Duck Season

It’s over. The 2020/21 winter waterfowl season at St. Marks NWR is essentially done. I did my February duck survey yesterday. It went quickly since most of the ducks were gone. I logged only 317 ducks of eleven species. For comparison, I had 3,794 ducks on my December survey, mostly Redheads, but including nineteen other species. In February, I would expect between 500 and 1,000 ducks on the refuge.

The general pattern for the winter duck population at St. Marks is a rapid buildup beginning in late October with high populations in December and January before dropping by half or even more in February. Duck numbers are variable in March and April, but by May there are only stragglers that may have health issues and a few transiting Blue-winged Teal coming back from Brazil. Numbers can fluctuate on either end of the season if ducks move early or late. This year, they left St. Marks early. 

Generally, ducks are weather migrants rather than calendar migrants. Because they migrate shorter distances – most North American ducks winter in the Southern US or Mexico – they can delay Southward migration in a warm Fall. If the weather suddenly changes, they don’t have far to go. Similarly, ducks deciding to stage Northward in the Spring can do so incrementally without the commitment of resources that would be needed for trans-Gulf migration. 

Calendar migrants, like Scarlet Tanagers or Pectoral Sandpipers, are usually transcontinental migrants. Because they are making a greater commitment of resources, their migration strategy is more conservative and they stay on a schedule.

This was a good duck year at St. Marks. A total of twenty-five species of waterfowl have been reliably reported this winter.  It was notable for the large numbers of Redheads on the interior ponds. Redheads are grazers that prefer seagrasses, but will eat almost any kind of aquatic vegetation. Tens of thousands of Redheads are found offshore every winter with only a few hundred opting for the interior ponds in most years. The seagrass beds in Apalachee Bay that they rely on are slowly degrading, but there has not been any cataclysmic event that would explain why 2,314 Redheads decided to feed on Mounds Pool III and Lighthouse Pond in December. This was five times as many Redheads as I have ever seen on the interior ponds.

This morning as I waited for the morning Wood Duck flight on the North Levee of Stony Bayou II at first light, I saw a wraith-like cloud of birds rise out of the marshes a mile to the East. I followed them with binoculars as they twisted and turned, gained altitude and disappeared to the North. It was probably a flight of migrating Tree Swallows. 

I am a student of seasonal change. I know that duck season inevitably gives way to the excitement of Spring migration. I look forward to it, but I confess to a slight sadness at seeing the ducks slip away from St. Marks on their annual journey back home.

It was a good duck year.