Comprehensive Site Development Plan ... - City of Kelowna

Avocets at Glenmore Landfill
6
3.5 Conservation habitat at Glenmore Landfill
If an engineered wetland at Glenmore Landfill is required to conserve the breeding population of
avocets then several factors must be considered. Several design factors are critical to consider
when designing a wetland suitable for breeding avocets.
Size: After studying the movements and territoriality of nesting pairs at Alki Lake, Weir
and Gyug (1999) suggest that each nesting pair requires 0.5 ha of foraging habitat. If we assume
12 breeding pairs (average number of breeding pairs in past 3 years) and 6 nonbreeding avocets (a
total of 30 adult birds), then 6.6 ha would be required based on 0.5 ha/pair and chicks and 0.1
ha/nonbreeder (Robinson and Oring 1997, Robinson et al. 1997). Since avocets tend to use about
2/3 of suitable habitat available (Girard and Yesou 1991), 10 ha seems more appropriate.
However, since other wetlands specifically engineered for nesting American Avocets have
increased densities markedly (e.g., Tulare Lake Drainage District 1996), there is potential for
providing habitat for more than 30 avocets in 10 ha.
Surrounding Area: Land areas surrounding compensation habitat should be relatively
flat and open with few trees so the area mimics prairie-like wetland habitat. In particular, all
perch sites used by raptors (predators of avocets) should be cleared within 150 m from
compensation habitat. To minimize human disturbance during nesting, the site needs to be
designed so that there are no work operations carried out within 150 m of the site during the
period when avocets are nesting (approximately May1 to August 15).
Substrate: Clay or clay-silt should be used as substrate of compensation habitat as it is
impermeable to water and thus stops underground water loss, forcing water losses through
evaporation which aids in increasing salinity and alkalinity.
Foraging Habitat: Shallow feeding areas of 1-17 cm depth are necessary in order for
avocets to forage. Water depth in the majority of feeding areas could average 10 cm and be in the
range of 5-13.5 cm deep. Small areas of deeper water (17-60 cm) should be scattered throughout
the compensation habitat as some invertebrate species used as food may need deeper water at
certain portions of their life cycles.
Water Control: As water levels in compensation habitats fluctuate, it will be necessary
to control water levels to keep nesting islands exposed in high water years and surrounded by
water in dry years, to keep water depth in foraging areas at an optimal level, and to achieve a
relatively constant water level through the incubation period. Outside the breeding season (May
1-August 15) these water levels can be manipulated for other landfill management purposes.
Other considerations with water level control are 1) salinity and alkalinity, which may be
reduced when water is flushed through the system instead of allowing solutes to build up through
evaporative water loss, 2) impacts on invertebrate prey abundance, and 3) vegetation control.
The site should be designed so water levels can easily be manipulated, particularly to raise water
levels on some occasions to prevent buildup of permanent vegetation on low nesting islands and
in shallow foraging habitat.
Water quality: Water should be highly alkaline (>400mg/L), highly saline (>12,000uS),
have high Total Dissolved Solids and low Dissolved Oxygen (Ambrozy 1999).
Manning, Cooper and Associates