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<br />and are characterized by oak brush, grassland, swales, and ponds. Typical plants include
<br />live oak (Quercus virainiana), red bay (Persea borbonia), and bluestem (Andropogon Spp,)
<br />(Stevenson and Griffith 1946, Allen 1952, Labuda and Butts 1979). During the last 20
<br />years, many upland sites have been grazed, mowed, and control burned (Labuda and Butts
<br />1979). The refuge maintains as many as 3300 ha of grassland for cranes, waterfowl, and
<br />other wildlife, Human visitation is carefully controlled, and other potentially conflicting uses
<br />of the refuge, such as activities associated with oil and gas exploration and pumping
<br />operations, are reduced when whooping cranes are present.
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<br />.
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<br />As noted previously, critical habitat was designated for whooping cranes in 1978, Critical
<br />habitat is defined within the Endangered Species Act as habitat which contains those
<br />physical or biological features, essential to the conservation of the species, which may
<br />require special management considerations or protection. Critical habitat was identified for
<br />nine sites in six states ~. Bml. Vol. 43, Number 94, May 15). The interested reader is
<br />referred to the Federal Reoister for a detailed description of the sites. However, these sites
<br />are: (1) Monte Vista NWR, Colorado; (2) AlamoSa NWR, Colorado; (3) Grays Lake NWR and
<br />vicinity, Idaho; (4) Cheyenne Bottoms State Waterfowl Management Area, Kansas; (6) the
<br />, Platte River bottoms between Lexington and Oehman, Nebraska; (7) Bosque del Apache
<br />NWR, New Mexico; (8) Salt Plains NWR, Oklahoma; and (9) Aransas NWR and vicinity,
<br />Texas.
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<br />0, Life History
<br />
<br />Wild whooping cranes were not individually marked until 1975 (Drewien and Bizeau 1978,
<br />Kuyt 197811,197911); consequently, some aspects of their life history and population biology
<br />remain uncertain. Current estimates suggest a maximum longevity in the wild of 22-24
<br />years (Binkley and Miller 1980). Captive individuals live 35-40 years (McNulty 1966,
<br />Moody 1931). 'Crip' was at least 33 years old when he died at San Antonio Zoo in 1979.
<br />. Josephine" was at least 27 years old at the time of her death (McNulty 1966), 'Can-US",
<br />a 29-year-old male, is still reproductively active in the captive flock at PWRC in 1993,
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<br />Whooping cranes are monogamous, but will remate, sometimes within only a few weeks,
<br />following the death of their mate (Blankinship 1976, Stehn 1992). Bishop and Blankinship
<br />(1982) documented several instances in which 2- and 3-year-old color-banded birds paired
<br />with unmarked birds. Kuyt (198111) observed two instances in which nesting pairs
<br />contained one member (a male in each instance) that was known to be 3-years-old, A 3-
<br />year-old female has also nested, but pair formation can be a lengthy process. Bishop (1984)
<br />observed pair bonds that developed over 1 to 3 winters from associations in subadult flocks
<br />on the wintering grounds. The average age of first egg production is slightly over 4 years
<br />(E. Kuyt, pers. comm. 1991).
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<br />Most pairs return to the nesting area in WBNP in late April, and begin nest construction and
<br />egg laying. Experienced pairs arrive first, show considerable fidelity to their breeding
<br />territories, and normally nest in the same general vicinity each year. These nesting
<br />territories--termed "composite nesting areas"-vary considerably in size, and range from
<br />about 1 ,3 to 47.1 km2 (Kuyt 1976a, 1976b, 1981a). From the initiation of laying until
<br />chicks are a few weeks of age, the activities of pairs and family groups are restricted to the
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