On the track of the African storks

2 Pages·2001·1.7 MB·

by  P A Whittington

On
the track of the African storks
P.A. Whittington andL.G. Underhill
Une petite population de Cigognes blanches Ciconia ciconia niche en Afrique du Sud en quatre
localites depuis les annees 1930. Contrairement aux Cigognes blanches europeennes, les nicheuses
sud-africaines restent toute l’annee dans les environs de leurlieu de nidification. Ceci n’esttoutefois
paslescasdeleurprogeniture. Afindedecouvriroulesjeunesvont, cinqoisillonsdu Capoccidental
ont ete munis de balisesArgos, permettant de les suivre parsatellite, en decembre 2000. Fin janvier
2001, lescinqjeunesavaientquittel’Afriquedu Sud. Enfevrier, quatred’entreeuxtrouvaientlamort,
respectivementauBotswana, enZambieetauZimbabwe(deux), danslazonequisubissaitl’effetdes
grossespluiesdubassindu Zambezequiprovoquerentdesinondationscatastrophiquesaucentredu
Mozambique. Le cinquieme se trouvait dans le sud du Mozambique pendant cette periode; il s’est
deplace vers le nord-est du Zimbabwe en mars; le 5 mai il s’est dirige brusquement vers le nord,
traversant la Zambie en direction de la Republique Democratique du Congo.
It is well known that White Stork Ciconia ciconia satellite transmitters on five White Stork fledglings in
breedsinEuropeandsouth-westAsiaandmigrates the Western Cape. Four of the transmitters were
toAfricaforthenorthernwinter. Mosttakeadvantage placed on nestlings in nests above the cages at the
of the narrowest sea crossings, passing south over Tygerberg Zoo, and one was attached to one ofthe
Gibraltar orThrace in August-September. Storks be- nestlingsintheonlynestnearBredasdorpin2000.As
gintoarriveinZimbabwefromaroundOctober, then partofacollaborativeprojectwiththeAvianDemog-
slowly move south, reaching the Western Cape of raphyUnit(ADU)attheUniversityofCapeTown,the
South Africa in November-December12 These birds team hoped to unravel the mystery ofwhat happens
.
do notbreed in southern Africa. However, there is a tothesebirdsaftertheyleavethenest.Themammalian
missing piece in the jigsaw ofthe White Stork story. inhabitants ofthe zoo watched bemused as an orni-
OnepairnestednearOudtshoorn,400kmeastof thologist climbed up a ladder, carefully took a chick
CapeTown, inthe 1930sandin19402. Since 1961,up from the nest and brought it into the shade. Here, a
tofourpairshavebredintheBredasdorpregion, 200 lightweight solar-powered satellite transmitter was
kmeastofCapeTownandveryclosetothesouthern fittedbymeansofaharness.Eachchickwasalsofitted
tipofAfricaatCapeAgulhas.Intheearly1970s,some withametalringononelegandacolourring, witha
oftheeggsfromthesenestsweretakentoTygerberg clearlydiscerniblenumber,ontheother.Thelattercan
Zoo and the chicks artificially reared. In 1975, wild bereadinthefieldwithbinoculars.Thosechicksthat
storks began building a nest on one of the zoo’s werenotsatellitetaggedweremarkedwithapatchof
cages.Theywereunsuccessfulthatyear,butby2000 yellow picric dye on one wing. The chicks remained
fivepairsoffree-flyingWhiteStorkswerenestingon remarkably docile during the entire performance,
various cages of the zoo, fours pairs having large permitting theirwings, bill and tarsi to be measured.
chicksbyearlyDecember.Homeyr3haspublishedan Theywerethenreturnedtotheirnests, tothereliefof
historical overview of White Stork breeding in the their bill-clapping parents.
Western Cape. Beforethebirdsleftthenestwewrote: ‘Mortality
Unlike those storks that breed in Europe, the among young birds is high and it is possible that
South African breeders appear to remain in the some, or all, of the young birds may die before
vicinity of the nest site year-round. However, their moving very far. However, any that do survive will
offspring do not. The question is ‘where do these help to solve the puzzle ofwhat happens to White
young storks go? Some clues have derived from Storks, born and bred in South Africa’.
ringing chicks at the Bredasdorp nests. Two of the Butwewere lucky, all five fledged successfully.
chicks in a 1961 nestwere found dead farther north During late December 2000 and earlyJanuary 2001.
in Africa: one in Free State, South Africa, and the thesignalsindicatedthattheyhadlefttheirnestsand
otherclosetothe Zambia-Tanzaniaborder. But, the were making short-distance trips into neighbouring
full story remained to be discovered. areas. By 21 January 2001 all were outside the
Withthisinmind,ateamofornithologistsfromthe borders ofthe Western Cape and by the end ofthe
MaxPlanckInstitute, Germany, andBirdLife Belgium month theywere all outside South Africa. Theyhad
travelled to Cape Town in November 2000 to place survivedthecriticalfirstfewweeksandwebreathed
On thetrackofAfricanstorks: Whittington& Underhill BullABC Vol8No2- 127
