American Crows are gregarious, especially during the fall and winter months. They can roost in forest borders where they likely find the best conditions for their nightly rest. The North Creek forest patch seems to be a favorite spot for this population of crows.
It has been 3-4 years now and thousands of crows are using the campus area. In 2008 they were using a clump of trees surrounding a parking lot in Kenmore (we observed this population for a lab in a Conservation Biology class I was TAing at that time) and it seems that they moved to UW Bothell from there. Why this spot? According to John Marzluff this forest area seems to be safe spot, mainly from predators. UW and UWB researchers are trying to find more details to answer this question and many others regarding this roosting site and its effects on this wetland habitat. A student will be posting more on this soon.
The arrival of crows to campus is an amazing show that starts at approximately 4:40pm (Winter Jan 2014) . The arrival time is slightly changing to a later time due to the increased length of daylight hours (we are documenting this right now, a student should post later about this too). You can see crows arriving from all directions and congregating on the building's roofs and on trees surrounding them, then they move to the forest patch by the wetland. It is a fantastic show that I highly recommend to observe and I am sure you will enjoy.
This video is from 15 Jan at around 5:40-5:50pm (I took it from the upper level parking garage in UW_Bothell campus). Students took data on arrival time, direction of arrival and behavioral activity. They should be reporting on that soon too. Many students commented on the magical moment of seeing this massive amount of crows during a full moon night. I completely agree.