WSP00190

• File Number: 8407
• Description: Platte River Basin - River Basin General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 6/2/1999
• Author: URS Greiner Woodward
• Title: Documentation of Existing Conditions in the Central Platte Valley - Delivery Order Number 86
• Water Supply Pro - Doc Type: Report/Study

SECTIONTHREE

Whooping Crane

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Habitat criteria applied in the Biology Work Group model were lack of disturbance, channel
width, width of water in the channel, and a function that evaluates a range of water depths (both
shallowly submerged sandbars with deeper water). Whooping crane authorities agree that
whooping cranes select roosting sites on the basis of the security offered by the site(s) (Shenk
and Armbruster 1986; FWS 1987b). The security value of whooping crane riverine roost sites is
a function of the following habitat criteria:

I. UnobstrUcted channel width: Whooping cranes require roosting sites free of visual
obstructions, or an unobstructed view, presumably to allow them to see approaching
predators.

2. Presence of water: Whooping cranes roost standing in water. The availability of water is an
inherent requirement in sandhill and whooping crane behavior.

3. Depth of water: Recent sightings indicate whooping cranes use shallow submerged areas
bounded by deeper water. On the Platte River, water conditions provide shallowly
submerged sandbars bounded by deeper water in main channels (FWS 1987b, 1993; Faanes
et al. 1992).

4. Water width: In addition to simply being present and having adequate depths, the expanse of
water surrounding the roost must be sufficiently wide to provide a sense of isolation and
security (Shenk and Armbruster 1986; FWS 1987b). Water width is defined by whooping
crane authorities as being the sum of all wetted widths (water-filled subchannels) within the
unobstructed ""idth.

The suitability indices of the roost habitat model were updated and refined as additional data
became available (FWS 1993; Carlson et al. 1990; Carlson et aI. 1994). Two alternative models
(C4R and C5R) were eventually produced (Carlson et aI. 1994) and included as a figure in the .
Kingsley Dam Biological Opinion (FWS 1997). They are based on different methods of
estimating habitat suitability related to depth. Both show a reduction in roosting habitat below
2,400 cfs, with a gradual reduction as flows decrease to 2,000 cfs, and more rapid reductions in
habitat as flows decrease below 2,000 cfs (Figure 3-5 top). Empirical data collected from
whooping crane roost sites supports the model (Figure 3-5 bottom), with the proponion of
whooping crane stopovers being disproportionately high between 2,000 to 2,500 cfs.

The existing whooping crane roost habitat model was based on the roost habitat data available at
the time and on the expert opinions of whooping crane scientists. Model C4R is currently being
updated and validated by the Midcontinent Ecological Science Center of the USGS (FWS 1999).
This work includes incorporation of new data from numerous recent whooping crane roost sites
and other work to improve the model and produce curves relating habitat to flow. The draft
report is scheduled to be distributed for peer review in October 1999.

The updated whooping crane roost habitat model may be used to develop baseline indices of
habitat quality for each bridge segment. A sample data presentation is provided in Table 3-5.
However, application of the model to individual bridge segments would likely require collection
of additional data to represent current baseline conditions. The model incorporates three
suitability indices-water depth, water width, and channel width. The fourth indicator
(disturbance) functions as an on- or off-switch. Updated information on channel width will be
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