Affiliation:
1. Department of Biology, University of New Mexico, Albuquerque, NM USA
2. Department of Biology, University of Massachusetts, Amherst, MA USA
3. DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
Abstract
We examined thermoregulatory performance in seven Sonoran Desert passerine bird species varying in body mass from 10 to 70g – Lesser Goldfinch, House Finch, Pyrrhuloxia, Cactus Wren, Northern Cardinal, Abert's Towhee and Curve-billed Thrasher. Using flow-through respirometry we measured daytime resting metabolism, evaporative water loss and body temperature at air temperatures (Tair) between 30° and 52°C. We found marked increases in resting metabolism above the upper critical temperature (Tuc), which for six of the seven species fell within a relatively narrow range (36.2° – 39.7°C), but which was considerably higher in the largest species, the Curve-billed Thrasher (42.6°C). Resting metabolism and evaporative water loss were minimal below the Tuc and increased with Tair and body mass to maximum values among species of 0.38 – 1.62 W and 0.87 – 4.02 g H2O hr−1. Body temperature reached maximum values ranging from 43.5° to 45.3°C. Evaporative cooling capacity, the ratio of evaporative heat loss to metabolic heat production, reached maximum values ranging from 1.39–2.06, consistent with known values for passeriforms and much lower than values in taxa such as columbiforms and caprimulgiforms. These maximum values occurred at heat tolerance limits (HTL) that did not scale with body mass among species, but were ∼50°C for all species except the Pyrrhuloxia and Abert's Towhee (HTL=48°C). High metabolic costs associated with respiratory evaporation appeared to drive the limited heat tolerance in these desert passeriforms, compared to larger desert columbiforms and galliforms that use metabolically more efficient mechanisms of evaporative heat loss.
Funder
National Science Foundation
Publisher
The Company of Biologists
Subject
Insect Science,Molecular Biology,Animal Science and Zoology,Aquatic Science,Physiology,Ecology, Evolution, Behavior and Systematics
Cited by
61 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献