In the winter in Colorado, Say’s Phoebes are “eBird rare”; though flagged as rare on eBird, they’re not especially newsworthy. Denver’s Christmas Bird Counters regularly find them during the city’s two counts, and many years, several are reported. Even so, it’s always a treat to encounter them in the cold months, as we wait for other, less hardy spring migrants to arrive.
Not all Say’s Phoebes that visit in the winter take to multi-story buildings, but three of my last four have. In February 2016, I had a Say’s Phoebe high up on an apartment complex adjacent to Denver Botanic Gardens. In February 2017, I had one on top of Sturm Hall at the University of Denver; I watched it from a window on the building’s fourth floor. Most recently (1/13/2019), I watched, from a second floor window at the Southglenn Library in Centennial, a Say’s Phoebe flycatching off of light fixtures on the 3rd through 5th floors of a nearby apartment building. Here’s a terrible, distant phot of that 2016 bird.
I’m not the only one. On January 1, 2018, a large group (CBC’ers, I presume) had a Say’s Phoebe on top of a building at Denver Botanic Gardens. (Checklist with photo here.) A December 2017 Say’s at Denver’s City Park was on top of the science museum. (Checklist with photo here.) Browsing through eBird photos of the bird in Colorado, with the date filter set to Dec – Feb, reveals many, though certainly not most, of reported phoebes are on human structures and often large ones at that. (Interestingly, Birds of North America describes most overwintering phoebes in Colorado at open streams and sewage ponds.)
Why would this be? According to one local birder (the state’s expert on birds, bugs, and the interaction among them), our buildings could house dead insects (often in webs), spiders and their eggs, cluster flies, and midges. I haven’t had a chance to closely observe the winter phoebes I’ve found, as most of my sightings are of the bird on residential buildings, patios, and windows OR incidental, when I’m doing something other than bird and my binoculars are taking some well-deserved alone time. But there may be something to phoebe’s exploiting food sources on buildings themselves. The one’s I’ve seen seem to fly straight up walls or straight at building fixtures and windows, not out and at moving targets in open air. Flying this way, the birds look to me to be frantic and disoriented. But certainly it’s more purposeful than it looks.