A bit late but might be useful for others heading to the Estepona area.
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Interesting stuff, Steve. Personally, I find birding in SW Spain in August is often a bit too hot for comfort and hence my birding time there is usually restricted to early morning and evening. It is certainly harder work (in my view) than earlier in the year, but as your report indicates you can still be very well rewarded and get a good range of species.
With regard to BW Kite at La Janda it's my impression that they're much easier later in the season and that in August the farmlands around Vejer and towards medina are better,