A network of seasonal sloughs extends from Watsonville to the coast at Pajaro Dunes. Together they comprise the county’s largest wetland system, including Watsonville Slough and its tributary sloughs: Gallighan, Harkins, Hanson, and East and West Struve. All are freshwater, except that the lower reaches of Watsonville Slough are seasonally brackish. The sloughs and their uplands support a diverse assemblage of waterbirds, raptors, blackbirds, sparrows, and other land birds. This area is interesting all year, but birding is generally best from August to April. Although the slough system is now widely recognized as an ecological treasure, parts of it, wetlands and uplands alike, continue to be lost in recent years to agriculture and to residential and commercial development. Fortunately, several areas have recently been purchased for conservation.
This account describes Harkins Slough, Struve Slough, and the upper reaches of Watsonville Slough. For lower Watsonville Slough see below, under Pajaro Dunes. Harkins Slough, in particular, has provided some superb birding over the years. Recently it has been the county’s best area for unusual fall shorebirds, and for many other waterbirds year round.
Birding these wetlands presents some difficulties, what with limited access to the best sites, and roadwork and construction projects expected to create further restrictions. But new public access may be in store for some parts of the sloughs. Be aware that car break-ins and theft have occurred over the years. Most areas can be birded while staying fairly near the car; keeping it at least occasionally in sight is a good idea, and make sure valuables are stored out of sight.
Directions. To reach good birding areas at Harkins Slough, take the Buena Vista Rd exit off Hwy 1. Turn west onto Buena Vista and go 0.8 mile to Harkins Slough Rd (before the county landfill). Turn left on Harkins Slough Rd (which bends to the right) and go 0.4 mile; Harkins Slough now appears below on the left. Park off the road here to survey waterbirds in the upper slough (a spotting scope is helpful) and raptors and blackbirds on and above the slopes. Continue 0.4 mile, bearing left and descending the slope to the slough, and park where a barrier closes the flooded road. Do not block or trespass on the private road on the right. Walk a short way back up the paved road to scan the lower slough, and past the barrier for other views. Scan the slough and slopes on both sides of the closed section of the road and carefully check the roadside and surrounding willows and weeds. The road closure has led to nice birding conditions, but eventually the road will probably be re-opened and substantially rebuilt.
Parts of Struve Slough are visible from various spots. Lee Rd offers views, and barriers usually close the road where it crosses the slough–a boon to birders. If coming from the south, take the Hwy 129 (Riverside Dr) exit off Hwy 1 and go west (seaward). The road quickly turns right and heads north; proceed north through the West Beach Rd intersection until you reach a gate. Park there to search for birds. To reach another nearby view that is great in winter and spring, back track a short way and drive all the way to the back parking lot of the yellow warehouses at Statewide Industrial Park (109-119 Lee Road) to view the slough. If coming from the north, take the Hwy 152 exit. Go 0.7 mile (big intersection) and turn right on Green Valley Rd (which becomes Harkins Slough Rd). Go 0.6 mile (crossing over Hwy 1) to Lee Rd and turn left. Park at the road closure (do not block driveways or the road closure) and walk on to the flooded segment of Lee Rd.
Ford St in Watsonville provides an overlook of upper Watsonville Slough. From Hwy 1 take Hwy 129 and go east for 1.2 miles to Walker St, turn left on Walker and go 0.5 mile to Ford St. Turn left on Ford St and go 0.1 mile to gain a view of the slough. This area is only interesting in winter and spring, when the slough and an adjacent agricultural field are flooded.
Birds. Ducks visit these sloughs seasonally (Harkins especially), in variety and abundance. Green-winged and Cinnamon teal, Mallard, Gadwall, Northern Pintail, Northern Shoveler, Canvasback, Lesser Scaup and Ruddy Duck are among the common species. Hooded Merganser and Blue-winged Teal occur each winter (the teal also in spring and fall), and Redhead and Greater Scaup are found occasionally. Mergansers are most often in Harkins Slough near Harkins Slough Rd, and at Watsonville Slough west of Lee Rd. All the freshwater geese and occasionally Tundra Swan occur in winter, again especially at Harkins Slough. Herons and allies are plentiful. American Bittern nests, and White-faced Ibis appears in late summer and spring. Common Moorhen nests in the sloughs, and Black-crowned Night-Heron nests there some years. American White Pelicans, numerous in summer and fall, favor Harkins Slough; a few may be about during winter and spring.
Of course, shorebirds follow appropriate water levels and other habitat conditions, but in recent years receding water levels at Harkins Slough have exposed mudflats in late summer and fall, creating great conditions for shorebirds. In dry years some linger through winter. Semipalmated Plover, Black-necked Stilt, American Avocet, both yellowlegs and both dowitchers, peeps, and others are present most years. Wilson’s Snipe can be numerous. Harkins has recently been one of the county’s best locales for Lesser Yellowlegs, Pectoral and Baird’s sandpipers, and Wilson’s Phalarope. Rarities here have included Ruff, Stilt, Buff-breasted, Semipalmated and Solitary sandpipers. Hundreds of gulls visit Harkins Slough from the nearby county landfill to bathe and drink (look for Glaucous in winter), and Caspian and Forster’s terns visit from spring until early fall.
Twenty-three species of raptors have been recorded here. White-tailed Kite, Red-shouldered and Red-tailed hawks, and Barn and Great Horned owls nest around the sloughs. Peregrine Falcon and Merlin are regular in fall and winter. Golden Eagles fly over in any season. Watch, too, for Ferruginous and Rough-legged (rare) hawks. Short-eared and Burrowing owls once were regular winter visitors, but they are seldom reported now. Fences and wires may have Loggerhead Shrike, migrant Western Kingbird, and wintering Say’s Phoebe. The wetlands, willows, and weed fields host abundant sparrows. Swamp Sparrow is regular; it is found most often where Harkins Slough Rd crosses the slough. Tree and Violet-green swallows winter here. Check blackbird flocks for Tricolored Blackbird (uncommon to rare in recent years), and Yellow-headed Blackbird (rare). Great-tailed Grackle has begun to nest in the sloughs, seen most frequently at Struve Slough near Lee Rd, but also at Harkins Slough. Many other rare landbirds have also been found in these wetlands, which merit full mornings of birding.