Exposure to elevated environmental temperatures produces large increases in ventilation and respiratory evaporation in birds (Calder & Schmidt-Nielsen, 1967; Bouverot, Hildwein & LeGoff, 1974; Richards, 1976). Some workers have reported severe blood alkalosis in panting birds due to lung hyperventilation (Linsley & Burger, 1964; Calder & Schmidt-Nielsen, 1968; Frankel & Frascella, 1968), others only a small decrease in arterial (Marder, Arad & Gafni, 1974; Marder & Arad, 1975; Krausz, Bernstein & Marder, 1977). It has often been suggested, following Zeuthen (1942), that intrapulmonary valves may shunt air away from the parabronchi during panting thus alleviating the risk of hypocapnic alkalosis but such valves have not yet been demonstrated in vivo.
Recently Bech, Johansen & Maloiy (1979) showed that flamingoes, Phoenicopterus ruber, avoid hypocapnia during panting by restricting hyperventilation to the respiratory dead space. This is...
