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<br />breeding territory. To date, the minimum distance recorded between nests has been 600m
<br />(Kuyt pers. comm" 1991),
<br />
<br />Eggs are normally laid in late April to mid May, and hatching occurs about 1 month later.
<br />The incubation period is from 29 to 31 days. Kuyt (1981.12: 126) reported that "Among 203
<br />clutches observed between 1966 and 1980, 184 (90.6 percent) contained 2 eggs, 16 (7.9
<br />percent) only 1 egg, and 3 (1.5 percent) 3 eggs," Eggs are light-brown or olive-buff overlaid
<br />with dark, purplish-brown blotches concentrated primarily at the blunt end, Eggs average
<br />100 mm in length and 63 mm in width (Bent 1926, Allen 1952, Stephenson and Smart
<br />1972), Whooping cranes may renest if their first clutch is destroyed or lost before
<br />mid-incubation (Erickson and Derrickson 1981, Derrickson and Carpenter 1981 ,Kuyt
<br />1981.12). Whooping cranes generally nest annually, but occasional pairs skip a nesting
<br />season for no apparent reason. When nesting habit~t conditions are unsuitable, some pairs
<br />do not attempt to nest.
<br />
<br />Whooping crane egg and tissue specimens examined for pesticide residues at Patuxent
<br />Wildlife Research Center have shown concentrations well below those encountered in most
<br />other migratory birds (Robinson et al. 1965, Lamont and Reichel 1970, Anderson and
<br />Kreitzer 1971, Lewis et ai, 1992), To date there is no evidence that pesticide
<br />contamination has affected the welfare of whooping cranes,
<br />
<br />Except for brief intervals, one member of the pair remains on the nest at all times, Parents
<br />share incubation and brood-rearing duties. Females tend to incubate at night (Allen 1952,
<br />Walkinshaw 1965, 1973) and take the primary role in feeding and caring for the young
<br />(Blankinship 1976). Parents 'and young return to the nest each night during the first 3-4
<br />days after hatching, After that time, the young are brooded by their parents wherever they
<br />are when night or foul weather overtakes them. During the first 20 days after hatching,
<br />families generally remain within 1,8 km of the nest site (Kuyt pers. comm,),
<br />
<br />Whooping cranes are omnivorous (Walkinshaw 1973), probing the soil subsurface with their
<br />bills and taking foods from the soil surface or vegetl!tion, Young chicks are fed by their
<br />parents and gradually become more independent in their feeding until they separate from the
<br />parents preceding the next breeding season, Summer foods include large nymphal or larval
<br />forms of insects, frogs, rodents, small birds, minnoWs, and berries (Allen 1956, Novakowski
<br />1966), Foods utilized during migration are poorly documented but include frogs, fish, plant
<br />tubers, crayfish, insects, and waste grains in harvested fields,
<br />
<br />Autumn migration normally begins in mid-September, with most birds arriving on the
<br />wintering grounds between late-October and mid-Nqvember, Occasionally, stragglers may
<br />not arrive until late-December, Nonbreeders and unsuccessful breeders probably initiate and
<br />complete fall migration sooner than family groups because young-of-the-year are rarely
<br />observed among the first birds arriving in southern Saskatchewan or Texas (Allen 1952, '
<br />Archibald et ai, 1976, Stephen 1979).
<br />
<br />Whooping cranes are less gregarious. than sandhill cranes, and normally migrate as a single,
<br />pair, family group, or in small flocks, sometimes in the company of sandhill cranes. Flocks
<br />of up to 1 0 subadult whooping cran\ls have been seen feeding in traditional migration
<br />stopovers (staging areas) in Saskatchewan during radio trl!cking studies (Kuyt 1992). They
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