Wednesday, July 31, 2019

Post #163 - Bay Area Bar-tailed Godwit - by bike!

Opened in 1967, the San Mateo Bridge stretches 7 miles across the middle of the San Francisco Bay. It is the longest bridge in California and allows nearly 100,000 vehicles to commute between San Mateo and Hayward each day. It does not, however, feature a footpath or bicycle lane, a complication making a mid-bay crossing impossible for pedestrians and cyclists. Those can use the Dumbarton Bridge ~12 miles to the south, but detouring to that span is an impossibility for walkers and a big inconvenience for riders.

Ariel view of San Mateo Bridge 

Enter Bar-tailed Godwit, an Old World species which also breeds in Western Alaska. The bird is a rare but regular vagrant on the Pacific Coast, and I figured one would eventually appear in my Bay Area surrounds, a suspicion confirmed when an individual was recently discovered at Ora Loma Marsh in Alameda County.

Breeding plumage Bar-tailed Godwit from Adak, AK
Photo from Laura Keene (check out her flickr account)

Bar-tailed Godwit records from eBird

Though Ora Loma March is 10 straight-line miles from my apartment, the bike ban on the San Mateo Bridge would force me south to the Dumbarton, a circumstance rendering the vagrant godwit 34 riding-miles from my home. At 68 miles round-trip, my pursuit would need be calculated and organized to maximize the prospect of success.

My godwit pursuit

The initial godwit report - not posted until 10pm Sunday, July 21st - noted the bird was observed on the late-afternoon high tide that day. The reflexive approach would have been to aim for the same tide on Monday, but I wanted to know the bird had established a minimal pattern before investing 68 riding miles into it. A 5- to 6-hour bike chase can wipe me out through the following day as well, so I need to be selective in which birds I chase. I'm generally willing to concede short-staying vagrants (i.e. one day wonders) to ensure a higher overall success rate on chasing birds which remain in their discovery areas. I can chase a rarity that is 15 miles away (~1 hour) without thought, but the calculation steepens as the intervening distance grows. It's a similar calculation in the car, albeit with infinitely fewer variables in the equation.

Panorama of Ora Loma March

When the godwit was reported on the same late-afternoon high tide on Monday, I knew Tuesday was my day. I powered south out of San Mateo at 2pm, crossed the Dumbarton, and continued north along the eastern bayshore to arrive at Ora Loma at 4:20pm. The rising water had already concentrated hundreds of shorebirds in the marsh, and another birder (James Watts) and I split the task of scanning the roosting throngs, him from one end of the assembly and me from the other. James spotted the bird within a few minutes, and I bounded the 100 yards to his scope for a killer view of the sought rarity. The bird spent the next hour resting and preening before being flushed by a low-flying Turkey Vulture at 5:30pm. Half a dozen others arrived in that interval, and all enjoyed point-blank views of the rare shorebird.

Phonescoped winter plumage Bar-tailed Godwit
Bay Area bike bird #288
Traditional ABA bird #733 (#731 Lower 48)

The WNW headwind riding back across the Dumbarton and along the western bayshore was heavily impeding, but I fought through it and returned home at 8:20pm. Bike-birding celebrations are always broken into two parts, the first half in the field when the bird is observed and the second half when I return home safely. The godwit was my longest single-day chase since moving to the Bay Area, so my sofa felt great when I finally collapsed onto it to watch Deadliest Catch at 9pm!

It's worth mentioning the godwit was seen again at 7pm on Tuesday evening (after I'd departed) but not on subsequent days. In this instance, delaying for a day was the perfect move, but I'm sure I'll get burned at some point. It's inevitable in this game......