They are invading America, crossing the Rio Grande without anybody’s permission and ending up near my house all the way up in New Jersey, where they spend the entire day looking for a free drink, singing out loud in their foreign language — and trying to catch bugs.

The yellow-bellied sapsuckers, cliff swallows and orange-crowned warblers have arrived in the Northeast on their spring migration from Mexico and points south.

I am a birder, one of those nuts with binoculars you sometimes see in fields and swamps. As a birder, I am also an environmentalist. I want the birds, as well as other animals, to have the undisturbed land they need to continue gracing us with their presence. But now I am told that I am to blame for environmental degradation.

The Sierra Club, the nation’s pre-eminent environmental organization, finds itself facing a takeover by anti-immigrant extremists less interested in protecting feathered migrants than in stopping people like me from seeking a better life in the United States.

Sierra Club members are voting in an election to fill five seats on the 15-person board of directors. Of the 16 candidates, three openly argue that the organization should change its neutral position on immigration in favor of a restrictionist policy. Three others have also been endorsed by a faction that favors the anti-immigrant platform. If all are elected, they and three current board members who also favor immigration cuts and who are not up for re-election this year will form a majority.

What does immigration have to do with environmental protection? Richard Lamm, the former governor of Colorado who is the best-known of the anti-immigration candidates, says that immigration results in population growth, and “population growth exacerbates all the environmental problems.”

But Lamm — who has a long history as an anti-immigrant activist and population-control fanatic, and who joined the Sierra Club just weeks before announcing his candidacy — fails to see what every environmentalist without a hidden agenda can see. As the Sierra Club’s executive director puts it, “Immigration restrictions don’t solve environmental problems, they merely shift them elsewhere.” In other words: Ending human immigration from Mexico, for instance, might mean less overcrowding here but does nothing to protect natural habitats where those yellow-bellied sapsuckers, cliff swallows and orange-crowned warblers spent their winter.

And if it doesn’t protect those habitats, how can it deserve the name “environmental policy”? The answer is that it cannot. It’s anti-immigrant policy, nothing more.

If Lamm and his anti-immigrant friends win, the Sierra Club will no longer have protecting the environment as its primary mission. The organization founded by John Muir, an immigrant himself, will instead become one more shrill voice in the chorus screaming to keep out undesirables who speak the wrong language. Will its 700,000 members put up with xenophobia dressed up in green?

Cuban-born Roger Hernandez is a syndicated columnist and writer-in-residence at New Jersey Institute of Technology.