Thong Chow Ngian sent in this documentation of 4 Green-imperial pigeons drinking rainwater in Singapore.
On 31 Aug 2021, I observed 4 Green Imperial pigeons (Ducula aenea) perching on the Footstool palm tree (Saribus rotundifolius) outside my apartment balcony during a heavy down pour. I noticed 2 of them drinking rain drops for at least 5 minutes each, while waiting for the rain to stop. I have included 2 photos and a video for reference.
A video of a pigeon in action.