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American Widgeons and Northern Pintails congregating in the newly restored wetlands.
The broad expanse of water that covered the Giacomini Wetlands during higher high tides in December and January resulted in an explosion in duck numbers. Numerous visitors and staff have commented on the enormous flocks of waterfowl that congregated on the waters of the newly restored Giacomini Ranch.
Jules Evens, a long-time local wildlife biologist with Avocet Research Associates (ARA) who performed the baseline and construction surveys for the project, noted that duck numbers were higher this fall and winter than prior to restoration, probably because the open water area is greater than previously, particularly during high tide.
Ducks near Dairy Mesa.
Prior to restoration, avian use of the pastures was seasonally variable. The northern portion of the East Pasture frequently hosted roosting Canada geese (Branta canadensis), great blue herons (Ardea herodias), great egrets (Ardea alba), and, occasionally, waterfowl species such as mallards (Anas platyrhynchos; ARA et al. 2002). The ditches in the East Pasture supported a low diversity of species that include occasional use by mallards, gadwall (Anas strepera), lesser scaup (Aythya affinis), eared grebe (Podiceps nigricollis), black phoebe (Sayornis nigricans), and even belted kingfisher (Ceryle alcyon; ARA et al. 2002). Buffleheads (Bucephala albeola) regularly used some of the old Duck Ponds created by the Giacominis (ARA et al. 2002).
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Ducks in Shallow Shorebird Area prior to restoration.
The greatest waterfowl and shorebird use in the pastures prior to restoration occurred in what is known as the Shallow Shorebird area in the northeast corner of the East Pasture, a unique habitat within the Project Area. This Muted Tidal Brackish Marsh-Flat/Panne typically flooded from December through April with surface runoff, precipitation, and tidal waters that flow into the East Pasture from a culvert in the levee of the Tomasini Creek berm, creating brackish water conditions. Many waterfowl species, especially dabbling ducks such as gadwall, wigeon, and teal, have been historically attracted to this area in the winter (ARA et al. 2002). Shorebirds also gathered here in rather high numbers to roost and forage when adjacent tidal flats are inundated at high tide (ARA et al. 2002). Some of the most common shorebird species included dunlin, dowitcher species ( Limnodromus sp.), greater yellowlegs ( Tringa melanoleuca), common snipe ( Gallinago gallinago), willet, and killdeer (J. Kelly, ACR, pers. comm.).
Waterfowl use of seasonally ponded areas in West Pasture prior to restoration.
In addition to these more persistent habitats, waterfowl also often congregated in large numbers prior to restoration in the southern portion of the West Pasture in seasonally flooded-ponded Meadows and Pastures that receive significant freshwater inflow after rain events from groundwater and small drainages flowing off the Inverness Ridge.
With restoration, waterfowl use of the Project Area was projected to remain similar to historic levels or increase slightly, while shorebird use was predicted to increase. However, in the first few months after breaching, these trends have beenwere seemingly reversed, with duck numbers seemingly greatly exceeding those of shorebirds, although, based on anecdotal information, shorebirds are occasionally present in high numbers.
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Northern Pintails on Giacomini Wetland waters.
During the mid-December extreme high tide series, where tides reached levels of 7.1 ft MLLW, Evens and colleagues counted more than 3,400 waterbirds during one morning survey (ARA, unpub. data). Approximately 25 different waterbird species were observed (ARA, unpub. data). Some of the species with the highest numbers were American wigeon ( Anas Americana) (1,700), northern pintail (850), green-winged teal ( Anas crecca) (230), and northern shoveler ( Anas clypeata) (150). Other duck species included gadwall, mallard, cinnamon teal ( Anas cyanoptera), bufflehead, and ruddy duck ( Oxyura jamaicensis).
Northern Pintail perched on log.
Shorebird numbers might have been expected to be higher than waterfowl based on predicted water levels. However, shorebird numbers were relatively low, according to John Kelly, wildlife biologist at Audubon Canyon Ranch (ACR), who has been conducting shorebird surveys with his staff and volunteers in the Giacomini Ranch and Tomales Bay. In early November surveys, monitors from ACR observed some short-billed and long-billed dowitchers (Limnodromus griseus and L. scolopaceus) and scattered groups of western sandpipers (Calidris mauri) and least sandpipers (Calidris minutilla) in the newly restored marsh, Kelly said. Evens noted at least 1,000 least and western sandpipers around the edges of the flooded marsh in early November (Evens, pers. comm.). Phalaropes (Phalaropus lobatus) were very common in the Project Area prior to breaching of the levees: phalaropes are transients, in large numbers during fall migration, Evens said. Kelly noted that many of the shorebirds observed in the area before mid-November may be fall migrants that do not winter locally in Tomales Bay. After mid-November, numbers and species observed should reflect the value of the wetland to locally wintering individuals, Kelly said.
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Flock of gulls near Railroad Point.
