Voorkant omslag

Living on the edge:Summary of

Wetlands and birds in a changing Sahel

About the importance of the Sahel as wintering area of European migratory bird species

ISBN 978-90-79341-03-0

This brochure is written on request of the Dutch Centre for Water Management of Rijkswaterstaat.

It gives a summary of

Living on the edge: Wetlands and birds in a changing Sahel

Leo Zwarts, Rob G. Bijlsma, Jan van der Kamp, Eddy Wymenga (2009).

KNNV Publishing, Zeist. 564 pag. ISBN 978-90-5011-280-2. To order see www.knnvpublishing.nl.

The graphs and maps (Dick Visser), water colours (Jos Zwarts) and photos (Floris Deodatus, Nicolas

Gaidet, Hans Hut, Ben Koks, Benny Klazenga, Jan van de Kam, Wim Mullié, Gray Tappan, Leo

Zwarts) are all taken from the same book. The references are given in Living on the edge.

There is also a French and Dutch edition of this brochure; “Résumé français de Living on the edge: wet-

lands and birds in a changing Sahel (ISBN 978-90-7934-104-7) and “Nederlandse samenvatting van Living on

the edge: wetlands and birds in a changing Sahel” (ISBN 978-90-5011-280-3).

Layout and printing: Brandsma Offset Ferwerd.

Living on the edge:Summary of

Wetlands and birds in a changing Sahel

Contents

Billions of birds from Eurasia spend the northern winterin Afrika....................................................................................................3Migratory birds connect continents

Europe’s long-distance migrants are in decline

Where do our migrants spend the winter in Africa?

Changes in the Sahel..........................................................................7Rainfall

Rivers and wetlands

Long-term changes

The decline of wetlands

Summary

Population trends in Sahel migrants.........................................21Winter mortality in dry years

The impact of Sahel conditions on return migration

and breeding performance

Population declines after dry Sahel years

Continuous decline

Are numbers of long-distance migrants governed by conditions

in the breeding or in the wintering areas?

Why some long-distance migrants show an increase

Year-round protection of migratory bird species................28Effective bird protection in the Sahel

Effective protection of long-distance migrants in Europe

In the summer of 1969, sharp-witted birders in various parts of Europe werestruck by the scarcity of Common Whitethroats on the breeding grounds.Remember: this was the era that stan-dardised monitoring of breeding birdswas still in its infancy (in Britain, andnowhere else). To be noticed on such ascale, the decline must therefore havebeen enormous, as it turned out to be.Some birders were quick to suggest thatperhaps something ominous might havehappened in the African winteringareas. It took several more years beforethe drought south of the Sahara madeheadlines in the newspapers: scorchedvegetation, livestock starving to deathand millions of emaciated people. Thathundreds of millions of European migra-tory birds were dying in Africa as well isnot surprising in hindsight, but at thetime this was a hotly debated issue.

1968 was the start of The Great Drought,a period of 25 years with consistentlybelow-average rainfall in the Sahel and ad-jacent vegetation zones. It was a humanita-rian tragedy, on top of an ecological disas-ter. The Sahara advanced to the south andexperts were convinced that the desertifi-cation was irreversible. Forty years later,this viewpoint appears to have been toopessimistic. Satellite images show thatsince 1992 the Sahel has become greeneragain in the wake of an increase in rainfall,bouncing back from drought-related de-vastation. Nonetheless, the current situa-tion is still unfavourable compared withthat of half a century ago. What has beenthe impact on bird populations?

Since the start of standardised monito-ring from the late 1960s onwards, popula-tion trends of many bird populations in Europe have become available, spanning20 years or more. Matching trends of long-

distance migrants with conditions in theAfrican wintering areas is now within ourgrasp, especially relevant because so manylong-distance are in rampant decline. If upsand downs of ‘our’ migrants are mainlytriggered by events occurring in the Afri-can wintering areas, (better) protection inthe breeding areas will not improve thefortunes of this group of birds. A legiti-mate question therefore is: to what degreeis European birdlife determined by the cir-cumstances in sub-Saharan Africa? That isthe leading question in the book Living onthe edge: Wetlands and birds in a changingSahel.

MIGRATORY BIRDS CONNECT CONTINENTSThe twice annual journey of migratorybirds between breeding and winteringgrounds is quite a feat. The exhaustedWheatears we saw on the beach in Mauri-tania are a case in point: they had just cros-sed the Atlantic Ocean in a single leapfrom East Canada or Greenland to WestAfrica, a distance of 5000 km. Garganeyand Ruff, breeding in the outer east of Si-beria, cover an even longer distance of15,000 km to reach their African winteringareas. They do it in several steps, but it remains as impressive.

Europe accommodates more than 500breeding bird species, by estimate some2000 millions of pairs. This equals 8000millions of post-breeding birds, of which aquarter winter south of the Sahara. For thesouthern European birds the fraction oftrans-Saharan migrants is smaller than forthe birds in northern Europe where itamounts up to 40%. Africa is of vital impor-tance for the long-distance migrants bree-ding between East Canada and East Asia,ranging in habitat from the Arctic tundrato the Mediterranean scrubland.

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Billions of birds from Eurasia spend the northern winter in Africa

EUROPE’S LONG-DISTANCE MIGRANTSARE IN DECLINEMigratory bird species are in trouble, bigtrouble. The population estimates of Euro-pean birds in 1970, 1990 and 2000, ascompiled by BirdLife International, clearlyshow the point: most species winteringsouth of the Sahara are in decline. Of the127 species crossing the Sahara, 16 showan increase (13%), 36 are stable (28%), but75 (59%) are in decline. This compares unfavourably with short-distance migrants(33% in decline) and residents (28% in decline).

These downward trends were particu-larly evident in birds wintering in the savanna (large decline in Egyptian Vulture,Pallid Harrier, Steppe Eagle, Stone-Curlew)and wooded savanna (large decline in BlackKite, European Roller, Common Redstart),

but equally so in waterbirds (large declinein Glossy Ibis, Ruff, Black-tailed Godwit). Alarge decline stands for a decrease of morethan 30% in the period concerned. Conver-sely, bird species wintering in the Africanforests (like European Honey-buzzard, Eu-ropean Golden Oriole and Pied, Spottedand Collared Flycatcher) seem to have beenless affected; although in decline, thedownward slope is less steep than in thespecies wintering in the Sahel. Many factors play their role, but it seems beyonddispute that the Sahel is a key factor indeed. Before embarking on a verificationof the causes behind the declines of long-distance migrants, we first have to distin-guish where in Africa they spend thewinter. After all, not all of Africa was asbadly hit by drought as the Sahel.

4Nearly all Garganey from Europe and Asia spend the winter in the Sahel, where they concentrate in the floodplains near Lake Chad, in the Inner Niger Delta and the Senegal Delta.

WHERE DO OUR MIGRANTS SPEND THEWINTER IN AFRICA?Very few European migrants winter in theSahara or in the tropical rainforests. Forthe Sahara this is what one would expectgiven the lack of food and cover. Forests,however, are teeming with birds, over-whelmingly of local origin. Perhaps this isthe main reason why northern migrantsare so rare here. The Collared Flycatcher isone of the few Paleartic species which isnot deterred by competition and whichcoexists with the many African flycatcherspecies.

