Look, a Hawk!

When a hawk is called out, bird-watcher or not, everybody turns their head and wants to see it. Even a botanist who is concentrated on plants will oblige and allow him/herself to be distracted for a minute. Perhaps being both prey and predator in our evolution history makes us feel simultaneously threatened by and attracted to a ferocious hunter on wings.

After several years of watching birds in the Botanic Garden, we have come to realize that Alnus (Alder) growing on the west bank of Wildcat Creek at the edge of Sierran Section is a favorite perch of Sharp-shinned Hawk (Accipiter striatus) and Cooper’s Hawk (Accipiter cooperii).

A juvenile Cooper's Hawk on Alder tree, September 3, 2018. Minder Cheng.

These two hawks are small in size, and skilled in weaving in and out of dense woods to catch songbirds for meals. Foliage and branches of broadleaf trees are great cover for the stealthy snipers. Once they strike, successfully or not, they do not linger, but fly away immediately to either finish the job or find another hideout.

Although every hawk discovered is a cause of elation, the larger it is, the more excitement it arouses. Red-shouldered Hawk (Buteo lineatus) is much bigger than Cooper’s and Sharp-shinned Hawks; moreover, it is photogenic. Our local subspecies (elegans) has orange-red breast and belly, so distinctive and conspicuous once you locate it in the tree. On a memorable day in November 2019, we spotted an adult Red-shouldered Hawk sitting in Fraxinus velutina (Velvet Ash). We were mesmerized by its beauty, and it didn’t seem to mind our goggling. It was silent for maybe half an hour, then suddenly burst into calls. We didn’t know what caused it to announce to the world its existence, but we were thrilled to have a magnificent hawk displaying its full regalia and its vocal talent.

Adult Red-shouldered Hawk, November 5, 2018. Bill Thomas.

In fact, we hear Red-shouldered Hawks more than we see them. Their sharp and penetrating kee-ah series have a ringing quality, and often continue for some time before stopping. Listen to this recording made by Denise Wight in Tilden Park.

The wildlife harbored by the Garden makes it a great hunting ground for Red-shouldered Hawk, whose varied diet includes small mammals, birds, amphibians, insects, and crayfish. Several times during our surveys we saw this large raptor flying quietly down the canyon of Wildcat Creek, moving from one tree to another along the water course. And more than once did we see the carcass of crayfish lying on the rail of the wooden bridge crossing the creek. No witness came forward to identify the killer, but Red-shouldered Hawk is definitely a suspect in these unsolved murder cases.

Red-tailed Hawk (Buteo jamaicensis) is even larger than Red-shouldered, and is by far the most commonly seen raptor in the Garden. It usually appears as a fly-over that circles above us, glides effortlessly in the thermals or drifts along the horizon. Imagine our surprise when an immature Red-tailed Hawk showed up on the roof of the nursery next to the solar-powered well pump. It was on a weekend, and many visitors of the Garden walked by oblivious to its fierce gaze. The young hawk seemed just as unconcerned by people, paying its full attention to movements on the grassy meadow below.

Juvenile Red-tailed Hawk, intent on movements of rodents in the meadow. September 9, 2018. Minder Cheng.

Judging from its deflated crop (a pouch in bird’s gullet where food is temporarily stored after being swallowed), the fleet-footed voles and gophers that lived underground had largely evaded its talons.

Using sounds for bird identification is the game of experienced birders, and sometimes the only recourse to successful identification (especially so for Empidonax flycatchers). However, here birders encounter the challenge of mimicking. Steller’s Jay often throws me off by a bewildering array of sounds it is capable of making, which includes the masterful mimicry of hawks. And Red-tailed Hawk seems to be its favorite target of imitation.

Go to the second to the last recording on this page for a Steller’s Jay’s excellent parody of Red-tailed Hawk.

