Condor 85:333-337 cc>The Cooper Ornithological Society 1983

SUMMER WATER TURNOVER RATES IN FREE-LIVING CHUKARS AND SAND IN THE NEGEV DESERT

A. ALLAN DEGEN BERRY PINSHOW

AND PHILIP U. ALKON

ABSTRACT.-The Chukar ( chukar) and the Sand (AW~MZO- perdix heyi) are permanent residents of the Negev desert, Israel. They are sym- patric between the 200 and 90 mm isohyets, with only Sand Partridges occurring in more arid areas. During the dry season,we measured total body water volume (TBW; as tritiated water space) and total water turnover rate, and estimated dry matter intake and components of water turnover in free-living of both species.Mean body mass(m,) of 40 Chukars was 460.8 g and of 42 Sand Partridges was 176.6 g. TBW, as a percentage of m,,, was lower in Chukars than in Sand Partridges (67.4% vs. 69.8%; P < 0.05). Mean water turnover was 44.1 ml/day for Chukars (n = 29) and 20.8 ml/day for Sand Partridges (n = 39). The mass- specificwater turnover rate was higher in Sand Partridgesthan in Chukars (122.5 ml kg-’ day-’ vs. 100.6 ml kg-’ day-‘; P < 0.05). However, when compared allometrically, per kg07s, water turnover rates were similar (8 1.7 ml kgmo.75day-l for Chukars vs. 78.5 ml kg-O.‘* day-’ for Sand Partridges). Assuming a diet of seeds,we calculated that drinking water amounted to about 70% of water turnover in both Chukars and Sand Partridges and we concluded that both speciesmust drink water when only dry forage is available.

Two phasianidsare permanent residentsof the of free-living Chukars and Sand Partridges in Negev desert in Israel, the Chukar (Alectoris order to examine whether this variable could chukar) and the (Ammoperdix account for their different distribution pat- heyi). Chukars have a wide southern Palearctic terns. We reasoned that interspecific differ- distribution and inhabit desertsat the margins ences in water turnover rates would be espe- of their range (Cramp and Simmons 1980). cially evident during summer and early autumn They are common throughout Israel where two when vegetation is mainly dry and dormant. subspeciesare present: A. c. cypriotesin the In addition, this is the period of highest am- Mediterranean zone; and the smaller, paler A. bient temperatures and solar radiation and c. sinaica in arid regions, including the Negev lowest water vapor pressures. (Nissani 1974). By contrast, Sand Partridges are wholly restricted to xeric habitats in south- STUDY AREA western Asia and northeastern Africa. In Is- We captured birds from June to October 198 1 rael, they occur principally in the Negev, the in Nahal Zin, a large canyon in the central Arava (Rift Valley), and the Judean Desert Negev highlands near Sede Boqer (30”2’N, (Dor 1975). The two speciesare sympatric over 34”7’E). This area is an “accentuated sub-des- much of their desert rangesin Israel within the ert” with up to 300 biologically dry days per area approximately bounded by the 200 and year (UNESCO 1963). Rain occurs in winter, 90 mm isohyets. and averages90 mm annually, with large fluc- Given the difference in their geographical tuations in total rainfall and in its temporal distributions, we supposedthat the two species and spatial distribution (Evenari 198 1). Dew might differ in total water intake, compared occurs on about 190 nights per year (Zangvil allometrically, as reflected by water turnover and Druian 1980). Summer and autumn are rates.Desert speciesgenerally have lower water characterized by intense solar radiation and turnover rates than species inhabiting mesic high air temperatures.During this study, mean and humid environments; this has been used maximum daily air temperatures were 3 1.3”C as a criterion for defining the distribution of in June, 32.2” in July, 32.1” in August, 30.9” some mammalian (Macfarlane and Howard in Septemberand 28.0” in October. Mean min- 1972, Nicol 1978) and avian (Degen et al. 1982, imum daily air temperatures were 15.6”C in Thomas 1982) species. June, 18.9” in July, 18.5” in August, 18.1” in We compared summer water turnover rates September and 14.9” in October (Desert Me-