Most trans-Saharan migrants do not migrate beyond the transient zone be-tween the desert and the Equatorial rain-forest. This zone of arid and woodedsavannas holds several very large wetlands.During the northern winter, birdlife inthese marshes, as well as in the savanna, isdominated by migrants from Eurasia.Among the waterbirds, the numbers oflocal species (Whistling and Comb Duck)pale into insignificance beside the hugenumbers of migrants (Garganey, Pintail,Shoveler). The same is true for the waders

where the local Egyptian Plovers and Pain-ted Snipes are pin-pricks amidst the flocksof Ruff and Little Stint. Similarly, the northern Sahel forests contain few Africanbirds, but all the more European birds (likeIberian Chiffchaff, Olivaceous, Bonelli’sand Subalpine Warblers).

During the northern winter, Africanbird species remain in, or move to, habitatswith a relatively stable flood supply, whereas the European migrants flood theareas largely vacated by African species.The latter areas vary considerably in theirfood supply, both within and betweenyears. Rainfall in the savannas falls in thefew months prior to the arrival of Eurasianmigrant. The amount of rainfall varies considerably from one year to the next, thevery reason why migrants wintering in theSahel face highly variable feeding condi-tions. Variations in rainfall have far-rea-ching consequences for ‘our’ birds inAfrica, as will be shown.

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The dry savannas south of the Sahara are dotted with several large wetlands, such as the Inner NigerDelta. When rainfall is abundant, the area of the Inner Niger Delta flooded during the northern winter may be as large as Belgium or The Netherlands.

From Sahara to rainforest only takes a (long) day’s journey from north to south, during which the traveller witnessesa gradual change of landscape from dry, ochre and bare into wet, green and lush.

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RAINFALL

Rain is a rare commodity in the Sahara(north of 15-20°N), but 1000 km to thesouth the annual rainfall amounts to1000-3000 mm (Fig. 1). Between both ex-tremes the rainfall gradually increasesfrom north to south, and the landscapechanges accordingly. The arid landscapeof the Sahara turns gradually into forest,via dry and treeless savanna, wooded sa-vanna and parkland. This zoning occursalong the entire southern edge of the Sa-hara, from the Atlantic Ocean to the RedSea, a continent-wide swath of 5500 km.

The Sahel is usually defined as the zonewhere the annual rainfall is at least 100mm and not more than 700 mm. The rainyseason in the northern Sahel is restricted toJuly-September. In the southern Sahel therains start a month earlier and end a month

later. In most years, the Sahel is devoid ofrain from October to May. For the migra-tory birds arriving in August and Septem-ber, the green, grassy plains gradually turninto dust-covered, bare soil, wetlands be-come drylands and most trees shed theirleaves. From the initially huge numbers ofinsects, either small (midges) or large (locusts), fewer and fewer remain. The pro-blem faced by trans-Saharan migrants is nothow to recuperate from the post-breedingmigration hazards, but how to stay alive inthe following months and - especially - howto find sufficient high-nutrition food tobuild up body reserves, necessary for theflight back home across the Sahara and Mediterranean Sea.

Rainfall is unpredictable in the Sahel, sometimes limited to a few cloudbursts inthe rainy season. Local variations in theamount of rainfall are enormous. Neverthe-less, taking all data from the many rainfall

Changes in the Sahel

1 – 2525 – 5050 – 100

100 – 200200 – 300300 – 400400 – 500500 – 600600 – 700700 – 800800 – 1000

1000 – 12001200 – 14001400 – 16001600 – 18001800 – 20002000 – 25002500 – 3000

annual rainfall (mm)

Fig. 1. The north of Africa is extremely dry and this holds - to a lesser degree - for the east and southwest. Central Africa, on the other hand, is extremely wet. South of the Sahara the transition from dry to wet south isamazing in its rapidity, with a doubling of rainfall for every 160 km southward.

Sahel

stations into account, some years and periods clearly stand out across the entireSahel. 1984, for instance, was catastrophi-cally dry, whilst the 1950s were typified byhigh rainfall. Long series of meteorologicaldata collected all over the Sahel are neededto elucidate the rainfall pattern for the entire region. The distribution and numberof raining stations allow such an analysisfrom 1900 onwards (Fig. 2). These dataallow two conclusions to be drawn.

First, there is, on average, a gradual decline of rainfall throughout the 20th

century. Over a longer period, the trend is

even more pronounced because the 19th

century must have been, according to historical sources, rather wet.

Secondly, periods with high rainfall(around 1925 and 1955) are alternatedwith dry periods (around 1910, 1940,1970). This cycle would predict high rainfall around 1985, but - in contrast - therain steadily declined (or remained at a lowebb) throughout the 1960s, 1970s, 1980sand early 1990s, only to partly recoversince then.

When the rainfall in the Sahel startedto decline in the 1970s and 1980s, the ge-neral opinion was that the people in theSahel were to blame. Deforestation, increa-sing livestock numbers and extension offarmland led to erosion and desertification,

to such an extent that climate changeseemed inevitable. Later research disco-vered, however, that the cause of the pre-sumed regime shift must be sought beyondthe Sahel, at least for a large part. Rainfallin the Sahel appears to depend on the seasurface temperate of the oceans: the Sahelis dry when the oceans in the tropics arerelative cool and those in the subtropics re-latively warm. If and how global warmingis going to affect the Sahel is still uncer-tain. The most likely scenario predicts afurther decline in rainfall by 10-20%, andpossibly even by 40%. Between 1980 and

2005, the average temperature in the Sahelhas increased by l °C, and current predic-tions allow for another increase by 2-7 °Cin the next 80 years. This would prove tobe disastrous in a part of the world alreadyhot as it is.

RIVERS AND WETLANDSA large part of rain in the northern tropicsis drained off by rivers running throughthe Sahel, i.e. the Senegal and Niger Riverin West Afica and the Blue and White Nilein East Africa. The Chari and Logone Riverin the central part of West Africa emptyinto Lake Chad. These rivers feed the largefloodplains and other wetlands in the semi-arid Sahel. The annual discharge of the ri-vers varies considerably. This is not caused

8

10

annu

al ra

infa

ll an

omal

y (%

)

1900 2000

–40

–30

–20

0

20

1920 1940 1960 1980

–10

30

40

Fig. 2. The annual rainfall in the Sahel(bars), given as percentdeviation from the aver-age of the 20th century.The line shows the run-ning mean calculatedover an interval of 9years (4 year before - 4 years after the yearconcerned).

by variations in rainfall in the Sahel proper(being too low to have an impact on theriver flow), but is closely correlated withthe rainfall further south.

The Senegal, Niger, Chari, Logone andNile lose a lot of water during their passageacross the Sahel, due to evaporation andseepage. Especially in dry Sahel years, therivers lose a large part of their flow. After aseries of dry years the ground water tablerecedes and the rivers consequently loseeven more water. River flows in the Saheltherefore not only depend on rainfall inthe preceding months, but, to a large extent, to rainfall in earlier seasons. Forexample, in the Upper Senegal the rainfalldeclined by 29% between 1950 and 1985,from 1550 to 1100 mm, but the annualpeak flow of the river in September declined by 60%, from 4500 to 1800 m3/s.

