What we need, he said, is "a lot more people who have some appreciation of birdlife and who will act on it - by supporting habitat protection, buying shade-grown coffee, planting native plants, laying off the pesticides. We need millions of perpetual beginners who will do these things."
The idea of reconnecting people - especially children - with nature is gaining resonance these days, not least from the Obama administration's Great Outdoors Initiative, announced in April.
So I called Kaufman and he emphasized he's not talking about merely naming species, but about knowing them - "actually connecting."
A lot of people claim to be interested in nature, but "they express it by watching nature programs on television," Kaufman said. So he doubts that many people could come up with a list of 25. Although, "if you stretched it to include elephants and lions and polar bears, then maybe the average person could barely squeak out 50."
Speaking of which, where he lives in northwest Ohio, inner-city Toledo kids come to a local nature center and are afraid bears will eat them.
People say they like butterflies, but then they'll squish a caterpillar, ending its life cycle before it becomes a butterfly. They recognize a robin in a book, but not on the lawn.
He doesn't blame the people, by the way, but nature education as a whole.
This matters because people aren't likely to care about something abstract. Kaufman likens it to not knowing anyone where you live. You'll be more likely to care what happens to the neighborhood if you know that the three kids next door like baseball, and that the widow next to them bakes great bread.
I made my own list of 50 plants and animals but was dismayed to see how many of the insects I considered pests - like ticks and mosquitos.
Patricia Zaradic of Bryn Mawr focuses on the connection between children and nature, and helped coin the term "videophilia" - the human tendency to favor sedentary activities involving televisions and computer screens and other electronic media.
"So much of a relationship with nature is having experience with it," she said. "Having a butterfly land on your hand, watching a robin pull an earthworm out of the grass."
She too thinks what's needed is building that relationship with nature.
Dennis Burton, executive director of the Schuylkill Center for Environmental Education in Roxboro, also agrees, but he worries about how that intimacy can happen.
With development pressures everywhere, the center has formally preserved its 300 acres so the landscape can't be disturbed. But while kids can walk through it, they really can't do much else.
Burton wonders if centers like his will, in essence, become "tree zoos." He says the wilderness ethic - take only pictures, leave only footprints - is "antithetical to experiencing nature," which he thinks includes "getting your hands dirty."
But he's heartened by his nieces and nephews. In his yard, he breaks off a mint leaf and offers it. At first, they go "eeauuw." But then they taste, and they're amazed.
Or he'll show them how to pet a bumble bee, which doesn't sting. And then, "the expression on their faces, there's something really joyous there." He's certain they leave wanting to know more.
So the advice of all three is to give nature a try. It can be as simple as stepping out into the yard and allowing one's curiosity to lead the way.
Even in the inner city. The beauty of Philadelphia is that parks proliferate.
Kaufman, among others, has written field guides, which are handy. And nature centers have interpretive exhibits and other information.
"Just go out and find something," Kaufman says.
Our conversation reminded him of when he was a kid and was rabid about birds - so much so that he didn't pay attention to anything else.
Then, someone interested him in butterflies. He began to see them everywhere.
It wasn't that they suddenly appeared. He was just noticing. "It was like magic."
Contact staff writer Sandy Bauers at 215-854-5147 or email@example.com. Visit her blog at http://go.philly.com/greenspace.