Sorry for the belated report. On January 24th, I spent the day bouncing around some of my favorite spots in Eastern Contra Costa county. Weather was far less than optimal, but I still managed to see a decent variety of unusual birds. Also, I have been asked by a reader to clarify my definition of "East county". By my definition this region refers to just the delta islands and associated lowlands, from Big Break to Clifton Court, modeled after Steve Glover's definition in years previous. Indeed, if one were to include the immediately adjacent foothills species that are rare to unrecorded in East county like Oak Titmouse and White-breasted Nuthatch would be commonplace.

Anyway, I arrived at Bethel shortly after 7:30 to find the entire area enshrouded in a thick blanket of Tule Fog. As a consequence, all nearby waterways and fields were, for the most part, invisible, and I spent my entire stay on the island sifting through passerines at various locations. I was hoping to start with dawn flight and get a count of the Mourning Doves, waterfowl, and shorebirds flying over the slough, but with that plan thwarted I instead walked around the entire slough willow/blackberry bramble trying to kick up passerines. In the dense fog activity remained low during my entire visit, but a few large flocks of sparrows spiced things up. 

From there I went on to Willowest Marina where activity was similarly subdued. So, I decided to take a breakfast break and returned to birding the neighborhoods on the south side of Bethel. Again, nothing earth-shatteringly rare but there were a healthy number of birds here including some nice sparrow concentrations. Highlights on Bethel included:

Golden-crowned Kinglet-3 was a good bird for East county
Orange-crowned Warbler-14
Fox Sparrow-15 of which all the birds I saw were sooty
'CASSIAR' DARK-EYED JUNCO-1 in the neighborhoods was a huge shock to me, as I am unaware of any non-Oregon type juncos ever recorded from East county, and it was certainly my first
White-crowned Sparrow-124
Golden-crowned Sparrow-188
Yellow-headed Blackbird-48 was a huge surprise, as this species is very uncommon on the island, and almost always just singletons. Perhaps the fog had something to do with pushing them out?
HOODED ORIOLE-1 continuing male at Willowest

Full eBird checklists here: https://ebird.org/view/checklist/S42199935 and here https://ebird.org/view/checklist/S42205803

Piper Slough appears to be going through somewhat of a transition right now. The large clearing just to the south of the trail near the entrance, formerly one of the best spots for migrant concentrations as well as chats, is now blocked by a mesh gate. There are extensive lines of black tarp spreading across the length of the slough that I fear may foreshadow more removal of vegetation along the entire length of the slough. In happier news, part of the edge of the willows has developed a healthy stand of small cattails and marshy grasses and is already occupied by several Marsh Wrens. Several more years of good winter rains and maybe we'll get back Piper Slough rails. 

After Bethel I headed on to Holland Tract where I spent a healthy amount of time working the Central Tract marshes. They didn't quite have the magic they possessed in August and kind of resemble most of the rest of the delta flooded fields in terms of bird concentration and numbers, but still highlights included:

Mute Swan-5 lowlight
Hooded Merganser-3
Ring-necked Pheasant-1 was my first on the tract in a while
Virginia Rail-3
Sora-6
Lesser Yellowlegs-1
CASPIAN TERN-1 over Frank's Tract
Horned Lark-1 singing male was the first of this species I have seen displaying on the tract, and likely means breeding is imminent
Yellow-headed Blackbird-3
Great-tailed Grackle-33 was a good count for east county

Full eBird checklist here: https://ebird.org/view/checklist/S42209632


From there I decided to mix up the route a bit and bird discovery bay, an area that's always interested me but that I'd never gotten around to birding. I was pleasantly surprised that the place was loaded with birds. I walked around the golf course and neighboring residences, which had a nice selection of passerines and waterfowl. Highlights included:
Greater White-fronted Goose-1
Cackling Goose-2 of which one was an "aluetian" and one a "minima"
Hooded Merganser-5
Green Heron-1
Swainson's Hawk-1
BROWN CREEPER-1 crawling up a building was a very good bird for east county
WESTERN BLUEBIRD-2 together in the neighborhoods are perhaps regular here, but overall thought to be very rare in east county
Yellow-rumped Warbler-125 was a great count anywhere in the county. This place was crawling with them

Full eBird checklist here: https://ebird.org/view/checklist/S42211597

I then wandered around the fields north of Clifton for a while, hoping to find a field with Larks to look for longspurs. I had originally planned to allocate several hours to this, but lost track of time and ended up only having a few minutes for the job. Ultimately, besides a few flocks of Pipits the only consolations was a single Burrowing Owl.

On to dusk at Clifton Court I'd planned on positioning myself well at sunset to sort through the gulls as they streamed in. Alas, the birds were still distant and it is likely a goody or two slipped through. Still, during my stay at the reservoir I found:
Sora-1
Ring-billed Gull-1,000
California Gull-10,000
Herring Gull-10,000
Barn Owl-1
Great Horned Owl-4
Merlin-1

Full eBird checklist here: https://ebird.org/view/checklist/S42215748 

A fun day in east county with 126 species observed.

Good birding,
Logan Kahle
San Francisco