Surely there are hummingbirds in Manhattan, at least the occasional blur in Central Park’s Ramble. But Dan Witz’s painted hummingbirds are better in one way: They hold still to be admired. The 24 year old Witz has been letting his birds light on anonymous walls and doors downtown for the past couple of years, and while time and fresh coats of paint have obliterated some, others can still be seen in their very unnatural habitat. Good birding locations are the west side of Lafayette Street near Canal, near the southwest corner of Baxter and Centre Streets, and on the south side of Howard Street near Broadway. But, Witz warns, people aren’t prepared for how small a hummingbird is. You have to be really determined to locate one.:For the not-so-determined, there’s also a photo show of Witz’s birds past and present.