Who we are: Gary Granger and Rebecca Provorse, avocational ornithologists and urban naturalists. We teamed up in 2016, bringing together our individual life-long fascinations with the natural world and deep love of birds. As corvidophiles, we became increasingly interested in the afternoon arrival of crows in downtown Portland, and in late 2017 we heard rumors of the urban crow roost. On a cold November night, after a dinner downtown, our curiosity overcame our desire for warmth and we took a late-night walk. The result was a hand-drawn map of several blocks of the city and scribbled numbers totaling 3,705 roosting crows. We were hooked.
Gary, who is staff at Reed College (and teaches birding classes), has ready access to research papers and historical documents. He dug up everything he could find. Rebecca, who holds a biology degree and is a physician, used her training and experience to wade through the research. In the process of reviewing scientific literature and ornithological writings on crow roosts, we realized there was little available in print about the dynamics of urban crow roosts over time.
That was the beginning of our Community Science Project: to observe pre-roost behavior and to scientifically document the number of crows coming in/out of the city center, including where they roost and when. The project has branched to encompass community education and crow advocacy as well.
Our census project: Based on repeated, consistent, careful nocturnal observations, we are documenting Portland's urban roost over time. Observations are in the evening, after the crows have settled into roosting locations and/or in the morning, before they begin to leave for the day.
We make observations on foot within the area of the city west of the Willamette river and bordered by the “C” shape of the 405 freeway. Within this area we determine the roosting locations for a given evening and then walk every street with roosting crows--and checking multiple blocks beyond the roost to ensure as complete a count as possible.
Over time we have refined our ability to estimate by using photographs of trees in the field to check our accuracy, after-the-fact. Because we are conservative in our estimates, we believe that our total numbers are routinely undercounts, but probably within 10% to 15% of the actual size of the roost.
All of our counts are documented on both hard-copy maps of the city and entered into eBird, along with photos of the completed maps, and often with representative photographs of roosting crows.
Since 2017 we have conducted over 120 observations, written a yet-to-be-published research paper, lead walking tours, trained volunteers, and presented to the lay community as well as local researchers .
We continue to monitor the roost.