TEMPERATURE REGULATION IN THE LITTU PAPUAN , OCELLATUS

ROBERT C. LASIEWSKI, WILLIAM R. DAWSON,

Department of Zoology Department of Zoology University of California University of Michigan Los Angeles, California 90024 Ann Arbor, Michigan 48104

AND

GEORGE A. BARTHOLOMEW

Department of Zoology University of California Los Angeles, California 90024

The avian order has proved were captured in mist nets set in a primary to be of unusual physiological interest. Physio- rain forest near our camp, approximately 32 logical data are available from five genera of km N of Madang, (5 ’ 2 ’ S), Territory of Papua caprimulgids (Phalaenoptilus, Chordeiles, Cap- and New Guinea. Members of this species oc- rimulgus, Eurostopodus, and Nyctidromus) cur in small numbers in forests from sea level and one podargid (Podargus strigokks). to 5666 ft in New Guinea, Northern Queens- Members of the order tend to have low and land, and adjacent islands (Rand and Gil- variable body temperatures, and, under some liard 1967). They take much of their food circumstances, can enter a state of torpidity from the ground at night. During the day (see Bartholomew et al. 1957; and Dawson they often sleep in trees with their bills point- and Fisher 1969, for pertinent references). ing upward, thereby simulating a broken Oxygen consumption has been measured in branch. four genera of caprimulgids ( Scholander et al. 1950: Bartholomew et al. 1962; Lasiewski and MATERIALS AND METHODS Dawson 1964; Dawson and Fisher 1969; La- The were housed in small cages placed in siewski 1969), and the standard metabolic an outdoor shelter. They were fed by hand on meal worms, a variety of locally captured , and small rates of Phalaenoptilus, Chordeiles, and Euro- pieces of fresh meat. They maintained weight, aver- stopodus are conspicuously lower than those aging approximately 145 g, and remained in good of most of their size. Under conditions condition throughout the period of study, May-June of heat stress, birds of these three genera 1969. All observations were made during the daytime on facilitate evaporative cooling by fluttering postabsorptive birds that had been maintained under the gular area. Gular flutter is an energetically the desired conditions of temperature and humidity economical method of achieving such cooling, for at least one hour. The birds were remarkably and this, together with a relatively low metab- quiet and docile, and remained virtually motionless during most periods of measurement. Oxygen con- olism, allows these birds to tolerate high am- sumption and evaporative water loss were measured bient temperatures. Indeed, they attain the with an open-flow system similar to that described highest ratios of evaporative heat loss to heat by Dawson and Fisher ( 1969). Flow rates were production of any birds so far studied (Bar- adjusted between 360 and 3000 cc/min so as to maintain humidity in the metal respirometer chamber tholomew et al. 1962; Lasiewski and Dawson (24 x 24 x 30 cm) as nearly uniform as possible. 1964; Dawson and Fisher 1969; Lasiewski Above ambient temperatures of 20°C only those runs 1969). The only physiological data on podar- in which water vapor pressures remained between gids of which we are aware are those of La- 10 and 18 mm Hg, as calculated with the equation of Lasiewski et al. (1966), were used for analysis. siewski and Bartholomew ( 1966) on the rela- Oxygen consumption was determined from the rate tion of breathing rate to body temperature in of air flow into the chamber and the difference in the , Podurgus strigoides, a concentrations of oxygen between the outflowing and species that pants but does not gular flutter at inflowing air (each dried and CO*-free). All gas high temperatures. volumes are corrected to STP, and all temperatures are expressed in degrees Centigrade. During the 1969 Alpha Helix Expedition to Ambient temperatures were controlled to within New Guinea, we had the fortunate opportu- 0.3” with a constant temperature cabinet. Ambient nity to examine in some detail the physiologi- temperatures, including those in the respirometer cal responses of podargids to heat stress. The chamber, were measured to within 0.1” with 30-ga copper-constantan thermocouples connected to a 12- two adult Little Papuan or Marbled Frog- channel Honeywell Electronik 16 recorder. At ambient mouths (Podargus ocellatus) that we studied temperatures below 40”, body temperatures were K=l The Condor, 72:332-338, 1970 TEMPERATURE REGULATION IN PODARGUS OCELLATUS 333

