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Gary, who is staff at Reed College, had ready access to research papers and historical documents and dug up everything he could find.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 document, as scientifically as possible, the number of crows coming in/out of the city center, where they roost and when. It has branched to contain other aspects: community education and crow advocacy.
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 by first determining a boundary for the roost and then walking/driving up and down every street with roosting crows--and checking multiple blocks beyond the roost to ensure a complete count.
Because we are counting at night, precise counts of each bird are often not possible. When a tree is large or when ground lights obscure our view, we make careful estimates of the number of crows based on counts of smaller areas that are representative. Over time we have refined our ability to estimate by using photographs of trees in the field to check our accuracy, after-the-fact. We believe that our counts are typically accurate to within +/- 10%. Because we include both exact counts and estimates in a total count, we represent our numbers in multiples of 10s.
All of our counts are documented on hard-copy maps of the city kept in our research notebook. We also enter all counts into eBird, along with photos of the completed maps, and often with representative photographs of roosting crows.
Over the past three years, we have conducted a total of 97 observations, have written a research paper, offer walking tours, trained volunteers and speak publicly to educate the community. We monitor the roost and count crows on a weekly basis.