Pesticides: learn tree swallows

This text is part of the special Research section

Recognized for its pretty colors and for its melodious song, the tree swallow has always delighted bird watchers. Unfortunately, there has been an annual decline in its North American population of around 5% over the past 20 years. A team of researchers from the University of Sherbrooke is studying the impacts of the use of insecticides in agricultural environments on this endangered species.

The decline in birds that feed on flying insects, first noticed in Europe, is now visible in North America. For the specialist in animal ecology and professor at the University of Sherbrooke Fanie Pelletier, and for her team, nothing more was needed to take an interest in the fate of these endangered species.

“We decided to look at the very source of the problem, which seemed to come from their diet,” explains the researcher. We wanted to know what was the direct effect of exposure of aerial insectivores to pesticides. “

The swallow, the ideal bird

Although there was no shortage of species on which to focus its research, the committee, made up of chemists, biologists and professors, set its sights on the tree swallow, generally present in the wetlands of southern Quebec, many of which have been destroyed in recent decades due to urbanization. The swallow, which particularly likes the stumps of dead trees on the edge of swamps to make its nests, has thus lost a large part of its natural habitat. To alleviate the problem, several farmers had already installed artificial nesting boxes, and at the start of the research project, others were installed in some forty farms in Montérégie and Estrie. Another advantage of the tree swallow is that it adapts well in a habitat modified by humans.

“Tree swallows are also very tolerant of touching their chicks, measuring them and putting them back in the nest,” says Fanie Pelletier. While some species of birds abandon their chicks altogether if they are imbued with an unknown scent. “

To understand the decline of the swallow, the research team first looked at the environment in which the species lives. The agricultural environments of Quebec are very varied, and each environment influences the reproduction of the species. How are the females living in the corn fields, where the use of pesticides is very important? And those who rather live with cattle, near pastures? Quid of reproduction in each of these environments? Here is, among other things, what the team wanted to know.

A diet that raises eyebrows

By noting the reproduction difficulties where intensive agriculture is practiced, the researchers made the link with the application of pesticides, which is a common practice there. For six years, experts have thus collected and studied food boluses, these insect balls that the female gives to her young to feed them. They were looking for traces of pesticides, insecticides and fungicides. The team has thus set up a unique process for detecting and analyzing up to 54 chemical compounds used in pesticides. However, 47 of them were found in said boluses.

“46% of boluses contain at least one of the products we tested,” says Mme Pelletier. We really found it everywhere, even on farms where we believed birds’ exposure to chemicals was minimal. “

First observation therefore, the impact of these chemical compounds on birds occurs on a large scale. Second observation, the number of different chemicals used by farmers is large. Thus, animals are exposed to a very wide variety of products, in small doses and continuously, and therefore chronically, explains the researcher.

However, this is a significant contrast to the way in which chemicals are tested by the authorities. When the government wants to ensure the safety of a product, it usually proceeds by feeding an animal population with a feed modified by a single product and over a short period of time. The reality in nature is quite different, which would change the impacts of these products on wildlife.

“To be able to measure the real impact of a product on an animal species, we must analyze the reproduction rate of that species,” adds Fanie Pelletier. How many eggs do females lay? How many hatch? Do the chicks survive? “

As research continues, some conclusions are already emerging, giving rise to recommendations.

“Anyone who lives near a wetland, a pond or a marsh must be careful with the use of chemicals,” concludes Fanie Pelletier. The swallow depends on these wetlands for its diet, but also for nesting. Anything in the water will inevitably move up the food chain. That’s why keeping our water sources clean is important for wildlife. ”

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