/I - +I- Podorgus : au / L$40- . /. l - 2 . . . L . . C3+* : . z P

32 \ , \. 0 ’ IO 20 30 40 50 IO 20 30 40 50 AMBIENT TEMPERATURE C‘ AMBIENT TEMPERATURE C‘

FIGURE 1. The relation between body temperature FIGURE 2. The relation between oxygen consump- and ambient temperature in Podargus ocelhtw. Val- tion of Podargus ocellutus and ambient temperature. ues were obtained following measurements of oxygen consumption on that had been maintained for at least 80 min at a given ambient temperature. sured with a YSI multichannel telethermometer and a sling psychrometer respectively. Air movements were measured with a vane anemometer. measured with a quick-acting mercury thermometer immediately following open-flow measurments of RESULTS oxygen consumption and evaporative water loss. At Body temperatures. At the ambient temper- higher ambient temperatures, body temperature was monitored continuously with a 30-ga copper-con- atures (25-35”) prevailing in the lowland trop- stantan thermocouple enclosed within a sphere of seal- ical forests where our experimental animals ing wax 2 mm in diameter. This thermocouple was in- were obtained, the body temperatures of rest- serted through the cloaca into the large intestine to a ing P. ocellutus were between 37 and 38.2” depth of at least 2 cm and was held in place by securing the leads to the rectrices with surgical (fig. 1)) which are low compared with those wound clips. At higher ambient temperatures, where of most birds of comparable size (approxi- hyperthermia developed, oxygen consumption and mately 3943” ) . However, they are similar to evaporative water loss were measured only after body values reported for other members of the order temperature had stabilized, generally within two hours. Caprimulgiformes (Bartholomew et al. 1962; As the investigation progressed, it became desirable to characterize the sites of evaporative cooling by Lasiewski and Dawson 1964; Peiponen 1966; making continuous measurements of temperatures Dawson and Fisher 1969). At ambient tem- within the pharynx and mouth. One fine (40-ga) peratures above 40” the birds were able to enamelled copper-constantan thermocouple was sewn maintain stable body temperatures as much as onto the midline of the floor of the mouth 12 mm posterior to the symphysis of the lower mandibles. 4” below ambient, although some hyperther- Another was sewn through the wall of the pharynx mia developed. At ambient temperatures be- 4 mm lateral to the trachea and 10 mm caudad to low 15” the body temperatures of resting birds the posterior edge of the horny floor of the mouth. were variable, with the minimal values (35.G The 4O-ga leads to the couples were held in place with dental wax, so that the junctions rested directly 36.5”) being 1-2” lower than those measured on the surfaces being measured. The leads were at 30-35”. Our data indicate a thermoregula- soldered to 30-ga duplex wire which was secured to tory capacity more than adequate to cope with the feathers on the back of the with surgical the thermal environment which this species clips and then connected to the recorder. The behavioral responses of the birds to heat were normally encounters. The physiological basis observed through an insulated window in the tempera- of this capacity is examined below. ture cabinet. Humidities within the cabinet were Oxygen consumption. The zone of thermo- measured with a Hygrodynamics Universal Indicator neutrality lies between 30 and 40”, but its used with a wide-range sensor. Breathing rates were counted visually and timed with a stop-watch. upper and lower limits are not sharply defined Heart rates were monitored on a Hewlett-Packard (fig. 2). The minimal rate of oxygen con- 180/AR oscilloscope used in conjunction with a Grass sumption of P. ocellatus resting in the dark P-8 a.c. preamplifier and a Grass AM-4 Audio-moni- within the zone of thermal neutrality approxi- tor. The electrocardiograms were taken from two tem- leads attached subcutaneously on the lateral surfaces mated 0.7 cc 02 ( g hr)-l. At ambient of the pectoral muscles. A third lead attached to peratures above 40”, the birds maintained one of the legs served as a ground. During measure- their body temperatures below ambient by ments of heart rate the bird rested in the dark at augmenting evaporative water loss through in- ambient temperatures of 31.0-385~~. creased respiratory rates (see below). The An outdoor experiment was performed to measure the responses of a frogmouth to mid-day sun and air cost of this augmentation is reflected in a rise movements. Temperatures and humidities were mea- in oxygen consumption. 334 ROBERT C. LASIEWSKI, WILLIAM R. DAWSON, AND GEORGE A. BARTHOLOMEW

120

1. . . . . 0 ’ ’ I IO 20 30 40 50 AMBIENT TEMPERATURE -C

FIGURE 3. The relation of evaporative water loss of 20. Podargus ocellatus to ambient temperature. At tem- -8 :. . IN CHAMBER : .: 0 IN SUN peratures above 20”, water vapor pressure was main- . tained between 10 and 18 mm Hg. 0 38 19 40 41 42 43

