AJP - Regulatory, Integrative and Comparative Physiology, Vol 237, Issue 1 58-R62, Copyright © 1979 by American Physiological Society
Independence of brain and body temperatures in flying American kestrels, Falco sparverius
M. H. Bernstein, M. B. Curtis and D. M. Hudson
Brain and body temperatures were measured via small thermocouples implanted
in the anterior hypothalami and colons, respectively, of five adult
American kestrels (F. sparverius, mean mass 119 g) during descending
flights in a wind tunnel at angles of 4 and 6 degrees below horizontal, at
10 m.s-1 air speed, and at 23 degrees C air temperature. For comparison,
temperatures were recorded from resting birds at 22.5-36.1 degrees C air
temperatures. Colonic (Tc) and hypothalamic (Th) temperatures both
increased after the onset of flight; steady-state levels were attained
after 1 min in the hypothalamus and after 5 or more min in the colon. The
steady-state difference (delta T = Tc - Th) averaged 1.2 degrees C, higher
by 0.5 degrees C than delta T in resting kestrels. The establishment of
delta T during flight may be correlated with increased respiratory and
corneal evaporation. The response apparently confines most stored body heat
to noncranial regions, thus protecting brain tissue from thermal extremes.
