I saw my first young black-billed magpies (Pica hudsonia) on May 24 2016 in a Tatarian honeysuckle bush near Parking Lot 10 of the University of Calgary. One sibling was on his own and the three others were together.
A few days later, on June 4th, I saw youngsters from another family, a couple of blocks away.
Young black-billed magpies are born altricial, with closed eyes and no feathers, and fledge 24-30 days later. They stay near the nest for 3-4 weeks and are fed by their parents for 6-8 weeks. 
Black-billed magpies build very large spherical or oblong-spherical nests with two, small, round openings on opposite sides. I’ve seen a lot of magpies and their nests around Edmonton but I haven’t seen any young ones yet. Below are some photos I took last year, in Calgary, of adult magpies and nests. Adult black-billed magpies have black bills and much longer tails.
 Trost, Charles H. (1999). Black-billed Magpie (Pica hudsonia), The Birds of North America (P. G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America: https://birdsna.org/Species-Account/bna/species/bkbmag1/breeding