WSP11050

• File Number: 8460.400
• Description: Platte River Basin-Platte River Basin Endangered Species Issues-Platte River Management Joint Study
• Basin: South Platte
• Water Division: 1
• Date: 3/1/1992
• Author: Ziewitz-Sidle-Dinan
• Title: Prairie Naturalist 24-1-Habitat Conservation for Nesting Least Terns and Piping Plovers on the Platte River Nebraska
• Water Supply Pro - Doc Type: Report/Study

UUU63~

14

Prairie Naturalist 24(1): March 1992

SUMMARY AND DISCUSSION

Our comparisons of sandbar area, channel width, mean elevation, and maxi-
mum elevation of nest sites versus systematic sample sites in the Lower
Platteand Central Platte study areas suggest that least terns and piping plovers
use wide channels with a large area of dry, sparsely vegetated sand. By these
two measures alone, habitat availability was considerably greater on the Lower
Platte than on the Central Platte. Although nest sites also had higher mean and
maximum elevation than systematic sample sites, these differences were not
statistically significant in either river reach. On the Lower Platte, nests were lo-
cated on significantly higher ground than the mean elevation of the nest sites.
On the Central Platte the mean elevation of nests was less than the mean site
elevation at half of the nest sites.
These differences between the nest and systematic sample sites and between
the Lower and Central Platte suggest that habitat availability is limited in the
river channel along the Central Platte. A greater number of least terns and pip-
ing plovers nest on sand pits than on the river along the Central Platte (Lingle
1988, 1989). This is consistent with our observation that riverine habitat is in
short supply.
Nests on the Central Platte were initiated at lower elevations above water
(x=0.39 m) than nests on the Lower Platte (x=0.49 m), despite the fact that 1988
nesting season flows were much greater on the Lower Platte. However, these
means were not significantly different (t=1.53, p>O.l).
Low flows followed by sudden peaks in early and late July resulted in the
inundation of 8 of the 13 nests surveyed at Central Platte sites. The median ele-
vation of these nests equates to a stage of about 82.0 cms (2895 cfs) at the
Grand Island gage (Table 5). Rows higher than 82.0 cms during 16 June to 31
August, the latter half of the nesting season, occurred in 18 of the 30 years from
1959 to 1988, suggesting that nest inundation is likely to be a common occur-
rence given present habitat conditions.
These facts coupled with the striking paucity of dry sandbar area in the
videography of the Central Platte, even at low flows, suggest that those
channels of the Central Platte wide enough to be attractive to terns and plovers
are too flat to provide safe nesting substrate. Higher portions of the river bed
that might have provided safe nesting substrate in the past have become
vegetated islands.

MANAGEMENT RECOMMENDATIONS

Recovery plans for the piping plover and interior population of the least tern
call for the maintenance of the distribution and range of both species, protection
of essential habitat, and the restoration of nesting habitat (USFWS 1988,
1990b). Essential habitat along the Platte River refers to sandbars in the river
channel. Given the degraded habitat conditions f9r these birds in the Central
Platte, channel habitat restoration is necessary."
Habitat restoration for least terns already has been accomplished elsewhere
in North America. It is the cornerstone of efforts for the recovery of the en-