Bay Area King Tides Dec 4-5 2021

Hello Bay Area iNatters!
Winter brings with it the King Tides, which will be 1-2 feet above the average high tide level. Aside from being a cool phenomenon and an indicator of future climate change, these tides are notable for their ability to draw out normally elusive species of birds and mammals from cover in marshes to the tops of plants, where they can be more easily observed.

For the coming King Tides on December 4th and 5th (Saturday and Sunday), I’d like to try walking the Lower Tubbs Island Trail at Napa-Sonoma Marshes Wildlife Area in San Pablo Bay one or both days, though a different location may be chosen for the second day. Particular target species would be:

  • California Black Rail (Laterallus jamaicensis coturniculus) (Endangered)
  • Salt Marsh Harvest Mouse (Reithrodontomys raviventris) (Endangered)
  • Saltmarsh Wandering Shrew (Sorex vagrans haliocoetes) (California Species of Concern)
  • Suisun Ornate Shrew (Sorex ornatus sinuosus) (California Species of Concern)

Other sites that have favorable King Tide reports or that seem suitable include:

  • Palo Alto Baylands Boardwalk
  • Hayward Regional Shoreline
  • Grizzly Island Wildlife Area
  • Arrowhead Marsh Boardwalk

In this thread, I’d like to open up the discussion to those with observation tips from past King Tides and see if there’s anyone who would like to meet up during this time (surely more eyes are better for finding a mouse in a saltmarsh, right?). If there’s any interest expressed, I may be able to plan an informal meet-up or pass the reins to anyone else interested in coordinating. However, note that his plan is fairly new and exact details are subject to change. If you would like to reach out personally, feel free to message me @okbirdman

Note there will also be King Tides on January 1-3, but I will not be around during that time.


I’d be interested in joining you for at least part of that, sounds like fun!

The one time I’ve seen a Salt Marsh Harvest Mouse, it was during heavy rains and minor flooding in the petaluma wetlands right beside the sheraton hotel (where I was attending a conference on sea level rise, go figure). I’m not sure how the tides will impact that area though.


That sounds really great! I’d be coming from Merced but I’d be interested in joining you if possible- Black Rail would be an incredible find for me, it’s a real bucket list species. Looking at eBird bar charts it might be a tricky species to come by but trying is always better than not trying!

My schedule is subject to change- I’m a grad student and am a Teaching Assistant this semester (and my partner is undergoing significant medical stuff right now) but if my schedule allows this sounds like it would be a blast. I’ve not gotten out for central coast king tides just yet so I’d love to learn.


Great! I’d love to have you both and anyone else who expresses in the next couple weeks join. I’ll add updates as the actual time gets closer.

I would love to join in! Black rail is a dream bird, also very interested in seeing salt marsh-adapted small mammals. I have to go to an event in Fresno at about 6PM on 4 Dec, so the best for me would be morning of 4 Dec.

Quick correction- I will be available either Saturday or Sunday.

Sounds great! Just an update: at this point, I think I’m still planning on hitting Lower Tubbs on Saturday the 4th in the late morning. Looks like high tide will be around 12:30 and it supposedly takes about an hour’s walk to get to the best viewing area, so I will probably aim to be there around 10:30 or 11:00. Depending on how things go on the 4th, on Sunday I will probably hit Hayward and/or Arrowhead Marsh because they are closer to where I am in the Bay. Anyone is free to join for either or both. If anyone would like to work out carpooling, message me privately.

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@graysquirrel @samfellows566 @Alex123 Tide forecasts project peak tide around noon on Saturday and Sunday. My plan is to be at the Lower Tubbs Parking area by 10 on Saturday because it is a bit of a hike to get to the main marsh area. On Sunday, I will be at Arrowhead Marsh around 11 because the boardwalk is right next to the parking lot

Good to know! I’m hoping to be able to join you one of the days this weekend, but I’ll see if I can make both work. Thanks for the update!

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Glad to hear it! Also if anyone coming has a spotting scope it could come in handy for spotting small distant critters in the marsh!

Looks like I won’t be able to make the Saturday trip after all, but still hoping for Sunday.

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i’d be interested in joining in at Arrowhead Marsh on Sunday Dec 5.

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For anyone still planning to join today a couple of us have already headed down the trail. Privately message me for contact info

Sorry for the last minute notice but I won’t be able to make it this weekend. Some stuff came up with the lab and I have to deal with that. Best of luck!

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I’ll be going to Alviso Marina County Park and probably portions of Don Edwards NWR because it’s closer and might be good for black rails. I’m not too familiar with the bay area, should I be concerned about car access/getting stranded/flooding of parking lots during the king tides?

Good luck everyone!

I haven’t been to either of those places, so I can’t say for sure. However, most refuges in the Bay area are built with tides in mind, so the parking lots are usually away from potential flooding areas. The same cannot be said about all the trails necessarily, especially salt marsh side trails, so high boots or water shoes are advisable.

Also, apologies for the late notice everyone, but due to something that came up, I will not be able to join at Arrowhead Marsh tomorrow. The boardwalk is highly accessible, so there shouldn’t be any problems finding it. The only thing worth noting is that the location you should put in on Google Maps is “Arrowhead Marsh Pier,” as “Arrowhead Marsh” misdirects. In terms of viewing tips, some of the links above provide good information. Beyond that, the harvest mouse tends to favor dense patches of glasswort or other shrubs (though there aren’t many shrubs at Arrowhead Marsh)

Is anyone still planning to go to Arrowhead Marsh today?

Anyone have success seeing black rails this way during the king tides?

I didn’t…