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Figures
- Fig. 1.
Arrangement of hardware for producing the pressure change, typical traces, and a schematic of the experimental protocol. (A) Schematic showing the arrangement of parts in the respirometry system, as well as of the bird, the isolation room and the video camera. (B) Calibration curve for the Venturi tube. Rate of air flow was measured independently by a rotameter, and the corresponding pressure difference in the Venturi tube was measured with a differential pressure meter. (C) Typical pressure traces for control and experimental (pressure change) treatments. The high-frequency noise in the traces originated in the house vacuum supply and was, for our purposes, unavoidable. (D) Schematic of the experimental protocol, showing timing of major events.
- Fig. 2.
Barometric pressure up to 24 h before snowfall at Tioga Pass.
- Fig. 3.
Baseline and maximal corticosterone as a function of barometric pressure decline over the previous 12 h.
- Fig. 4.
CO2 emission (blue and red lines) and behavior (black lines; arbitrary units) during the control run (A), in which chamber pressure was not ramped down, and during the pressure change treatment (B). Pressure was ramped starting at time 0. These traces are for bird number 5; plots for the other birds are available in supplementary material Figs S2, S3. (C) Power spectrum from fast Fourier transformed behavioral data of bird 5 (pressure run). The highest power occurs at low frequencies, about 0.00069 Hz. This frequency corresponds to 24 min, which describes the spacing of major behavioral bouts visible in B. (D) Cross correlation of behavioral and metabolic data, indicated by the major positive and negative peaks around lag=0 min. The cross correlation is also apparent visually in A and B: whenever bouts of activity occur, metabolic rate increases.
- Fig. 5.
Corticosterone (CORT) levels 0–3, 15 and 30 min after completion of the barometric pressure experiment. Data shown are means ± s.e.m. Inset: integrated CORT over the entire 30 min. Birds were held in cloth bags between sampling times.
- Fig. 6.
Foraging behavior was elevated during the third hour of declining barometric pressure change as compared with the control treatment. (A) Absolute number of food pecks during the third hour. (B) The same data corrected for hour 1 behavior.
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