Ibis

(2003),

145

, 499–501

© 2003 British Ornithologists’ Union

Blackwell Publishing Ltd.Oxford, UKIBIIbis0019-1019British Ornithologists' Union, 2003? 2003145?

Short communication

White Storks wintering in ChadJ. Brouwer, W.C. Mullié & P. Scholte

White Storks

Ciconia ciconia

wintering in Chad, northern Cameroon and

Niger: a comment on Berthold

et al

. (2001)

JOOST BROUWER,

1

*

WIM C. MULLIÉ

2

& PAUL SCHOLTE

3

1

Brouwer Envir. & Agric. Consultancy, Wildekamp 32, 6721 JD Bennekom, the Netherlands

2

c/o Projet Locustox, FAO, BP 3300, Dakar, Senegal

3

Centre of Environmental Science, Nieuwe Teertuinen

12C, 1013 LV Amsterdam, the Netherlands

Berthold

et al

. (2001) presented much new information onthe results of satellite tracking White Storks

Ciconia ciconia

of the eastern population, and showed the power of thisnew technology when sufficient resources are available.However, they were left with a number of unconfirmedsuspicions and unanswered questions. In this contributionwe comment on those suspicions and try to answer someof the questions, taking as a starting point what is knownof the western population of the White Stork in the centralSahel.

HISTORICAL RECORDS OF WHITE STORKS WINTERING IN CHAD

Berthold

et al

.’s (2001) paper concerned the easternpopulation of the White Stork, migrating via the MiddleEast, and not the whole White Stork population. Salvan(1967), Ledant (1986) and Dorst (1962, in Moreau 1972)had reported concentrations of up to 10 000 White Storksin Chad before the 1970s. From 1970 to 1990 there was avery marked decline in numbers of Storks observed inChad, followed by a partial recovery from 1991 until atleast 1994 (Mullié

et al

. 1995). We ascribed these trends tochanges in numbers of observers, population sizes and/orclimatic conditions.

It is interesting to note that the areas in Chad with themost observations of satellite-tracked White Storks in therecent past (Berthold

et al

. 2001) appear to coincide withsites with records of appreciable numbers of Storks inthe more distant past, as presented in Mullié

et al

. (1995).In the area of Berthold

et al

.’s most easterly concentration

of observations, just south-west of Abéché (13

°

N, 20

°

E),2000–3000 Storks were seen in October and again inDecember 1964 (Salvan 1967). At Bokoro (12

°

30

′

N, 17

°

E)800 Storks were seen in December 1992, and another1300 quite recently, in November 2000, at nearby Ngoura(12

°

55

′

N, 17

°

E; P. Scholte pers. obs.). Berthold

et al

.’sthird concentration, near Ati (13

°

N, 18

°

20

′

E), is only80 km from Lac Fitri, where thousands of Storks were seenin the early 1960s (Dorst 1962, in Moreau 1972).

MIXING OF EASTERN AND WESTERN POPULATIONS

Giraudoux

et al

. (1988) mentioned a White Stork ringedin Estonia and trapped near Zinder in south-central Niger(14

°

N, 9

°

E). In the same publication mention was madeof recoveries, at the same wetland as well as further east,of Storks ringed in Spain, Morocco, Tunisia and Germany(20 km south-east of Bremen: Heim de Balsac & Mayaud1962). Hence this demonstrated mixing of White Storks ofthe eastern and western populations within their winteringgrounds. There are other ring recoveries also that illustratethis mixing, as the Radolfzell group will be the first toacknowledge (P. Berthold, pers. comm.). But the satellitetracking study of Berthold

et al

. is indeed the first to showby which route such mixing might take place.

MOVEMENTS IN THE WINTERING AREA AND FOOD AVAILABILITY

Berthold

et al

. (2001) wondered why a number of Storksleft Chad and western Sudan between October and theend of November to go back east to the Nile Valley andthen on south again. We suggest that this is due to theavailability of food. White Storks arrive in the Saheltowards the end of the rainy season, which runs from Juneto September. With primary production coming to a haltin September–October, secondary production (of insects)will decline shortly after. Mullié

et al

. (1995) present agraph from Mestre and Chiffaud-Mestre (1991) of thedensity during September 1989–June 1990, at three sitesin south-west Niger, of

Ornithacris cavroisi

, a grasshopperspecies likely to be taken by White Storks. Average densitywas zero grasshoppers per hectare in September, 7000 inOctober and 6000 in November, sharply dropping to lessthan 1000 in December, January and February, and thentailing off further. Peak densities found were more than11 000 grasshoppers per hectare during October andNovember, and no more than 2000 during December–February. Storks in the western Sahel have to make dowith other sources of food than

Ornithacris cavroisi

afterNovember, before returning north.

