The phrase "are quickly dwindling" is correct and usable in written English.
It can be used to describe a situation where something is rapidly decreasing in number or amount.
Example: "The resources available for the project are quickly dwindling, and we need to find a solution soon."
Alternatives: "are rapidly decreasing" or "are swiftly diminishing".
Those alternatives are quickly dwindling.
Open spaces and trees belong on Long Island (although, unfortunately, they are quickly dwindling).
Sure, Japan still has some neat stuff (especially with their uses of RFID) that hasn't taken off stateside, but the differences are quickly dwindling.
But Brady is 36 and Manning is 37, so the opportunities for the two of them to face off against one another are quickly dwindling, and this could very well be their final matchup.
By Thursday they were on their fourth printing, and stock was quickly dwindling.
Milian explains that some still have hope the borders will reopen, though such hope is quickly dwindling.
Faith in the government of Emmerson Mnangagwa, who was cheered when he deposed longtime leader Robert Mugabe in 2017, is quickly dwindling.
It is a date in the first half of 2009, and the number of those left is quickly dwindling.
Just this week, researchers at the University of British Columbia published an analysis revealing that a large roster of fish species have been on the move in response to rising temperatures for at least the last four decades, and that in some marine ecosystems, particularly in the tropics, fish abundance was quickly dwindling.
Not only is Boyle able to capture the vast and expansive beauty of the canyons to create a stunning backdrop, at the same time he can take us right down to the bone - literally - in a CSI style shot of the inside of Ralston's arm, or from the p.o.v. of the bottom of a water bottle whose supply is quickly dwindling as Ralston's tongue laps up whatever's left.
Her chances were rapidly dwindling.
