Unseen City

“Unseen City: The Majesty of Pigeons, the Discreet Charm of Snails & Other Wonders of the Urban Wilderness” by Nathanael Johnson explores the natural world as it encroaches on our cities. He examines several different species of synanthropes to see how they’ve adapted to our built environment and why they excel there.


  • Facts are stupid things,” the nineteenth-century naturalist Louis Agassiz observed, “until brought into connection with some general law.”
  • Invasive species – When scientists have gone back to follow up, they have never found that the new arrivals created a single-species wasteland. The native species might not be present in the same abundance, might not be in the same places, but they are there.
  • Invasive species – On balance, it seems, the result of ecological immigration isn’t gray uniformity, but just the opposite: Naturalizing species have given us richer biodiversity.
  • The media wasn’t interested in reporting that zebra mussels were only thriving because the lakes were so polluted. Zebra mussels eat the polluting algae, and in the long run have probably done more good than harm
  • Most humans, I suspect, don’t learn by memorizing decontextualized data. It’s almost the opposite: We learn by trying to solve a problem, or working out a mystery.
  • Before I started researching plant chemistry, I divided the world of potential foods into two categories: things that are poisonous and things that aren’t. But in reality everything is a little bit poisonous.


  • Like breast milk, it is stimulated by the hormone prolactin; in fact, scientists discovered prolactin while studying pigeons
  • Katie Hinde has written on her blog, Mammels Suck: “The production of milk independently arose after the divergence of avian and mammalian lineages over 300 million years ago. However, these milks seemingly serve the same function: body-nourishing, bacteria-inoculating, immune-programming substances produced by parents specifically to support offspring development.”
  • “Pigeon feeders are often individuals who have no one to care for. The pigeons play an important role in replacing emotional ties,” Haag-Wackernagel wrote in a report on the project. But it’s not just unfortunate, slightly crazy people. Animal-rights groups and at least one neighborhood organization have reluctantly begun feeding large quantities of grain to pigeons because they feel a moral obligation to prevent the birds from starving. This is ridiculously wrongheaded, according to Haag-Wackernagel, because while feeding pigeons may indeed prevent some from starving, it increases the sum total of pigeon suffering.
  • Juveniles have brown eyes, whereas adult pigeons have shockingly bright, reddish-orange eyes.
  • The young back up to the edge of the nest and poop off the side, building up a rim of guano.
  • The genetic rules that govern pigeons are complex, but pigeon breeders developed folk knowledge that comprehended recessive characteristics, sex-linked attributes, trait suppression, and other principles long before the time of Gregor Mendel or Charles Darwin. Much of Darwin’s theory of evolution, in fact, comes from observing the techniques of pigeon breeders


  • The snail, writes Bailey, “is the only known land animal able to find calcium by smell.” And because the snail carries chemical receptors in each of its tentacles, it can smell in stereo.
  • I also came across a diagram of snail anatomy and was confused by the fact that the organ labeled “anus” seemed to be inside the shell. A little more digging confirmed that I was not misreading it: Snails poop on their own heads.


  • Neuroscientists studying crows have shown that they can quickly and accurately infer the cause of an unexpected event. They also, like humans, can make mistakes about what causes what; in other words, crows can develop superstitions.
  • When the birds come across a dead body of their own kind, they call in their neighbors. This can go on until a giant congregation is present. Scientists have observed crows placing objects near bodies, and even outlining them with sticks. Haupt has also witnessed what she called a “crow hospice”—a silent gathering around a bird that was dying.


  • One day the golden leaves are aloft, and the next they are spread in a circle around the trunk. The fall is so dramatic that for many years the townspeople of Monroe, Wisconsin, held a competition to see who could most accurately guess the date the old tree outside the library would shed its leaves. “Ginkgo has the most synchronized leaf drop of any tree I know,” Crane writes.
  • Ginkgo owes its resurgence in historical times not just to its utilitarian value but also to some kind of irresistible biological charisma


  • E. O. Wilson, the patriarch of ant science, has said that insects are so important that if all the land arthropods disappeared, humans wouldn’t be able to survive for more than a few days.


  • There are between five and twenty male squirrels for every female.