Least exilis

The is the smallest and most secretive to breed in Vermont. Al­ though often regular in its preferred habi­ tat-extensive cattail and sedge marshes-it is rarely seen even by the most determined or fortunate observers, and then often is only drawn to the open by tape recordings of its call. A weak flier, the Least Bittern seldom flushes, preferring instead to slip stealthily away, or, if alarmed, to freeze with head and neck upright in the characteristic hiding position of the larger American Bit­ tern. It migrates long distances, wintering from southern Florida and Texas south to stems gathered from the immediate vicinity . Migration dates are poorly de­ and" placed on a clump of the previous year's fined because of the species' retiring nature, vegetation. Overhanging vegetation is pulled but it apparently arrives in Vermont nest­ down and incorporated into the nest, with ing areas in mid May and departs in late the more resilient stems forming a canopy. August. The male performs most of the nest build­ Although the Least Bittern's breeding ing, but both sexes continue to add to the range includes much of central North Amer­ structure throughout incubation. Courtship ica and extends south through subtropical and territoriality have been inadequately , it is locally distributed; it is studied; copulation occurs at least occasion­ most common in regions with extensive ally at the nest. The sexes are dimorphic, marshes, and may be rare or absent from the male exhibiting a much darker mantle, large blocks of the overall range. This pat­ but the significance of this dimorphism is tern is maintained in Vermont, with nearly unknown. A rare dark color morph known all records coming from the marshes of the as Cory's Least Bittern was sighted in Ver­ Champlain Lowlands and the West Rutland mont in July 1975 at the West Rutland Marsh. Whether Least are as re­ Marsh (W. J. Norse, pers. comm.). stricted in distribution in eastern Vermont Four to 6 pale blue to pale green eggs are as the single Atlas Project record indicates typically laid, with incubation commencing remains to be seen. Certainly the Lake early in the nesting cycle. Incubation ex­ Memphremagog and the Connecticut River tends 17 to 18 days from the laying of the marshes seem to offer suitable habitat, and last egg, with hatching occurring over a the species is regularly recorded farther 3-day period. Although the female performs south in the Connecticut River valley. a greater portion of the actual incubation Least Bitterns prefer to nest in emergent (Weller 1961), parental ties to the nest are vegetation, usually near the open-water side strong in both sexes; there are numerous of a marsh (Weller 1961). Although tech­ references to incubating being lifted nically waders, Least Bitterns are adept at from the nest by researchers. This atten­ climbing about on emergent vegetation and tiveness limits the chance of locating a nest therefore frequently nest and forage over by flushing the adult. water considerably deeper than would be ac­ Perkins and Howe (1901) indicated that cessible through wading. The nest is little the Least Bittern was rare in Vermont by more than a platform of coarse sticks and 1900, although it had once been more

36 Species Confirmed as Breeders in Vermont No. of priority blocks in which recorded 44' TOTAL 7 (4%) Possible breeding: 3 (43 % oftotal) Probable breeding: 2 (28.5% of total) Confirmed breeding: 2 (28.5% of total)

Physiographic regions in which recorded % of % of species' no. of region's total priority priority priority blocks blocks blocks

Champlain Lowlands 6 I9 86 rn Green Mountains 0 0 0 o North Central 0 0 0 Northeast Highlands 0 0 0 30 40 SO I East Central 0 0 0 43' o Taconic Mountains 6 I4 10 20 30 I I I Eastern Foothills 0 0 0 o n' common. Data are insufficient to indicate Least Bittern has been regularly reported in whether there has been a real change in the the West Rutland Marsh since the early species' status in the past century. The spe­ I900S (L. H. Potter, pers. comm.); 3 birds cies is considered fairly commoh in the at once were seen there in the air during a Champlain marshes by state waterfowl biol­ Vermont Conference field trip on June ogists (J. Stewart, pers. comm.), but is rarely 17, 1973· found by most observers. The Least Bittern DOUGLAS P. KIBBE is proposed for Species of Special Concern status in Vermont, and the Nature Conser­ vancy reports a decline in its population throughout the Northeast. Because of its re­ strictive habitat requirements the species is vulnerable to any alteration in the state's marshland; other factors that may influence its statewide distribution are unknown. The

Least Bittern 37