Staking out the Birds

Like hunters, bird watchers who have patience and perseverance often capture more birds by their binoculars than those who don’t. An especially fruitful practice for bird-hunting by either guns or glasses is to stake out our objects of desire at promising spots. Food is the foremost lure of wild animals. So finding (or setting up) a place with things they like to eat is an obvious first step.

For plant lovers, your keen observations of the yearly cycle of leafing, blooming, fruit-setting, leaf-shedding, etc., come handy in choosing a stake-out point. In fall, the ripened fruits on many plants attract birds large and small, from band-tailed pigeons, cedar waxwings, American robins, red-breasted sapsuckers to towhees, sparrows and chickadees. A tree, shrub or vine with a heavy load of bright-colored ripe fruit is a perfect location for a birder to sit and wait.

Early this week, we saw hermit thrushes galore; they were taking Summer Holly’s (Comarostaphylis diversifolia) orange drupes up in the trees and down below the trees. They have a discriminate taste, picking only the healthy fruit.

Hermit Thrush on Summer Holly, November 7, 2017, by Minder Cheng.

Last week, a hermit thrush was in the bush of Snowberry (Symphoricarpos albus) by alpine granite bed, sometimes perching gingerly on the thin branch, sometimes hovering in the air, and sometimes walking around on the ground, all for the purpose of getting the most palatable fruit. In my eye, the waxy white drupes looked the same. Endowed with greater visual acuity, the bird knew which ones were best. Once it inspected one fruit that had dropped, and left it there. We walked up after it flew off, and even we could see that this berry had a yellowing spot at one end, apparently an indication of its inferiority.

The Snowberry rejected by Hermit Thrush. November 1, 2017.

For me, it’s often the birds that alert me to the fruits that I would have missed. Without seeing a hermit thrush flying into Hackberry (Celtis reticulata) two weeks ago, I wouldn’t know that the small berries were ripening. Two years ago, we also saw a fox sparrow pecking at the berry’s thin pulp.

This year from October up to now, several other bird species were also seen eating fruits in the garden: purple finch on Twinberry (Lonicera involucrata), golden-crowned sparrow on Snowberry, pine siskin on Mountain Alder (Alnus incana ssp. tenuifolia) seed, and Steller’s jay carrying acorn (Quercus) in its beak. The latter two kinds of food, botanically speaking, are parts of fruits borne by angiosperms.

If you want to experience intense observations of bird feeding (other than setting up a bird feeder), go to those plants in the botanic garden with fruits at their prime, stand or sit at some distance, and wait. Your patience will be handsomely rewarded.

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.

Moon Eclipses Bird Action in the Garden

Eclipse Day! I was amazed at all the bird activity in the garden at 9 a.m. this morning - singing, calling, chasing, feeding - in all garden habitats. Very "birdy." With the temperature at 59 degrees and a heavy cloud of fog overhead, I expected a quiet start, even quieter during the eclipse, which I came to observe. Instead, bluebirds were sallying out over the lawn below the sierra granite bed and poking around in the grass, next to robins both mature and speckled immature. The Black Phoebe was noisy as it picked insects out of the air. Dark-eyed Juncos were the most prevalent including immature following their parents, both in the Sierra and along the Freeway below the Island Section. Both mature and immature Spotted Towhees were noisily foraging and calling. A Red-tailed Hawk cruised low over the garden, possibly seeking one of the voles we've been observing recently. Nine other species were present including Wilson's Warbler, Song Sparrows, Nuttall's woodpecker but only one Anna's hummingbird, vocalizing.
I could find no pollinators, and none of the poppies were open, so most of my observations were focused on the garden birds.
As darkness fell towards totality (76% here), the birds fell silent except for one adult Spotted Towhee who at last was quiet. A chill set in. But as soon as the light started to return, within six minutes, all the birds became active, flying and vocalizing. Yet after half an hour, it was overall much quieter than when I had arrived. Curious!
Did anyone else have an observation of bird behavior through the eclipse?

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.

Wilson’s Warbler (Cardellina pusilla ssp. chryseola) had a baby

(Written on June 10, 2017)
On the first Wednesday of June, a foggy morning, we heard cha-cha-cha-cha-chchchch and spotted a Wilson’s Warbler singing on the branch of a Western Red Cedar (Thuja plicata) as we were about to enter Pacific Rain Forest from Sea Bluff.

