Energy relations of winter roost-site utilization by American goldfinches (Carduelis tristis)

Abstract

American goldfinches (Carduelis tristis) were observed roosting in Colorado blue spruce (Picea pungens), which comprised part of a mixed stand of conifers. Their winter roost-sites were distally situated among the most densely-needled branches on the leeward sides of these trees. Heated and unheated taxidermic goldfinch mounts were placed within these sites and at the same height in an adjacent clearing. The radiative and convective characteristics of these locations were monitored simultaneously and compared to predicted power requirements of live goldfinches (based on laboratory calibration of heated mounts) and operative temperatures (T ; based on body temperatures of unheated mounts). The winter roost-sites significantly reduced radiative and convective heat exchanges between goldfinches and the environment. Based on body composition data for winter goldfinches, all but two birds sampled could endure a 15-h roost period at average overnight T 's as low as-40°C. In contrast, if these birds were prevented from feeding the following day, only 30% could survive the imposition of a 39-h fast at average T 's of-2°C. Winter roost-site selection may be more constrained by thermoregulatory considerations in small birds than in larger species.

Life and Death: Metabolic Rate, Membrane Composition, and Life Span of Animals

“…Experimental studies have demonstrated that both early breeding and high fecundity reduce longevity of kestrels and goshawks (74,182), but these traits foster higher rates of annual reproduction and are, therefore, beneficial to species such as Galliformes that have high extrinsic rates of mortality. The tendency of MLSP to increase directly with size in mammals and birds may also be influenced by size-related differences in extrinsic mortality rates (299), due in part to larger animals being less prone to predation and coping better with periods of food deprivation than smaller forms (7,46).…”

Functional Morphology of the Paratympanic Organ in the Middle Ear of Birds

“…1986]. Birds are sub ject to considerable displacements of the tympanic mem brane as a result of barometric variations and altitudinal fluctuations [Pohlman, 1921[Pohlman, , 1922, Barometric informa tion (sensing of upcoming winter storms) may be particu larly important for the survival of smaller bird species [Buttemer, 1985]. Behavioral experiments have demonstrated that pigeons can detect small changes in atmospheric pres sure (10-20 mm H ,0) that correspond to changes of 10-20 m in altitude (Kreithen and Keeton.…”

Can Large‐Scale Climatic Models Be Linked with Multiscale Ecological Studies?*

“…One of the assumptions of these calculations is that ambient temperature is an adequate index of an individual's thermal environment. Certainly, microhabitats and wind conditions have great influence on the energy expended to keep warm (Buttemer 1985). Nevertheless, average minimum January temperature appears to describe, to the first order, the wide-scale thermal environment of many species; but certainly more study is needed.…”