GENERALNOTESDrinking behavior of sandgrouse in the Namib aud Kalahari deserts, Africa.
--In the past 30 years it has become commonplaceto state in general works thatsandgrouse,family Pteroclidae, drink by a pumping or sucking mechanism,with thebeak continuouslyimmersedduringimbibition,as do dovesand pigeons,family Columbidae (E. Stresemann,Handbuch der Zoologie, vol. 7, Aves, Berlin, W. de Gruyter,
1927-34, see p. 762; E. A. Armstrong, Bird display and behaviour, London, Lindsay
Drummond, 1947; N. Tinbergen, The study o/ instinct, Oxford Univ. Press, 1951;
O. L. Austin, Birds o/ the world, New York, Golden Press,1961; R. Meinertzhagen,pp. 711-712 in A new dictionary o] birds, A. LandsboroughThompson,ed., New York,
McGraw-Hill, 1964). In fact, this case has become widely accepted as a classic
exampleof the utility of a behavior pattern to indicate phylogeneticrelationshipsin asituation where morphology fails to provide an unequivocal answer to the question.
In this instance the result has been relating two families to the same order.
All statementsabout the phylogeneticimplicationsof this method of drinking canapparently be traced back to K. Lorenz (Verhandl. Deutsch. Zool. Ges., 41 [Zool.
Anz. Suppl. 12]: 69-102, 1939) who said, as best we can translate: "For example,one
can recognizethe order of doves by the exclusiveapplication of morphologicalcharacteristicsonly througha tangledcombinationof thesecharacters:carinate,insessorial
bird, with weak, soft-skinned,blisteredbeak, medium-longpointed wings, short perching or schizopodalleg, etc. There are exceptionsto each of the named characters.
Goura is not an insessorialbird, and besideshas round, generally chicken-likewings,Didunculus,a generallydifferent bill, and so forth. On the other hand, one recognizes
the order by the single behavioral characteristic,namely that in drinking the wateris pumped up by peristalsisof the esophagus,which occurswithout exceptionwithin
the order. The only other group, however, which shows the same behavior, thePteroclidae, is placed near the doves just by this doubtlessly very old characteristic
even more than by many morphological characteristicswhich point to the sameconclusion."

The phylogenetic significanceof this type of drinking went unchallengeduntil
W. Wickler (Zeit. fiir Tierpsych., 18: 320-342, 1961) called attention to previously
published observationswhich indicate that other groups of birds (Estrildinae andSylviidae) also contain specieswhich drink by sucking. In addition, Cade and Greenwald (Auk, 83: 126-128, 1966) have found that mousebirds(Coliiformes) drink byexactly the same method.
Wickler (op. cit.) also cited the old statement of Bartlett that the aberrant andapparently primitive Tooth-billed Pigeon (Didunculus) drinks, not like other columbids but like geese,by putting its beak down into the water and then quickly raising
up its head. Similarly, L. SchiSnholzer(Der zool. Garten [NF] 24: 345-434, 1959)
took motion pictures of sandgrouse(Pteroclesquadricinctus) in a zoo, showing that
individuals of this speciesdrink by sucking in a draft and then raising their heads
up high to swallow.
In field work carried out in January, 1964, from June to September, 1964, andfrom October, 1964, through January, 1965, we have had numerous occasionsto

verify and extendSchiJnholzer'sobservationsfor two additionalspeciesof sandgrouse,Pteroclesnamaqua and P. burchelli,which are commoninhabitantsof the Namib andKalahari

deserts in southern Africa.

Mostof our observations were made at theNamib Desert Research Station, located at Gobabeb approximately 70 miles inland124Jan.]

1966

GeneralNotes

125

from Walvis Bay, in South West Africa and in the Kalahari GemsbokNational Park,
Republic of South Africa. At Gobabeb,an open pit dug down through sand to thewater table in the dry bed of the Kuiseb River providesone of the few sourcesof
surface water for thousands of square miles. In January, 200 to 300 Namaqua
Sandgrousecame to water every morning, but in July and August the number wasusually 50 or less,and flocksdid not fly to the water hole every day. A number ofgame-wateringtanks distributedalong the Nossoband Auob rivers in the KalahariPark attract thousandsof sandgrouseof both species.Most of our observationsin
the park were made at the Mata Mata, Craig Lockhart, and Houmoed game wells.
We have observed thousandsof sandgrousedrinking at these water holes, often
watching from hides or vehiclessituated only a few feet away from the birds. InJanuary, Cade spentmost of three days in a hide at the Gobabebwater hole observing
birds drinking at a distance of about 10 feet, and in July and August, Cade andWilloughby made three dawn to dusk surveillancesof this water hole from a hidelocated about 20 feet from the water.

