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SEellONTHREE Whooping Crane I I I I I I I I I I I I Whooping cranes spend most of the winter in the brackish bays, estuarine marshes, and tidal flats in and near Aransas National Wildlife Refuge. As spring approaches, dancing, unison calling, and flying increase in frequency and are indicative of migratory restlessness (NGPC 1994). Family groups and pairs usually depart first. First departure normally occurs between March 25 and April 15, with the last birds usually leaving by May 1. Occasional stragglers may not leave till mid-May, and some birds may spend the summer at Aransas National Wildlife Refuge. Parents separate from their young of the previous year during or shortly following the spring migration. Most juveniles and subadults spend the summer near their natal area. Courtship displays, involving dancing, begin in early spring on the wintering grounds. On the nesting ground, adults carry out an elaborate courtship display, including bobbing, weaving, jumping, and calling with their mates. The nesting grounds within Wood Buffalo National Park are in poorly drained areas where muskeg and boreal forests intermix. Most pairs return to the nesting area in Wood Buffalo National Park in late April and begin nest construction and egg laying. Experienced pairs arrive first, and normally nest in the same general vicinity each year. The nesting territories vary considerably in size, and range from 1.3 to 47.1 Ian'. Nests are large mounds of dried bulrushes about 4 feet wide with the flat-topped central mound up to 5 inches above the water. Individual nests are often used for 3 to 4 years. Whooping cranes generally nest annually, though some pairs skip a nesting season if habitat conditions are unsuitable or for no apparent reason. Parents share incubation and brood-rearing duties. Whooping cranes may renest if their first clutch is lost before mid-incubation. Two eggs are normally laid in late April to mid-May, and hatching occurs about one month late. The eggs in each nest hatch at different times, and the second egg or chick is often pushed out of the nest or starves to death. The young birds are able to fly 80 to 90 days after they hatch. Autwnn migration begins in mid-September, with most birds arriving on the wintering grounds between late October and mid-November. Nonbreeders and unsuccessful breeders probably initiate and complete fall migration faster than family groups. Whooping cranes are omnivorous, probing the soil subsurface with their bills and taking foods from the soil surface or vegetation. Summer foods include large nymphal or larval forms of insects, frogs, rodents, small birds, minnows, leeches, and berries. Foods utiiized during . migration are poorly documented but include frogs, fish, plant tubers, crayfish, insects, and waste grain in harvested fields. Wintering cranes eat crabs, clams, crayfish, and small fish in the tidal marshes, and acorns and wild fruits in the uplands. 3.3.2 Migration Habitat The spring, or northward, migration from Aransas begins in late March with whooping cranes arriving at Wood Buffalo in late April. The fall or southward migration from Wood Buffalo begins in mid-September, and whooping cranes begin arriving in the Aransas area during October. Migrating cranes usually are observed as separate flocks of two to eight subadults or unsuccessful breeding adults, family groups (two adults, one juvenile), or single birds. Whooping cranes occasionally migrate with sandhill cranes. 3-4 6SF0D972S6OO/r1 doe 612/1999(9:52 AM)/URSG'NCFS1:2 _1IBiaer WIIoth.anI /:IJIfe FetItltaI Serrtces