Why does a jay want to sound like a hawk? Donald Kroodsma says in Birdsong for the Curious Naturalist (2020): “Ornithologists have no solid answers, but are prone to speculate, of course. Maybe the jays are trying to scare other birds, or trying to warn their jay companions of a hawk or other danger nearby. Then I wonder, how often do jays call like hawks when we humans are not there to hear them?”

Next time you hear a hawk calling from somewhere in the trees, take note of the vocal quality. If it is a little too scratchy, not forceful enough, and doesn’t repeat a good number of times, then the calls may not come from a hawk. Try to follow the sound to its source, you may find a hidden jay singing away.

Extra:

Do you want to test your Accipiter ID skills? The difference between a Cooper’s Hawk and a Sharp-shinned Hawk is the perennial puzzle faced by hawk watchers. The following pair of photos were taken in the Garden; one has a Cooper’s and the other a Sharp-shinned. Please tell us how you decide which is which in comments. The answer will be posted after 3 days.

Note:

Jerry Ting and Bob Lewis, two esteemed birders in our area, helped me with Sharp-shinned Hawk and Cooper’s Hawk identification in many photos.

Sugar Thieves

Have you seen birds with feathers sticking up around their beaks as if they had a bad facial hair day? It happens often in late winter in our area to small birds with short and thin bills, such as Ruby-crowned Kinglet, and a number of warblers. These birds are insectivorous for the most part, but when there is nutrient-rich plant food around, they don’t hesitate to tuck into it.

Ruby-crowned Kinglet, near Jewel Lake. Feb. 8, 2016. By Minder Cheng.

When warblers pick bead-like berries, such as fruits of Pacific Wax Myrtle (Morella californica) and exotic palms, both favorites of Yellow-rumped Warblers, they swallow them in whole, and no feathers are messed up. The irresistible sugary tree sap, on the other hand, is a treat that leaves tell-tale sign on the guilty parties.

Yellow-rumped Warbler, Tilden Nature Area. Feb 1, 2016. By Minder Cheng.

Coming upon sap wells drilled by sapsuckers (and sometimes by other woodpeckers, see for example Kozma 2010), warblers and kinglets have to press their heads against the holes, and thrust their short beaks as deep as they can, in order to lap up the sweet liquid inside. That’s because the circumference and depth of the holes are made by bills much bigger than theirs, and if the sugary residue around the hole touches the base of a small bill, it can gum up the feathers surrounding the bill.

Orange-crowned Warbler, Valley-Foothill Section of Regional Parks Botanic Garden.
May 7, 2019. By Minder Cheng.

Here is a blog post that documents a Townsend’s Warbler visiting a Red-breasted Sapsucker’s handiwork in Fort Mason, San Francisco.

Hummingbirds, well-known for their love of sugary drink, actively pursue, and even defend, sap-producing holes (Sutherland et al 1982). I once saw an Anna’s Hummingbird dipping its bill into a sap well, then it got excited and zapped a Red-breasted Sapsucker working on other sap wells in the same tree. The feisty hummer chased the rightful owner away in no time.

But we don’t see hummingbirds with any matted facial feathers. They maintain their immaculate look because they have longer beaks, plus very long tongues adapted for nectar drinking (watch this video for the way their tongue works. They simply hover outside the holes, and let their bill and tongue do the job cleanly.

Tree sap is such an important part of hummingbird diet that it’s believed that the northern limit of Ruby-throated Hummingbird’s breeding range is affected by the availability of the sweet sap provided by Yellow-bellied Sapsuckers. In the west, the same relationship likely exists between Rufous Hummingbird and two sapsuckers, Red-naped and Red-breasted. (Miller and Nero 1983)

Rufous Hummingbird and Red-naped Sapsuckers. Painted by William Zimmerman.
Life Histories of North American Woodpeckers, 1992.

