Where do all them ducks go

What: A few winters ago I spotted large numbers of mallards (200-400) flying westward towards the lake around 4:30pm or so, just around dusk. Despite Burlington Bay being frozen at the time, as it is now, the ducks were still flying that direction. My interest was piqued and I wondered where o where those ducks were all spending the night. I spent the next few nights out around the same time trying to spot them. Sure enough, around the same time, a large flock of ducks would fly westward over Centennial Woods.


Audio of the ducks. You can hear them flapping their wings as scores of them would leave and others arrive. Our presence seemed to make them jumpy.  

As with the crows (I have yet to follow the ring-billed gulls) I decided to track them down and see where they were roosting each night. A few days after seeing them for the first time, I fortuitously wound up spotting - or rather hearing - them while out on a run. As I was coming north on the bike path, I passed the water treatment center's clarifiers (those big circular tanks with exposed water) and heard some noises. I peeked over the fence and there they were!

Mallards landing in circulator

I hadn't been back in a while, and the recent postings on the Vermont Birds list host about ice closings on the lake inspired me to back last Thursday night with Jon. We were greeted with a raucous reception. Our estimate put the number of mallards in just one of the clarifiers well over 1000. In the photo above, there were probably about 20% of the original number of ducks.

The other question is where do they go during the day? I would assume that there are a number of small openings in rivers, industrial parks, and other spots where they have access to open water (eBird gives a good sense of this with birders' postings from around Vermont: Map)