One evening in November, the setting sun washed downtown Victoria in a fleeting blush of pink, just as a biting chill began to creep in from the coastline. People down Government Street had stopped in place and were pointing up to a black cloud of motion, buzzing above the empty high rises and the construction cranes, in a synchronized, balletic dance, punctuated only by a symphony of trills and chirps.

The European Starlings had returned for the winter.

According to the Smithsonian Magazine, the invasive bird has been in North America for more than 100 years— introduced on a colonial whim to bring every bird mentioned by Shakespeare into the continent.

That poetic, albeit absurd, notion led to an explosion of starlings across the US and Canada, and the birds happily began stealing nests and roosting cavities from native species like chickadees and woodpeckers. Today, flocks of starlings winter in Victoria and scatter again for the summer to breed.

The weaving murmurations—a birder term to describe hundreds, or thousands, of birds flying in synchrony—help the flock to avoid predation, find roosting sites and warm up for the night. It’s been speculated that some birds flock in their noisy groups at dusk to exchange information about feeding sites.

But despite the starlings’ impressive evening performances above the Victoria skyline, local birders say their numbers have dropped significantly, and it’s not exactly clear why.

“We have seen large flocks in Victoria of late,” said Jacques Sirois, chair of the Victoria Harbour Migratory Bird Sanctuary. “Somebody reported 1,500 in the city centre recently.”

By “somebody,” Sirois means a birder. The birders send Sirois their information, or provide it directly to the Victoria Natural History Society.

“Fifteen hundred is large, but we used to see larger flocks in the past of 3,000 or 5,000,” Sirois said.

Half a century ago, there was a rumoured murmuration of 50,000 starlings, he added—a rumour, he emphasized, but said he wouldn’t be surprised if it were true. Starlings eat almost anything, and are adept at finding—or rather, thieving—habitats from other birds. They’re also known to roost in rooftops and warehouses (“wherever there is a hole for them to nest in,” Sirois said) earning a reputation as pests among those who have to deal with clogged gutters, droppings, and incessant chirping.

So the population decline of such a hardy little bird, while good news for other species, remains a mystery. A not-unwelcome mystery, to Sirois at least.

“They don’t really belong here,” Sirois said. “I’m pleased to know that they are declining.”

Ann Nightingale, a Central Saanich naturalist and bird expert who volunteers with Rocky Point Bird Observatory, is a bit more equivocal. She said a mysterious population decline—even among an invasive species—is cause for concern.

“I feel positive about starlings declining—but whatever is affecting starlings may be affecting native species as well,” she said. “So from that perspective, I feel negatively about the population decline.”

Nightingale pulled up data from the Victoria Natural History Society’s annual Christmas Bird Count, revealing a drop from 18,183 European starlings in 1984, to a count that over the last decade has ranged from as high as 6,927 to as low as 2,548.

“I don’t think we honestly know the answer to why they are declining,” Nightingale said. “They reproduce very efficiently.”

Their nests can be raided by raccoons or rats, so it’s possible the birds are being eaten by predators on the ground—or by predators in the air.

“There may be more predators in the area in terms of falcons and hawks, [and] American kestrels, but we’re talking small numbers still. I don’t think the number of falcons or hawks would have a real effect,” she added.

For the region’s raptors, the starlings present an evening delicacy. Sirois loves to watch nature in action, when peregrine falcons, kestrels and eagles dive into the starling swarms and pluck out their dinner.

He wonders if the resurgence of raptors, following the ban on DDT more than 50 years ago, could have something to do with the declining starling numbers.

“Recently people have been noticing these peregrine falcons diving into these large flocks,” he said. “It creates quite a spectacle.”

“The return of the peregrine falcon in the last two or three decades is a huge conservation success story,” Sirois added. “The big flocks of starlings in the city centre are good news for us, because of the potential to draw in the falcons.”

Sirois often goes to the cruise ship dock, where the Greater Victoria Harbour Authority installed platforms that allow eagles to nest—a smash hit with the region’s falcons, who use the platforms to dive at unsuspecting prey.

“I go there at dusk and I watch the peregrine falcons hunting the starlings,” he said. “It’s beautiful.”