BODY TEMPERATURE *C

Oxygen consumption was inversely related FIGURE 4. The relation of breathing rate to body to ambient temperatures below approximately temperature in Podargus ocellatus. Shaded circles rep- resent rates obtained while the birds were in a con- 30”. The relationship appears to be linear and stant temperature cabinet. The unshaded circles show and is described by the following equation, de- values obtained while a bird was exposed to direct rived by least squares regression analysis: solar radiation. y = 2.00 - 0.044x f 0.07 where y is oxygen consumption, x is ambient geal cavity was conspicuously enlarged, temperature, and t 0.07 represents the stan- thereby exposing the richly vascularised mu- dard error of estimate. cosal surfaces of the upper digestive tract to Evaporative water loss. Evaporative water enhanced movements of tidal air. The moist loss (fig. 3) increased more than 15 fold over mucosa of the pharynx had a markedly re- the range of ambient temperatures studied duced surface temperature during active pant- (4.5-46.8”). About two-thirds of the increase ing (fig. 5). In the absence of panting, the occurred above 40”, where the animals panted glottis rests just behind the posterior margin vigorously ( see below ) . of the horny floor of the mouth. As the pant- Breathing rate. At rest, breathing was al- ing response develops, the glottis moves back most imperceptible and minimal rates approxi- into the cavity created by the expanded phar- mated 10 breaths per min. At body tempera- ynx. This facilitates the direct movement of tures above 39”, the rate and amplitude of air over the moist pharyngeal surfaces and breathing increased regularly, the former be- :should contribute to the enhancement of ing maximal at NO-107 breaths per min at evaporation in panting frogmouths, in a man- body temperatures of 42” and above (fig. 4). ner similar to the changes in location of the Heart rate. The heart rate of resting birds glottis during gular flutter in heat-stressed maintained in the dark for 3.5 hr at ambient cormorants described by Lasiewski and Sny- temperatures of 3136.5” were between 124 der ( 1969). and 148 per min, with a mean of 133 f 5.3 SD. Effects of solar radiation on body tempera- Buccal and pharyngeal temperatures during ture. Since the specific situations in which evaporative cooling. Simultaneous measure- P. ocellutus spend the hours of daylight are ments were made of ambient, cloacal, buccal, poorly known, it seemed reasonable to exam- and pharyngeal temperatures in one of the ine their responses to the most extreme condi- frogmouths. The tongue and floor of the tions of solar radiation and air temperature mouth are cornified in frogmouths and do available in their general habitat. A frogmouth not appear to be important sites of evapora- was tethered to a wooden perch, 1 m above tive cooling; however, we observed increased the grass in full sun between 13:30 and 15:00 vascularity in the underlying tissues during on 30 May 1969. It was oriented so that its heat stress, and this should enhance convective back was approximately perpendicular to the heat transfer when the temperature gradient is suns’ rays. The course of body temperature favorable. As respiratory rate increased at during the test is shown in figure 6. During high ambient temperatures, the buccopharyn- the initial exposure to direct sun and a gentle TEMPERATURE REGULATION IN PODARGUS OCELLATUS 335

MOUTH CLOSED,--+- PANTING

35- 0 20 40 60 80 MINUTES FIGURE 5. The relation of the temperaturesof the cloaca,pharynx, and lower bill to ambienttemperature in PodargusoceZlatus. Between min 75-81 the bird was restlessand struggledintermittently.

breeze varying between 0.3 and 1.3 m/set, not significantly different from that obtained body temperature rose and stabilized near 41”. in the laboratory where the heat load was im- When body temperature had remained stable posed predominantly by convection (fig. 4). for approximately 15 min, we reduced air From this test, we conclude that, at rest, P. movement around the bird by placing a series ocellatus can adequately regulate its body of 4 x 8-ft panels of fibrous insulating board temperature, even in full sun at the ambient on the windward side of the bird. The con- temperatures prevailing during the warmest sequent reduction in forced convective cooling part of the day in its habitat, as long as mod- resulted in a sharp and sustained rise in deep erate air movement is present. body temperature, despite progressively more vigorous and rapid panting by the bird. Dur- DISCUSSION ing this phase of the experiment, the tempera- Little Papuan Frogmouths are remarkably ture on the surface of the shoulder feathers lethargic, and values for the physiological reached 49.8”. To avoid excessive hyperther- functions we measured fall far below those of mia, when the cloaca1 temperatures reached other birds of similar size (table 1) . Like 43” we removed the wind baffles and provided other members of the order Caprimulgiformes shade for the bird. The resulting increase in which have been studied in detail, the frog- convection, together with the reduced radiant mouth has a low standard metabolic rate (less heat load, permitted a decline in body tem- than two-thirds that predicted for similar-sized perature of about 0.1” per min. Breathing nonpasserine species). Breathing and heart rates were measured throughout the experi- rates are also remarkably low. Evaporative ment. Despite the radiant heat load, the rela- water loss, on the other hand, is only about 10 tion of breathing rate to body temperature was per cent below the predicted level, although 336 ROBERT C. LASIEWSKI, WILLIAM R. DAWSON, AND GEORGE A. BARTHOLOMEW

