“…the crane is wildness incarnate.”
-Aldo Leopold (“Marshland Elegy”)
In recent years islands and sandbars along the Wisconsin River have hosted ever-growing numbers of Greater Sandhill Cranes as they prepare to depart for their wintering areas. In Fall 2015, flocks that swelled to upwards of 10,000 birds converged on the stretch of the river above and below Aldo Leopold’s Shack. That’s a large proportion of the cranes that now nest in Wisconsin. Why has there been such an impressive resurgence in the crane population since Aldo Leopold worried about its impending extirpation 80 years ago, and what attracts all these birds to the vicinity of the Shack?
We almost lost the Greater Sandhill Crane from Wisconsin primarily because of unrestrained hunting, coupled with wetland habitat loss. The Greater Sandhill Crane did disappear as a breeding bird from Illinois in 1890, Iowa in 1905, South Dakota in 1910, Ohio in 1926, and Indiana in 1929, and it was nearly extirpated throughout the rest of the Midwest. Until that is, protection conferred by the Migratory Bird Treaty Act of 1918 (MBTA) ended the uncontrolled killing and allowed cranes and other migratory birds to recover. As we approach the centenary of that pioneering piece of conservation legislation, the sandhill cranes of the upper Midwest bear witness to its effectiveness. But, in his 1937 essay “Marshland Elegy,” Aldo Leopold wasn’t very confident that sandhill cranes would long survive, and he wrote of the approaching day when “…the last crane will trumpet his farewell and spiral skyward…”
Leopold reckoned that there were just a few dozen cranes in Wisconsin in the 1930s. From a low point at the time when protection of the MBTA came into effect, cranes began a slow recovery. Since they don’t reach sexual maturity for several years (up to 4 years on average), raise at most one or two young per pair per year, and relatively few pairs actually succeed in raising any young, crane numbers can’t increase rapidly. Their recovery started slowly, gathered momentum after the mid-20th century and will eventually slow as the population has now occupied most of the available breeding habitat in Wisconsin.
After their breeding season, sandhill cranes follow a predictable pattern as they prepare to migrate to wintering areas. For our Wisconsin cranes, depending on food availability and weather conditions, that could be as near as Indiana or as far south as the Gulf Coast. My student, the late Scott Melvin, and I described this pattern after studying sandhill crane migration 35 years ago. In late summer, breeding pairs and their offspring start losing their territorial defensiveness and begin to spend time foraging with other nearby family groups and non-breeders before returning to their home territory each evening. Eventually, usually by late October, most sandhill cranes leave their summer habitat and converge on “traditional staging areas” which are typically within a single day’s flight from home.
These traditional staging areas, as the term implies, are used year after year by large numbers of cranes as they prepare for the upcoming longer distance migration. Parent cranes lead their offspring to the same locations each fall, maintaining the tradition through many generations. Cranes from throughout a region will gather at these staging areas that always offer the co-occurrence of two essential requirements: an abundant source of food (usually waste grain available after the harvest) and nearby nocturnal roosting sites where the flocks of cranes feel safe from nighttime threats (often on an island). The daily routine for the assembled flocks consists of leaving the roost in the morning and heading out to nearby foraging areas before returning to the roost at sunset. An evening roost can contain thousands of cranes packed into a particularly desirable area. Once they have congregated at a staging area they will remain there throughout the fall until the food supply is no longer available and winter weather sets in, usually by early to mid-December.
The stretch of the Wisconsin River within the Leopold-Pine Island Important Bird Area (IBA) fits the bill perfectly. River islands and sandbars provide ideal nocturnal roosts and nearby cornfields provide abundant waste grain. Furthermore, the surrounding region of central Wisconsin is the core area for breeding cranes in the state. The crane staging area was one of the key justifications for the IBA’s creation.
As this autumnal gathering of thousands of cranes has grown, literally in our backyard, the Aldo Leopold Foundation recognized that it presented an unparalleled opportunity to share this impressive spectacle with the public and educate them about crane biology and conservation. For the past five years I have been leading crane-watching field trips for friends of the Foundation, and the response has been overwhelmingly positive. The staff has erected blinds that allow groups to watch the cranes from the south bank of the river just behind the Shack. Four or five weekends each year we gather at the Center for a briefing before heading out to the blind for an hour or so of crane watching until after sunset when the cranes have settled in for the night. We are fortunate to be hosts to this spectacular ornithological show and delighted to be able share this awe-inspiring display with others.
Aldo Leopold lamented the decline of sandhill cranes in Wisconsin, and he never imagined the day would come when the marvelous sights and sounds of flocks of thousands would be a regular autumnal phenomenon near his beloved Shack. Nonetheless, his poignant words in “Marshland Elegy” resonate as well today, when cranes are back among us, as they did when cranes seemed destined to disappear from Wisconsin:
“When we hear his call we hear no mere bird. We hear the trumpet in the orchestra of evolution. He is the symbol of our untamable past, of that incredible sweep of millennia which underlies and conditions the daily affairs of birds and men.”