Species, such as Whinchat, Common Nightingale, Tree Pipit and Spotted Flycatcher, which winter in the humid zone of Africa – stretching across the continent from southern Senegal to Nigeria and beyond - show the most dramatic declines: the indicator for this group of species has dropped by just over 70% since the late 1980s. This contrasts with species, such as Sand martin, Common Whitethroat and Sedge Warbler, wintering in the arid zone (just below the Sahara desert). These species have fluctuated considerably since 1970, but show a less than 20% decline overall. - Halil

One of the most dramatic declines is that of the European Turtle-dove with a decline of 88% since 1995. The following species have also declined over the same period: Wood Warbler, 66%; European Pied Flycatcher, 53%; Spotted Flycatcher, 49%; Common Cuckoo, 49%; Common Nightingale, 43%; and Yellow Wagtail, 43%. - Halil

If wildlife crimes are at the root of this, ie birds being caught in nets during their migration and then sold off as either pets or food delicacies, then the root cause is most likely poverty as some wildlife crimes are driven by poverty. So the question is how do you address that issue, but I'm only speculating that the birds are being trapped during their migratory paths. - Halil