Whooping Crane Recovery Plan - Laserfiche WebLink

Home Browse Search

13 are diurnal migrants and make regular stops to feed and rest. Although whooping cranes will use a variety of habitats for foraging and roosting during these stopovers (Armbruster 1990, Lingle et al. 1990, they seem to prefer isolated sites away from human activities. This preference and the birds' rarity, result in few authenticated sightings during migration each year. For almost half of the year, whooping cranes occupy winter quarters on and adjacent to Aransas NWR. Although close association with other whooping cranes is tolerated at times on the wintering grounds, pairs and family groups typically occupy and defend relatively discrete territories. Recent studies indicate a declining territory size as the population increases. The recent average is 117 ha (Stehn and Johnson 1987). Subadult and unpaired -adult whooping cranes form small flocks and use areas outside occupied territories (Blankinship 1976, Bishop and Blankinship 1982). Subadults tend to winter near the territories where they spent their first year (Bishop e)of aired cranes (Bishop Ill en locate their first winter territory near the winter territory of o Stehn and Johnson 1987). Animal foods -- especially blue crabs Cvrto (Caineredia sapidus), clams pth wier lus I i i caMa ri (Tao and d, i 2lur 956 , min r Ran is omnte in e nte the plant wolf berry (Lycium coinim iet en Uhler and Locke 1970, Blankinship 1976). Most foraging occurs in the rackish bays, nn they marshes, and salt flats lying between the mainland and barrier islands. virainiana),,,snlails, fly to upland sites when attracted by foods such as acorns (Que cus particularly crayfish and insects, and then return a rainfall, burned to reduce pant cover or when food is attractive when partially flooded by r whooping less available in the salt flats and marshes obut agricultural croplands adjace t to t e cranes use upland sites frequently in most Y ea s Aransas NWR are rarely visited. High fall tides and heavy rains sometimes flood tidal flats. In these circumstances, the birds r and forage almost exclusively on blue crabs and w� ifobeer tides, and the b ids mouse ntoeshal ow January, tidal flats typically drain as a result oonally bays and channels to forage primarily r although significant blue dietarystem when,w ter depths captured while probing the bottom. Clams are a crab are low, temperatures cold, and during when high or lesssn,w width) are blue ed whole. population. Most clams and small blue crabs (5 cm Larger crabs are pecked into pieces before being swallowed (Blankinship 1976). As spring approaches, dancing, unison calling (Archibald 1976), and flying increase in frequency, and are especially indicative of pre- migratory restlessness (Allen 1952, Blankinship 1976). Family groups and pa fit which typically occur at rst to th s ti of yea wintering grounds, assisted by strong southeast w First departure dates normally occur between March rn 2howevepr,linger with the birds in usually leaving by May 1. Occasions stragglers 16 years in the period 1938 -1992, one rtotal) or remained mates of bids Aransas NWR throughout the summer. Some of these bsds were Il or rippled which were crippled.