Most Sahel rivers had a natural flowuntil about 1980, but this state haschanged dramatically since then. Due tothe construction of the Manantali dam inthe Upper Senegal River, a huge reservoirof 11 km3 came into being. During therainy period a large part of the inflow isstored in the lake to be gradually releasedin the dry months. In this way electricitycan be produced and irrigation of farmland

is possible during the dry period. The Selin-gue dam has a similar impact on the UpperNiger River as the Manantali on the Sene-gal, although less dramatic. In North Nige-ria and Cameroon dams have also affectedthe river flow, with dire consequencesdownstream for the seasonal floodplainsand marshes.

By combining the daily flow of the rivers in the Sahel with satellite images, itwas possible to reconstruct the annual surface area of the floodplains and subse-quently compare this with changes in birdpopulations. Migratory birds concentratedin the floodplains (Night Heron, PurpleHeron) show a clear relationship betweenflood extent and population change. How-ever, population changes in bird speciesfound in the savanna (White Sork) orwooded savanna (Wryneck) correlated better with variations in annual rainfall inthe Sahel.

LONG-TERM CHANGESPeople The key factor of change in the Sahelis the growth of the human populationwith 3% per year, causing a doubling of thepopulation per 28 years. Around 1950,only 20 million people lived in the eightcountries of the western Sahel (Chad,

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Rainfall south of the Sahel converts tiny streams temporarily into wide rivers. After the rainy seasonhas passed, the water level in Sahelian rivers and floodplains gradually declines again; in the NigerRiver near Mopti, for instance, between September (left) and February (right) by 3-5 cm daily.

Niger, Mali, Burkina Faso, Mauritania, Senegal, The Gambia, and Guinea-Bissau),contrasting with the 60 million at the startof the 21st century and an expected 130million in 2030. The claim on the land in-creased proportionally. The average densityis still low with 11 people per km2 (forcomparison: in 2009, this is 398/km2 inThe Netherlands), since the combined sur-face area of the just mentioned eight coun-tries is 5.3 million km2. However, even alow density of people can have a large im-pact on the environment. Moreover, thereare large regional differences in the popu-lation density. Very few people live in thedry northern Sahel, but further south thedensity may increase to 200 inhabitantsper km2. River valleys and wetlands areespecially crowded. Unfortunately, wet-lands are also favoured by huge numbersof birds, and any change in land use maythen have a large impact on migratory birdspecies.

Agriculture Only 1.6% of the total surfacearea of the eight western Sahel countrieswas cultivated by farmers in 1962, butforty years later this had increased to 4.1%.Farmers use no, or hardly any, fertilizers,but instead use fallow to improve soil fer-

tility. The fraction of land laid fallow hasshown a decline in past decades, however.Bird density and diversity on fallow landare higher compared with cultivated land.The declining acreage of fallow land musthave negative consequences for migratorybirds, but only few data are available toback up this statement.

During the Great Drought, farmersalong the rivers started to use pumps to irrigate their land. Besides, large irrigationschemes have been constructed along theSenegal and Niger River, and also in Northern Nigeria and Cameroon. Wet ricefields attract many birds, but it is usuallythe common species that profit, such asYellow Wagtails and Cattle Egrets. Scarceand rare species are concentrated in thefloodplains and largely absent from irriga-ted fields. The latter therefore cannot beregarded as a substitute for floodplains lostto irrigation schemes.

Cattle breeding According to the FAO, Africanumbers more than 700 million cows,goats and sheep. Livestock are absent inthe desert, and rare in high-rainfall areasalong the equator, the latter giving rise tothe designation of Green Desert. The pre-sence of tse-tse flies has prevented the in-

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Millions of people struggle for life in the Sahel. The question is how to sustain a decent living withoutfurther degrading the habitat

troduction of livestock in areas with fre-quent rains. Consequently, 60% of all Afri-can livestock is to be found in the Sahel.

Cattle breeders in the Sahel move longdistances with their herds. They migrate tothe north in the early rainy season andmove back as the temporary food supplyon the grass plains whithers or becomesdepleted. Since livestock have to drink re-gularly, the grazing grounds do not extendbeyond a distance of 15 km from rivers,lakes and (temporary) pools. This used tolimit the radius of action. After thousandsof wells had been constructed, many newgrazing grounds came within grazinggrasp. At present, an estimated 30% of theSahel is being subjected to grazing withlivestock.

The 400 million cows, goats and sheepin the Sahel remove the vegetation whichused to be the food for huge numbers ofantelopes, gazelles and other wild animals.Travelogues of the first Europeans visitingthe area indeed refer to large flocks of wildanimals. These original inhabitants of thegrassy plains have virtually disappearedfrom the western Sahel, but not (yet) fromthe eastern Sahel (Chad, Central AfricanRepublic and Sudan). Especially SouthSudan still harbours a suite of wild herbi-vores. The difference between west andeast is most likely due to the human popu-lation, being higher in the western than inthe eastern Sahel.

The Great Drought in the 1970s and1980s greatly diminished the number oflivestock, but numbers have recoveredsince then. At the start of the 21st century,the Sahel counted twice as many cows andthree times as many sheep and goats as 40years earlier. Without grazing the Sahelwould look completely different. Not onlywould there have been many more indige-nous trees and shrubs, but also huge seedand fruit stocks from grasses and shrubs.The increased grazing pressure effectivelyreduces the availability of seeds and fruit,with negative consequences for specieslike European Turtle Dove and CommonWhitethroat. Other species may have profi-ted from the increase in livestock, for in-

stance birds following the herds (CattleEgret, Yellow Wagtail). This may be alsotrue for species depending on locusts andgrasshoppers. The present grazing pressureresults in a more open landscape withfewer trees and shrubs, providing, for themoment, excellent feeding and breedinggrounds for local grasshoppers. The latterform a reliable food resource for manyacridivorous bird species. However, notorious locust-eaters, such as Lesser Kestrel and Montagu’s Harrier, do not appear to have increased in numbers.

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It is hard to imagine how the Sahel would looklike without human action. Although the humanpopulation density is low, large areas are grazed

annually or burned in the dry season.

Forest The people living in the Sahel needwood to cook their meal. Each day, children and women collect dead wood orcut off branches from the trees near thevillages. City dwellers often use charcoal,which is transported from afar. The increa-sed need of fuel led to an ever expandingimpact on trees away from human habita-tion. Moreover, many acacias died in thenorthern Sahel during the Great Drought.Further to the south, forests were successi-vely depleted and trees in agriculturalfields were removed, resulting in a moreopen, park-like or bare landscape. The de-forestation in the Sahel is clearly evident

from comparisons between high-resolutionsatellite images and detailed aerial photo-graphs taken dozens of years ago.

Nowadays, there is much afforestationgoing on, mainly with Neem (an exoticfrom Burma) in the villages and towns, Pro-sopis (an exotic from Chile, to prevent sand-drifts), and Eucalyptus (an exotic fromAustralia). These tree species are not attrac-tive to European migrants, as their foliageand bark harbour few insects. These newforests offer the migrants no solace fromthe loss of indigenous forests.

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In the long run, livestock grazing prevents afforestation, but it also has a direct impact on the vegeta-tion cover, and thus on the food supply of birds feeding on the ground. The photo shows at the rightside an area where, because of an experiment, livestock has been excluded.