a little easier. But, a bit too soon. We had reckoned we anticipated that it would spend the rest of the
without the rains over the Zambezi River valley in southern winter there. Suddenly, on 5 May, Saturn'
February 2001, which brought devastating floods to got itchy wings and headed north. It made hops of
Mozambique. c200 km per day and within a week had crossed
‘Tiger’ set out fromTygerberg Zoo on 8January Zambia and was just south of the equator in the
and by 27 January was in the Luangwa Valley in Democratic Republic of Congo, near the shores of
north-east Zambia, some 4,000 km away. It spent Lake Tanganyika. Its progress will continue to be
nearly two weeks there, the daily satellite positions reportedontheADUwebsite http://www.uct.ac.za/
being from different places within the valley. Pete depts/stats/adu.
Leonard, one ofZambia’s leading birders, reported: We are still digesting what we have learnt. The
‘Thearea is notdenselypopulatedwith people. The biggestsurprisewasthatthebirdslefttheirnestareas
valley has rolling hills covered in scrub and poor soearly. Wehadexpectedthemtoheadnorth atthe
miombowoodlanduntilyou hitthe escarpments on time we believe the European breeders migrate, in
eithersideandgetintodecentwoodland. Thestorks late February-March. We were surprised at the long
make use of the oxbows on the main river but are distancesflowneachdayandthatthebirdsfollowed
probably more often on the smallish floodplains suchdirectroutes; allexcept‘Saturn'weretakingthe
along the tributaries’. ‘stork highway’ to Europe, determined by a decade
Wedonotknowif‘Tiger’madethisjourneyinthe of satellite tracking of Northern Hemisphere birds.
company ofadultWhite Storks returning to Europe, This is what makes us believe they were in the
but this appears likely. If the storks had continued companyofadultsreturningtoEurope.Thisyear,the
travellingnorthatthespeedtheyhadbeentravelling, main route took the birds into a hostile weather
theywould have arrived in Europe while it was still system, and the only individual to survive was that
winterthere. TheLuangwaValleyisprobablyoneof which initially took the unorthodox route through
the feeding areastheyuse en route, and where they the Kruger National Park to Mozambique.
remain for a few weeks before moving on. The Vogelwarte Radolfzell of the Max Plank
ByearlyFebruary, siblings ‘Misty’ and‘Leo’were Institute in Germany has been so intrigued by the
both in the vicinity of the Kariba Dam, on the results that they intend repeating the exercise in the
Zambezi River between Zimbabwe and Zambia, comingbreedingseason. SokeepwatchingtheADU
while ‘Rembrandt’ was in Botswana and ‘Saturn' in website.
the Save River floodplain in southern Mozambique.
Then the rains came and regular signals were re- Acknowledgements
ceived only from ‘Misty’ and ‘Saturn’. This was not TheWesternCapeNatureConservationBoardgranted
causeforalarmbecausesunnyconditionsareneeded permission for the satellite-tracking devices to be
to powerthe solartransmitters and signals transmit- attached.John Spence at theTygerberg Zoo inCape
tedtothesatellitesdonoteasilypenetratethickcloud Town was exceedingly helpful. Many other people
or rain. Suddenly, on 28 February, the ‘activity playedkeyrolesintheoperation,andwearegrateful
counter’in‘Misty’s’satellitetagbecamestuckon 166, for all their assistance. '%>
indicatingthatthisbirdwasdefinitelydead.Towards
the end of April the dreaded letter from Zambia References
arrived. ArthurZyambohadfoundsatellitetransmit- 1. Allan, D.G. 1997. White Stork Ciconia ciconia. In
ter no. 20527 on a dead and half-eaten stork on the Harrison, J.A., Allan, D.G., Underhill, L.G.,
banks of the Luangwa River during February. This Herremans, M., Tree, A.J., Parker, V. and Brown,
was (orhad been) ‘Tiger’. ‘Leo’ and ‘Rembrandt’ are C.J.(eds)TheAtlasofSouthernAfricanBirds.Vol1.
almost certainly also dead. Having surmounted the Johannesburg: BirdLife South Africa.
hurdle of the first few weeks out of the nest, and 2. Underhill, L.G., Tree, A.J., Oschadleus, H.D. and
having covered over 2000 km, it was disappointing PWaartkeerrb,irVd.s i1n9S99o.uthReervnieAfwriocaf.RCianpgeRTeocowvne:riAevsiaonf
that four out offive birds were lost in such a short Demography Unit, University ofCape Town.
period oftime. But these are the realities oflife for 3. Hofmeyr, J.H. 2001. An overview of White Stork
White Storks, and for most wild animals history in the SW Cape. Promerops 246: 9-12.
By mid-May, only ‘Saturn’ remains alive. On 13
March, this bird crossed from Mozambique into the AvianDemography Unit, DepartmentofStatisticalSci-
eastern highlands ofZimbabwe. Itspent a month in ences, University of Cape Town, Rondebosch, 7701,
the vicinity of Harare, in north-east Zimbabwe and SouthAfrica.
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