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5    Discussion

5.1   Bird distribution	5.2    Habitat types and breeding bird distribution
5.3    A comparison of breeding bird communities at Wadi Rum (1999) and Azraq (early 1960s)	5.4    Breeding bird numbers
5.5    Non-breeding species	5.6    Conclusion

5.1    Bird distribution

Maps 4-6 reveal some interesting patterns in bird distribution with marked differences between breeding and migrant species.

      On map 4 there are five squares (3474, 3272, 3472, 2066 and 3468) which stand out as supporting particularly high species diversity. However, as mentioned briefly in Results, three factors could possibly be influencing their apparent importance – observer coverage, habitat diversity and geographical location.

5.1.1       Observer coverage

The issue of variable observer coverage and assessing how it affects results is addressed in maps 5 and 6. Both maps present data on breeding species and breeding territories: darker squares contain more species and larger circles represent more territories. Observer coverage is the only variable between the maps: map 5 uses all data for all squares, collected throughout the survey (with widely varying observer coverage from square to square, see map 3), whilst map 6 uses only data collected during the standard two hour survey visits. Map 6 thus presents similarly collected data for each square and highlights the importance of squares – black squares on this map actually do support higher numbers of species and probably contain exceptionally good or varied areas of habitat.

      What map 5 clearly shows is that the two hour survey visits do not reveal the full story – more time and effort will almost invariably reveal more species and more territories, giving a truer picture of species' distributions and breeding ranges. However, overall the two maps show broadly similar patterns of distribution – map 6 pin-points the centres of population which are expanded upon in map 5.

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5.1.2       Habitat diversity

Habitat diversity appears to influence both breeding and migrant species diversity, with more diverse habitats providing more ecological niches for species to exploit. Overlaying vegetation maps on any of the maps in this report, and particularly maps 5, 6 and 7, may help to reveal the reasons why some squares support more species than others. This is illustrated by squares 3474, 3272 and 3472 (around Rum village) which all contain gardens or vegetation by permanent water, habitats which are scarce or absent elsewhere. Elsewhere the high breeding bird diversity is less easy to explain but varied habitat may be provided by structural diversity in the topography as well as variation in the vegetation. For migrants safe roosting and feeding habitat is important, and stands of Retama are especially favoured. Interestingly Retama appears to be virtually unused by breeding species.

      As mentioned in Results, a high numbers of territories in a square is generally due to an abundance of one or two species (desert lark, white-crowned black wheatear and trumpeter finch for example) and not to a broad spectrum of species in high numbers. This is probably true of all deserts, as habitats are rarely of sufficient quality to support species at high densities.

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5.1.3       Geographical location

Geographical location only appears to be a key factor for migrants. Squares 2066 and 3468, which recorded the greatest abundance of migrants during the two hour survey visits (see map 7), are probably located on natural 'flyways', created by wadi corridors, used by migrants passing through the area. Interestingly, the pattern of occurrence of migrants differs between these two squares with 2066 having both a high species diversity and a high number of individuals recorded whilst 3468 has high species diversity and a low number of individuals. This may reflect the erratic and potentially higher level of disturbance to birds using 3468 (the northern end of Khazali and entrance to the siq).

5.2    Habitat types and breeding bird distribution

The table below shows the jebels and jebel margins to be important breeding habitat. This is probably due to the abundance of nest sites they provide – ledges, caves and holes – many of them also potentially less disturbed sites due to their difficult access (although it should be noted that grazing livestock was observed in all areas apart from the steepest cliffs and highest mountain tops).

      Of the larger plants in the area, Anabasis seemed to provide good feeding, was used as a songpost by several species, and provided a nest site for scrub warbler; Haloxylon (the tallest tree in the absence of Acacia) was used as a song post by several species, especially mourning wheatears; Acacia always held birds and were used for feeding and as a nest site by great grey shrike; as already noted, Retama did not appear to be used at all by breeding birds though it was extremely important for passage migrants.

5.3      A comparison of breeding bird communities at Wadi Rum (1999) and Azraq (early 1960s)

      From the available literature, there would appear to be no studies of desert breeding bird populations directly comparable with the survey carried out at Rum – most other studies have tended to concentrate on oases or wetlands rather than open desert. An exception is the study of the breeding birds of Azraq and surrounding desert areas carried out in 1963, 1965 and 1966, Wallace (1983). However, in that study bird numbers were assessed by counting individuals along transects of known length; the results were expressed as individuals per km and separate records were kept of actual breeding birds noted, so still no direct comparison of breeding bird numbers is possible. However, the overall breeding bird communities recorded in the two studies are remarkably similar – 34 species at Wadi Rum and 29 at Azraq.

      As can be seen from the table overleaf, the differences between the two communities can largely be explained by their geographical locations, geology/topography and recent changes in the distribution of some species in Jordan.

Summary	Introduction	Objectives	Methods
Results	Discussion	Recommendations	Appendices