TABLE 1. Comparison of values for physiological parameters measured in Podargus ocelkztus and those pre- dicted for a 145-g bird.

Predicted Physiological fo;;r;5-g Observed in % of paE3lll.ZterS Equation Source a P. ocellatus predicted

Standard metabolism log M = log 78.3 Lasiewski and 19.4 11.7 60 (kcal/day) + 0.723 log kg Dawson 1967

Evaporative water loss at 25°C log E = log 0.351 Crawford and 7.3 6.6 89 ( g HaO/day 1 + 0.613 log g Lasiewski 1968 Heart rate fh = 763 g-“.” Calder 1968 242 124 51 (beats/min)

Breathing rate fb = 146 g-O.a ’ Calder 1968 31.2 10 32 (breaths/min)

a All values are calculated from equations for nonpasserine birds, with the exception of that for heart rate, which is from an equation for all birds. the available data for evaporative water loss than the environment, thereby facilitating heat in birds are not well standardized. loss via heat transfer and reducing the require- The data on resting body temperatures of ments for evaporative water loss. Its low rest- birds are too variable and unstandardized to ing body temperature and its tolerance of hy- allow the development of adequate predictive perthermia (see figs. 1, 6) in theory afford P. curves. Nevertheless, it is clear that the body ocellutus the possibility of storing significant temperatures of resting P. ocellatus (37-38”) quantities of heat in warm environments. The are distinctly lower than those of most land situation, however, is complicated by the tend- birds of similar size. ency of this species to initiate active evap- Many birds exposed to heat stress appear to orative cooling at relatively low ambient and benefit significantly from hyperthermia for body temperatures (fig. 3). Podargus ocellu- this frequently allows them to remain warmer tus is unusual among birds in achieving parity

Podargus

TA = 31.1-33.6”

WVP = 22.4 MM HG

WIND = 0.3- 1.3 M/SEC

I \ SUN AND WIND+SUN, NO WIND+;;DE-

1 I 1 I 20 40 60 80 I

MINUTES

FIGURE 6. The course of body temperature in Podargus oce1kztu.sduring exposure to various combinations of wind and solar radiation. TEMPERATURE REGULATION IN PODARGUS OCELLATUS 337

TABLE 2. Thermal conductancein Podmgus me,?- latus.

Total thermal Ambient conductancea Dry thermal conductanceb temperature l - . 2 . -10 u cco2x Cal x kcal X % Y “C (ghr”C)-1 (ghr”C)” (mahr”C)” >,.o_--___-__------_ 0, t - . 5 4.5 0.053 0.24 1.32 -5 10.3 0.049 0.21 1.15 0.5 - . 18.7 0.072 0.29 1.60

. l 23.9 0.072 0.27 1.49 . 0.. 29.7 0.086 0.25 1.38 10 zo 30 40 SO0 34.7 - 0.16 0.88 PlMBlENT TEMPER.4T”RE C‘ 42.5 - 0.35 1.93 FIGURE 7. The relationof the ratio of caloriesdis- 44.7 - 0.84 4.62 sipatedby evaporationand caloriesproduced (EWL/ 45.3 - 0.35 1.93 HP) to ambient temperaturein Podargus ocellatus. 46.8 - 1.27 7.00 Predicted ’ 0.068 - -

