Nature Obscura. Kelly Brenner

decapitate their prey and eat only the brains, leaving the rest of the body behind. A crow roost at night in the dark countryside can be easy pickings for this large owl, which has the benefit of night vision.

      Crows, as diurnal animals, have poor night vision, and some scientists also believe that the lights of a city help keep crows safer by helping them see a predator coming before it catches them unaware.

      In rural areas where shooting is allowed, humans are crows’ second most deadly enemy. Over most of our complex history together, some humans have spent a great deal of time and effort killing crows. As John Marzluff and Tony Angell point out in their excellent book In the Company of Crows and Ravens, crows that are used to being regularly hunted by humans are much more wary of humans. Those crows even recognize particular hunters, by their appearance, their weapons, and their cars or trucks. Country crows are much more wary of people, having endured a continued persecution that city crows generally escape.

      Finally, crows have long collective memories, and it’s entirely possible that some crows may have always roosted and gathered in a specific locale long before humans moved in and that place became a city. The birds may have found that the more urban environment suited them just fine.

      I often encounter murders of crows when I happen to be out before dusk, in places such as Genesee Park in south Seattle, which, I discovered, used to be a landfill, a popular foraging opportunity for many birds. Crows gather in these large groups all over the city, and for the uninitiated, the gatherings can be confused for roosts; but what the crows are doing is called staging. The closer to the roost that these gatherings occur, the larger they are, as more and more birds congregate before making the final push to their nighttime roost. Why crows do this is still a mystery. One thought is that these staging areas are crossroads of sorts, where the commuters from one aerial road meet up with others, and they offer a last chance to forage before continuing on to the roost.

      Another big question that preoccupies scientists is, where do the crows at each roost come from? Somewhere in Seattle there’s an invisible divide, with the crows on the north side of that line going to Bothell, and those on the south side, for example, flying over our house in southeast Seattle to Renton, at the south end of Lake Washington. Some crows may travel to some of the smaller roosts around the city, but these roosts have not yet been well documented or observed.

      Which individual birds go to which regional roosts is not yet entirely understood, but it’s likely somewhat flexible depending on where the crows are at the end of a day of foraging. It’s probable that resident pairs—those mated birds that have established territories—are more likely to go to the same roost each night. Younger birds without territory to defend may be more flexible in their choice of roost, depending on where their source of food is at that time or if they’re looking for information about a new source.

      Crows abandon their roosts from time to time as well. Until recently, for many years crows roosted on Foster Island, right across Union Bay from the University of Washington campus in Seattle. In the morning they would land at a nearby parking lot by a place locally known as “The Fill” but officially called the Union Bay Natural Area. The nickname gives a hint to its past—it was once the local landfill, an attractive place for crows to forage. The landfill is long gone, but the crows remained roosting near there and gathering each morning by The Fill before the roost finally dissolved and the birds established a new one at the UW Bothell campus. It is unknown what led them to yet another UW campus several miles to the northeast—perhaps they have a preference for purple and gold.

      Although—or perhaps because—I had experienced the full roost in Bothell, I wanted to find and experience the roost where my crows—the birds flying over our house—went each night. Based on blog posts and listservs, I had a general idea that they roosted somewhere near Renton, and I used that information as a starting point. So one January evening, my husband and daughter joined me and we headed to the south end of Lake Washington to find our crows.

      We didn’t have any trouble locating the birds as we drove; we just picked up and followed one stream of crows until we found all the streams converging and landing in Renton. With my husband behind the wheel, I was free to keep my eyes on the sky. I could see the crows gathering in the middle of a large block of industrial and commercial buildings—they were tantalizingly close, but at that time of night, the driveways that could give us access were all gated and locked.

      As I watched the crows arriving, we continued around the block to try and find a way in. Finally I saw an open driveway, and as we pulled in, I saw the crows in the middle of a giant parking lot surrounded by twos-tory buildings.

      We drove through the lot—excitement building with each parking aisle we passed and as the numbers of crows grew and grew—until we came to the center of the chaos. I yelled to my husband to stop the car, but before the car fully stopped, I had already jumped out.

      Thousands of crows covered every surface—trees, buildings, streetlights, curbs—even the parking lot’s tarmac was covered in crows. They perched in the branches of scrawny trees, silhouetted against the orange horizon and setting sun. They sauntered along the railroad tracks that divided the parking lot in half. More and more flew in from different directions. As I was trying to fathom the number of crows, I looked up, and my jaw dropped. A huge flock of starlings, a hundred feet across, had snuck up behind me and now flew directly overhead. The tight mass of small starlings flew higher, creating a cloud over the looser group of larger crows. The quickly fading deep blue of the sky filled with thousands of moving shadows—the starlings going one way and the crows going every way. The combined spectacle of starlings and crows was like the grand finale of a fireworks show.

      I stood in awe watching the crows and starlings in constant movement. The murmurations of starlings flew out of sight, only to return larger in size, one moment a long, sinuous shape, the next a tight ball of black. Then the flock broke apart and there were two groups of starlings, then three. While the starlings were silent shadows, the crows’ caws echoed a thousand times over, creating a ruckus to rival Bothell’s massive roost.

      Cars kept driving by me, and then I finally noticed small shuttle vans before realizing I was standing in the overflow parking lot for the nearby IKEA store. A security truck pulled up just across the train tracks from me, and the guard simply yelled out that the birds do this every night. Before I could ask any questions, he was gone, driving slowly through the rabble of crows.

      SPRING PRELUDE

       . . . greenness grew over those brown beds, which, freshening daily, suggested the thought that Hope traversed them at night, and left each morning brighter traces of her steps.