I got all of those because I go there a lot, rather than because it's an especially excellent spot for birds, of course. What's exciting about it is that it means if you really pay attention, you can see a lot of cool birds in places you wouldn't expect.

If you look at the bar chart, you'll see the warblers and thrushes and several other unusual birds for Cambridge stop by there during migration - mostly May and October. There are some summer residents (like chimney swifts) who are gone in winter, and some winter residents (such as juncos) who are gone in summer. Click the bar chart on the left sidebar.

Also, because it's a small urban park with playground, it gets enough people that shyer species go away later in the day. But you probably know birds are most active early in the morning. So if you do want to visit and submit lists there (which would be very cool!), arriving during the hour after sunrise is usually best. Some species are bolder - robins, jays, grackles (in summer), cardinals, house sparrows, mockingbirds - and will still be around when there are more people.