a Total thermal conductance was computed as M/(TwTa), where M is metabolism in cc (g hr)-I, TB is body temperature, between evaporative cooling and heat produc- and Ta is ambient temperature. tion at the low ambient temperature of 37-38” b Dry thermal conductance was computed as ( M-E)/(TB- TA), where M is metabolism (1 cc 02 = 4.8 al), E represents (fig. 7). Most birds attain such parity only at calories evaporated (1 m Hz0 = 0.58 al). Surface area was computed from the formu T a, S = 0.1 Wo,“, where S is surface much higher (42-45” ) ambient temperatures area in ma, and W is weight in kg. c Minimum total thermal conductance predicted for a 145-g (Lasiewski et al. 1966). The effectiveness of bird by the equations of Herreid and Kessel (1967) and thermoregulation of P. ocellatus at high tem- Lasiewski et al. (1967). peratures is linked with its inherently low level of heat production and the low cost of its al. 1969), which pants at a relatively constant panting. The latter is of particular interest be- level, several times higher than resting rates. cause most birds that rely solely on panting During panting in P. ocellutus the dilation of are unable to achieve ratios of EWL/HP (i.e., the upper digestive tract and the caudad calories dissipated through evaporation over movement of the glottis mobilize additional calories produced) much higher than 1.0 mucosal surfaces for evaporative cooling. (Lasiewski et al. 1966). Podmgus ocellatus, Values for total and dry thermal conduct- on the other hand, reached the unprecedented ance in P. ocellatus are given in table 2. Dry value for panting birds of 1.8. (It should be thermal conductance reaches its minimal levels noted that we maintained humidity below 18 ( i.e., insulation is maximal) at temperatures mm Hg water vapor pressure, whereas in most below 30”. Total thermal conductance is about other studies humidity has been relatively un- 70 per cent of that predicted for a 145-g bird controlled. ) EWL/HP ratios of this magni- by the equations of Herreid and Kessel (1967) tude have previously been associated with and Lasiewski et al. ( 1967). The values for birds employing gular flutter (Bartholomew dry conductance show no tendency to return et al. 1962; Lasiewski and Dawson 1964; to minimum levels at ambient temperatures Calder and Schmidt-Nielsen 1967; Dawson between 42.5 and 46.8”, indicating that this and Fisher 1969; Lasiewski 1969). species does not maximize its insulative capac- The metabolic rate of P. ocellatus rises very ities at high ambient temperatures in a manner little with panting except at the most extreme serving to reduce heat gain. This contrasts ambient temperatures to which we subjected with the pattern noted by Dawson and them. Since a portion of the augmented me- Schmidt-Nielsen ( 1966) in the jack-rabbit, tabolism at higher temperatures must reflect Lepus alleni, but is consistent with the infor- the acceleration of metabolism with increasing mation available for other birds (see, for ex- body temperature, the cost of panting in P. ample, Calder and Schmidt-Nielsen 1967; and ocellutus must be low indeed. Dawson and Fisher 1969). A gradual increase of breathing rate with Podargus ocellatus possessesa complete and body temperature in P. ocellatus is similar to effective repertoire of thermoregulatory re- that described by Lasiewski and Bartholomew sponses although it lives in a uniform, equable, (1966) for P. strigoides, and by Kendeigh tropical environment. The effectiveness of the ( 1944) for the small passerine, Passer domesti- thermoregulation of this species at high ambi- cus. This contrasts with the pattern reported ent temperatures demonstrates with unusual for the Ostrich, Struthio carmAu.s (Crawford clarity one benefit of an inherently low level and Schmidt-Nielsen 1967; Schmidt-Nielsen et of metabolism. 338 ROBERT C. LASIEWSKI, WILLIAM R. DAWSON, AND GEORGE A. BARTHOLOMEW

