I found a Brewer's Blackbird nesting in a potted (for sale) Colorado Spruce tree in the Moscow Wal-Mart garden center. The nest was about 3' up in the 4-5' tree and contained 5 eggs. As I approached, the female would fly off the nest into a nearby maple tree in the median, often joined by 1 or 2 males. This is what initially attracted my attention to the nest location.
See pictures of the nest and nest location below.
** note: anybody actually buying this tree will be getting a very angry female Brewer's Blackbird as part of the deal!