Very little is know on the threats to migrating kestrels in their wintering areas. It is important, however, to identify these threats so conservation action plans can address the real reasons why populations are in decline.
While there is little published information on threats, the following points may affect migrating kestrel populations in their wintering areas:
Roost destruction
Some roost trees have been removed and the kestrels no longer roost in those towns. In these cases we have no idea what the impact of removing the roost tree had on the kestrels that roosted there. Do they easily find a new roost or join another roost, or do these birds now show a higher mortality because they cannot roost in their prefered place?
Road mortalities
Ronelle Visagie and Mark Anderson have recently documented a large number of Lesser Kestrels killed on the road in the Hopetown-De Aar area. Maybe this is a bigger problem than what we think.
Pesticides and spraying of locusts
I got the following response from Steven Evans, Manager of the Poison Working Group of the Endangered Wildlife Trust:
I have gone through the EWT-PWG Database of wildlife poisoning cases and find no records for Lesser Kestrel, Amur Falcon of Red-footed Falcon. Keep in mind that this database contains information from cases where wildlife was deliberately poisoned usually poisoned meat put out for Jackal, Lynx or Leopard etc that was subsequently eaten by scavenging birds of prey resulting in secondary poisoning. This would not impact on the insect eating species. As for information on pesticides and spraying for locusts affecting the Lesser Kestrel in the Karoo I have no solid information. If there is information available, keeping in mind that it may be mostly anecdotal, the person to contact would be Peter Ferreira. Peter is a farmer in the De Aar area that is totally against the spraying of locusts in the Karoo and may consequently have collected info on non-target species mortalities due to the spray operations. Marina of the Nama Karoo Foundation may also be able to provide you with information. Marina does work quite closely with Peter on this issue.
Something else to keep in mind is that avian mortalities would have been far higher in the bad old days when various organochlorines and organophosphates where used to spray locusts. Many of the products used in the past (Lindane, gamma BHC) where highly toxic to birds. Currently only Deltamethrin (Pyrethroid) is used and it has a very very low toxicity to birds. It is doubtful there would be any direct impact (mortalities) birds currently even if they ate poisoned locusts. I spoke to Penn Lloyed of the Fitspatrick Institute about the locust spraying operations in the Karoo and what he felt the impacts may be. His impression was that the spraying affected such a small area of the total Karoo that the impact was negligible. Birds attracted to the locust swarms where mostly Wattled Starlings and the impact on them would be indirect due to the loss of the locusts as a food source due to the spraying. The spraying did not appear to kill any starlings, although this was speculative. As for impacts on Amur Falcons and Red-footed Falcons in the grasslands I am going to guess and say the impact would probably be indirect as a result of a loss of their insect food source. I doubt that any of the products currently used would kill birds.