SUMMARY CRAWFORD, E. C., JR., AND K. SCHMIIYT-NIELSEN. 1967. Temperature regulation and evaporative Standard metabolism of Podargus ocellutus ap- cooling in the Ostrich. Amer. J. Physiol. 212: proximated 0.70 cc 02 ( g hr)-l which is 60 347-353. per cent of that predicted for 145-g nonpas- DAWSON, T., AND K. SC~~MIDT-NIELSEN. 1966. Ef- serine birds. Below 30” metabolism increased fect of thermal conductance on water economy in the antelope jack rabbit, Lepus alleni. J. Cell. linearly at 0.044 cc O2 (g hr “C)-l. Near 40” Physiol. 67:46%471. and above, frogmouths enhance evaporative DAWSON, W. R., AND (3. D. FISHER. lQ6Q. Re- cooling by increased respiratory rates (pant- sponses to temperature by the Spotted Night- ing). Evaporative water loss ranged from 1.3 jar ( Eurostopodus guttutus). Condor 71:49-53. HERREID, C. F., AND KESSEL, B. 1967. Thermal to 20.2 mg Hz0 (g hr)-l at 4.5 and 46.8”, conductance in birds and mammals. Comp. Bio- respectively, and increased markedly above them. Physiol. 21:405-414. 38°C. The low metabolic cost of panting, to- KENDEIGH, S. c. 1944. Effect of air temoerature on gether with the low metabolic rate, enabled the rate of energy metabolism in the English &arrow. T. EXD. Zool. 96: l-16. frogmouths to maintain body temperatures be- LASIE&KI, R. “C. i969. Physiological responses to low environmental temperatures of 40” and heat stress in the Poor-will. Amer. J. Physiol. above. P. ocellatus achieved parity between 217: 1504-156Q. heat lost through evaporation and metabolic LASIEWSKI, R. C., A. L. ACXXTA, AND M. H. BERNSTEIN. heat at the relatively low temperatures of 37- 1966. Evanorative water loss in birds-I. Char- acteristics of the open flow method of determina- 38”. At 46.8” the ratio of evaporative heat loss tion, and their relation to estimates of thermo- metabolic heat reached the unprecedented regulatory ability. Comp. Biochem. Physiol. 19: level for panting birds of 1.8. 445-457. Resting breathing rates approximated lO/ LASIEWSICI, R. C., AND G. A. BARTHOLOMEW. 1966. Evaporative cooling in the Poor-will and the min, and increased regularly with body tem- Tawny Frogmouth. Condor 68:253-262. perature to lOO-107/min at 42”. Resting heart LASIEWSKI, R. C., AND W. R. DAWSON. 1964. Phys- rates averaged 133/min. Breathing and heart iological responses to temperature in the Com- rates of resting P. ocellatus were 32 and 51 mon Nighthawk. Condor 66:477-490. per cent, respectively, of levels predicted for LASIEWSKI. R. C.. AND W. R. DAWSON. 1967. A re- examination ’ of the relation between standard 145-g birds. metabolic rate and body weight in birds. Condor 69:X3-23. ACKNOWLEDGMENTS LASIEWSKI, R. C., AND G. K. SNYDER. 1969. Re- This research was carried out during the 1969 Alpha sponses to high temperature in nestling Double- Helix Expedition to New Guinea and supported by crested and Pelagic Cormorants. Auk 86:52Q- 540. NSF Grants GB8406, GB8445, GB5139, and GB3656. LASIEWSKI, R. C., W. W. WEATHERS, AND M. H. LITERATURE CITED BERNSTEIN. 1967. Physiological responses of the Giant Hummingbird, Pat~gonu gigas. Comp. BARTHOLOMEW, G. A., T. R. HOWELL, AND T. 5. CADE. Biochem. Phvsiol. 23:797-813. 1957. Torpidity in the White-throated Swift, PEIPONEN, V. A.- 1966. The diurnal heterothermy Anna Hummingbird. and Poor-will. Condor 59: of the nightjar (Capdmulgus europaeus L.). Ann. 145-155. - ’ Acad. Sci. Fenn. A. IV. 101: l-35. BARTHOLOMEW, G. A., J. W. HUDSON, AND T. R. RAND, A. L., AND E. T. GILLIARD. 1967. Handbook HOWELL. 1962. Body temperature, oxygen of New Guinea birds. Weidenfeld and Nichol- consumption, evaporative water loss, and heart son, London. rate in the Poor-will. Condor 64:117-125. SC~IDT-NIELSEN, K., J. KANWISHER, R. C. LASIEWSKI, CALDER, W. A. 1968. Respiratory and heart rates J. E. COHN, AND W. L. BRETZ. 1969. Temper- of birds at rest. Condor-70:35&365. ature regulation and respiration in the Ostrich. CALDER. W. A.. AND K. SCXMIDT-NIELSEN. 1967. Condor 71:341-352. Temperature regulation and evaporation in the SCHOLANDER, P. F., R. HOCK, V. WALTERS, F. JOHN- pigeon and the Roadrunner. Amer. J. Physiol. SON, AND L. IRVING. 1950. Heat regulation in 213 :883-889. some arctic and tropical birds and -mammals. CRAWFORD, E. C., JR., AND R. C. LAS~VSKI. 1968. Biol. Bull. 99:237-258. Oxygen consumption and respiratory evaporation of the Emu and Rhea. Condor 70:333-339. Accepted for publication 16 October 1969.