 www.helenair.com/ It’s that time of year again - time for crows to congregate in the most unfortunate of city parks, streets, and yards. Sinister seems invented to describe the atmosphere of hundreds of crows roosting in the darkness above you, rustling and softly calling to each other, unseen yet…sinister, a scene out of Poe appropriate to this season. And, as an author in the Michigan Daily noted during my time in grad school, “the crow sh*t falls like rain.”
Places like the University of Michigan’s campus and Forman Park and Oakwood Cemetery in Syracuse struggle with how to pull the crow welcome mat back in. Screeching recorded bird calls seem to be a favorite tactic of campuses. Other places try fireworks or gunshots. Really, not much seems to work reliably. Of interest here is that crows are recognized as being remarkably intelligent birds, with recently published research even reporting their use of tools. A memorable 2010 episode of PBS' Nature showed how crows remember the appearance of people who hassle them, and react when the same person returns. This same intelligence and responsiveness to their environment must be the key to persuading crows to roost in places we deem acceptable. In the winter months I often see flocks of crows flying overhead, high enough and dispersed enough that you don’t notice them at first glance. As you watch, though, you realize that crows continue to pass overhead, on and on, because there are a very large number in the flock. They are all going somewhere, and I speculate that when I see these flocks in the late afternoon, they are heading for roosting spots in town (an attempted murder! Sorry. There had to be at least one “murder” pun). If they are flying from out here, 15 miles away, to spots in town, the choice of those roosting spots must be intentional, because it’s obviously not proximity or convenience at play. What makes a good spot for a murder? What dictates the landscape preference of crows? I don’t know. Crows aren’t my thing. But revealing the physical environment as a key factor in life in cities is, and so I say: there are environmental characteristics that must matter here, and if we identify them, we can manipulate them, and make the crows decide to sleep somewhere else. There’s got to be somewhere else, though - like every “undesirable” in the city, crows have to be somewhere, so banishing them from one place means their arrival somewhere else. The task of research-based urban crow management might then be to eliminate those characteristics from places where we don’t want crows, and add those characteristics to places where we do want them. For a bonus point, we could draw crows to places where their abundant droppings (falling like rain!) could add needed fertility to the soil. You probably don’t want that to be any place you’re growing food for human consumption, but a degraded brownfield could be the ideal site. So what do crows like? If I list sites where I’ve personally witnessed mass roosting of crows, I list the north edge of Syracuse’s Oakwood Cemetery, Syracuse’s Forman Park, and the University of Michigan’s Diag (a central campus quad). Far from an exhaustive list, but even with just these three sites, we can compile a short list of possible crow-attracting environmental characteristics. First, most obviously: mature deciduous canopy trees. In these three sites, those canopy trees have open understory beneath them, with either lawn or low-growing perennials and shrubs. Perhaps the crows feel more secure with open space beneath the canopy and less cover for predators. All three sites also have substantial masonry buildings adjacent to them, and at least some paving - perhaps the thermal mass raises the nighttime temperature? It’s interesting that all three sites have a fair amount of human activity, including both cars and pedestrians. These aren’t isolated natural areas. The cemetery edge abuts the edge of campus, specifically a back drive serving faculty parking, a busy place at dusk in the fall and winter. Given the demonstrated attention of crows not just to human activity, but to specific humans, it seems implausible that this is a coincidence. Perhaps the crows want to be near us because we scare off more dangerous wildlife. Perhaps they know we generate tasty trash and roadkill. Perhaps they like the heat from our buildings and cars. Maybe we’re just entertaining. To you and me, a tree might just be a tree (well, really, to me a tree hasn’t just been a tree since 1992, when I took my first plant identification class), but to a crow, I very much doubt trees are all the same. Might the species matter? Is an elm better than a maple, but not as good as an oak? Crows don’t mind noise, artificial light, and urban air quality. Do these environmental characteristics actually attract roosting crows? The question here is whether crows really prefer urban sites to rural ones for winter roosting, or whether we humans only notice them in urban sites. If a murder roosts in a forest and no one is there to complain, would we know about it? Urban heat islands would seem to be a likely explanation, but surely these intelligent birds have their reasons for selecting between the many possible roosting areas available in the warm city. We have to look at the wild city through crow’s eyes to see those reasons. |
