Tail of Black Phoebe (Sayornis nigricans)

Thursday volunteers who propagate plants for the garden are familiar with the nest of Black Phoebe. It’s a sloppy-looking mud nest with plant material sticking out here and there. One such nest is attached to the wall under the eaves and above the door to Juniper Lodge (or the potting shed). In fact, wires were added by humans to the nest to make it structurally sound (and even seismically safe?).

But the garden has another Black Phoebe nest, which is hidden from view to the general public, yet well known to gardeners: it was affixed to the outside wall of their office located at the far corner of Pacific Rain Forest section. And this year a pair produced fledglings successfully.

Being a year-round resident in the botanic garden, Black Phoebe is a familiar sight to us. It’s conspicuous in many ways, first and foremost being its choice of perch: an out-stretched branch, the tip of a conifer, a trail signpost, a plant label in the garden, or any other thing that sticks out and gives it a vantage point. Its black and white plumage is elegant and offers no camouflage. Its preference for ponds and riparian habitats make it a lot more visible than other flycatchers that hunt in shrubs and trees. What is more, it often announces its presence by loud calls either perched or flying. Its adaptability in using artificial structures as nest sites is certainly another help for people to find it. Black Phoebe is often the first flycatcher that many learn to recognize in California.

Black Phoebe sometimes moves its tail up and down when it is on a perch. David Allen Sibley quotes a study that suggests the tail-pumping be a deterrent to predators--it is a signal sent by phoebes to hawks saying: “I see you.” Granted that there is a statistically significant association between the presence of predators and the bobbing of phoebe’s tail, I have reservations on the idea that the latter is an active signal. Unless the predators are shown to be attuned to the tail-bobbing and be so mesmerized by it as to forget about attacking, I doubt the validity of the theory.

Watch videos on the internet of tail-bobbing Black Phoebes, and you may come up with an alternative hypothesis.

Immature Black Phoebe in Sierran section, July 30, 2017. By Minder Cheng.