British Birds VOLUME 83 NUMBER 1 JANUARY 1990

Habitat of Slender-billed Curlews in Morocco

Amoud B. van den Berg

The Slender-billed Curlew Numenius tenuirostris is one of Europe's most endangered and least-known migratory birds. It breeds in central

Asian USSR, and is a long-distance migrant to Northwest Africa and perhaps also to Iran and Iraq. Less than a century ago, it was still abundant as a passage and wintering bird in southern Europe and northern Africa, but numbers are now believed to be very small.

To investigate the present status of this species in Morocco, the International Council for Bird Preservation (ICBP), in co-operation with the Dutch Working Group on International Wader and Waterfowl Research (WIWO), carried out a census along the Moroccan coastal wetlands during the winter of 1987/88. This survey resulted in regular sightings of Slender-billed Curlews at the Moulay-Bouselham lagoon, Merja Zerga, during December-February, when a maximum of four were seen together.* No Slender-billed Curlews were found at any of the other

*It is our considered view, and that of the experts whom we consulted, that publicity, rather than secrecy, will benefit this tiny, endangered population in its restricted Moroccan wintering area. We agree with the author of this paper that naming the locality in print will alert the Moroccan authorities to the importance of this vulnerable site. Ens

[Brit. Kith 83: 1-7,January 1990] 1

2 Slender-billed Curlews in Morocco

1. Slender-billed Curlew Numenius tenuirostris, Morocco, January 1988 (Arnoud B. van den Berg)

wetlands visited. During the survey, the behaviour and habitat preferences of the curlews were recorded, and these are summarised here.

Information on the identification of this species is given by various authors, including Smith (1963), Brosselin (1968), Marchant (1984), Porter (1984), Wijmenga & van Dijk (1985) and van den Berg (1988).

Geography, salinity and climate of Merja Zerga The lagoon at Moulay-Bouselham, better known as Merja Zerga, is situated on the Atlantic coast of Morocco (06°18'W, 34°53'N), and has only a single outlet to the sea (fig. 1). The coastline runs NNE-SSW; west and southwest winds prevail. It is the largest lagoon in Morocco, with an area of about 35 km . The northward extension of the lagoon, Merja Kahla, some 3 km2 in area, becomes dry at low tide.

The hydrology of the shallow lagoon is influenced by three elements: fresh water from Oued Drader and Canal de Nador (created in 1953 to drain Merja Daoura), tidal inflow from the Atlantic flooding the lagoon, and, to a lesser extent, ground-water. Annual rainfall is 700-750 mm, most of which occurs in autumn and winter. The average annual temperature is 18°C, but this varies considerably; daily averages range from 4-6°C for the coldest month, January, to 30-32°C in July (Beaubrun 1976). In summer, large areas of the lagoon become saline owing to evaporation and lack of rain; seawater floods the entire lagoon and flows upstream into the Oued Drader. In winter, fresh water displaces the seawater, and even the centre of the lagoon remains only slightly saline. These seasonal and tidal changes have a profound influence on the vegetation and benthic fauna, and, as a consequence of the shallow depth of water and the peculiar hydrological regime, a great biological diversity has developed, and large numbers of fish and birds are present at certain times of the year.

In some years, the mouth of the lagoon is blocked naturally by littoral drift, but it is re-opened periodically by the local villagers. Since 1938, the mouth of the lagoon has become blocked for periods of four to five years

Slender-billed Curlews in Morocco 3

and re-opened for a year or so. Between 1955 and 1976, the lagoon was kept open to the sea permanently (Beaubrun 1976). More recently, the situation has apparently changed frequently. In 1985, the mouth of the lagoon was open, whilst in December 1986 it was closed. In May 1987, the villagers again re-opened the connection to the sea (D. Koch in litt.).

When the outlet is closed, the local fields become flooded and the lagoon fills with fresh water to the detriment of the eel-fishing and mosquito control. During the survey, the lagoon's connection to the sea

Fig. 1. Map showing local topography and habitats around Merja Zerga, Morocco

4 Slender-billed Curlews in Morocco

was narrow and shallow, and tidal variations in the lagoon level appeared small. The meadows were flooded by rain-water, and even at the lagoon shoreline the surface water tasted only slightly brackish.