Pictures of the same savanna in Senegal in 1984 and 1993 show the clearing of acacias; the trees still present have lost many branches due to cutting.

Bird captures In Mali and Senegal lead shotcosts 46 euro cent, too expensive for hun-ters to shoot small birds. Shooting is there-fore targeted at large species living inflocks, such as Glossy Ibis. However, mostbirds ending up in the cooking pot are notshot, but captured. We estimate that people in the Inner Niger Delta capture upto 70,000 Garganey annually, using stan-ding nets at night, and still larger numbersof Ruff. Especially in dry years this methodof capturing birds is lucrative.

Another method of getting hold of free-flying protein in the Sahel, as well aselsewhere in Africa, involves the use ofsnares. The numbers thus captured mustbe large, but we have no indication of howlarge. Barn Swallows are captured on their

nocturnal roosts with umbrella-like devices tipped with glue, and during thedaytime ‘fished’ from the air with a flyingtermite attached to a thin thread with ahook. In this way, millions of Barn Swallows are captured each year in SE Nigeria, SW Cameroon and the CentralAfrican Republic.

The numbers of captured birds has in-creased over the years, not only becausethere are more people, but also becausenylon nets, not available before 1960, arenow widely used. The opportunities totrade captured birds have also improved,either by storing them (ice) or by fast trans-portation to the market (improved roadsystem).

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Garganey in the Inner Niger Delta are easy to capture in the weeks prior to the return migration, when mostfloodplains have dried out and the birds are concentratedin the few remaining wet areas.

Fish capture The handful of extensive flood-plains and marshes in the Sahel attractmany water birds. The floodplains becomeflooded between August and December,and gradually dry up thereafter. Hundredsof thousands of fishermen capitalise onthis seasonal regime and capture the drif-ting fish with temporary dams, fykes andnets. Fishing nowadays is so effective andmassive that - although it may seem unlikely - nearly all available fish is removed. As a consequence, the averagelife expectancy of fish does not exceed halfa year anymore.

In 1960, the fishermen in the InnerNiger Delta used nets with a mesh width of50 mm, compared with 33-41 mm in 1985.

At present, fishermen started using plasticnets with a mesh width of only 10 mm.The fish have adapted to this predationpressure by reproducing at a much earlierage. Big fish of 50 cm and more have become scarce in the course of the pastyears. Although the fishermen nowadaysemploy more nets, the daily capture perfisherman has declined over the years. Forfish-eating birds, this overexploitation hasnot yet harmful consequences, since thedecrease in average fish size meant a boostin food supply. Nevertheless, the increasedfishing still has a direct negative impact onthe birds, because many thousands perisheach year in fykes and due to hooklines.

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The time has gone that NilePerches of 1.5 m were captu-red in the Inner Niger Delta.The fish do not have the timeto grow that old. For fish-ea-ting birds (here Spotted Reds-hanks and Little Egrets) foodsupply has increased as smallfish abounds. The dark side ofthis trend is that many birdsare killed by hooklines.

THE DECLINE OF WETLANDSSenegal Delta The Senegal Delta has a uni-que ecosystem because sea water can enterthe floodplains, hence the gradient frommarine to fresh. In the past an area of3400 km2 was inundated in wet years, butin the course of the years the Senegal Deltahas been embanked. The floodplains wereturned into irrigated farmland, mainly ricefields; other floodplains were inadvertedlytransformed into salt plains. Before theconstruction of dams, the water level varied by 3.5 m during the course of theseason. After the construction of the Manantali dam in the upper river and theDiama dam in the river mouth, the varia-tion in water level was reduced to 0.5 m.Not much is left of the floodplains in theSenegal Delta. Permanent water bodieshave become overgrown with dense vegeta-tion, to the chagrin of people and to thedetriment of wildlife: extensive cattailstands or dense floating mats of exotic, in-vasive plant species (Water Lettuce, Kariba

Weed) now cover huge areas of open water.No wetland in West Africa has changed tothe extent as the Senegal Delta. From thehundreds of thousands of Ruff counted inthe 1970s, no more than 30,000 remainedafter 2000. At the same time Black-tailedGodwits declined from 20,000 to about3000. In contrast, dabbling ducks stand outwith up to 20,000 Shovelers, 100,000whistling ducks, 150,000 Pintails and200,000 Garganey.

Some of the ecological disasters associa-ted with the loss of the floodplains wereoffset by the creation of National Parks.The Djoudj was appointed as National Parkin 1971, the Diawling in 1991 (each 160km2). These parks are not, fortunately,‘paper parks’, for without enforced protec-tion, the breeding colonies of Long-tailedCormorants, White Pelicans, herons andegrets would have disappeared. Both sitesare now important wetlands for migratorybird species.

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Black-tailed Godwits and Ruff have all but disappeared from the Senegal Delta, but other waterbirdswere able to persevere, despite the large changes following the embankment of the floodplains.

Inner Niger Delta The Inner Niger Delta inMali is huge. On topographical maps fromthe 1960s, a total surface of 36,000 km2 isdesignated as floodplain. When the waterlevel starts to rise in July in the southwes-tern part of the Delta, the plains in thenortheast are still dry. By the time that thenorthern plains become flooded twomonths later, the water level is already de-clining in the south. The area covered bywater at any one time amounts to 25,000km2. Such a large flood extent is only pos-sible when the combined inflow of Nigerand Bani, the major tributary, exceeds 55km3 in the rainy season. In most years, theinflow is smaller. During the disastrousdrought in 1984, the inflow was only 15km3, and the flood extent did not exceed5500 km2.

The Inner Niger Delta not only standsout because of its size, but also due to itshydrological dynamics. Between July andDecember the water rises by more than 6 m in wet years, to decline by the sameamount in the following months. In extre-mely dry years, however, the flood levelrises only by 3 m. For waterbirds the largeannual differences in flood extent are amatter of life and death. A high flood guarantees a multitude of pools and lakeswith shallow water throughout the nort-hern winter, at least up to the time of de-parture to the breeding grounds. Conver-sely, during a poor flood most water bodiesdry up long before March. Waterbirds arethen forced to concentrate along the edgeof the river and in the few permanentlakes connected to the river. Many birdsthen die from starvation or are easy prey to

the local people. In wet years the birds aremore thinly dispersed across the entiredelta, and the local people do not even attempt to catch them. The drier the InnerNiger Delta the fewer migrants survive thenorthern winter.

Large numbers of waterbirds have beencounted in the Inner Niger Delta, amongwhich 900,000 Garganey, 300,000 Pintails,25,000 Glossy Ibis, 9000 Gull-billed Ternsand 3500 Caspian Terns. For these species,this constitutes a substantial part of the entire population. The significance of thisarea for European migrants can hardly beoverestimated.

The Inner Niger Delta is for the largerpart covered by grasses adapted to large variations in water level. The local namefor these grasses, having stems up to 6 m,is bourgou. Birds feeding in these floatingmeadows may easily be missed during stan-dard waterbird counts; this is particularlytrue for small or unobtrusive bird species.Their numbers were estimated from 1617density counts in random plots (3 ha, onaverage) stratified according to habitat andwater depth. This resulted, for example, intotals of 315,000 Cattle Egrets and 960,000Yellow Wagtails for the entire Inner NigerDelta. Both totals are close to the numberscounted at nocturnal roosts. The densitycounts also suggest the presence of 50,000Purple Herons and 183,000 Squacco Herons. These are, compared with the European breeding population, huge numbers. We have to conclude that manybirds wintering in the Inner Niger Deltamust originate from Asia.

