The danger of poisons: Blue Cranes in the firing line in the Overberg


When four Blue Cranes are found dead in the Overberg – close to each other – there’s reason for concern. 

When it becomes clear that these cranes have been poisoned, there’s additional reason to worry.

The four cranes were discovered in August: two pairs at two small dams near each other among wheatfields in the Overberg. All four had consumed a poison known as diazinon. It’s an organophosphate insecticide found in products such as Dazzel, which is used to treat fly larvae in sheep. It’s highly toxic to birds and most wildlife.

CapeNature’s Corné Claassen responded to the call by the worried farmer who found the birds. “The birds showed no indication of external physical injuries, with no overhead powerlines in the vicinity.” He immediately sent the birds to a laboratory to understand what had caused their deaths.

He found that the birds had consumed large amounts of diazinon – up to 10 times the lethal dose. This is most unusual and it’s unlikely that the birds picked up the poison accidently.

In fact, it seems to suggest that this was a deliberate act to place bird feed laced with the substance to actively target wild birds. It’s not clear whether the cranes were the targeted birds, however.

A return to past ways

In the past, Blue Cranes experienced mass mortalities in the Overberg as a result of poisoning. There were many reasons for the poisonings. Among them, people living on farms poisoned birds in order to eat them, or to sell the meat. Although geese, spurfowl and guineafowl were often targeted, this didn’t stop Blue Crane from eating the poisoned seeds. 

Corné says, “The seeds were most probably dipped in a substance, from which it absorbed a high concentration of the active ingredient, diazinon. Considering the high dose of diazinon found in the birds, it is highly likely that the birds succumbed with 5km radius from the locality where the poison was ingested.” 



It’s vital to know that diazinon is also dangerous to humans, whether people come into contact with it physically, or whether they eat the meat of birds that have died as a result of consuming the poison.

The poison has been banned for residential use in countries such as America, because of its risk to human health, especially the nervous system.

However, it is still widely available in South Africa. Organophosphates such as diazinon can lead to respiratory failure for humans if the product is not applied strictly according to the label safety instructions.

Corné says, “The majority of these pesticides are freely available from agro-chemical suppliers. It is vitally important that the end users utilize these products in a responsible manner, with strict adherence to the manufacturers label instructions.”

Here are four tips for pesticide use: 


He says, “Handling and the application of agro-chemical products should take place in terms of the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act, 1947.”

The OCG and CapeNature have worked extremely well with land users over the past 30 years. In fact, the OCG was started by a group of concerned farmers and CapeNature officials following severe poisoning incidents in the early 1990s.

Working with farmers and farmworkers

Kevin Shaw, the Chair of the OCG says, “We’ve come such a long way since those days where Blue Cranes faced such persecution. At the time we ran big campaigns to raise awareness of the importance of our national bird, and the threat of these poisons – not only to wildlife but also to humans. We must be sure to not fall back to these old ways.” 

Corné says he has worked well with the land users where the four Blue Cranes were found. “This shows us that farmers in the Overberg are no longer in conflict with Blue Cranes, as used to be the case. We’re extremely grateful to the farmers for their support in bringing the incident to our attention and helping us address this threat.”

He adds, “The death of these cranes serves as an important reminder of the dangers of these poisons, and the need for custodians of the land, farmers and farmworkers, to do everything in their power to protect Blue Cranes and other bird species – especially those that are threatened.”

Image credit: Corne Claassen