424 SHORT COMMUNICATIONS these studies.We thank D. Lemmon for comments on jays-with a theory for the evolution of altruism the manuscript. We thank Roland Wauer, Michael and communal breeding. Am. Zool. 14:63-80. Fleming and the National Park Service for their help BROWN,J. L. 1986. Cooperative breeding and the and permission to work in Big Bend National Park. regulationof numbers. Proc. XVIII Int. Ornithol. Congr. (1982):774-782. LITERATURE CITED BROWN.J. L.. AND E. R. BROWN. 1985. Ecoloeical correlatesof group size in a communally breeding BRANDT,H. W. 1940. Texas bird adventures. Bird bird. Condor 87:309-3 15. ResearchFoundation, Cleveland. LIGON,J. D., AND S. L. HUSAR. 1974. Notes on the BROWN,J. L. 1963. Social organizationand behavior behavioral ecology of Couch’s Mexican Jay. Auk of the Mexican Jay. Condor 65: 126-l 53. 91:841-843. BROWN,J. L. 1964. The integration of agonistic be- VAN TUNE,J. 1929. Notes on some birds of the Chi- havior in the Steller’s Jay Cvanocitta stelleri SOSMountains of Texas. Auk 46:204-206. (Gmelin). Univ. Calif. Pub11Zobl. 60:223-328. WAUER,R. H. 1973. Birds of Big Bend National Park BROWN,J. L. 1972. Communal feeding of nestlings and vicinity. Univ. of Texas Press, Austin. in the Mexican Jay (Aphelocomaultramarina): in- WOOLFENDEN,G. E., AND J. W. FITZPATRICK.1984. terflock comparisons.Anim. Behav. 20:395-402. The Florida Scrub Jay: demography of a cooper- BROWN,J. L. 1974. Alternate routes to sociality in ative-breeding Bird. Princeton Univ. Press, NJ. The Condor 89~424-426 0 The CooperOrnithological Society 1987 METABOLIC, WATER AND THERMAL RELATIONS OF THE CHILEAN TINAMOU ’ PHILIPC. WITHERS,”RICHARD B. FORBES,AND MICHAELS. HEDRICK’ Department of Biology,Portland State University,Portland, OR 97207 Key words: Tinamou; waterloss; metabolism; tem- Four Chilean Tinamous (mean mass 458 f SE 8 a) perature:phylogeny. were obtained from the Washington State Departmem of Fisheries and Wildlife in June 1980. Thev were We presenthere some basic aspectsof the thermal and maintained outdoors under natural photoperiod and metabolic physiologyof the Chilean Tinamou (Notho- ambient temperature throughout the year. The exper- procta perdicaria). Tinamous (Tinamidae) are quail- iments reported here were conductedin late November like ground birds widely distributed throughout the and in December of 1980 and 1982. A standard flow- neotropics from Mexico to Patagonia.The taxonomic throughrespirometry systemin a constanttemperature statusof tinamous is controversial,but Cracraft (198 1) cabinet was used for the measurement of oxygen con- includes Tinamidae in Palaeognathiformes. Hence, sumption rate (Vo,: ml O,.gm*.hr-I) and evaporative tinamous are suspectedto be closely related to the water loss (EWL: mg H,O.g-l,hrml) at ambient tem- ratites, although they are carinate and therefore may peratures(T,: “C) from - 10 to +30. All experiments be more closely related to other birds than to ratites. were conductedduring the light portion of the ambient The metabolic physiology of tinamous is thus of par- photoperiod (1O:OOto 16:00). The flow rate of dry air ticular interest becauseratites have been shownto have (dew noint < - 5°C) was regulatedwith a Gilson mass considerablylower basal metabolic rates than do car- flow controller and meter. E>currentair was monitored inates (Calder and Dawson 1978, Withers 1983). for 0, content to *O.Ol% with a Servomax 570A para- magnetic0, analyzer calibrated with dry, CO,-free ni- trogen (0% 0,) and room air (20.94% 0,). Incurrent and excurrent air was monitored for water vapor con- ’ Received 19 May 1986. Final acceptance6 October tent to +O.O5”C dewnoint with an EG&G Dew-All 1986. hygrometer(NBS traceablehygrometer calibration). The * Present address:Department of Zoology, Univer- percent 0, and dewpoint were continuously recorded sity of Western Australia, Nedlands, W.A. 6009, Aus- with a dual channel Honeywell stripchart recorder. tralia. Dewpoint was converted to absolute humidity (STP) 3Present address:Department of Zoology, Univer- usingthe equationsof Parrish and Putnam (1977). The sity of British Columbia, Vancouver, B.C. V6T 2A9, Vo, (STPD) and EWL were calculatedusing the equa- Canada. tions of Withers (1977). EWL was not measured at SHORT COMMUNICATIONS 425 T, < 5°C since excurrent water condensedor froze in the air lines. Body temperature (Tb: “C) was measured with a Bailey Instruments Bat-4 thermocouple meter I .5 immediately after the bird was removed from the res- pirometry chamber, using a thermocouple inserted 4 cm into the cloaca. Values are presented as mean t I .o standarderror with the number of observations,or as least squareslinear regressionanalysis with the cor- =I 0.5 relation coefficient (Zar 1984). .