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Compared with other wetlands in theSahel, capturing waterbirds is widespreadin the Inner Niger Delta. The main threatcomes, however, from outside. Large irrigation works and a water reservoir inthe Niger upstream of the Delta take somuch water that the floodplains are nowalready 7.5% smaller than in the natural situation. Since 2007 another dam in theBani River has been constructed; a seconddam in the Bani and a large dam in Guineaare under study. Were these dames constructed, the Inner Niger Delta is goingto lose another 15-20% of its floodplains.Another danger is a large dam downstreamof the Inner Delta; large areas will be per-manently flooded, opening the way to theinvasion of cattail (as in the Senegal Delta).

Lake Chad and surroundings From 1870 to1970 Lake Chad was very large, varying insize between 15,000 and 25,000 km2. Lakesize declined to 5000 - 10,000 km2 since1980. Between June and December thewater level increases, due to rainfall and tothe discharge of the Chari and Logone Ri-

vers, and declines thereafter due to evapo-ration. As a consequence, on average 2000km2 is deflooded annually. In dry years,evaporation is larger than the inflow,which results in a decline of the waterlevel. In wet years, it is the other wayaround. Although climate has been considered as the only culprit for the smaller Lake Chad (e.g. the movie An Inconvenient Truth), the main reason is waterloss due to irrigation along the Logone andChari Rivers.

Before 1973, Lake Chad was a large,shallow lake with 90% open water. The restwas covered with reed, cattail, papyrus andbourgou. The northern half dried up after1973 and became partly covered by Prosopis, an exotic tree species. The southern half covers 1500 km2 of openwater and 3500 km2 of seasonal flood-plains with a bourgou vegetation.

All in all, birdlife in Lake Chad musthave changed a lot, but hard data are lacking. We know that only few birds usethe open water and the dense vegetation ofcattail and papyrus, but also that the flood-plains attract many waterbirds during de-

18

During the flood the Inner Niger Delta is covered with floating grasses. During the deflooding, herons walk ona dense mat of floating stems, here on top of a water column of 1 m deep. The photo shows five Purple Herons,but the six Squacco Herons which we put up later, are still hidden in the vegetation.

flooding. Although Lake Chad was reducedin size, the floodplains increased in size,which spells good news for foraging birds.Aerial counts show that between 1999 and2007 400,000 to 700,000 Garganey werepresent, about the same as counted in the1980s. Unfortunately, the older countswere incomplete, so a decline (as found inPintail: 550,000 counted in the 1980s, butonly 50,000 to 200,000 twenty years later)is likely.

Lake Fitri, situated 300 km east of LakeChad, is a mini Lake Chad. Its surface areavaries between 400 and 1300 km2. Aerialcounts show that large numbers of water-birds can be present, among which100,000 whistling ducks.

Large floodplains are found 100 to 300km south of Lake Chad, along the Chariand Logone, of which Waza-Logone (8000km2) in Chad and northern Cameroon iswell studied. The water level varies seaso-nally with only 50 cm. Two complete birdcounts reveal its significance for local species (12,000 Black-headed Herons, 7200Black Herons, 1800 Marabou Storks and3600 Sacred Ibis), but also for migrants(23,000 Squacco Herons, 900 EurasianMarsh Harriers and 146,000 Ruff).

The Hadejia-Nguru floodplains are situa-ted west of Lake Chad in North Nigeria.The size of the inundated area varies annu-ally, depending on the river discharge, be-tween 300 and 3600 km2. There are 20dams upstream of the Hadejia-Nguru, ofwhich the two largest are operational since1972 and 1992. The floodplains have beenreduced by all these dams to 300-500 km2.A large part of the water withheld in thereservoirs during the wet season is re-leased in the dry months to follow. Conse-quently, a part of the floodplains remainscovered by water and has subsequentlybeen overgrown with cattail. The 11 birdcounts, performed between 1988 and1998, show that numbers are related to thesize of the floodplains: 300,000 waterbirdswere counted in wet years (145,000 Garge-ney and 60,000 Ruff), but only 50,000 indry years.

Sudd The Sudd is a floodplain along theWhite Nile in South Sudan. Much rain incentral East Africa drains to Lake Victoria.The discharge of the White Nile dependsmainly on the level of Lake Victoria. In thewet year of 1964 35,000 km2 of the Suddwas flooded. The flooded area gradually de-clined in the years thereafter to about10,000 km2 at the start of the 21st century.

The water level in the Sudd varies seaso-nally by only 50 cm, a big difference com-pared with the other Sahelian floodplains.A large part of the area is permanently co-vered by water and overgrown with densevegetations of reed, papyrus and cattail.Very little is known of the birds in theSudd. We expect few waterbirds in thedensely vegetated marshlands, apart fromrails and some reed warbler species. Onthe other hand, the area is very extensiveand access on foot or by boat is difficult.Moreover, human density is low. The largebird species have been counted three timesalong aerial transects between 1979 and1981. In this way 3% of the entire area(69,000 km2) was covered. After extrapola-tion, 5000 - 6500 Shoebill Storks and15,000 - 37,000 Black Crowned Craneswere estimated to occur in the Sudd, morethan anywhere else in Africa. High num-bers were also estimated for Goliath Herons and six stork species. Smaller birdspecies were not counted, so numbers andspecies of most migrants in the Sudd arestill in the dark. Similarly, no informationis available whether species compositionand numbers have changed in relation tothe size of the flooded area. At present, thecomplicated political situation prevents afull assessment of the ornithological signi-ficance of the Sudd.

19

20

SUMMARY The wetlands in the Sahel have graduallylost ground in the wake of a decline inrainfall. This process accelerated after1970, due to embankment of floodplainsand the construction of water reservoirsand irrigation works upriver. Regulation ofthe river discharge resulted in a decline offlood extent and an enlargement of the

area being permanently covered by water. This reduction of dynamics led to a changein the vegetation, being negative for water-birds. If the bird density counts in the Se-negal and Inner Niger Deltas wererepresentative for all Sahelian floodplains,the number of waterbirds in these areasmust have declined by 40% since 1960.

Which indications do we have that thechanges in the Sahel have repercussionson the birds which spend the northernwinter there? We have to distinguish between long-term changes, such as theimpact of habitat loss from deforesta-tion, and short-term variations due toannual fluctuations in rainfall or locustabundance.

WINTER MORTALITY IN DRY YEARSWe have several clues that fewer birds sur-vive the winter in the Sahel in dry years.• In dry years waterbirds are forced to

concentrate in fewer sites, which makesthem highly vulnerable to catching withstanding nets by the local people. In theInner Niger Delta very few Garganey areoffered for sale on the market in wetyears, but up to 70,000 are traded in dryyears. The same difference was found inPintail and Ruff.

• All bird species for which we analysedthe ring recoveries showed the same pat-tern: many recoveries in dry years, few inwet years. Since rings reported from theSahel mainly refer to birds shot or captu-red, this indicates differential humanpredation (although not necessarily diffe-rential winter survival).

