Feral Cities (24 page)

Corvids may be the birds that understand how best to use roads, but other birds have also figured out that traffic can work to their advantage. Among them is the marabou stork, a strong contender for the title of the world's ugliest bird. No one will be asking these African storks, also known as the undertaker bird, to deliver babies anytime soon. They look as if they've escaped out of someone's nightmare. They stand five feet tall and have huge blue-gray wings, but when stomping around on the ground they hunch themselves up so their sharp swordlike beaks rest on the wobbly, inflatable sacs of bare pink flesh that dangle from their necks.

Their calls are a mix of chilling clattering noises and grunts, and their dark-gray legs usually appear white because they are covered in the stork's own excrement, which helps the birds stay cool in the hot sun. The bald scalps of their featherless heads help them stay clean when tearing flesh from the rotting carcasses that form much of their diet. Not that they only eat the dead. They often prey on other animals, swallowing live turtles whole and even taking down young flamingoes in the lakes of Africa.

They are graceful fliers though, so that balances things out.

The marabou stork's natural home is savannah and grassland, but they are common sights in many African cities. In the fast-growing Kenyan capital of Nairobi, marabou storks nest in the thorny fever trees that line the busy Uhuru Highway close to the Nyayo National Stadium. It's a handy spot for picking up roadkill or for paying a visit to the city's slaughterhouses. The storks also turn up at the miserable Dandora garbage dump on the edge of the city, where they join the estimated ten thousand people who spend their lives trawling through the filthy mountains of waste for anything they can eat or sell.

Though the birds' excrement has turned the sidewalk of the Uhuru Highway rusty white, the marabou stork is largely welcomed in Nairobi. Rather than seeking to expel them, the Kenya Wildlife Service regards them as unpaid cleaners, who help to keep the streets free from muck.

Birds do not just come to cities for the food. They also come for the weather.

Cities have powerful effects on the local environment, and one of the most startling is the urban heat island effect. This phenomenon can make city centers as much as twenty-two degrees Fahrenheit hotter than the rural areas surrounding them. The effect is the result of replacing vegetation and soil with buildings, roads, and sidewalks. First, the removal of vegetation means the cooling effect of the water vapor released by plants and the shade offered by trees is lost. Then there are the concrete and asphalt surfaces that replace the natural flora. These materials absorb rather than reflect sunlight. During the day they soak up sun rays, storing them as heat that is then released at night. It's like a battery that charges in the day and releases its energy at night.

Traffic, industry, and air conditioning also play a role, pumping out more heat, while buildings block out cooling winds. In dense city centers filled with skyscrapers, the heat island effect can be
even greater, because glass windows concentrate the light onto the street below and the heat released at night becomes trapped, boxed in by buildings on all sides.

The urban heat island effect isn't universal. In fact, the exact opposite happens in cities like Phoenix and Abu Dhabi, where irrigation makes them cooler than the hot desert around them. But for most cities, the urban heat island effect is at work, dialing up the temperature.

The extra heat has a noticeable impact on life in the city. Plants flower earlier and insects become active earlier too—which is great news for the birds that eat them. In the wine-making city of Zielona Góra in western Poland, researchers found that black-billed magpies start building nests and laying eggs earlier than those outside the city, thanks to the supply of food and the warmth. As a result, the city's urban magpie population was growing three times faster than the rural population.

City lights produce similar effects, with blue tits laying eggs a day or two earlier in areas with streetlamps. Light also causes birds to start singing earlier in the morning and later at night, an effect that is more pronounced on cloudy days when more of the urban light is reflected back toward the ground.

So far, so good, then, for the urban birds. They can feast on our bird feeders, raid our trash, and forage on our dumps. They also get to enjoy a warmer climate and get to stay up later thanks to the lights. But these benefits come at a cost: noise.

Cities are noisy places, filled with the din of traffic, the sound of construction, and the bustle of people. Some areas are exceptionally noisy. Not least the Champs-Élysées in Paris, where the traffic thunders past at an ear-splitting eighty decibels. For urban songbirds, overcoming the blare is vital. If they can't make themselves heard above the traffic, they could miss out on attracting a mate, fail to hear their chicks crying for food, or not hear another bird's warning of a predator.

Songbirds have come up with different strategies for dealing
with the noise. Some resort to singing when the city is quiet. In the Spanish city of Seville, house sparrows and spotless starlings sing early to avoid the rush-hour traffic. Blue tits, European blackbirds, and European robins do the same.

Others pump up the volume. One bird that does this is Australia's noisy miner, a gray-bodied bird with yellow patches next to its eyes that make its eyeballs look bigger than they really are. As their name suggests, these honeyeaters are loud birds at the best of times, but when they take up residence along the busy arterial roads of Melbourne, which carry more than five thousand vehicles a day, they get even louder. In some cases noisy miners drown out the traffic by letting out alarm calls at a whopping ninety decibels.

Traffic also forces birds to change their tunes. Most urban noise consists of low-pitch sounds, so birds often sing higher to avoid having their lower notes missed in the cacophony. It's a strategy favored by great tits, which also sing shorter and faster songs in cities.

