Spring at San Luis NWR

It is a wonderful time of year, probably the best time of year, to be a naturalist in the Great Central Valley!  Spring has arrived, bringing with it ample sunshine and mild temperatures, and the wild lands are leafing out and bursting forth with new life.  Rainfall was low this year, so the wildflower displays won't be anything above average, but the flowers are certainly out there, blooming away and making the most of their short growing season.

On the bird front, this is a time of great transition, a changing of the guard as overwintering birds begin to depart for their breeding grounds, and birds that have been absent, wintering in Central and South America, begin to return.  At the end of March, we are perched right on the brink of that delightful time in the birding year known as spring migration.

A year-round marsh resident, this Red-winged Blackbird shows off his impressive red epaulettes. 

A couple of days ago, we spent a beautifully warm, sunny day out at San Luis National Wildlife Refuge, driving the looping gravel roads through the marsh and wandering down winding trails even deeper into the lush landscape.  We spotted some beautiful birds out there, thousands of individuals belonging to 77 different species!  

Tracks of the Raccoon Marsh Trail follow a levee between a tule marsh and willow-lined slough.

We began our day at the West Bear Creek unit of the San Luis NWR, following the two-and-a-half-mile auto tour route to the trailhead for two nature trails; taking the westernmost route, the Raccoon Marsh Trail meanders along for half a mile or so between a wetland to the west and wooded slough to the east.  The slough offered plenty of evidence of beaver activity, including a well-constructed dam and freshly chiseled trees.  In the marsh, a few Greater White-fronted Geese and Canada Geese lingered, while the mudflats were favored by sandpipers and dowitchers.

A beaver dam along the slough.

The big, charismatic birds that star in the Central Valley's winter pageant are almost entirely gone: the Snow Geese and Ross's Geese, the Tundra Swans, and the Sandhill Cranes.  All of the duck species (nearly a dozen) are still present in the wetlands, though in somewhat reduced numbers.  Smaller winter songbirds, like White-crowned Sparrows and Yellow-rumped Warblers, are still here in large numbers, however.

A month or two ago, this wetland was full of Sandhill Cranes, Tundra Swans and thousands of ducks. 
At the end of March, only a few hundred ducks (and many coots!) are left.

From the West Bear Creek unit, we headed south a few miles to the headquarters of the San Luis National Wildlife Refuge, and set out on the eight-mile waterfowl auto tour route.  The fence posts surrounding the tule elk enclosure are a favorite perch for Loggerhead Shrikes, and Savannah Sparrows are common along the roadside.  Northern Harriers coursed back and forth over the grasslands, while White-faced Ibis waded along grassy marsh edges.

A Loggerhead Shrike, perched on an advantageously-situated fence post.

At the north end of the auto tour route is the Chester Marsh trail, a one-mile loop around a tule marsh that includes a short spur trail out to the San Joaquin River and the site of a historic ferry crossing and hotel.  (Remains of these used to be visible, but the vegetation seems to have covered the pilings and other evidence of settlement.)  The marsh was burned over the winter as part of the refuge's management plan, and the newly emerging tules were only about one foot tall and rather sparse.  This is usually a good place to see, or at least hear, American Bitterns, but not this year!  Even in wetlands, fire is an important tool in managing the health of the ecosystem.

Recently burned Chester Marsh, showing signs of new growth.

A stand of willow and cottonwood trees that reaches out into the marsh provided quite good birding, however.  We spotted a female Phainopepla in a cottonwood tree, along with several California Scrub Jays, and watched a busy flock of Bushtits move frenetically through the trees.  

A glimpse of a Phainopepla's red eye and jaunty crest.

Both Downy and Nuttall's Woodpeckers hitched along tree trunks, and we found a Red-breasted Sapsucker sharing a tree with a few Western Kingbirds, the perfect illustration of this transitional period in the birding year.  The sapsucker will very soon be heading out of the Valley, returning north or upslope into the Sierra, while the kingbirds have only just arrived from Central America.  

A Western Kingbird, only very recently arrived for the season from Central America.

Other summer breeding birds that have already arrived are Barn Swallows and Cliff Swallows, as well as Swainson's Hawks.  For some local resident species, the breeding season is already underway.  Red-tailed Hawks are sitting on nests, and we spotted a recently-fledged House Wren begging incessantly as it chased after its parent through the underbrush.  

A Swainson's Hawk, a long-distance migrant that spends the winter months in Argentina.

Along the eastern leg of the auto tour route, the half-mile (one way) trail to the Sousa Marsh passes between a wetland bordered by a wooded slough, and a flooded grove of cottonwood trees that is attractive habitat for Wood Ducks (we heard a few but didn't manage to see any).  While I stopped to listen to an Orange-crowned Warbler, a river otter slid quietly past, barely making a ripple in the still water of the slough.  Other resident mammals we spotted throughout the day included desert cottontails, California ground squirrels, a coyote and a couple of mule deer, wading quietly through the marsh.

Mule Deer, wading through the marsh.

The shallow wetland edges and mudflats hosted the usual array of shorebirds and waders, including Black-necked Stilts, American Avocets and Greater Yellowlegs, along with egrets and herons.

A Black-necked Stilt, reflected in the still waters of the marsh.

All day, Song Sparrows provided a continuous stream of music, the soundtrack of springtime in the marsh.  We were never out of earshot of one of these enthusiastic songsters, and more often than not it was accompanied by the chatter of one or more Marsh Wrens, while Common Yellowthroats chimed in periodically.  From the reeds, we listened for a few of the other often mysterious sounds of the marsh: Pied-billed Grebes, Soras, Virginia Rails and American Bitterns.  (Click on the links to listen to a selection of sound recordings from the Macaulay Library.)

A Song Sparrow, winner of the award for most frequently-heard song throughout the day!

Every ecosystem, it would seem, has its own blackbird: Red-winged Blackbirds reign in the tule marshes, while just across the levee road lies the grassland realm of the Western Meadowlark.  And beyond that, the riparian forests host fiery orange Bullock's Orioles, neotropical migrants in the blackbird family.  The orioles are just one of the many brightly-colored migratory songbirds that are returning to the Valley this spring: also keep an eye out for brilliant Blue Grosbeaks and Lazuli Buntings, Yellow Warblers, and Western Tanagers as they pass through on their way to coniferous forests.

A Western Meadowlark, perched in the grass.

As the angle of the sun dropped lower, we bade farewell to the wetlands for the day.  But as we were leaving, we spotted a Great Blue Heron perched at the edge of a canal facing the sun, its drooping wings outspread, we surmised, to absorb the warm rays.  I snapped a few photos and we went on our way, only to see several more of these beautiful birds, all perched motionlessly in the same position, wings held back and dropped low, facing the sinking sun and basking in its warmth.  Admittedly, this one looked pretty funny when seen from the back!

A Great Blue Heron, soaking up some spring sunshine!

For more information about the various trails and auto tour routes offered at the San Luis National Wildlife Refuge, visit their website.