48-Year-Old Dung Deposit Links DDT to Bird Decline

DDT is famous — infamous — for its effects on birds including eggshell thinning. Research recently published in the Proceedings of the Royal Society B has found that DDT can be linked to the long-term decline of insect-eating birds in North America.

Researchers from the Paleoecological Environmental Assessment and Research Lab (PEARL), analyzed 50 years of bird droppings inside a large chimney no longer in use on the campus of Queen’s University in Ontario. Chris Grooms, a PEARL research technician, discovered the deposit in the chimney. That half-century of guano provided evidence that DDT and bird diet have played a role in the long-term decline of insect-eating birds.

The chimney had once been a roosting point for chimney swifts, whose numbers have been declining; the birds have been listed as threatened for several years by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). As summarized on Science Daily, the researchers found that the use of DDT had peaked at the very same time as there was “a dramatic reduction in the abundance of beetles — insects especially susceptible to DDT — in the diet of swifts,” after analysis of a pile of droppings.

A 50-year pile of bird droppings in an abandoned chimney is, of course, not the pleasantest of materials to study. It was indeed a “stinky job, but someone has to do it ,” commented biology professor and co-author John P. Smol, Canada Research Chair in Environmental Change. For archaeologists, koprolites — the preserved dung of ancient animals — provides valuable information about the diet, health and habits of animals long lost to time. One of the difficulties in figuring out the causes of the insectivorous bird population has been a sheer lack of long-term data: The chimney’s deposit enabled the scientists to study the diet of chimney swifts from 1948 – 1992, a period of 48 years and provide further proof that DDT, by dramatically altering the population of insects, has had similar effects on swifts and other birds.

While it hardly seems necessary to note the adverse effects of DDT on birds, fish, mammals, humans and many more animals and the environment as a whole, the Canadian scientists’ study shows how pesticide use has not only immediate consequences but long-term, far-reaching ones, and provides compelling further evidence to why it is necessary to continue to ban the use of DDT and seek sustainable alternatives — and to ensure the survival of chimney swifts.

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Photo by dominic sherony


Duane B.
.4 years ago

Thank you for sharing.

Mark Jones
Mark Jones5 years ago

That's right Beth, no its not, in case you think I did. The fact remains that this is very old news (study ended in 1992)and if someone is going to hit out at a country, get the facts straight.
I have dealt a huge amount with wildlife and poisons. It will haunt my nightmares for life. DDT is arguably in the top 5 worst things humans have ever invented. The guy who invented it won a Nobel prize, crazy or what!

Beth K.
.5 years ago

When DDT was banned in the US, they simply sold all the remainder to Mexico. Who sprayed it on all the crops they imported to us.

Mark, no it's not ok.

Mark Jones
Mark Jones5 years ago

Hi Warren F, DDT was used by South Africa. It was used in 2000; this was after a severe flood caused a heavy outbreak of malaria in the northern parts of Kwa-Zulu Natal. We (people of the world) have used so many pesticides that they (insects), due to their quick breeding ability, have built an immune system to most of them. This is why they keep making "better" poisons every year. We've all seen the ads for "new and improved" poisons. This is why. These mosquitoes in KZN were found to be immune to all but DDT. Nobody liked this, but it was eventually endorsed by their (S.A.) wildlife trust. They sprayed in houses and roofs only. Not nice, but don't forget that malaria still kills nearly 2 million every year (humans). We're still trying to find something "better".
Don't forget that Botswana still sprays poisons over the Okavango to eradicate the Tsetse fly, is that OK?

Mark Jones
Mark Jones5 years ago

Sorry Aimee A, this news is not that new. Its fairly obvious to all in the wildlife industry how bad DDT has been, is, and will be.
The fact remains that cats in the US kill millions of birds every year and about 1 Billion mammals. Its a whole lot more devastating than DDT is right now.
DDT traces is in fact found in most humans around the world, although it is by now almost completely banned. The Inuit show the highest traces of DDT in their systems even though they have never used the stuff. It comes from the seal blubber, their food source. DDT stays in your system forever, remaining in your fatty reserves until you need to tap into that fatty reserve, then it kicks in, makes you ill, with potentially lethal effects.

Aimee A.
Aimee A5 years ago

And the ABC loves to blame feral cats for all of the bird deaths. Funny how they never factor in things like this. Thanks for posting!

Dieter Riedel
Dieter R5 years ago

At last some common sense, who would have thought that toxins targeting insects would effect their predators and even humans eating these birds... Is this not all interconnected... Think again before you apply the next round of insecticides...

Christine Stewart

Poor little birds- damn indiscriminate use of pesticides!

Lilithe Magdalene

Question is, why does is this chemical still being manufactured at all?

Chad A.
Chad A5 years ago

DDT used to be safe and those who criticized it were decried by industry. Turns out they were right. No wonder we are so cynical.