The state Department of Health is investigating citizens' complaints about feral cats at Kakaako Waterfront Park, but the problem is not limited to that Honolulu neighborhood and the public nuisance needs to be dealt with islandwide.

The unfettered cats, and the malodorous urine and feces they leave behind, pose a potential health risk, make public parks less hospitable to people and present a tainted image to tourists who think of Hawaii as paradise.

Well-meaning souls who feed the animals without also collecting them to be sterilized exacerbate the problem, which is obvious throughout the urban core and into Honolulu's suburbs.

A 2006 report by the American Bird Conservancy documented how feral cats have decimated Hawaii's bird population, including some rare native species.

That report said the islands' mild climate allows the cats to breed year-round, with a single female giving birth to up to 18 kittens a year. The lack of natural predators — there are no snakes or coyotes in Hawaii — leaves the population unchecked.

The Hawaii Cat Foundation and Hawaiian Humane Society have collaborated effectively for more than a decade on a program that encourages people to feed only those feral cats that have been caught, spayed or neutered (at no cost to the caregiver) and then returned to the feline colony.

The system, known as Trap, Neuter, Return and Manage, has prevented the births of tens of thousands of unwanted kittens. Last fiscal year alone the Humane Society sterilized some 2,400 feral cats brought in by 400 people on Oahu; the “;fixed”; cats are recognizable by their notched ears.

Both nonprofit groups also work to educate the public on the downside of acquiring a cute kitten on impulse, only to abandon it once it grows up.

But cat owners who abandon their pets continue to fuel the feral cat population, as do people uninvolved in the TNRM system who feed free-roaming felines without having them sterilized. What those folks consider a kind deed is actually a misdeed, and should be deterred — whether by the property owners where the feeding takes place, or by the state or county departments tasked with enforcing existing applicable laws and policies.

The investigation of the burgeoning feral cat population should not begin and end at Kakaako Waterfront Park.