The thermoregulatory limits of an Australian Passerine, the Silvereye (Zosterops lateralis)

(1) The thermal capabilities of Australian silvereyes (Zosterops lateralis, 11 g) were investigated both at low and high ambient temperatures (T-a) du ring the photophase and scotophase. (2). The peak metabolic rate (FMR) indu ced by helium-oxygen (79:21 %, He-O-2) exposure during the photophase was 1 5.64+/-1.55 mt O-2 g(-1) h(-1) at an effective lower survival limit T-a (T- pmr) of -39.7+/-6.1 degrees C. (3). Above the thermoneutral zone (TNZ), met abolic rate, body temperature (T-b), and thermal conductance increased stee ply, but they were able to withstand a T-a of 39 degrees C. (4). Our study shows that silvereyes are able to tolerate an impressive range of T-a from about -42 degrees C to at least +39 degrees C and an able to produce enough heat to maintain a thermal difference between T-b and T-c of up to 80 degr ees C. (C) 1999 Elsevier Science Ltd. All rights reserved.