[3331 334 A. A. DEGEN, B. PINSHOW AND P. U. ALKON teorology Unit, Blaustein Institute for Desert From analysis of crop contents, it appearsthat Research). Vegetation was dry and dormant; seeds were the principal dry season food of however, surfacewater was available through- both species.Existence energy (EE), as defined out the study. by Kendeigh (1970), for birds on a dry mash or seed diet was calculated as approximately METHODS 210 kJ/day for a 450-g Chukar and 105 kJ/ CAPTURE AND HANDLING OF BIRDS day for a 175-g Sand Partridge (Pinshow et al. Chukars and Sand Partridges were captured in 1983). Assuming a 50% increase in energy sorghum-baited, wire mesh traps (90 X 90 X intake over EE during field activity (West 1967, 60 cm) having funnel entrances. Traps were Robe1 et al. 1974) and that 1 g of feed (mixed checked twice daily (between 07:OOand 0800 graminaceous seeds)contains 0.106 g of pre- and between 16:OOand 17:OO;shortly after we formed water, and that 1 g of dry matter (DM) observed birds to be most active), and cap- has an energy density of 15.4 kJ and yields 0.5 tured birds were brought to our laboratory, a g of metabolic water (Thomas and Maclean 15-min drive from trapping sites. The birds 1982) we calculated the DM intake and total were marked with leg bands and individually water obtained from food for both species. identifiable numbered back tabs (Alkon 1974). Method II was based on the ratio of DM Only fully grown birds having adult plumage intake to water turnover rate. We assumed a were used. constant ratio of DM intake of dry forage to Methods used to estimate total body water water turnover as has been reported for var- (TBW) and water turnover rate were described ious domestic mammals (e.g., Benjamin et al. by Degen et al. (198 1). Birds were weighed (to 1977). DM intake for cagedChukars and Sand the nearest 0.1 g), and injected intramuscularly Partridges fed a dry ration and tap water ad with 0.1 mCi/kg body mass of tritiated water libitum was 0.50 and 0.59 g per ml water turn- (TOH) in 1.O ml (weighed to the nearest 0.1 over, respectively. Using these ratios, DM in- mg) sterile avian saline solution for Chukars take was estimated for both speciesfrom their and 0.4 ml for Sand Partridges. After allowing water turnover rates, and preformed and met- 45 to 60 min for TOH equilibration with body abolic water intakes were calculated as in fluids, birds were weighed again, and a blood method I. In both methods water drunk was sample was taken from the basilic vein to es- calculatedas the difference between total water timate TBW (as TOH space).The mean of the turnover and water intake from food. two body masseswas used for subsequentcal- DATA ANALYSIS culations. The birds were then released at the capture sites. In order to estimate water turn- For interspecific comparisons between Chu- over rates, based on the decline in specific ac- kars and Sand Partridges, we expressedwater tivity of tritium over time, blood sampleswere turnover rates per unit body mass”.75according collected from birds that were recaptured at to the allometric equation of Pinshow et al. least two days after TOH injection. On occa- (1983). Means (expressed f SD) were com- sion, blood sampling and weighing of recap- pared using Student’s t-test, and statistical tured birds were done in the field. We assumed methods followed Sokal and Rohlf (1973). that TOH spaceremained a constant fraction RESULTS of total body mass during the capture-recap- ture interval, and that any changein TOH space Mean body mass (m,) for 40 Chukars was was linear with time. 460.8 * 56.0 g, and for 42 Sand Partridgeswas Blood sampleswere centrifuged and sera re- 176.6 * 2 1.4 g. Mean TBW, as percentagemb, moved. To measurespecific activity of tritium, was lower in Chukars than in Sand Partridges 0.05ml serum sampleswere added to 5 ml of (67.4% vs. 69.8%, P < 0.05; Table 1). Mean Bray’s solution. Duplicate samples were water turnover rate was 44.1 -t 6.7 ml/day for counted for 10 min in a liquid scintillation Chukars, based on 29 measurements (m, = counter (Packard Tri-Carb, model PLD) and 444.5 I 52.2 g) in 21 individuals, and was countswere corrected for 6% serum dry matter 20.8 i 4.1 ml/day for Sand Partridges, based content and for quenching. Serum samples on 39 measurements(m, = 173.1 * 2 1.9 g) in from three non-labelled birds were used to 31 individuals. Water turnover per day measure background counts. amounted to 10.1% of m,,, or 14.7% of TBW for Chukars and 12.3% of mb, or 17.2% TBW ESTIMATION OF FOOD INTAKE AND for Sand Partridges.Mean water turnover rates COMPONENTS OF WATER INTAKE per kg”.75were similar for the two species;82.3 We estimated food intake and the components ml/day for Chukars and 80.3 ml/day for Sand of water intake using two methods. Method I Partridges. was based on the birds’ energy requirements. From method I, we estimated DM intake as WATER TURNOVER RATES IN DESERT PARTRIDGES 335

TABLE 1. Body mass, tritiated water (TOH) spaceand TABLE 2. Estimated dry matter intake and components water turnover rates of free-living Chukarsand Sand Par- of total water turnover for free-living Chukars and Sand tridges in the Negev desert, July to October, 1981. Values Partridges.Method I is basedon energyrequirements and are means i SD. method II on dry matter intake to water intake ratio. Val- ues are means and, in parentheses,percentages of total SIgnif- water turnover. Chukars Sand Partridges icance’

