Dawn Chorus Update #12: A Filter-Trippin' Good Time at Tennant Lake

[Stephen Chase]

Hi Whatcom Birds,

The days are still getting longer, but hardly. Although the solstice doesn't take place until June 21, our earliest sunrise of the year is only eight days away, on June 16. This morning I was on site at the WDFW parking lot on Slater Road at 4:24 AM, one minute before first light.

My goal today was to trip some filters. Let me explain. I love eBird! I think it's simply brilliant. It's widely regarded as the world's largest citizen science project, and the world's largest biodiversity project. eBird touts 2 billion plus sightings recorded, over 1 million users, and data incorporated in over 550 scientific publications. More than that, it has done wonders for introducing birds and birding to Gen Z, a generation known for wanting to make a difference in the world and excited by the natural tie-in between birding as a hobby and birding for a cause. No doubt it's not perfect; the gamification of birding can lead to unethical behavior that warrants carefulness when deciding what to submit, and how, and when. But overwhelmingly, eBird is a cause for good - reigniting in a generation an interest in the natural world, a deeper understanding of the complexities of ecosystems and bird behavior, a greater awareness of how connected are world is, and so much more!

eBird Central recognizes that such an enormous amount of crowd-sourced data is inherently going to be imperfect. (In the Pacific Northwest, nowhere is that more obvious than with gulls; it feels like no one quite knows how to make sense of our messy hybrid gull swarm.) But eBird is willing to put up with a small degree of statistical error for the sake of building such an enormous database. That said, eBird is built in with filters to help birders recognize what to expect (and what not to expect) and to help appointed reviewers catch erroneous reports. That's what eBirders call the "filter." Every county has one; for every day of the year it designates what birds are expected in the county and how many might be considered too many. It's absolutely a challenging process to determine, and eBird reviewers are constantly refining it. For the most part, it works. For example, on June 8 (that's today!), the eBird filter is set to "trip" at 26 Common Yellowthroats and 26 Northern Yellow Warblers. Record that many, and you'll need to provide some extra documentation to explain why you recorded so many of each species. Did I say need to? I meant to say get to! You had an epic day out birding, so you get to provide some extra documentation! For the vast majority of the county, 25 of each of those two warbler species would be a reasonable high count that would be hard to top. But at Tennant Lake, well, a birder can trip that filter without much of a problem - especially if such a birder chose to be up for the dawn chorus at 4:24!

My targets today were to count as many Common Yellowthroats, Northern Yellow Warblers, and Swainson's Thrushes as I could. Generally when I'm birding, ensuring that I'm not double-counting is tedious, but during the dawn chorus when birds are more likely to be singing from a dedicated perch, it's much easier to do. Generally it means walking for a hundred feet or so, listening for 30 seconds or so to triangulate the same individuals heard 100 feet earlier, recording any more I hear up ahead, then rinse and repeat. For both Common Yellowthroat and Yellow Warbler, that's fairly easy; in peak breeding season males often sing up to 10 times a minute, which gives me lots of time to confirm how many I'm hearing and what direction they're coming from. By 4:54, 30 minutes into my walk, I had tripped the filter for Common Yellowthroat. Three minutes later I tripped the filter a second time by reporting my 26th Yellow Warbler. How fun - now I have to get to provide some extra documentation to defend my observations! In the end I picked out an impressive 43 Northern Yellow Warblers - an all-time high count for Whatcom County!

For Swainson's Thrush, eBird's filter was set to 50. That means I'd need to find 51 birds in order to trip it. That felt ambitious, but I was up for the challenge! Spoiler alert: I ended up counting exactly 50. (For the record, 50 isn't even close to the all-time county record of 80, which occurred on this very date exactly 13 years ago at Lake Padden.)

Considering the general decline in bird populations, 2026 has actually been quite a good year for all-time high counts. The primary reason has been a near-historic herring spawn in January and February, which pulled in exceptional numbers of seabirds. So far in 2026, eBirders have recorded all-time high counts for Whatcom County of 18 species, including Brandt's Cormorants (1,800), Redhead (29), Red-necked Grebe (550), Double-crested Cormorant (3,000), Pelagic Cormorant (1,000), Red-breasted Merganser (4,000), Common Tern (1,700), Cinnamon Teal (21), Townsend's Warbler (50), and Wilson's Phalarope (21). It's worth noting that these are some of the high counts that have actually made it to eBird. There's a lot of historic data that has not (yet) made it into the eBird database. Some current data too, I imagine.

Peruse my checklist for notes about my sightings this morning, and take a look at some of those numbers! Tennant Lake is truly a local gem of a location!

In Everson,

Stephen Chase