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The Christmas Bird Count is the longest-running bird census in the country — 15-mile-diameter circles, one count day between 14 December and 5 January, every bird seen or heard tallied by volunteers — and Indiana's own CBC history is dated: the state's first count was held at Richmond on 25 December 1908, and the modern 15-mile circle form dates from the 1950s. Two established circles stand within reach of this township, and the test this article was ordered to run is whether either of them covers Walkerton's ground. The South Bend circle's own feeder guide fixes its geometry exactly: "The South Bend count circle center is at the intersection of Washington and Michigan Streets in South Bend. The circle covers 15 miles (7.5-mile radius from the circle center)." Walkerton lies roughly fifteen miles south-west of that corner — about twice the radius. The South Bend circle does not cover this ground. Its record is nonetheless the county's counted-bird literature at one remove: in the 122nd Indiana CBC summary (2021–22 season) the South Bend count produced the state's first CBC Tennessee Warbler and its second Nashville Warbler, 47 years after the first; in the 121st it tallied 21 Brown Creepers and two Red Crossbills. Counted birds, dated and specied — for the county seat's circle, not for this township.
The nearer circle is Bremen's, in Marshall County — a confirmed count for Saturday 20 December 2025 under compiler Leland Shaum, in Indiana Audubon's current list — and the Bremen circle is a strong counter: in the state summaries its landfill produced all five of the season's Iceland Gulls in the 122nd count and 488 of its Herring Gulls in the 123rd, with 44 Red-headed Woodpeckers, 99 Northern Flickers and 231 White-crowned Sparrows in the 122nd and a Palm Warbler and 482 Northern Cardinals in the 123rd. Whether the Bremen circle's 7.5-mile radius, centred on Bremen, reaches west far enough to take in Potato Creek or the township's eastern edge could not be settled from any published circle map reached, and no count named for Walkerton, North Liberty or Potato Creek appears in any Indiana CBC list reached. The finding therefore prints at its result: no Christmas Bird Count circle is documented as covering Walkerton's ground; the township's winter birds are counted, if at all, at a neighbouring circle's edge, and the instrument that would settle it is named below. The Elkhart County count — 31st annual, set for 2 January 2027, its circle from the state line to Waterford Mills — documents the region's CBC culture whole and touches none of this ground.
The rookery test prints at its result beside it. Chapman lists the heron family visiting this region — great blue heron, least bittern, green heron, night heron, American bittern — as visitors and marsh birds, never as a colonial nesting rookery on this ground, and no heron rookery sited in Lincoln Township was found in any modern source reached: Potato Creek's birding record, the richest for this ground, lists herons among its wetland birds without a rookery. The negative prints as a searched negative at the strength of the sources named; a rookery is a conspicuous, mapped feature in the state's natural-heritage practice, and none is mapped here.
Sources: Indiana Audubon, "Counting Birds at Christmas: Indiana's CBC History" and the 2025 confirmed-count list (Bremen, 20 December 2025, Leland Shaum); National Audubon Society, 121st–123rd Indiana CBC summaries; South Bend–Elkhart Audubon Society, South Bend CBC feeder guide (circle centre and radius as quoted) and Leaves, November 2026 (Elkhart County count, 31st annual); Indiana Birding Trail, Potato Creek birding account; Chapman (1880), p. 343 (herons as visitors). Closure: MIXED — the South Bend exclusion is DUG from the circle's own published geometry; the Bremen-circle western edge and the rookery negative are NAMED GAPS at the strength stated, settlers: the National Audubon CBC circle map for the Bremen circle, and the Indiana Natural Heritage Data Center element-occurrence record for Lincoln Township.