Who doesn't love swans? They're beautiful and graceful creatures celebrated for their loyalty to one another. But New York wants to eliminate its mute swans -- not all of them, as the state proposed last year in its first attempt at a management plan, but enough to reverse the damage they supposedly cause to the environment.

To which we say: Slow down. You haven't proven your allegations. Get the data, then we can talk.

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Mute swans technically are an invasive species, brought from Europe in the 1800s to grace wealthy estates. Then some flew off and began multiplying. The state Department of Environmental Conservation says they are so aggressive around their nests and eat so much vegetation that they threaten native waterfowl, whose numbers are declining. But the mute swan population -- 1,600 and steady or dropping on Long Island, 2,200 statewide -- is a fraction of New York's waterfowl. Evidence of wide vegetation devastation is spotty, and concerns about dwindling native waterfowl must be squared with the fact the DEC allows hunters to shoot them.

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In terms of being a verified threat, mute swans are not like deer, where the impacts of overpopulation have been well-documented. Or monk parakeets, another gorgeous nonnative species with the unfortunate habit of building large communal nests on or near power transformers, causing them to burst into flame with resulting outages.

A bill with multiple Long Island sponsors -- passed by the State Senate and on track to be approved by the Assembly -- asks the DEC to delay its culling plan, which includes oiling swans' eggs. The DEC would have to document the harm swans do and hold public hearings. The bill was vetoed last year by Gov. Andrew M. Cuomo, who should sign it this time around.

If mute swans are indeed a menace, reducing their numbers makes sense. But let's prove the case first, before we apply the penalty.