But cities are not just loud, they get louder over time, as the male white-crowned sparrows of the Presidio of San Francisco know all too well. Since 1969 these birds, which despite their name have black and white stripes on their heads, have been trapped in a melodic arms race with the growing noise from the Golden Gate Bridge. To cope, the brown-winged birds have been singing higher and higher as they try to avoid being drowned out by traffic.

The resulting tune has changed so much that the sparrows no longer recognize the songs they sang back when hippies rather than techies roamed the San Francisco streets. When researchers played them recordings of their present-day songs, the birds reacted as if it was an intruding rival, but they paid no attention at all to the songs they sang in the 1960s.

Noise is not the only challenge for urban songbirds. The structure and architecture of cities plays havoc with their songs, which bounce off glass, get dulled by pavement, and echo around buildings. The sonic interference from the artificial surfaces and buildings
means songbirds face the risk that their songs will get distorted, missed, or canceled out altogether.

To deal with urban acoustics, birds adjust their songs to take account of the artificial surfaces. Often their response reflects how high or low they usually sing. In Washington, DC, and Baltimore researchers examined how the songs of six songbirds changed in response to how built-up the local area was. They found that gray catbirds and Northern cardinals sang higher to avoid the low notes of their songs while higher pitched singers, like the American robin and house wren, went the opposite way, cutting back on the top notes to compensate for the effect of urban surfaces.

But as the white-crowned sparrows of San Francisco show, urban birds can't sit still. The city is constantly changing, and birds hoping to cash in on the food available in the city need to keep pace with an ever-changing environment. For some birds that challenge is just too much. “There's two very different sides to the story,” says Kimball. “In order to create cities like L.A., we totally obliterated hundreds of square miles of habitat, some of it very specialized with very unique species. We destroyed it all. Some birds are habitat specialists and don't tolerate urbanization.”

Others thrive for a while only to end up defeated. One such bird is the spotted dove, a pigeon-like bird with a dusty pink breast. Native to Southeast Asia, they were brought to Los Angeles in 1915 and soon became a regular sight around the city. “It became one of the most abundant birds in urban and suburban Los Angeles and beyond,” says Kimball. “Then, starting in the 1970s, their populations just started dropping. People hardly even noticed until they were virtually gone by the 1990s. Now we just have a few little pockets of them here and there.”

Why the spotted dove went from urban success story to near-extinction remains a mystery. Nest-raiding by crows is a possibility, disease another, but the truth is no one knows for sure. “Why were urban habitats so good for them and then suddenly, within a couple of decades, did they die out? And why did they die out when we
still have mourning doves all over L.A.? Presumably they eat more or less the same things and have more or less the same predators, so why are mourning doves still common? Maybe the mourning doves are having the same problems, but there are millions more of them elsewhere in Southern California that are constantly recolonizing the city.”

While birds like the spotted dove shine brightly but briefly in the city, for others it is nothing but a death trap.

It's quarter past five in the morning and Chicago is dark and enveloped in fog. I'm waiting outside the Wrigley Building on North Michigan Avenue for Annette Prince, director of the Chicago Bird Collision Monitors. She's just called to say she's running late and suggests I check for injured or dead birds near the chewing gum giant's headquarters while I wait.

This is what the hundred or so Chicago Bird Collision Monitors do. Early every morning, while most of the city is asleep or getting ready for work, these volunteers are combing downtown streets looking for birds that have crashed into skyscrapers.

With time to kill, I figure what the hell and start scanning the sidewalk. It looks empty. The only signs of life are a few eager joggers, some night shift workers waiting for the bus home, and a homeless man, who is methodically checking the bins.

Oh, and the woman in the median of Michigan Avenue.

She stands out. Mainly because she's standing on the concrete surrounding the median's flower bed, singing a mournful hymn.
Her voice is beautiful but she looks deranged, her eyes glaring at the city as she belts out what sounds like a Hildegard of Bingen number to an imaginary audience. With her haunting vocal cutting through the mist, it all feels very gothic and it's about to get even more so.

Out of the corner of my eye I see something on the floor next to a ground floor window. I can't tell what it is from where I am; it might be a leaf or some litter. I head over for a closer look.

It soon becomes clear what it is: a dead bird about the size of a pigeon. Its yellow breast faces up to the sky, its black wings patterned with white lines. As I get nearer, I notice that its head is missing. Then, I see the ants.

Thousands of tiny ants are crawling all over the headless bird. Gruesome as the sight is, I'm kind of impressed that so many ants could eke out a life in this concrete corner of the city. For them the arrival of the dead bird must be like having all their Christmases come at once, a gift from the ant gods.

Just as I'm wondering where the bird's head is, I see it. It's twenty feet away resting upright in the middle of the sidewalk. A jogger runs right over it, missing the head with its scarlet crown and neck by less than an inch. She didn't even seem to notice it was there.

As I'm taking in this macabre scene, complete with ghostly mist and the eerie melody of the woman on the median, Annette calls me again. “Almost there,” she says.