All of a sudden a Wilson’s Warbler landed on the trail next to the wooden bridge by several Yellow Skunk Cabbages (Lysichiton americanus). The bird was on the ground for less than a minute, then a second warbler appeared. Both flitted in the lower branches of conifers. Their plumage looked identical to each other; both had a dark cap, olive-green upperparts and bright yellow underparts (an exception to the description in most field guides about female having a lighter cap). We were sure that they were a mated pair because they were amiable to each other, not chasing the other away as happens often in territorial defense in breeding season. Soon their couple-hood was confirmed: one stood on the bridge fence briefly before going down to feed a baby on the mossy bank behind skunk cabbages.

No sooner had the short feeding session done than the adult flew up, leaving the young bird sitting in a small Heuchera. The tiny chick was brown and dark, quiet and motionless. It would have been invisible if we had not seen it being fed earlier.

We stayed about 30 feet away to look at it with our binoculars, then walked quietly past it. It turned its head to look at me as I crossed the bridge. Seeing its large pink beak was a thrill—this is my first time seeing a pink-billed chick of any warbler!

Tips on watching Wilson’s Warbler:
1. Learn its songs, and they will be the best clue to its presence. (Go to Macaulay Library. This is one example.)
2. 2015 and 2016 surveys of botanic garden show that they arrive in late March and are gone in early August.
3. Leave them a lot of space when you see nesting pairs and young birds. Please go quietly past them after you have viewed them no more than 5 minutes. I learned from Jon Young’s book What the Robin Knows that animals take many cues from observing our behavior. I wouldn’t want to interfere with Jays’ hunting of eggs and chicks of smaller birds; nor would I want to aid them.

If you want to know more about Wilson’s Warbler, some online resources about our local subspecies are below.
A study of female singing in Tilden, 1999
Photo of a banded bird in Tilden, 2015
Three subspecies may turn out to be two species, 2015
Why coastal Wilson’s Warbler subspecies chryseola declines, 2016

Parking lot of Regional Parks Botanic Garden, May 4, 2016, by Minder Cheng.

Juvenile Spotted Towhee (Pipilo maculatus)

(Written on July 5, 2017)
At the border of the Franciscan and Canyon Sections, there is a tributary that flows down by the greenhouse and joins Wildcat Creek under the bridge. Near the bridge there grow red elderberry (Sambucus racemosa) and California pipevine (Aristolochia californica). This rushing side creek becomes a trickle or disappears altogether in the dry season. In July, instead of water, there is lush vegetation on the canyon floor. This is the favorite habitat of brush-loving birds.

Walking up the steep trail from the bridge to the greenhouse, we saw, on the right slope, a dark brown bird with thick beak and a sparrow-like streaky pattern on its underside. It was larger than a sparrow, approaching the size of a thrush. Then we saw its very long tail. Near the tip on the underside of the tail, two distinct white almost rectangular marks stood out from the ground of gray tail feathers.

Three outer tail feathers.
Evolution of the Colors of North American Land Birds by Charles A. Keeler. 1893

The white tail spots told us right away that it was a juvenile Spotted Towhee. Lacking the adult’s rufous flanks, lines of white spots on the sleek black back, or red iris in the eye, this young bird did not at all resemble its parents in plumage; but in body shape it was very much a towhee. Towhees (Pipilo) are a genus of New World sparrows. The adults do not share the intricate brown and black streaks that we commonly associate with sparrows. However, in the developmental stage of the young birds, a remarkable resemblance to sparrows is apparent.

When we stood under the valley oak (Quercus lobata) near the grind stones, an adult Spotted Towhee started singing its fast dry trills from a low manzanita. It sounded a little agitated. Soon a juvenile flew out and went on to walk on a horizontal branch of coast redwood (Sequoia sempervirens) trying out its balance beam skills. Another adult showed up by the path toward the greenhouse and repeatedly called out “wrang-ng” loudly. Then the second juvenile appeared.

Based on their proximity to one another, we believed they were one family. The parents were chaperoning their children’s foray into the world!

Juvenile Spotted Towhee, probably from the second brood of the year.
Southern California Section. September 10, 2015. By Wen Hsu.