Urban crow roosts made an appearance in downtown Portland starting around 2013. Every night during the winter season, crows enter the city before sunset and settle in trees or buildings for the night in roosts reaching sizes that can be up to 3000 crows. The roosting period is silent after the crows fall asleep, although, the crows are quite talkative and tend to fly in weaving patterns just before roosting. Noticeable consequences of the crows’ transition to an urban setting are the loud noises of their “caws” as well as the presence of crow waste on the sidewalks. An ongoing debate about the influence and harm of the arrival of crows inspired a project in downtown Portland to “haze” the roosts by sending hawks to the roosting locations and convince the crows to relocate to areas of less human involvement.
These events motivated the Portland Crow Roost Community Project to investigate whether the marked locations of Portland are reflective of the hazing attempts to transport the crows. By courtesy of this community project, a census of crow roosts has documented the location and magnitude of roosts weekly for the past three years.
The data collected in this package came from a team of field workers who travel by foot along the sidewalks of downtown Portland and observe the crows sleeping, which typically lasts around six hours. Many factors are involved in the uncertainty of these estimates, two of which are the darkness of the night along with the tendency of the crows to roost in locations unobserved by the field team. After having two people cross check their estimates and also comparing these estimates to exact counts made from photographs, the project has determined that the estimates are accurate to within 10%.
The following dataset includes the counts recorded over three separate dates: 9/23/2019, 1/9/2020, and 12/1/2019. The dataset consists of 228 observations for six variables: block, date, side, count, latitude, and longitude. Block number is treated as an index variable corresponding to the following map of streets in downtown PDX:
Side is a categorical variable indicating whether the crows are located on the north side, south side, east side, or west side of the block. Count is the estimated number of crows in multiples of 10s. And the longitude and latitude variables correspond to the center location of the blocks.
pdxCrows, the average number of roosting crows in downtown Portland is 16050 a night with the maximum count being 24430 on December 1st, 2019 and the minimum count of 10940 on January 9th, 2020. The following visualization depicts a heat map of crow counts for downtown Portland:
More information about this data, including the source as well as the amount of uncertainty in the estimates, can be accessed here.