Eastern Phoebes building nest

While looking for spring migrants at Tempel Grove north of Lamar, Colorado on Sunday I spotted a pair of Eastern Phoebes building a nest--well, actually building at least two and possibly more nests on ledges under a small vehicle bridge over the Ft Lyon Canal. I observed a phoebe work on each of two nests and I saw more partially built nests that they might also be working on. This type of behavior has been observed before as reported by the Vermont Center for Ecostudies: "females were seen attempting to build as many as 15 nests in a season before completing one (Smith 1942)." All of these nests were 'statant' nests; that is, they were built on supporting ledge as opposed to 'adherent' nests that are 'plastered to a vertical surface.'

One of the pair was a first spring bird and the other appeared to be in adult plumage. I do not recall seeing any Eastern Phoebes building nests when I frequented the Tempel Grove area last spring. SeEtta