• That winter survival actually differs during dry and wet years in the Sahel isvisible in the return rate of birds on thebreeding grounds. From a ringed popula-tion of British Lesser Whitethroats, only4% of the adult birds returned after thedisastrously dry winter of 1984, against10-25% after wet years. Essentially thesame results were found for WhiteStorks, Sand Martins and Common Whi-tethroats, with lower return rates afterdry Sahel years.

The higher mortality in dry Sahel years ismainly driven by food shortage, a mecha-

nism also known from elsewhere in Africa.Barn Swallows in the Okavango Delta inBotswana, for example, have lower weightsin dry years (when insects are scarce) thanin wet years (insects abound), and theirmoult takes 1-2 months longer. Garganeyand Ruff are also known to suffer fromfood shortage in dry years. Garganey attempt to compensate by extending theirfeeding bouts into daytime, but to no avail;they are in such a poor condition duringextreme droughts that they can be approa-ched closely. Garganey and Ruff have toincrease their body weight by 40% to beable to fly back to Europe, but duringdroughts they lose weight instead and aredoomed to die in their wintering quarters.

THE IMPACT OF SAHEL CONDITIONS ONRETURN MIGRATION AND BREEDINGPERFORMANCE The birds returning from Africa to theirnorthern breeding areas have to fly manythousands of km. They need extra body reserves to fuel their intercontinentalflight and therefore start fattening 1-2months before their planned departure.Whimbrels on the Banc d’Arguin (Maurita-nia), for example, increase their daily foodintake in the pre-migratory period by 40%compared with their consumption in themonths before.

The birds wintering in the Sahel do thesame, but they have to fatten up in a desic-cated landscape where not a drop of rainhas fallen in the past six months andwhere food resources have dwindled. Put-ting on weight is particularly difficult indry Sahel years. The chances are that theydepart with insufficient fuel reserves tosuccessfully navigate the Sahara, resultingin high mortality. This is borne out by thering recoveries from the Sahara. Conside-ring the slim chance of reporting a ringed

21

Population trends in Sahel migrants

bird from the Sahara (de facto an emptyquarter), and the short time it takes tocross the desert (a few days at most), thecomparatively high reporting rate in theSahara in spring, set against the reportingrate in the Sahel, came as a surprise. In theEURING database, for instance, only tworecoveries of Common Redstarts camefrom the Sahel, the wintering area wherethey spend six months each year, but 99were reported from the Sahara, nearly allfrom April. The same dichotomy was foundin Spotted Flycatchers and several warblerspecies. Many more recoveries were repor-ted in spring than in autumn, despite thefact that the number of migrants in autumn is at least twice as high as inspring (with a higher proportion of young,inexperienced birds). The higher numberof spring recoveries is an indication thatcrossing the Sahara in spring is a moreexacting enterprise than in autumn.

An analysis of the recoveries further-more shows that the number of reportedbirds from the Sahara in spring is higherafter a dry year in the Sahel than after awet year. This was found in, for example,White Storks, Barn Swallows, Yellow Wag-tails, Reed Warblers, Common Chiffchaffs,Willow Warblers and Spotted Flycatchers.Apperently, even birds not wintering inthe Sahel are affected by droughts in thisregion, as visible in the Barn Swallow(which winters well south of the Sahel);this species refuels along the way and istherefore vulnerable when encounteringadverse conditions in the Sahel in dryyears.

These data show that many birds crossthe desert with insufficient body reservesafter having experienced dry conditions inthe wintering quarters. The alternativewould have been to extend the pre-migra-tory fattening period, and thus postponethe return flight to the breeding areas.Black-tailed Godwits indeed arrived later inPortugal after a dry year in their Africanwintering areas. Similarly, the arrival ofBarn Swallows in Spain during the last 60

years appeared to be positively relatedwith rainfall in the Sahel and to a lesser degree with spring temperature in Spain.

During the last dozens of years manyEuropean long-distance migrants started to return earlier on the breeding grounds.Many researchers have related this trend toclimate change. That may be true, but ignores the obvious relationship betweenrainfall in the Sahel and arrival date in Europe: birds return earlier after a wetyear in the Sahel. Since rainfall in theSahel shows some increase between 1985and 2005 (especially after 1990), the ad-vanced arrival in past years may partly beattributed to the conditions in the Sahel.The impact of climate change on the arri-val of long-distance migrants on the bree-ding grounds is presumably smaller thansuggested so far and needs to be studiedover more years.

The circumstances in the Sahel alsohave an impact on the breeding perfor-mances of long-distance migrants. WhiteStorks are known to skip or delay breedingafter a dry Sahel year, although the repro-ductive output of those that do breed is similar to that after a wet year. BritishSedge Warblers and Lesser Whitethroatshave a lower fledging success after drySahel years. The difference with the bree-ding performance after wet years was notlarge, though, and was not found in otherlong-distance migrants. That is hardly sur-prising. Even if birds arrive in a good con-dition after a wet Sahel year, they may stillhave to face a cool and wet summer. Onthe other hand, birds arriving late and inpoor condition may encounter favorablefeeding conditions in their breeding areaand thus may recuperate fast and have ahigh reproductive output.

POPULATION DECLINES AFTER DRYSAHEL YEARSIf mortality in long-distance migrants du-ring winter and spring migration dependson the circumstances in the winteringarea, annual fluctuations rainfall and flood

22

extent in the Sahel should be reflected inthe breeding population, either directly orwith a delay. Indeed, after the dry Sahelwinter of 1990/1991 Common White-throats declined across Europe, on averageby 18.5%. The winter of 1994/95 was wetand the population increased in much ofEurope, on average by 17%; Sedge Warblerseven increased with 40%.

Winter mortality of long-distance mi-grants depends on rainfall in the winteringareas, but also on population size. In 1968,when rainfall in the Sahel dipped after aseries of very wet years, Common White-

throat numbers crashed. In the much drieryears in the 1970s and 1980s, Whitethro-ats showed smaller declines. The explana-tion must be that the population hadalready declined to very low numbers in1969, lessening the competition with con-geners when conditions further deteriora-ted. Winter mortality therefore relates torainfall (and its correlates), but is also den-sity-dependent.

A nice example of density-dependenceis provided by Black-crowned Night Heronsbreeding in the Camargue, where the num-ber of nests since 1967 varied between 230and 940 (see Fig. 3). The numerical fluctua-tions closely follow the extent of the flood-plains in the Inner Niger Delta (where

many winter); for each extra 100 km2 offloodplain, 3.6 nests of Night Herons wereadded to the local population. Populationgrowth was largest after wet Sahel years(up to 50%) and when numbers were smallto begin with (little competition). Declineswere noticed after dry years, especiallywhen the breeding population was large(much competition). The same combinedimpact of winter drought (measured byrainfall, rather than flood extent as used inBlack-crowned Night Herons) and popula-tion size was found in the Sand Martin (Fig.4).

Populations of various other wetlandbirds, such as Purple Heron and Sedge War-bler, have increased since 1995 - just as theNight Heron - when floodplains recoveredfrom drought-related reductions in the1970s and 1980s. The presumed increaseof bird exploitation in Africa and habitatdegradation on the breeding grounds, haveapparently - generally speaking - a muchsmaller impact on these species.

