SIOUX FALLS, S.D. (KELO) — What are those noisy birds gathering in the trees?

Some Sioux Falls residents are starting to see large flocks of blackbirds or grackle.

A grackle is a type of blackbird. Generally, grackles make a sound that most bird experts say is not musical.

Grackles are highly social and colonial birds, according to the American Bird Conservancy. They migrate, winter and roost in large flocks. Grackles can be seen roosting, or gathered, with blackbirds, including redwing blackbirds and others.

All About Birds from the Cornell lab of Ornithology describes grackles as “blackbirds that look like they’ve been slightly stretched. They’re taller and longer tailed than a typical blackbird, with a longer, more tapered bill and glossy-iridescent bodies.”

Grackles are often noisy as they make different squeaks or croaks. Some of their sounds have been described as awful or unpleasant by bird experts.

In contrast, bird experts have described the blackbird song as more mellow and pleasant.

Both grackles and blackbirds can gather in large flocks. They can be seen gathered on the ground as they search for food.

Grackles and blackbirds aren’t the only birds that will be flying across, or returning to, South Dakota.

“There will be a tremendous amount of migrating birds over the next several weeks,” said Kyle Kelsey just before April 1. Kelsey is a wildlife biologist with the U.S Fish and Wildlife Service in Madison.

Many of those migrating birds will be in flocks.

Lots of wild birds migrate in flocks, Kelsey said.

Snow geese, for example, are a colonial bird. “They migrate in flocks. There is no exact science to how they stick together,” Kelsey said.

The make up of the flock could change as the snow geese migrate across the U.S. and into Canada.

Ducks will also migrate in flocks as well as shoreline birds and warblers, he said.

Once those migrating birds reach their destination, they may split up. Kelsey said birds may still congregate but not at the level of migration.

The migration stages will vary across South Dakota as temperatures warm and more water opens in areas such as the southeastern region.

Bird watchers have already noticed the flocks of migrating snow geese near Yankton. Ducks and Canada geese have already been seen near open water in eastern South Dakota, south of Sioux Falls.

Those tend to be the first birds seen during migration, Kelsey said.

The shorebirds are usually next in the migration stage, he said. Those birds fly in flocks in the jet stream, which means they are often hard to see until they stop.

Warblers and similar birds start around time shorebirds travel but they may lag behind a bit.

Kelsey said the winter weather may change the migration for some birds. Birds and waterfowl wait for warmer temperatures and open water but they are also in hurry to get to their final destination to nest.

Snow geese want to get to Canada. Sometimes, birds may skip much of South Dakota if they have been delayed for a week or more in the southern part of the state, Kelsey said.

But, Kelsey advised, the curious may want to start looking for migrating birds or those returning here for the summer these days.