Occurrence of Slender-billed Curlews at Merja Zerga The winter of 1987/88 was the third in succession during which a few Slender-billed Curlews were recorded at Merja Zerga. In both previous winters, single records of four to five birds were reported, on 26th January 1986 (Brit. Birds 79: 287) and 16th-18th November 1986 (Nigel Redman in litt.). Those in November 1986 had been found in exactly the same place as those in January 1988, and in winter 1988/89 three individuals were present there again. A few earlier records indicate that this species may have been regularly present in recent decades in spite of the lagoon's ever-changing water-regime.

Habitat at Merja Zerga in 1987/88 On each day in 1987/88 that Slender-billed Curlews were seen, they were found either roosting at the mudflats or foraging at a muddy meadow grassland area on the eastern shore of the lagoon, south of the outflow of Oued Drader. The latter area is 1-2 km wide and runs along the shoreline for more than 4 km. It is situated between hilly agricultural fields in the east and the lagoon's mudflats in the west. A very narrow belt of mown sedges Juncus separates the meadows from the mudflats, while rather dense sedge vegetation borders the north and south sides of the meadow. Most of the meadows were wet, flooded with a few centimetres of fresh water. The soil was muddy, blackish and finely textured, the abundance of earthworms being indicated by numerous worm-casts.

The meadow was heavily over-grazed by cattle and horses. Thousands of Black-tailed Godwits Limosa limosa, hundreds of Golden Plovers Pluvialis apricarius, Grey Plovers P. squatarola, Lapwings Vanellus vanellus and Ruffs

2. Slender-billed Curlews Numenius tenuirostris, Morocco, January 1988 (Arnoud B. van den Berg)

Slender-billed Curlews in Morocco 5

3. Slender-billed Curlew Numenius tenuirostris, Morocco, January 1988 (Arnoud B. van den Berg)

Philomachus pugnax, and several Snipes Gallinago gallinago, Curlews N. arquata, Redshanks Tringa totanus and Greenshanks T. nebularia were present on these and similar meadows elsewhere alongside the lagoon. Apart from the eastern shore (about 3 km southwest of the road junction to Souk el Arba and Kenitra), areas with apparently similar extensive, wet, grazed meadow habitat were available, in the northwest (about 3 km east of Moulay-Bouselham) and in the southeast (about 8 km southwest of the road junction to Souk el Arba and Kenitra). Slender-billed Curlews were, however, never found in the latter two areas, nor in small patches of apparently suitable wet grassland within dense sedge vegetation which held numbers of other large waders.

Other habitat preferences It is not clear to what extent Slender-billed Curlews use other habitats. Those at Merja Zerga in 1987/88 seemed to prefer foraging in a freshwater habitat, but, on 20th December, two were found in a sticky, muddy, saltwort Salicomia habitat, where they had perhaps been foraging in brackish water, and, on 29th January, one was foraging in a recently ploughed field. Some records show that the species thrives in saline habitats (e.g. Smith 1963). Earlier reports of large numbers foraging in extremely saline sandy areas, such as the Lagune de Khnifiss, Tarfaya (Blondel & Blondel 1964), suggest that the Slender-billed Curlew shares some of the adaptive abilities of its larger congener, the Curlew.

This is confirmed by observations at Merja Zerga in January-March 1989, when the majority of records were from a small area of upland agricultural fields bordering the muddy meadows. The birds were usually present in fallow fields, but also in cultivated plots with short wheat, and often in groups of Curlews (Hildreth Cooper in lift.).

Threats to Slender-billed Curlews at Merja Zerga The dramatic decline in the population of Slender-billed Curlews is probably the result of a combination of factors in the breeding, migration

6 Slender-billed Curlews in Morocco

and wintering areas. There has been a general decrease in wetland, and a corresponding increase in hunting in countries such as Hungary and Italy. A number of factors can also be found in its main wintering area, northwestern Morocco, where in recent decades marshland has been reclaimed for agriculture (Thevenot 1989). The remaining wetlands, such as Merja Zerga, are not satisfactorily protected, and only small areas seem to have a suitable habitat for Slender-billed Curlews.

