The small number of migrant warblers - flycatchers and thrushes - 
captured was probably due to the diffusion of migrants in tropical Africa 
in contrast to their concentration in the vegetated parts of northern 
Egypt on passage. Other migrants, such as wagtails, swallows and shore- 
birds, were not rare, but could not be captured. Attempts to isolate 
live virus from the blood samples were negative. 
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