For the third year running, Great Blue Herons are working on their nests in the cottonwood trees along the Marymoor Park riverside in preparation for the arrival of this year’s babies.

People are invited to take a look through Eastside Audubon members’ high-powered spotting scopes from 9-11 a.m. on Saturday.

The scope viewing point and the trails to reach it are inside the off-leash dog area. Parking fee is $1.

To find the viewing spot, go to Lot D. Take the trail that runs alongside the river, heading south (upstream toward Lake Sammamish). After about a five-minute walk, attendees will reach a point with an open area on the left and wide steps into the river on the right. Ahead on the left is a stand of cottonwoods with numerous heron nests high in the treetops. Turn left into the open area, then look for the Eastside Audubon members on the right on the other side of that stand of cottonwoods.