GREENE CO., MO. — Charley and I headed down to Taney County this afternoon, hoping to locate a robin roost in preparation for the CBC on Dec. 30. We failed completely. After checking several known roost sites, all we had seen was a small flock of robins flying high and fast.

The Taney County winter robin roost is legendary in GOAS circles. During the 1990s, robin numbers were estimated at or above one million on three of the counts.

I have never seen numbers that high; the roosts have not held that many birds for several years now, if estimates are reasonably accurate. But this year, there doesn’t appear to be any concentration of the birds at all. Not even a small number like 100,000.

My curiosity piqued, I turned again to the Audubon CBC database. What I found was intriguing.

The count data show a near-perfect alternation between “high” years (an active roost with hundreds of thousands of robins) and “low” years (a few hundred birds scattered around the count circle). Last year, the count was “high” (though quite low compared to previous “high” years), so it shouldn’t be a surprise that this year is low.

What factors influence these swings? Do junipers have some sort of biennial fruit production cycle? It’s fascinating data … I’d like to find out more.

Though we missed the robins, Charley and I did encounter a flock of white, fluttering Bonaparte’s Gulls. They plunged into the water after prey, submerging themselves completely — much more like terns than their larger larid cousins.

Trackback This Post | Subscribe to the comments through RSS Feed