The Fen out by Happy Isles, at the east end of Yosemite Valley, is perhaps the most diverse and interesting habitat in Yosemite Valley. From sunny scrub, to shadowy forests to well-irrigated wetland, it's all there. Being wet, white alder grows in abundance, which attracts the Red-breasted Sapsucker (Sphyrapicus ruber). With their thin bark, alders are an excellent choice for a drink of sap, so the Red-breasted Sapsucker is a common sight in the Fen. There's one alder, well worked, where I frequently see them. Yesterday (August 10), in between programs, I decided to wander the now-dry perimeter of the Fen to see what I could see.
In dense tree cover, I saw a Red-breasted Sapsucker on a different alder tree. Always a pleasure, but as I say, a common site. I stopped to watch for a while and suddenly, in come three hummingbirds. They were silhouetted against the sun, but based on size, I believe they were Anna's Hummingbird (Calypte anna). Two of them flew beak-to-beak in an undulating up and down flight, each oscillation taking in about 2-3 feet. Mostly though, they focused on what they had come for: drinking sweet sap from the sapwells created by the sapsucker. After a time they left and the sapsucker returned. Then the sapsucker left, and at least one hummingbird came back and so on.
It turns out that many species of hummingbird will horn in on sapsucker sapwells [1,2], a fact that was noticed at least as early as 1891 with the observations of Frank Bolles . Interestingly, ornithologist Laura Erickson, working in Wisconsin, found that Eastern Phoebes, Ruby-Crowned Kinglets and other birds also drank from the sapwells when the sapsucker rested. The hummingbirds, however, would chase off any bird other than the sapsucker. Since hummingbirds eat less than phoebes, in protecting its food source, the hummingbirds was also doing a favor to the sapsucker . Though different ornithologists have made differing observations, some have documented hummingbirds following sapsuckers, specifically the Yellow-bellied Sapsucker being followed by the Ruby-throated Hummingbird . It certainly seemed to me from this observation, and one later in the day (which I'll get to next), that the hummingbirds were on the sapsucker's trail.
So that was a pretty great sighting and I continued to wander, finding bear tracks and poop all over and eventually making my way back to the Happy Isles Nature Center to give a Junior Ranger Walk. We began our walk and as we approached the Fen, I looked and there was a Red-breasted Sapsucker on a white alder! I did an emphatic "Shhh" with my finger and the kids crowded around. The poor sapsucker was on the tree looking like it was suffering from heat exhaustion. On the trunk, it's beak wide open, it stood still as a statue, panting off the heat of the near-record 97-degree day (according to the Happy Isles weather station). In its torpor, it was reluctant to move and all the kids got a nice long look. So then I started explaining how they feed on the sap and that sometimes hummingbirds will also feed from the sapsucker holes. And right on cue, in flies the hummingbird! The kids were also in torpor from a day out in the 97-degree heat, but when I asked if anyone besides me thought that was amazing, all the hands went up.
They were, however, less than convinced when I told them I would, without hesitation, trade twenty bear sightings for what we had just seen.
Photo Credits and Sources
Photo of the red-breasted sapsucker by Kevin Cole via Wikimedia Commons and the photo of the Anna's hummingbird is by Alan Vernon also via Wikimedia Commons
1. All About Birds: Red-breasted Sapsucker
2. "A partnership that works. Sapsuckers and Hummingbirds" on Journey North.
3. "Ruby-throated Hummingbird Observed Following Yellow-bellied Sapsucker: Evidence for Keystone Bird Species in Northern Hardwood Forests," by David Flaspohler and David Grosshuesch, in The Passenger Pigeon, vol. 58, no. 3 (1996); download PDF