, chickadees exhibited a mid‐afternoon peak in, while on days when the feeder was empty, chickadees exhibited a mid‐morning minimum in. Treatment‐related differences in diurnalpatterns and ambient temperature effects align with effects reported in earlier studies, though they are notably smaller in magnitude. We attribute the differences in effect sizes to the fact that our manipulations involved removal of supplemental food, rather than complete food deprivation, and that we measuredin active individuals. Although the observed effect sizes forwere small, this study is an important step toward understanding how access to a reliable food source during winter may shape energy management in small wintering birds. Future studies that obtain measures ofoutside of when individuals are actively foraging are needed to elucidate how food availability shapes the overall use ofadjustments as an energy management strategy. We experimentally manipulated the presence of supplemental food at a bird feeder and monitored subcutaneous temperature () in 15 overwintering black‐capped chickadees () during feeder visits to investigate whether food availability shapes daytime. We observed treatment‐related differences in diurnalpatterns and ambient temperature effects that aligned with effects reported in earlier studies, though they were notably smaller in magnitude. graphical