> The relationship between Vo, and ambient air for tinamous is typical ofendothermic vertebrates(Fig. 1). OI There was a significantrelationship between Vo, and -10 0 IO 20 30 T, 5 lO.O”C(Vo, = 1.05 - O.O37T,;n = 24; Y = 0.73) but not at T, 2 lO.o”C. The basal VO, at T, 2 10.0 AMBIENT TEMPERATURE (C)‘ was 0.69 + 0.03 ml.g-l.hrrl (1.76 W, assuming 1 ml FIGURE 1. Relationship between metabolic rate 0, = 20.1 J). The predicted basal metabolic rate for a (VO,: ml O,.g-I .hrr') and ambient temperature (T,: 458-g ratite bird is 0.48 ml.g-l.hrl (Withers 1983) “C) for the Chilean Tinamou. Solid line is the best-fit and for a carinate nonpasserineis 0.79 (resting phase) least squareslinear regressionanalysis. Upper broken to 0.98 (activity phase) rnl’g-l.hr-l (Aschoff and Pohl line indicatesthe predicted Vo, valuesfor a 458-g non- 1970). The lower critical temperature of the thermo- passerinecarinate during the active phase(Aschoff and neutral zone, determined from the point of intersection Pohl 1970, Aschoff 1981) and the lower broken line of the Vo, - T, regressionat T, 5 1O.o”C and the mean indicates the predicted Vo, values for a 458-g ratite Vo, at T, 2 lO.o”C, was 9.8”C. The EWL(mg.gml,hr-I) (Withers 1983) with a thermal conductanceof 0.026 was significantlyrelated to T, (EWL = 0.133 + 0.055 ml O,.g-l .hrrl.“C-I. Predicted relationshipsare forced T,; n = 19; r = 0.80). There was a significant relation- to extrapolatethrough T, (39.6%) from below the low- ship betweenEWLlVo, (mg H,O/ml 0,) and T, < 20°C er critical temperature. (EWL/Vo, = 0.08 + O.O9T,; n = 13; r = 0.87). The mean EWLlVo, of 2.07 + 0.07 mg/ml 0, at T, > 18°C for tinamous is similar to the value expectedfor ratites T, = 39.6, was 0.027 i 0.006. This value is statistically (2.1) and greaterthan the value for carinate birds (1.4) identical to that calculatedas Vo,/(T, - T,) for T, < becausethe Vo, is lower (Table 1). T, was independent 20°C of0.026 & 0.001 ml.g~*.hr~l.OC~l(n = 27). The of T,; the mean value was 39.6 ? 0.2”C (n = 32). This conductanceofthe tinamou (at T, > 20°C) was 0.039 ? is similar to T, values for some ratites, but it is within 0.006, ranging from 0.027 to 0.063; the higher values the lower range for carinate nonpasserinebirds (Table were similar to that predicted (0.049). The correspond- 1). ing dry conductance,calculated as C, = C - EHL/T, - Thermal conductance(C: ml O,~g~l.hrl~“C1), es- T3 for all T., was 0.025 -t 0.002 ml.g~l.hrl~“C1 (n = timated as the slope of the regressionbetween VoZ and 2 1); EHL is the evaporative heat loss calculatedfrom T, 5 lo’%, was 0.035 * 0.009 (n = 21). However, this EWL assuming 540 cal.gmIlatent heat of fusion and regressionbetween Vo, and T, extrapolated to T, = 4.8 cal’ml 0,-l. The predicted dry conductancefor a 28.4 & 7.43”C at Vo, = 0, which is significantlylower 458-g bird is 0.025 (Aschoff 1981). than the observed T, of 39.6”C. Consequently, 0.035 The thermal, metabolic, and EWL values measured is only an approximate overestimate of C. An alter- here for tinamous are generally more typical of ratite native estimate of conductance,the slope of the Vo,- birds than carinate birds (Table 1). The basal Vo, of T, relationship for all data, forced through Vo2 = 0 at tinamous measured during the daytime (active phase TABLE 1. Thermal, metabolic, and evaporative water loss values for the Chilean Tinamou compared with predicted values for a 458-g ratite and a nonpasserinecarinate. Values for tinamous are mean f standarderror. Tinamou Ratite Carinate Body temperature (“C) 39.6 + 0.2 38-400.~ 39-42d Basal Vo, (ml.g-l ’hr-I) 0.69 i- 0.03 0.48”,” 0.98 (a)’ Wet conductance(ml O,.gml’ hrL.“C1) 0.026-0.039 - 0.0498 Dry conductance(ml O,.g-l.hrrl.“C1) 0.025 - 0.027~ Lower critical temperature (“C) 9.8 - 20h Evaporative water loss (mg.gml.hrl) (20-30°C) 1.49 f 0.14 - 1.37b EWLlVo, (18-30°C) 2.07 + 0.07 2.1’ 1.40b pWithers (1983). b Crawford and Lasiewski (I 968). GFamer et al. (I 956), King and Famer (I 96 I), Crawford and Schmidt-Nielsen (1967). d King and Famer (1961). e Calder and Dawson (1978). f(a)Daytime, Aschoff and Pohl (I 970). gAschoff(l981). h Calculated from Aschoff and Pohl (1970) and Aschoff (1981) as 39.6 - (basal Vo,lconductance). 426 SHORT COMMUNICATIONS of their circadian cycle) was intermediate between the Emu. Comp. Biochem. Physiol. A. Comp. Physiol. predicted values for ratites and nonpasserinecarinate 60:479-48 1.