Sand TOH space Chukars Parlridges Sample size 40 42 Body mass (g) 460.8 f 56.0 176.6 i 21.4 * Method I TOH space (ml) 310.1 ? 39.9 123.1 i 15.1 * Dry matter intake (g/day) 20.4 10.2 (% body mass) 67.4 t 2.5 69.8 + 4.0 * Water turnover (ml/day) 44.1 (100) 20.8 (100) Water turnover rate Total water from food (ml/day) 12.6 (29) 6.3 (30) Sample size 29b 39 Preformed water (ml/day) 2.4 (6) 1.2 (6) Body mass (g) 444.5 i 52.2 173.1 f 21.9 * Metabolic water (ml/day) 10.2 (23) 5.1 (24) Water turnover Water drunk (ml/day) 31.5 (71) 14.5 (70) (ml day-l) 44.1 t 6.7 20.8 i 4.1 * (ml kg-’ day-‘) 100.6 i 19.8 122.5 f 31.9 * Method II (ml kgmo.75day-l) 81.7 * 14.0 78.5 + 18.4 ns Dry matter intake (g/day) 22.1 12.3

a * = P < 0.05; ns = non-significant. Water turnover (ml/day) 44.1 (100) 20.8 (100) b Based on 21 individuals. Total water from food c Based on 3 I indiwduals. (ml/day) 13.7 (31) 7.6 (37) Preformed water (ml/day) 2.6 (6) 1.4 (7) Metabolic water (ml/day) 11.1 (25) 6.2 (30) 20.4 g/day for Chukars and 10.2 g/day for Sand Water drunk (ml/day) 30.4 (69) 13.2 (63) Partridges;from method II, equivalent values were 22.1 and 12.3 g/day (Table 2). Using the DM values estimated by method I, we calcu- lated water drunk as 3 1.5 ml/day for Chukars and 14.5 ml/day for Sand Partridges;these val- tant determinants of their distributions. For ues amounted to 7 1% of the total water turn- example, free water was available to the birds over in Chukars and 70% in Sand Partridges. studied throughout the dry season, perhaps Based on method II, Chukars drank 30.4 ml/ thereby obscuring interspecific differences in day or 69% of their total water turnover and minimal water requirements that might be ap- Sand Partridges drank 13.2 ml/day or 63% of parent in water-scarce habitats. It is also con- their total water turnover. ceivable that Sand Partridgescan more readily satisfy their water requirements from pre- DISCUSSION formed water contained in summer forage than Studiesof mammals (Macfarlane and Howard can Chukars, and so occupy areas where sur- 1972, Nicol 1978) and birds (Degen et al. 1982, face water is scarce. Thomas 1982) suggestthat desert endotherms We observed birds of both speciesdrinking may have lower water turnover rates than their in the wild. Previous reports revealed that mesic and humid-zone counterparts. Thus, it Chukars concentrated at open water sources might be expected that the Sand Partridge, a during the summer (Alcorn and Richardson inhabiting only arid and very arid envi- 195 1, Christenson 1958, Alkon 1974), and in- ronments would have a relatively lower water ferred that they depended on free water when turnover rate than the Chukar, a bird of wide succulentforage was not available (Bump 1953, mesic and semi-arid distribution. However, we Christenson 1954, McLean 1955, Harper et al. found that dry season water turnover rates, 1958). Little information is available on the allometrically compared per kg”.75,were sim- dependence of wild Sand Partridges on free ilar for free-ranging birds of the two species. water. Meinertzhagen (1954) reported that This similarity indicates that the Chukar Sand Partridgesoccurred only near open water, subspecies,A. c. sinaica, can inhabit the same but recent observations in the Negev indicate areas as Sand Partridges; however, Sand Par- that Sand Partridges inhabit areas where sur- tridges do inhabit extremely arid areas (i.e., face water may not be available (G. Illani, pers. the Arava) where Chukarsare absent.This may comm.). be due to interpopulation differences in the Assuming that the birds fed only on seeds, water economies of the Sand Partridges we we calculated that drinking water comprised studied and those inhabiting more xeric en- about 70% of daily water intake in both species. vironments. However, we suspectthat phys- Becauseofthe low moisture content ofthe diet, iological variables other than water turnover large errors in DM intake would cause rela- rate, as well as behavioral differences between tively small errors in estimatesof water drunk. Chukars and Sand Partridges may be impor- In Sand Partridges,for example, the two meth- 336 A. A. DEGEN, B. PINSHOW AND P. U. ALKON

TABLE 3. Estimated daily intakes of dry forageand greenvegetation required to fulfill energyand water requirements in free living Chukars and Sand Partridges:See text for details.

