Birding along Alviso Slough Trail at Don Edwards National Wildlife Refuge

My recent hike along the Alviso Slough Trail at the Don Edwards National Wildlife Refuge included many bird sightings.  I was anticipating this, and planned to take my time completing the 9-mile loop trail so that I could enjoy the bird life as well as the walk.  I saw an interesting variety of shorebirds and waterfowl, all listed among the “common” or “abundant” species on the extensive bird list that’s available at the Wildlife Refuge Visitor Centers.

As mentioned in my post about the hike, I started at the Alviso Marina County Park in Alviso and walked around the Alviso Slough Trail clockwise.  (See that post for my GPS track.)  The birding part of my visit started almost immediately: barely ¼ mile from my car the trail was on a levee between Alviso Slough and one of several salt ponds, where I saw a number of sandpipers feeding at the water’s edge.  Sandpipers can be difficult to identify, so here I’ll show the two types I could distinguish.

photo of sandpiper at the edge of a salt pond

Sandpiper at the edge of a salt pond

The first one had browner plumage, while the second had somewhat greyer plumage.  They both seemed to have dark legs and medium-sized bills.  Due to the season, I assume they were in non-breeding plumage.  Of course they were busy running around and peeping, with no interest whatsoever in posing for good identification pictures!  They are probably western or least sandpipers (some did seem to have yellowish legs).

picure of another sandpiper

Another sandpiper

A short distance farther along, I noticed a small, low island out in the middle of the salt pond.  There were quite a few such areas, where the “top” was barely a few inches above the water level.  Here there was a flock of waterfowl, and I took several pictures for later identification.  Although many of the ducks in the picture appear to be resting, the male in the center and the female in the foreground were more active.  The color patterns and bills identified them as shovelers.

image of a group of shovelers, mostly resting

Group of shovelers, mostly resting

Near one of the levees that separate the salt ponds, I came upon an American egret.  Its plumage makes a wonderful contrast to the color of the water, and even the details of its eye are clearly visible.

photo of American egret

American egret

Farther out along the slough, about 3 miles from the trailhead, I saw several mallards.  This is a very common duck to be seen in lakes, ponds, and so on.  This particular male seemed happy to be photographed and even seemed to be showing off his distinctive plumage, including upturned tail feathers.

picture of mallard showing off his distinctive plumage

Mallard showing off his distinctive plumage

Nearby there was a bufflehead, a smaller duck with a large distinctive white patch on the head.

image of bufflehead


Nor far away there was a male ruddy duck.  His most distinctive features are the white patch on the cheek and the erect tail.  Note the tendency for some of the ducks to swim away from the intruding person (me!).

photo of male ruddy duck

Male ruddy duck

At the northwest corner of the loop trail I saw a snowy egret feeding in the salt pond.  With the sun coming from the side, its feathers were beautifully backlit.  Every time it took a step, a tiny circular wake radiated away.  I paused to watch it for several minutes.

picture of snowy egret

Snowy egret

As I traveled along the north levee, which separates the lower San Francisco Bay from the salt ponds, suddenly I noticed that a large flock of birds was flying around near the far side of the salt pond.  It seemed that the flock would rise up anywhere from a few feet to several yards above the surface of the water, fly perhaps 100 yards in a big wave, settle back down for several seconds, and repeat.  It was almost as though the entire flock was acting as a huge elastic being – it was fascinating to watch this activity.

image of flock of unidentified shorebirds, on the move just above the surface of the salt pond

Flock of unidentified shorebirds, on the move just above the surface of the salt pond

I think I only saw common or abundant species throughout my walk, but I was still hopeful to see something more unusual.  I did see a heron-like bird that I haven’t yet identified, and I saw what I presumed to be different individuals in two locations about 2 miles apart.  Although the coloring is much like great blue herons, the legs are too short, the body too stocky, and the neck much too short.  I have never seen a great blue heron perch or roost with its neck drawn in like both of these individuals are demonstrating.  So for now they are mystery herons.

phot of mystery herons

Mystery herons

On the east leg of the trail, heading south, I encountered more sandpipers, along with some greater yellowlegs feeding at the edge of the salt pond.  Here the leg color is unmistakable.

picture of greater yellowlegs at the edge of a salt pond

Greater yellowlegs at the edge of a salt pond

I also saw a variety of even more-common birds, such as Canada geese and California gulls.  I also saw a raven feeding on a small carcass at the side of the levee trail.  On the water I identified American coots and what I think were eared grebes.  The latter would be a new life list entry, but I wasn’t sure enough of the identification to add it to my list.  These are diving birds, and when they are swimming on the water surface between dives they look a bit bedraggled.  I also saw a couple of cormorants, but every time I tried to take a picture, they would dive just before I could snap the shot – and when they emerged again, tens of seconds later, they were far away from their previous location and would dive yet again before I could compose a picture.  I got several shots of the water surface just after a dive!

I am finding it to be a pleasant change of pace to make some of my walks birding walks.  This walk is exceptional as a birding walk because the entire loop is on levees right next to water (salt pond, slough, or bay).

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2 Responses to Birding along Alviso Slough Trail at Don Edwards National Wildlife Refuge

  1. Pingback: Alviso Slough Trail: Don Edwards National Wildlife Refuge | trailhiker

  2. Pingback: Birding along the San Francisco Bay Trail at Redwood Shores | trailhiker

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