We expect that conditions further east in the Sahel, i.e.in Chad, resemble those in south-west Niger. Many of theWhite Storks in Chad, however, are apparently from theeastern migration route, and have the option of going back

*Corresponding author.Email: brouwbar@bos.nl

500

J. Brouwer, W.C. Mullié & P. Scholte

© 2003 British Ornithologists’ Union,

Ibis

,

145

, 499–501

east to the Nile Valley, and then further south if necessary,to where the rains have just ended (East Africa) or are stillfalling (southern Africa), with associated greater foodavailability.

We would add here that dependence of White Storks onlocusts like the Desert Locust

Schistocerca gregaria

, duringnormal years without swarm outbreaks, appears unlikely.During recession years Desert Locusts are confined to areaswith less than 200 mm annual precipitation (Steedman1990), while our data show that White Storks in West Africawinter largely in areas with more than 200 mm annualprecipitation (Mullié

et al

. 1995).Also worth noting is the apparent importance of tempo-

rary and (semi) permanent isolated wetlands in the Sahel(Mullié

et al

. 1995), as opposed to just the floodplains ofthe large rivers. Such wetlands can be found in their thou-sands all over the Sahel. We found White Storks at suchwetlands almost always during the hottest part of the day,when they use these sites for resting and probably for ther-moregulatory purposes. Earlier in the morning and later inthe afternoon they feed in the fields, which are almost bareat that time of year, and in fallow and open shrublandareas. At these times of day White Storks are much moredifficult to find. The same pattern of resource use wasobserved in the Abdim’s Stork

Ciconia abdimii

in easternNiger in September 2001 (W. C. Mullié pers. obs.). Wesuggest that when trying to locate White Storks duringtheir wintering in West Africa, one should normally con-centrate on wetland areas in the 200–600 mm rainfall zone,visit these between 11:00 and 15:00 hours, and try tocollect information from local herdsmen and farmers.

We say ‘normally’, because the 200–600 mm rainfallzone in West Africa is not as it once was. Relative tothe 1945–1969 period, isohyets during 1970–1990 hadshifted southwards by 100–150 km (Sivakumar 1992,Sivakumar

et al

. 1993). This will have caused a decreasein food availability and in wetland area in the zone whereWhite Storks normally occur. During the 1970s and 1980sthe Storks may therefore have been more dependent thanusual on the floodplains of the larger rivers (see also ourobservations in northern Cameroon), and they may haverun out of resources because the more wooded areasfurther south are not suitable for them (Mullié

et al

. 1995).This may have been one cause of the decline of the westernpopulation of the White Stork at that time. Over the past10 years rainfall in the region seems to have increased again,and western White Stork numbers certainly have also.

THREATS TO WHITE STORKS IN THE SAHEL

Regarding threats to White Storks, as discussed byBerthold

et al

. (2001), we do not consider pesticides to bea great problem in Niger, as their use in the wintering zoneof the White Stork is rather limited at present. CentralChad is in many ways similar to Niger, and the use of

pesticides there is also likely to be limited. Pesticide usemay be higher in areas of market gardening at the edges ofwetlands, but we have no data that indicate that this posesa threat to Storks. Use of pesticides to control swarminglocusts usually takes place north of the normal winteringareas of White Storks in the Sahel. Hunting, includingthe use of baited hooks on lines, seems no longer to be a pro-blem in Niger, Cameroon and Chad, although in Nigeriathe situation may be different (Ezealor 1995).

In our opinion one of the most important threats islikely to be degradation of the wetlands the Storks use forresting and thermoregulation. Owing to human popula-tion increases and changes in rainfall patterns, pressure onsuch wetlands is increasing every year (Brouwer & Mullié1996). At the same time there is almost no managementof this resource, let alone integrated management involv-ing all stakeholders (Brouwer & Mullié 1994). In the nearfuture there may be little left of a number of these wetlands,either for herders, farmers and fishermen, or for WhiteStorks. This has already happened at, for instance, LakeMadarounfa near Maradi in southern Niger, formerly a sitefor White Storks (Giraudoux

et al

. 1988, Mullié

et al

. 1995).