CONTINUOUS DECLINEThe vicissitudes of wetland-inhabitinglong-distance migrants depend largely onthe meteorological and hydrological condi-tions in their wintering area. If correctedfor that, the apparent long-term decline in

23

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Senegal DeltaInner Niger DeltaCamargue, France

400

Fig. 3. Number ofbreeding pairs ofthe Black-crownedNight Heron in theCamargue (left-hand axis), compa-red with themaximum flood ex-tent in the SenegalDelta and InnerNiger Delta in thepreceding winter(right-hand axis).

these species disappears. This is very different in migrants wintering in savannaand wooded savanna: the decline remains,independent of rainfall.

The Wryneck declined with 75% be-tween 1965 and 1990 across Europe. The-reafter, the population remained stable,albeit at a low level. The decline was steep-est during the drier Sahel years. Small re-coveries have been noted in the few yearswith an above-average rainfall in the Sahel,but such small upsurges were insufficientto prevent a collapse of the population.

An even longer time series is availablefor the Common Redstart. Since 1911 nest-box occupation has been monitored in TheNetherlands. Initially, the Redstart was,after the Great Tit, the most common birdspecies, occupying 30% of the boxes. During the 20th century this has graduallydecreased to less than 1% since 1970. Concomitant changes in the breeding habi-tat may also have played a role, but similartrends were found in farmland, orchards,gardens and forests elsewhere in The Netherlands, Switzerland and Germany.Based on ten long time series from Westand Central Europe, the Redstart is suppo-sed to have declined by 95% between 1940and 2000 (Fig. 5). The average declineamounted to 4.7% per year, being largest indry Sahel years but also evident during wetSahel years. This shows that, beside Sahel

rainfall, other factor(s) may be involved.The Common Redstart in the Sahel is a

bird of open savanna woodland. We frequently recorded the species in the Acacia forests in the Sahel. Redstarts musthave lost a considerable part of their win-ter habitat due to deforestation. If so, wewould expect the same trends in Olivace-ous, Bonelli’s and Subalpine Warbler, species occupying the same habitat in theSahel. Bonelli’s Warbler indeed show a de-cline, but trend data for the other speciesare lacking or of insufficient length. Red-starts clearly illustrate the point that longtime series in monitoring schemes are ofvital importance to understand long-termfluctuations in population size: the longer,the more reliable. Although Redstart num-bers have been largely stable, or slightlyincreasing, during the last 20 years, thepresent population level is still ten timeslower than 30-40 years before.

ARE NUMBERS OF LONG-DISTANCE MI-GRANTS GOVERNED BY CONDITIONS INTHE BREEDING OR IN THE WINTERINGAREAS?If numbers of long-distance migrants fluc-tuate in synchrony with Sahel rainfall, thechances are pretty good that populationsize is determined in the wintering area.But what to think of steady declines partly

24

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Schleswig-Holstein, Germany

Fig. 4. Numbers ofbreeding pairs ofSand Martins inSchleswig-Holstein(northern Germany)and The Netherlandsshowed wide fluctua-tions (left-hand axis.The trends are highlysynchronised and arerelated to rainfall inthe Sahel in the prece-ding winter (bluebars; right-handaxis).

or wholly irrespective of rainfall in theSahel? Are then conditions in Africa still atthe core of the observed trend direction, asplausible for Redstart (deforestation), orare problems on the breeding grounds toblame? This question is relevant because somany long-distance migrants are in ram-pant, and continuous, decline in the pastdecades. This surely hints at a common denominator in Africa.

One of these species is the Back-tailedGodwit. More Godwits are shot in Africaduring dry winters, but this has no impacton the population trend in NW Europe.Much more important is the intensificationof farming in Europe: very few Godwits areable to produce fledglings in the intensi-vely managed grasslands of Western Eu-rope, where the majority of the nominaterace breeds. It is saying a lot that 30% ofthe ringed Dutch Black-tailed Godwits recovered in Africa in the 1950s and 1960swere in their first year of life, against not aone since 1990. This explains why Black-tailed Godwit numbers in Senegal and Gui-nea-Bissau (where the NW European birdsspend the winter) have declined by 80%,whilst the birds in the Inner Niger Delta(where East-European birds winter, a popu-lation much less subjected to changes infarmland) remained largely stable.

Of the European species wintering in

the Sahel and adjacent vegetation zones,the Black-tailed Godwit may be an excep-tion in that conditions on the breedinggrounds have an overriding impact ontrends. A comparison of trends in long-distance migrants depending more or lesson the Sahel reveals that the Sahel has become a trouble zone. Of the 73 specieswintering in the Sahel, 49 (67%) show aconsistent decline. Migrants winteringfurther south fare better: only 9 of the 25species showed decline in 1970-2005 (36%).The same pattern is found within species.In Swedish Chiffchaffs, the subspecies win-tering in the Sahel shows a large decline,but the subspecies wintering in South Europe and North Africa is doing fine. Although the available studies are still ina-dequate to pinpoint the relative impor-tance of changes on the breeding andwintering grounds, and in between, onbird numbers, the overwhelmingly poorperformance of long-distance migrants is atelling story. More than one factor may beinvolved, but Africa (notably the Sahel)most likely plays a key role.

Of the bird species wintering in Africathere was a decline in 70% of the birdsbreeding in western Europe, but only in20% of eastern European birds (Fig. 6). Ob-viously, this may be attributed to the largechange in the landscape in West Europe

25

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iss,

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y an

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ethe

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annual decline4.7%

Fig. 5. Common Redstart trend in 10study areas ( forests, parks and or-chards) in Switzerland, Germany andThe Netherlands. The average in 1940is set at 100, the other years are in-dexed relative to 1940. The black lineshows the average decline as runningmean, averaged over 9 years. Theaverage annual decline amounts to4.7% (red line). The decline can be com-pared with the rainfall in the Sahel(blue bars; right-hand axis). The de-cline was steeper after a dry Sahelwinter, and less so after a wet Sahelyear. NB: population size on the left-hand axis is presented on a loga-rithmic scale.

compared to the (still) small changes inEast Europe. But that is not the entirestory. The majority of the birds from eas-tern Europe spend the winter in the eas-tern Sahel (and southward to South-Africa),and most birds from West Europe in thewestern Sahel (Fig. 7). The western Sahel is

more densely populated and the landscapehas also changed more. This is likely amajor, additional explanation why long-dis-tance migrants from West Europe are moreoften in decline than their congeners fromeast Europe.

26

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Fig. 6. Many long-distance migrants wintering in Africa have declined between 1950 and 2007, but the proportion of long-dis-tance migrants in decline is smaller in East than in West Europe.Blue symbols refer to breeding populations in ten countries (ab-breviations; see map), red symbols to numbers captured in astandardised way during the spring or autumn migration ( figu-res; see map).

WHY SOME LONG-DISTANCE MIGRANTSSHOW AN INCREASENot all long-distance migrants wintering inAfrica are in decline. Six species show aclear increase, which can be accounted forby species-specific responses to the impactof man’s activities:• The upsurges in species like Little Egret,

Osprey, Eurasian Marsh Harrier and Mon-tagu’s Harrier are recoveries from deple-tion in the past (due to persecution anduse of pesticides), effectuated by legalprotection and bans on the use of organo-chlorines in farming. Moreover, thelower hunting pressure on White Storksand Ospreys in North Africa and SouthEurope improved the annual survivalrate.