During a survey of the Giacomini Wetlands on November 17, 2008, ACR monitors observed 98 shorebirds (Kelly and Condeso, unpub. data). Most of these birds were greater yellowlegs (21), Wilson's snipe ( Gallinago delicata) (18), killdeer ( Charadrius vociferous) (30), least sandpiper (26), and short-billed dowitcher (3) (Kelly and Condeso, unpub. data). On December 3, 2008, even fewer shorebirds were observed: 15 in total – 5 killdeer, 2 greater yellowlegs, 5 Wilson’s snipe, and 3 least sandpipers (Kelly and Condeso, unpub. data). These numbers represent shorebird use at moderate tide levels (approximately 2.5-4.0 feet above MLLW). During the survey by Evens and colleagues on December 13, 2008, shorebird numbers were slightly higher, with 30 greater yellowlegs observed, as well as more than 100 gulls of different species.
Great Blue Herons and Great Egrets in wetlands.
Kelly noted that many of the shorebirds observed in the area before mid-November may have been fall migrants that do not winter locally in Tomales Bay. After mid-November, numbers and species observed should have reflected the value of the wetland to locally wintering individuals, Kelly said.
Audubon Canyon Ranch conducted additional shorebird counts during the late winter season. During censuses, ACR observers counted a grand total of 538 shorebirds in the new Giacomini Wetlands, according to Emiko Condeso of ACR.
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| SPECIES OBSERVED DURING LATE WINTER ACR SURVEY |
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Species
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1/29/2009
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2/12/2009
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2/27/2009
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| Great Blue Heron |
10
|
12
|
6
|
|
Great Egret
|
13
|
14
|
10
|
|
Snowy Egret
|
4
|
7
|
7
|
|
Northern Harrier
|
7
|
6
|
1
|
|
White-tailed Kite
|
6
|
3
|
3
|
|
Red-shouldered Hawk
|
5
|
2
|
|
|
Red-tailed Hawk
|
4
|
3
|
|
|
Osprey
|
|
2
|
|
|
American Kestrel
|
4
|
2
|
1
|
|
Peregrine Falcon
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2
|
1
|
|
|
Killdeer
|
12
|
55
|
32
|
|
Greater Yellowlegs
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11
|
13
|
|
|
Least Sandpiper
|
95
|
120
|
20
|
|
Dowitcher species
|
2
|
|
|
|
Wilson's Snipe (Common snipe)
|
8
|
27
|
8
|
Although shorebird use remained low relative to established feeding areas in Tomales Bay, shorebird abundance within the restoration area did seem to increase a bit compared to the first half of the winter monitoring period, though species composition remained similar, Condeso noted. Species known to be associated with ponds and flooded pastures continued to have a strong presence, such as Great Blue Herons, Great Egrets, Snowy Egrets, Greater Yellowlegs, Killdeer, and Wilson’s snipe. Least Sandpipers, which were observed in low numbers during our early winter counts (Nov–Dec) turned up in higher numbers during late winter counts (Jan–Feb). While dowitcher numbers remained low during formal surveys, Condeso noted that flocks of dowitchers were obwerved within the restoration area on non-survey days. Though the distributions of shorebirds varied among counts, most of the shorebirds observed occurred in specific areas, including the East Giacomini Marsh (Shallow Shorebird Area in northern portion of East Pasture), the goby pond in the northern portion of the East Pasture, and the Triangle Marsh Area (Tomasini Triangle Marsh in central portion of East Pasture). These ponded areas of the newly restored Giacomini Wetland provide habitat that seems suitable for a number of species, Condeso said.
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Raptors (juvenile Northern Harrier shown) continue to visit the newly restored Giacomini Wetlands in large numbers.
In addition to water level and fluctuations, other less obvious factors could be affecting shorebird use, including changes in the availability of prey and the traditional use of other areas in Tomales Bay by resident wintering shorebirds, Kelly noted. Ultimately, Kelly hopes that the Giacomini Wetlands will provide an important feeding area for shorebird flocks during high tides and periods of heavy stormwater run-off when tidal flats in Tomales Bay become inundated. In addition, the type of shorebirds that use ponded areas rather than mudflats are typically more abundant in fall and spring rather than winter, passing through during migration, Evens noted. These fall and spring migrants—yellowlegs, sandpipers, dowitchers—will likely congregate in high numbers in areas with muted tidal action or where upland runoff creates shallow ponds (e.g. Tomasini Triangle marsh). The value of the Giacomini wetlands for these shorebirds may become more apparent this spring and the following fall as breaching of the levees occurred after most of the fall migration in 2008 had already occurred, and shorebirds were already beginning to settle into wintering areas, Condeso noted.
ACR conducts simultaneous shorebird counts throughout Tomales Bay and would like to expand its monitoring at some point to monitor shorebird use at different tide levels. Experienced "birders" with the requisite skills interested in contributing to these counts should contact Emiko Condeso of the Cypress Grove Research Center of ACR at 415-663-8203 or email) for more information.
Special thanks to Galen Leed Photography for the wonderful photos!
Citations:
Avocet Research Associates (ARA) (2002). Giacomini Wetland Restoration Site: special status animal species - reconnaissance and compliance, Final report to Point Reyes National Seashore, National Park Service.
KHE (2006a). Hydrologic Feasibility Assessment Report: Giacomini Wetland Restoration Project. Point Reyes National Seashore. Point Reyes Station, California, Prepared for Point Reyes National Seashore.
-- Content for this page was composed by Lorraine Parsons, Project Manager, Giacomini Wetland Restoration Project, Point Reyes National Seashore
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