Northern Prairie Wildlife Research Center
Communal Roosting and Foraging Behavior of Staging Sandhill Cranes
Introduction
Sandhill Cranes of the midcontinent population acquire nutrient reserves for
migration and reproduction while on staging areas along the Platte and North
Platte rivers in Nebraska (Krapu et al. 1985). Cranes roost communally at night
in shallow waters of wide river channels or other wetlands and spend the days
foraging in flocks on surrounding uplands (Krapu et al. 1984, Folk and Tacha
1990). Little is known concerning the specific functions of communal roosting
and flocking to staging cranes beyond a probable advantage of reducing the risk
of predation through increased predator detection (sensu Pulliam 1973, Caraco
1979) or evasive behaviors unique to groups. In some species of birds, communal
roosts may serve as information centers, increasing foraging efficiency (Ward
and Zahavi 1973; Waltz 1982, 1987; but see Bayer 1982; Stutchbury 1988 for contrary
opinions). Foraging efficiency can also be increased through local enhancement
(Hinde 1961) or use of alternative diurnal roosts (Caccamise and Morrison 1986,
1988).
In the Platte River Valley, loss of communal roosting habitat has resulted
in high densities of staging cranes (Krapu et al. 1984) prompting a need to
evaluate spatiotemporal use of existing habitat and choice of foraging sites.
In this paper, we examine (1) characteristics and use of activity ranges relative
to energy expenditure and food availability, (2) the role of communal roosts
in foraging behavior, (3) habitat preferences, and (4) influence of group
size and predation on foraging and other behaviors. We also discuss social
factors as they pertain to staging behavior in Sandhill Cranes.
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