RELEVANT CONSERVATION ACTIVITIES

Berthold

et al

. (2001) also discuss future conservationactivities for the White Stork along its migration routesand in its wintering areas, in co-operation with the coun-tries concerned. We feel that, as part of this, extendedsurveys of wetlands and White Storks, as well as otherwaterbirds, in the Sahel are urgently needed. To do this,use could be made of the network of the African WaterbirdCensus, which is managed by Wetlands International fromDakar, Senegal, and which covers more than 35 countriesthroughout Sub-Saharan Africa. Based on the results ofthese surveys new conservation activities could be devel-oped. An overview of present conservation and naturalresource management activities in Chad, relevant to birds,is given in Scholte and Robinson (2001). Among these is arecently formulated wetland management project at theaforementioned Lake Fitri, which involves the Chadiangovernment as well as the Global Environment Facilityand the Lake Chad Basin Commission.

We thank two anonymous referees for their constructive comments

.

REFERENCES

Berthold, P., Van Den Bossche, W., Fiedler, W., Kaatz, C.,Kaatz, M., Leshem, Y., Nowak, E. & Querner, U.

2001.Detection of a new important staging and wintering areaof the White Stork

Ciconia ciconia

by satellite tracking.

Ibis

143

: 450–455.

Brouwer, J. & Mullié, W.C.

1994. The importance of smallwetlands in the central Sahel.

IUCN Wetlands ProgrammeNewsletter

9

: 12–13.

© 2003 British Ornithologists’ Union,

Ibis

,

145

, 499–501

White Storks wintering in Chad

501

Brouwer, J. & Mullié, W.C.

1996. Case study: the Sahel. InOquist, M.G., Svensson, B.O., Groffman, P. & Taylor, M. (eds)

Non-Tidal Wetlands

.

Chapter 6 of Climate Change 1995:Impacts, Adaptations and Mitigation of Climate Change:Scientific-Technical Analyses

.

Contribution of Working GroupII to the Second Assessment Report of the IntergovernmentalPanel on Climate Change [Watson, R.T., Zinyowera, M.C. &Moss, R.H. eds]: 215–239. Cambridge: Cambridge UniversityPress.

Ezealor, A.

1995. Wintering White Storks in Nigeria. In Biber, O.,Enggist, P., Marti, C. & Salathé, T. (eds)

Proceedings ofthe International Symposium on the White Stork (WesternPopulation), Basel, Switzerland, 7–10 April 1994

: 213–218. Schweizerische Vogelwarte Sempach, Switzerland.

Giraudoux, P., Degauquier, R., Jones, P.J., Weigel, J. &Isenmann, J.

1988. Avifaune du Niger: état des connaissancesen 1986.

Malimbus

10

: 1–140.

Heim de Balsac, H. & Mayaud, N.

1962.

Les Oiseaux duNord-Ouest de l’Afrique

.

Paris: Lechevalier.

Ledant, J.P. (ed.)

1986.

Aperçu Des Zones de Grand IntérêtPour la Conservation Des Espèces D’oiseaux Migrateurs de laCommunauté En Afrique

. Rapport EUR 10878. Luxembourg:Commission des communautés européennes.

Mestre, J. & Chiffaud-Mestre, J.

1991.

Activités du ProjetAcridométéorologie PRIFAS/FAC/AGRHYMET

. Rapport dufin de projet. Niamey: PRIFAS.

Moreau, R.E.

1972.

The Palaearctic–African Bird MigrationSystems

. London: Academic Press.

Mullié, W.C., Brouwer, J. & Scholte, P.

1995. Numbers, distri-bution and habitat of wintering White Storks in the east-central Sahel in relation to rainfall, food and anthropogenicinfluences. In Biber, O., Enggist, P., Marti, C. & Salathé, T.(eds)

Proceedings of the International Symposium on theWhite Stork (Western Population), Basel

,

Switzerland, 7–10April 1994

: 219–240. Schweizerische Vogelwarte Sempach,Switzerland.

Salvan, J.

1967. Contribution à l’étude des Oiseaux du Tchad.

L’Oiseau R

.

F

.

O

.

37

: 255–284.

Scholte, P. & Robinson, P.

2001. Chad. In Fishpool, L.D.C.& Evans, M.I. (eds)

Important Bird Areas in Africa andAssociated Islands; Priority Sites for Conservation

: 177–184.BirdLife Conservation Series no. 11. Cambridge and New-bury, UK: BirdLife International and Pisces Publications.

Sivakumar, M.V.K.

1992. Climate change and implications foragriculture in Niger.

Climate Change

20

: 297–312.

Sivakumar, M.V.K., Maidoukia, A. & Stern, R.D.

1993.

Agro-climatology of West-Africa: Niger

, 2nd edn. ICRISAT Informa-tion Bulletin no. 5. India: Patancheru.

Steedman, A., ed.

1990.

Locust Handbook

, 3rd edn. Chatham,UK: Natural Resources Institute.

Received 26 October 2001; revision accepted 20 September 2002