• Although the Osprey is doing poorly inSahelian wetlands, this has no impact onthe population level since the large majo-rity winters along the West African coast.

• The European Spoonbill in NW Europehas increased from 150 to 2500 pairs inthe past 40 years. Wintering numbers inthe Senegal Delta remained stable, butthe number of birds wintering on the

Banc d’Arguin (Mauritania) boomed, andan increasing number of Spoonbills now-adays remains in SW Europe to winter.Other species, such as White Stork, Eura-sian Marsh Harrier and Little Egret, alsoincreasingly winter in Europe rather thanin Africa, profiting from warmer winters,new food supplies and better protection.

Hence, the increase of these six long-distance migrants is not related to circum-stances in the Sahel, but rather to changeselsewhere. A flexible migratory strategymay be profitable.

27

Fig. 7. Long-distance migrants from West Europe on average have a more westerly distribution in the Sahelthan those from East Europe; the extent of overlap various between species. This may be illustrated with reco-veries south the Sahara of Glossy Ibis (left; including some recoveries north of the Sahara) and the EurasianMarsh Harrier (right).

EFFECTIVE BIRD PROTECTION IN THESAHEL

Effective protection of migratory birdspecies demands safeguarding breedingand wintering areas, and - if necessary -also stopover sites used during migra-tion. But how to protect our migrants inAfrica? Certainly not by, as now occurswith our support, embanking flood-plains and constructing dams in rivers.Also, not by, again with western sup-port, planting non-indigenous tree species which are largely avoided by Palearctic migrants (which would, instead, profit from the restoration ofindigenous forests).

The construction of dams and dikes inthe Senegal River, made possible with wes-tern support, converted the floodplains inthe Senegal Delta into large rice polders.However, at the same time two large birdsanctuaries were delineated where protec-tion was (and is) enforced. These reservesharbour huge numbers of Palearctic migrants, beside large colonies of Africanwaterbirds. Although Black-tailed Godwitsand Ruff have nearly disappeared from theSenegal Delta, many other species are stillpresent in large numbers.

Another example of successful protec-tion refers to the Black-headed Heron inNorth Cameroon. This African speciesbreeds in colonies of some dozens up to150 nests, but in the village Andirni thelocal colony increased well beyond thatnumber; in 2001 even 2479 nests werecounted! This was possible through the ac-tive involvement of wardens of the nearbyWaza National Park living in this village.Their presence guaranteed an undisturbedbreeding site, something not to be foundin the wider surroundings, not even in the

Waza National Park itself. Protection isalso the key to success in two flood forestsin the Inner Niger Delta, where up to80,000 breeding pairs of 16 species (mainlyCattle Egret, egrets, Long-tailed Cormo-rants and other fish-eating species) arefound in the Dentaka Forest alone. Nowa-days, such sites are extremely rare in theSahel, and - apart from a telling figure ofthe biological richness of the area, - it is areminder of how few sites remain in theSahel for birds to settle and nest withoutdisturbance. These sites need constant vigi-lance in order to prevent the local popu-lace from exploiting the colonies toextinction. On the other hand, it showsthat if birds are offered protection, theyrespond immediately. Actual protection ofour migrants in Africa is thus possible.

EFFECTIVE PROTECTION OF LONG-DIS-TANCE MIGRANTS IN EUROPESuppose that the Black-crowned Night Her-ons in the Camargue, due to habitat ma-nagement, can exploit a larger number ofbreeding and feeding sites. Taking this op-portunity may not automatically lead to apopulation increase, since population sizein this species is mainly regulated by con-ditions on the African wintering grounds.For most long-distance migrants, the rela-tive impact of the winter period on popula-tion fluctuations is unknown. Notwith-standing this lack of knowledge, it is obvi-ous that effective protection of the bree-ding areas is necessary no matter what.The Black-tailed Godwit illustrates it all:despite huge efforts on the breedinggrounds and along the migratory pathway,both in manpower and in money, the de-cline continues unabated, and even accele-rates. Without a fundamental change infarming practices in NW Europe, the de-cline will continue.

28

Year-round protection of migratory bird species

Natura 2000 is an initiative of the Euro-pean Union to create a network of sites inorder to protect threatened habitats andspecies across Europe. It is not just paperwork, since EU Members are obliged totake nature protection seriously. In total194 (sub)species are protected by Natura2000, listed in Appendix I of the EuropeanBird's Directive. At least 50 of these winterin Africa south of the Sahara, of which 20in wetlands (i.e. Glossy Ibis, Osprey, GreatSnipe, Aquatic Warbler), 2 in forests (Euro-pean Honey Buzzard and Levant Sparrow-hawk), 20 in wooded savannas (e.g. BootedEagle, European Nightjar, Barred Warbler,Lesser Grey Shrike) and 8 in savannas (e.g.

Black Stork, Lesser Kestrel, Corn Crake,Tawny Pipit).

The success of Natura 2000 depends onthe selection of sites, and their subsequentmanagement. However, to safeguard popu-lations of long-distance migrants from de-clines, conservation of their breedinggrounds is in itself inadequate. These birdslive in multiple jeopardy, and protection oftheir wintering areas and stopover sites isjust as important. This will prove to be animportant challenge for future nature con-servationists: bird protection does not stopat the borders of Europe but extends wellinto Africa.

29

No matter how important the wintering area may be for the annual survival of birds, it is the breeding areawhere the offspring is raised. Without offspring, a population is doomed to extinction. A good example is theBlack-tailed Godwit breeding in farmland. Large-scale changes in the West European grasslands have dealt adeathblow to Black-tailed Godwits. The above pictures, taken in Fryslân (northern part of the Netherlands),show a productive grassland with many flowers (already a far echo from the grasslands in the early 20th cen-tury, but good Godwit habitat) and a monoculture of a single-species, highly productive grassland where birdsare almost completely absent and where successful breeding is anathema. The latter fields nowadays predomi-nate.

Many tens of thousands of Ruff are annually captured in Mali; on the market of Mopti they are sold for 17 euro cent apiece. In the few weeks before their departure to Europe, they are in high demand due to theirthick layer of fat. Since the captured birds have survived the rigours of winter, and thus belong potentially tothose standing a good chance of returning to the breeding grounds, and most of them are females, this humanpredation can have a serious impact on the population level.

What have Greenlandic Wheatears, Siberian Ruff, DutchBlack-tailed Godwits, Kazakh Squacco Herons and SpanishSubalpine Warblers in common? At first sight, not much. Ex-cept that they spend the winter in Africa. Of the 500 speciesbreeding in Europe, altogether 2 billion breeding pairs, aquarter cross the Sahara. These long-distance migrants farebadly compared with short-distance migrants and residents.Most species migrating to Africa show a – often catastrophic– decline, especially those wintering in the Sahel. Wherehave all the European Turtles Doves gone? What is going onsouth of the Sahara? Or are the changes in the breeding areato blame? This brochure summarises Living on the edge: Wet-lands and birds in a changing Sahel, a book which deals withthe vicissitudes of Eurasian birds wintering in the Sahel, setin a context of climate change and habitat degradation.

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