At present, Merja Zerga has the status of 'reserve biologique', which should preserve it from hunting, fishing and camping. There is, however, little enforcement of this, and in the winter of 1987/88 the Slender-billed Curlew and its habitat were threatened both by human pressure and by plans for changing the economic use of the area. In 1987/88 the feeding areas of the curlews were intensely grazed, and as a result large flocks of waders were often disturbed by herdsmen and other local people. The sedge vegetation border ing the meadow was frequently cut for the manufacture of matting, and parts of the meadows had freshly dug ditches for drainage or irrigation. Moreover, there is probably both illegal fishing and poaching. Thus , the economic situation of the villages surrounding Merja Zerga is such that many people depend on the natural resources of the lagoon, and any conservation programme for the area will have to involve improvements to the local economy.

Other disturbances at Merja Zerga result from forms of tourism. Even in winter, tourists are invited by local boatmen to go out on the lagoon to see Greater Flamingos Phoenicopterus ruber, the flamingos being purposely flushed to improve photographic opportunities. At the same time, many waders and other birds are disturbed by these actions. More seriously, a hunting agency 'Sochatour' appears to have rights to shoot birds in the immediate vicinity of Merja Zerga. During several days of the 1987/88 survey, French shooting parties were encountered in the northern part of the area, only a kilometre or so from the Slender-billed Curlews' roosting area. Areas where shooting had occurred were devoid of birds.

It is possible, too, that existing management plans for the development of this reserve may be detrimental to the Slender-billed Curlew. For

4. Slender-billed Curlew Numenius tenuirostris (left) with Black-tailed Godwit Limosa limosa, Morocco, January 1988 (Arnoud B. van den Berg)

Slender-billed Curlews in Morocco 7

instance, a reduction in the number of cattle grazing on the meadows might change the attractiveness of the area for large waders as a result of a decrease in nutrients and an increase in the growth of vegetation. Nor can current plans for tree-planting be regarded as favourable for the Slender-billed Curlews.

Conclusions The survey in 1987/88 showed that Merja Zerga's muddy overgrazed freshwater meadows, full of earthworms and bordered by vast brackish or saline mudflats, is a favoured habitat of the Slender-billed Curlew. In 1988/89, the species was regularly seen in fallow agricultural fields bordering the meadows. The area is probably a regular winter haunt of this vanishing species, for which appropriate protection and conservation measures need to be taken.

Acknowledgments Drs. C. A. Bosraan assisted with the whole of the survey, while R. Eve, G. Hibberd and M. Ribi made important contributions. Drs. W. Verheugt played an important role in establishing contacts between ICBP, WIWO and EF, and in the preparatory work, and M. Y. Alaoui, Dr P. Beaubrun, Dr G. C. Boere, A. Gretton, Rene Pop, Dr M. Rands, E. Smith and M. Thevenot assisted with logistic matters. H. Cooper, V. Dupont, Drs. N. Groen, H. Kachiche, D. Koch, R. Martins, N. Redman and D. Tanger helped in various ways with fieldwork.

References BEAUBRUN, P. C. 1976. La lagune de Moulay-Bou-Seelham, etude hydrologique et

sedimentologique. Bull. Inst. Sci. Rabat 1: 5-37. BI.ONDFX, J., & BI.ONDFX, C. 1964. Remarques sur l'hivernage des limicoles et autres oiseaux

aquatiques au Maroc (Janvier 1964). Alauda 32: 250-279. BROSSEI.TN, M. 1968. Observation d'un Courlis a bee grele Numenius tenuirostris en Vendee. Nos

Oiseaux 29: 274. MARCHANT, J. H. 1984. Identification of Slender-billed Curlew. Brit. Birds 77: 135-140. PORTER, R. 1984. Mystery photograph 96: Slender-billed Curlew. Brit. Birds 77: 581-586. SMITH, K. D. 1963. The identification of the Slender-billed Curlew. Brit. Birds 56: 294-295. THEVENOT, M. 1989. L'hivernage du Courlis a bee grele au Maroc Numenius tenuirostris

Vieillot. Alauda 57: 47-59. VAN DEN BERG, A. B. 1988. Identification of Slender-billed Curlew and its occurrence in the

winter of 1987-88. Dutch Birding 10: 45-53. WIJMENGA, E., & VAN DIJK, K. 1985. Slender-billed Curlew in Tunisia in February 1984. Dutch

Birding 7: 67-68.

Drs. Arnottd B. van den Berg, Duinlustparkweg 98, 2082 EG Santpoort-Ztdd, The Netherlands