3.0 Affected Environment - Knik Arm Bridge and Toll Authority

Knik Arm Crossing DraftFinal EIS
Affected Environment
shorebirds, and raptors and moderate numbers of several gull species use the Study Area
within Knik Arm. Four species of gull—herring gulls (Larus argentatus), glaucous-winged
gulls (L. glaucescens), mew gulls (L. canus), and Bonaparte’s gulls (L. philidelphia)—are the
primary marine birds using these estuarine habitats within Knik Arm. Other species,
including small numbers of sea ducks, primarily greater scaup (Aythya marila) and scoters
(Melanitte spp.), and occasionally dabblers, such as mallards (Anas plattyrhynchos),
American wigeon (Anas americana), and green-winged teal (Anas crecca), occasionally
make use of open water habitat. Arctic terns (Sterna paridisaea), listed as a Bird of
Conservation Concern (USFWS 2002), are present on a regular basis on both sides of Knik
Arm in early summer. Other studies have documented 24 species of marine birds within
Eagle River Flats and other tidal salt marshes just north of the Study Area (USDOA 2003).
There were very few observations of shorebirds using the tidal flats in the Study Area during
the 2005 field survey (KABATA 2006s). On the west side of Knik Arm, a few spotted
sandpipers (Actitis macularia) were observed along the shore. Several flocks of red-necked
phalaropes (Phalaropus lobatus) and small numbers of red phalaropes (Phalaropus fulicaria)
were seen flying and swimming off the western shore during migration. One group of
12 small sandpipers (“peeps”) landed on the east side flats during spring migration but flew
off within a few minutes. A pair of greater yellowlegs (Tringa melanoleuca) was observed at
the outflow of Sixmile Creek on a number of occasions, and probably nested nearby. At
Cairn Point, one semipalmated plover (Charadrius semipalmatus) and a few spotted
sandpipers (Actitis macularia) were observed. In comparison, during the peak spring and fall
migration periods the tidal flats near Westchester Creek were host to dozens of Hudsonian
godwits (Limosa haemastica), semipalmated plovers, greater and lesser yellowlegs, and
hundreds of dowitchers (Limnodroma griseus), all actively foraging or resting on the mud
flats.
The osprey (Pandion haliaetus) is a raptor that occasionally forages in the off-shore and
nearshore estuarine waters on both sides of Knik Arm (KABATA 2006s). A pair of osprey
nested on a transmission tower south of Sixmile Creek on Elmendorf in summer 2005. 56
The waters of Knik Arm, with its heavy silt load, provide little foraging habitat for many
marine birds. However, marine birds have been observed foraging along the tidal rip in Cook
Inlet (Moulton 1997). This behavior was also observed with phalaropes in the fish survey
conducted for this Study in August 2005 (KABATA 2005b). The scarcity of infaunal and
epifaunal invertebrates in the exposed tidal flats provide little food for waterfowl and
shorebirds (KABATA 2005b). Based on field studies conducted for the proposed KAC
project, estuarine habitats in lower Knik Arm are primarily used by birds for moving between
Upper Cook Inlet and areas farther up Knik Arm and to a lesser extent for resting or foraging.
In contrast, tidal flats off Ship Creek and at Westchester Lagoon at the mouth of Chester
Creek near Anchorage (outside the Study Area) provide habitat for moderate numbers of
migrating shorebirds and waterfowl (KABATA 2006s).
56 Personal communication, Herman Greise, Wildlife Biologist, Elmendorf, telephone conversation with David
Erikson, September 2005.
3-204 12/18/07