Maclean carried out intensive watches eachof several hours' duration on nine days during October and November at Houmoedwater hole, either from a hide or parked vehicle. During all of these periods ofobservation,we have never seenone of thesesandgrousedrink like a dove or pigeon.
In our areas of study, the difference in drinking between sandgrouseand doves is
at once obvious, becausefrequently three speciesof doves, Streptopelia capicola,
Stlgmatopeliasenegalensis,
and Oena capensls,and the SpeckledRock Pigeon, Columba
guinea, cometo drink at the same water holes with the sandgrouse.Thus, the behaviorof sandgrouseand doves can often be compared as they drink side by side. All ofthese columbid speciesstick their beaks into the water and suck to satiety before
raising their heads.
Drinking by the sandgrousestudied is a brief act requiring no more than 5 to

10 secondsfor completion after the water is reached. At Gobabeb, a typical sandgrousewould suck and raise its head 4 or 5 times (range 3 to 10) before flying away.
In the Kalahari, Maclean obtained the following figures: for 141 counts of male
Pteroclesnamaqua the average number of drafts per drink was 9.6; for 145 females,9.4; for 136 male P. burchelli, the average was 7.4 drafts; for 133 females, 7.0. The
range was from 1 to 24 drafts. (We use "draft" here to mean one immersion of thebeak followed by raising the head and swallowing.) Cade (in press) discussesthe
probable adaptive significanceof this rapid drinking in connection with predation by
diurnal raptors around water holes.
It has been reported in the Russian literature that individuals of P. orientalis shotat watering holes in the Soviet Union held up to a "cup" of water in their alimentarytracts, and G. W. Salt and E. Zeuthen (pp. 363-409 in Biology and comparative physiology of birds. vol. I, A. J. Marshall [ed.], New York: Academic Press, 1961) bave
estimated this amount to be about 150 mi. P. namaqua and P. burchelli apparently
drink much smaller quantities. Individuals netted at Houmoed after drinking had
an estimated 5 to 10 ml of water in their crops. At Gobabeb, we measured theamount of water consumed at one time by three Namaqua Sandgrousewhich had
been deprived of water for many days. A male, which had been kept in a small
outdoor cage in the shade without water for 25 days, drank 12 ml at once, raising hishead 7 times in the process; four minutes later he drank 3 more ml, raising his head
3 times. The average amount of water consumed per draft was 1.5 ml. A female,which had been subjected to the same condition, drank 15 ml, raising her head 14
times, for an average of 1.1 ml per draft. A secondfemale held for 17 days withoutwater consumed 12 ml in 6 drafts. These figures probably represent near maximum

126

GeneralNotes[ Auk1. Vol. 83

consumptionsfor this species,but the possibility that breeding birds with chicks
drink

more should not be ruled out.

We have been unable to find a published account of actual observations of any
sandgrousedrinking by holding its beak in the water and sucking continually like apigeon or dove, although Meinertzhagen (op. cit.) says that "as many as 44 gulps
have been counted." On the other hand, three speciesare now known definitely not
to drink in this way. Until someinformation on other generaor speciesof sandgrouse
becomesavailable, we feel compelledto abandonthe long-held notion that the family
Pteroclidae can be related to the family Columbidae on the basis of a common,
distinctive method of drinking.
This study was supportedby a grant from the U.S. Public Health Service (Environmental Health) ES 00008. We thank Dr. C. Koch for making facilities at the Namib
Desert Research Station available to us, Mr. O. P.M. Prozesky of the Transvaal
Museum for much good assistancein the field, and the National Parks Board ofTrustees, Republic of South Africa for permission to carry on field work in theKalahari Gemsbok National Park.--To•
J. C^D•, ER•r•sr J. W•LLOUCHmr, andGom>o•rL. M^CLEA•r,Department of Zoology, Syracuse University, Syracuse, NewYork and Department of Zoology, Rhodes University, Grahamstown, South Africa(M^c•^•).

Drinking behavior of mousebirds in the Namib Desert, southern Africa.-Both the White-backed Mousebird (Colius colius) and the Red-faced Mousebird(Colius indicus) occur in wooded sectionsof the Namib Desert, usually along dry rivercourses.In field work carried out between 18 and 23 January 1964 and between 5 Julyand 11 August 1964, we had frequent opportunitiesto observe flocks of these two
speciesforaging in the riparian acacia woods (A. giraffae and A. albida) associatedwith the dry bed of the Kuiseb River. Our observationswere made around the Namib
Desert Research Station located at Gobabeb, approximately 70 miles inland from
Walvis Bay, in South West Africa. The riparian vegetationallows a number of avian
speciesto extend their rangesinto the desert region from the more extensively wooded
highlands flanking the east side of the Namib.
In the vicinity of Gobabeb these mousebirdsfed extensivelyon the young leaves,
flowers, and green or ripe berriesof the widespread,vinelike shrub, Salvadora persica.
Since this plant appears to undergo at least two cycles of fruiting a year in thisregion, the mousebirds are able to exploit a more or less constant source of food.

Ripe Salvadora berries are the preferred parts of this plant; these have a high watercontent. For example,a sample of 30 freshly picked ripe berries weighed 7.75 g; onoven drying to a constantweight at 80øC the weight was 2.45 g, of which the seeds,
which are not digestedby mousebirds,accountedfor 0.38 g. Thus, the water content
of these berries averagesabout 66 per cent of the wet weight.
Becauseof the high water content of their food, mousebirdsare not greatly dependent on drinking in order to maintain water balance even in the desert, and except
for one brief period they were never seen at the isolated water holes in the bed of
the Kuiseb River where many other forms of birdlife gathered in large numbers todrink. In January, when daytime temperaturesranged above 35øC, we never saw
mousebirdsat water. This period correspondedwith a time when the Salvadora
busheswere in full fruit, and both specieswere feeding heavily on the ripe berries.
Again, in July and August when temperatures were moderate to cool, we neverobservedWhite-backed Mousebirds drinking, but between 30 July and 2 August