Call it birth control for birds.
A corn-based feed containing the drug nicarbazin, which stops female birds from producing eggs or causes them to lay eggs that do not hatch, has helped to significantly reduce the pigeon population outside Masjid Haji Muhammad Salleh mosque.
The 400 birds there have shrunk to 120 to 160 pigeons.
The Agri-Food and Veterinary Authority (AVA) revealed the results of the year-long trial of the drug, which concluded last month.
Said Mr Mohamed Idris, secretary of the management board of the mosque, which is in Palmer Road, near Shenton Way: "There has definitely been a visible and positive improvement. A stark difference, and the best thing is it was achieved without culling".
He said that while the birds still find their way into the mosque sometimes, this happens much less. Also, fewer people are getting soiled by the birds that lurk in the area too.
"In the past, the dropping might hit you as soon as you stepped out," he added.
3,500 Number of pigeon-related complaints and feedback from January to October
4,000 Number of complaints and feedback last year
2,500 Number of complaints and feedback in 2014
6,400 Complaints and feedback about all kinds of birds, including pigeons, from January to October this year
He said the mosque management is open to extending the trial and has discussed this with the AVA.
The drug does not harm the birds and is not toxic to animals or humans if taken in small amounts. It would take 40kg of the feed to see toxic effects in dogs and cats, and 60kg for a child.
Commenting on the trial's results, the AVA said, however, that the drop is unlikely due to the effect of the drug alone, and that other factors may have contributed.
For example, the AVA found 15 dead pigeons at the trial site in April which, post-mortem examinations found, were due to dehydration.
The agency added that it has been keeping watch on the area to prevent people from feeding the birds. Since October last year, it has issued around 60 warning letters and fines to individuals caught feeding the pigeons there.
Feeding pigeons is illegal and those found to have flouted the rules face a fine of up to $500. A total of 109 warnings or fines were given for feeding pigeons between January and last month.
Pigeons are a cause for worry because they can spread diseases such as psittacosis, a bacterial infection of the lungs with pneumonia-like symptoms.
As the effectiveness of the nicarbazin feed remains inconclusive, the AVA started another year-long trial using the same feed in Waterloo Street outside the Sri Krishnan Temple in September. There are about 150 pigeons there.
The Waterloo Street trial will also study if the level of human traffic, which is closely linked to the amount of food left for the birds, impacts the effectiveness of the feed. The birds will be fed once a day by a temple employee.
As of last month, the AVA had received feedback 13 times regarding pigeons in the Waterloo Street trial area since the start of the year. This compares to 20 times last year.
Overall, the AVA received 3,500 pigeon-related complaints and feedback from January to October this year.
Last year it received about 4,000, an increase from about 2,500 in 2014.
It has also received some 6,400 complaints and feedback about all kinds of birds, including pigeons, over the same period this year. About 7,300 messages were received last year, and about 5,700 in 2014.