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.

Fruit- and Insect-Eaters Abounding

Birds were very busy in the garden on a recent day in mid-July. Robins and their speckled young were literally mobbing the fruits of a Hawthorn shrub (Crataegus) located at the southwest side of the pond, providing amusement for us birders. We were able to approach quite closely as the birds gorged themselves.

Insects were in high demand by four species of flycatchers, by hummingbirds, and by warblers and a vireo, among others. While the warblers and vireo were busy gleaning insects from the trees and shrubs, the flycatchers and hummingbirds were sallying out to catch insects on the wing.

With all the competition, you have to ask if there are enough insects to go around. The flycatcher species are exemplary. Olive-sided flycatchers sit at the top of the tallest trees, calling and sallying out.  The Pacific-slope flycatchers tend to sit mid-tree or shrub adjacent to open areas where they may spy flying insects. The Western Wood Pewee tends to sit lower in trees and shrubs. Potentially, they are eating insect species that separate themselves by habitats high, medium and low in the environment.

The garden's resident Black Phoebe seems to be flexible, perching at a variety of levels from low fences to the taller trees.

In an exciting flash of yellow, red, black and white, we had a quick view of a male Western Tanager darting over the upper creek. In fall and winter, these birds eat berries and other fruit. In summer, their diet is dominated by insects, especially if they are feeding chicks.

The brilliant red head feathers are due to pigments. Unable to make the pigment themselves, Western Tanagers probably obtain it from insects in their diet. Great information about this and other birds may be found at Cornell's website: www.allaboutbirds.org.
Here's a photo by George Grover from Flickr.