Demystifying science | Are there fewer birds and butterflies?

Every week, our journalist answers scientific questions from readers.

Some species are more numerous, others less, but there is not a general trend.

Among the species whose population has declined the most, we find those that benefit from agricultural environments, explains André Desrochers, ornithologist at Laval University. Because farms have changed in recent decades. Today, “they are more efficient and clean, more sterile,” remarks André Desrochers. Previously, there were “cedar fences, manure everywhere and therefore, lots of insects” to feed the birds.

But we must understand that these were artificial environments, created by man, recalls Mr. Desrochers.

Country species that benefited from less clean farms included the barn swallow, bobolink, and brown-headed cowbird.

Another category of species in decline includes “shorebirds”, such as plovers and redhorses. “Many of these birds are migratory,” says Mr. Desrochers. They nest in the Far North, passing through us at the end of spring during their migration from Central and South America. The causes of their decline are less well understood. But it could be linked to the frequentation of coastal areas, beaches, by people with their dogs, here in Quebec. »

As for the most abundant species, the prize goes to the geese. “They have learned to live close to humans,” explains Mr. Desrochers. We don’t really know how they understood that there was no danger, but it’s like the gulls, who one fine morning understood that they would find food in the garbage dumps. »

There are also turkey vultures, which are finding more deer carcasses near roads because of the increase in populations of these mammals and that of cars; and sandhill cranes which survive the winter better and devastate agricultural fields.

A species less numerous than before here, the black swallow, is also more abundant in the west of the country. “It seems that there is a shift in the distribution area,” says Mr. Desrochers.

As for butterflies, there is less data, according to André-Philippe Drapeau-Picard, entomological information officer at the Insectarium.

There is a lot of talk about the monarch, which migrates to Mexico.

Another rarer butterfly, the spotted skipper. “We haven’t had one in Quebec for decades and it’s starting to be rare in Ontario,” says Mr. Drapeau-Picard. His problem is that he is a specialist, he only eats a few species of plants, including a shrub which is also targeted by deer, and which suffers from the flooding of the Gatineau. »

“Another trend to note is the appearance of new species of butterflies,” says Mr. Drapeau-Picard. The common blue and the day peacock are spreading around Montreal, probably because of climate change. We also see the greater hairstreak more frequently. »

As for bees, the most obvious phenomenon is the decline of wild species in cities due to the explosion of urban hives. “Bees in hives compete with wild bees and also bring diseases,” says Mr. Drapeau-Picard.