Total intake (T) D/T

Chukars Fresh matter (g) 13.76 40.50 54.3 0.25 Dry matter (g) 13.34 8.10 21.4 0.62 Water, preformed plus metabolic (g) 7.67 36.45 44.1 0.17 Energy (kJ) 205.44 124.74 330.2 0.62 Sand Partridges Fresh matter (g) 8.53 17.84 26.4 0.32 Dry matter (g) 7.63 3.57 11.2 0.68 Water, preformed plus metabolic (g) 4.74 16.16 20.8 0.23 Energy (kJ) 117.50 54.98 172.5 0.68

ods used to estimate DM intake yielded energy The energy content of dry seedsequals 15.4 X intakes of 150 and 193% of existence energy; 0.896 X D (kJ), and of the vegetation equals yet the calculated values for water drunk were 15.4 X 0.2 X G &I). Therefore: similar, i.e., 13.2 and 14.5 ml/day. 13.7680 + 3.08G = 330.2 (kJ). The apparent dependence of wild Chukars and Sand Partridges on drinking water when Solving for D and G, we calculate that if Chu- only dry forage is available was supported by kars obtain at least 38% of their dry matter our laboratory studies. When offered a dry ra- from greens,and are above their minimal water tion under caged conditions, both speciesre- requirements, they do not require drinking quired drinking water in order to maintain body water (Table 3). A similar calculation for Sand mass (Pinshow et al. 1983). However, at least Partridges shows that if they obtain at least Chukars are able to maintain body mass with 32% of their dry matter from green vegetation no free water when succulent vegetation is they do not need to drink. available in addition to dry food (unpubl. data). Fractions of greenssimilar or larger than the This has also been found for a number of quail above calculated minimal intakes have been species(see review by Bartholomew and Cade found in Chukar crops in winter and early 1963). spring (unpubl. data). It is, therefore, likely During this study crop contents were col- that Chukars and Sand Partridges must drink lected from Chukars from the same wild pop- during the hot summers, but do not need to ulations as those birds used for experiments. do so if an adequate supply of green vegetation Analysis of thesecrops revealed that birds were is available. The smaller proportion of vege- eating almost exclusively dry food. However, tation required by Sand Partridgesto maintain during the other seasonswe found both dry positive water balance in absenceof drinking seeds and green vegetation in crops. Green water might explain, in part, the ability of this vegetation contained 80% water (unpubl. ob- speciesto penetrate very arid areaswhere Chu- serv.), and we assumed that it had an energy kars are absent. content of 15.4 kJ and a metabolic water pro- duction of 0.5 g per gram dry matter. Using ACKNOWLEDGMENTS these values and the values for dry seeds,we We thank Hana Amon, Victoria Meltz, Peter J. Shaw calculated the approximate ratio of dry forage and Rafael Frumkin for technical assistance.This study (i.e., seeds) to green vegetation that Chukars was done in the Lady Edith Wolfson Laboratory for En- vironmental Physiologyin the Mitrani Center for Desert must consume in order to obtain 44.1 g of Ecology and was supported by United States-Israel Bi- water and 330.2 kJ (mean of values calculated national ScienceFoundation grants249618 1 and 29 1l/82. using methods I and II) of energy per day, Berry Pinshow is a Bat-Sheva de Rothschild Fellow. which would allow them to maintain energy balance and not have to rely on drinking water. LITERATURE CITED

The volume of preformed water in a unit ALCORN,J. R., AND F. RICHARDSON.195 1. The Chukar mass of dry forage (D) equals 0.106 X D, and Partridge in Nevada. J. Wildl. Manage. 15:265-275. the volume of metabolic water equals 0.5 X ALKON,P. U. 1974. Social behavior in a population of Chukar Partridge (Alectoris Chukar cypriotes) in Is- 0.896 X D. The volumes of preformed and rael. Ph.D. diss., Cornell Univ., Ithaca, N.Y. metabolic water in a unit mass of green vege- BARTHOLOMEW,G. A., AND T. J. CADE. 1963. The water tation (G) equal 0.8 X G and 0.5 X 0.2 X G economy of land birds. Auk 80:504-539. respectively. Therefore: BENJAMIN,R. W., M. CHEN,A. A. DEGEN,N. ABDULAZIZ, AND M. J. AL HADAD. 1977. Estimation of the dry- 0.5560 + 0.9G = 44.1 (g H,O). and organic matter-intake of young sheep grazing a WATER TURNOVER RATES IN DESERT PARTRIDGES 337

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