|Title:||Waders and other waterbirds in the United Arab Emirates, autumn 1994 & spring 1995|
|Author(s):||Guido O. Keijl, Paul S. Ruiters, Tom M. van der Have, Abraham bij de Vaate, Eric C.L. Marteijn & Ruurd Noordhuis|
|PDF-download:||Waders and other waterbirds in the United Arab Emirates, autumn 1994 & spring 1995|
In autumn 1994 and spring 1995 several coastal wetlands in the United Arab Emirates were surveyed for waders and other waterbirds. In Khor Dubai, a shallow lagoon just east of the city of Dubai, holding high numbers of waders and other waterbirds, a more detailed wader study was carried out. The study focused on Broad-billed Sandpipers, as part of this species' migration route and wintering grounds are still unclear. The main aims of this project were:
Waders and other waterbirds were counted in 13 marine and one fresh water wetlands. Khor Dubai held most waterbirds, both in spring and in autumn. Waders always formed the dominant taxonomic group, except along the east coast, where gulls and terns were found in highest numbers. Khor Dubai was counted once every 3-7 days in order to be able to construct migration patterns. Peak migration of most species occurred during the last week of April and the first week of May.
Khor Dubai holds some hundreds of Flamingos, which migrate north to their Iranian and Russian breeding colonies. Numbers are however kept artificially high by feeding.
Broad-billed Sandpipers migrate through the UAE, mainly through Khor Dubai, in autumn and spring. In autumn 1986 about 4000 were counted in Khor Dubai, but before and after this year numbers exceeding 1000 individuals have never been seen again in this area any more.
The total number using the area is unknown, as information on turn-over rate is lacking. Broad-billed Sandpipers migrating through Khor Dubai probably spend the winter in Barr al Hikman, Oman, with c. 5000 individuals. It is not known where the majority of the Fenno-Scandian population winters, but the Arabian Gulf, including the Iranian coast, and Barr al Hikman and possibly West-Pakistan probably hosts the entire population.
Khor Dubai is an important breeding area for Kentish Plovers (150-200 pairs). The breeding birds and their offspring are being threatened by alterations of the area, disturbance by people and dogs, and by future building activities. Conservation measures for Khor Dubai and its breeding birds are proposed.
Densities of waders in Khor Dubai (number of birds per hectare) were much higher than elsewhere in the UAE. From the density counts the estimated number of waders present at one particular moment in coastal wetlands during mirgration was calculated for spring and autumn. A comparison is made between numbers and densities in the UAE and elsewhere.
For Grey Heron and Western Reef Egret, the heron species occurring in highest numbers densities and total numbers staging in the UAE were also established. No information from other countries is available for comparison. Khor Dubai holds especially high numberts of Grey Herons. Up to 7% of the West-Asian population of Western Reef Egrets may use the UAE wetlands during autumn and spring.
Other waterbird species occur in the UAE in important numbers as well: Socotra Cormorants (15-33% of the world population), Sooty Gulls (up to 7%) and various species of terns.
Data on migrating waders were collected during late afternoon at Khor Dubai. A total of 39 flocks (13 species, 1194 individuals) was seen leaving. Curlew Sandpipers and Little Stint left in largest numbers. The largest emigration coincided with the largest drop in numbers presen in the area. Numbers of waders leaving from Saudi Arabia were used for comparison, and to enlarge the data set. Most waders left in a northerly or northwesterly direction. A positive correlation was found between breeding latitude and departure date.
During eight nights in spring 1995 74 waders were caught, mainly Curlew Sandpipers, Lesser Sandplovers and Kentish Plovers. Between early and late April these birds increased in weight (Curlew Sandpiper 30%, Lesser Sandplover 19%); for the first two species a positive correlation was found between weight and departure date. In Kentish Plovers such an increase was not found, and all birds probably belonged to the local breeding population.
Foraging intensity was found to be high for all species. Food intake of Broad-billed Sandpipers, Curlew Sandpipers, Pacific Golden Plover, Lesser Sandplover and Grey Plover was studied in detail. All these birds were feeding mainly on ragworms. Broad-billed Sandpipers were almost exclusively feeding in the softest mud and caught relatively small ragworms. Energy intake was calculated to be lower than energy expenditure. Curlew Sandpipers and the three plover species on the other hand selected very large ragworms. A marked difference was found between calculations from ragworm jaw lengths from faeces and from estimated worm lengths in the field. However the results may be, intake rate of Lesser Sanplover was extremely high.
Food for waders was studied in detail in Khor Dubay, but samples on macrozoobenthic animals were taken in six other areas as well. Compared to the toher sampling areas Khor Dubai is rich in mudsnails and worms. Mudsnails however are not eaten by waders, probably because of their hard shell. Especially hight numbers of mudsnails were found near the planted mangroves. In most coastal areas waders are feeding on worms, while birds feeding on bivalves were more common in autumn than in spring. Waders fedding on crabs make up only a small proportion.
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