In fact, many birds enjoy swiping the sweet drink that the hard-working sapsuckers make available by drilling down to phloem or xylem tissue of trees. According to The Audubon Society Encyclopedia of North American Birds (1980) by John K. Terres, American Goldfinch, Pine Siskin, White-crowned Sparrow, Evening Grosbeak, Northern Cardinal, nuthatches, waxwings, and juncos are all sugar thieves. If we know there is free syrup out there in the woods, won’t we flock there, too?

Note:

Another source of matted facial feathers is the viscous nectar of Eucalyptus flowers. Let me quote David L. Suddjian (2004) “Birds and Eucalyptus on the Central California Coast: A Love–Hate Relationship”:

The great attraction of flowering eucalyptus for foraging birds may have its downside, though. As the birds spend time feeding amid the flowers, the feathers on their faces become matted with a black pitch-like residue (or gum) from the nectar. This affects their ability to maintain those feathers, and in some cases the gum may plug their nostrils or bills, and prevent breathing or feeding. Australian birds that regularly feed at Eucalyptus flowers in native settings have longer bills than North American species that feed at eucalyptus flowers, apparently permitting them to feed there without being affected by the gum.

Articles published in the Point Reyes Bird Observatory newsletter (Stallcup 1997) and in Audubon magazine (Williams 2001) have suggested that the effects of this black pitch cause substantial mortality among the North American species that feed at eucalyptus flowers. It seems to be a reasonable conclusion, and Stallcup (1997) cites some instances of mortality. But in my experience, and the experience of a number of other long time field ornithologists, we have seen very little evidence of such mortality. It has been argued that the bird carcasses do not last long on the ground before they are scavenged. However, when observers spend hundreds of hours under these trees over many years but find hardly any evidence of such mortality, then it seems fair to question whether the incidence of mortality is as high as has been suggested.

Reflections on birds of 2019

Reviewing the data collected last year, we are happy to report five new species being added to our checklist compiled through 2018. Carrying out a pre-dawn birding operation in January, Kitty and Ellen nabbed a Northern Saw-whet Owl in the dark. May and June brought us respectively a male Yellow Warbler in Canyon Section and a White-Throated Swift flying over the Garden. Two large-sized and unmistakable species joined us in the latter half of 2019: ten beautiful White Pelicans shone in the blue October sky; a Great Egret granted the Garden staff an exclusive view in December as the graceful bird checked out the pond, the small pool, the creek, then departed for the golf course.

Survey data of 2019 with the complete list of 74 species can be found here.

If you are an avid eBird user, you know that Regional Parks Botanic Garden is a birding hotspot. Searching through 2019 eBird reports by birders who visited the Garden, you will come across quite a few interesting species that were not sighted during our surveys. Since these reports were submitted nearly all by reputable birders, they are worth our attention. Let’s look at, first, a number of birds that are in our checklist, but were not seen in last year’s surveys.

What we missed in 2019: Lazuli Bunting, Lincoln’s Sparrow, Red-breasted Sapsucker, Willow Flycatcher, House Wren, Red Crossbill, Pine Siskin, and American Goldfinch.

The most glaring miss is perhaps Red-breasted Sapsucker. There are active sap wells on several trees in the Garden. In fact, one winter weekend I had a glimpse of the bird in Channel Island Section, but alas, it was outside the survey time. So even though we did not have the bird in our 2019 data, we know it was in the Garden.

Second, there are five reported species that are not even in our checklist: Western Screech Owl, Chipping Sparrow, White-breasted Nuthatch, MacGillivray Warbler, and Brown-headed Cowbird.

Now that we have been alerted to their occurrence in the Garden, albeit transiently, we will keep an eye (and ear) out for them!

In addition to numbers and lists, below are some memorable moments we had in 2019.

Ellen:
One morning our intrepid surveyors ventured into the Canyon Section where the tall redwoods have been living for a very long time. Here it feels truly wild. Traversing the west facing hillside, we heard it: the Pacific wren. The song is pure liquid music.

On this particular morning we were well above the creek. The bird seemed intent on coming to investigate these tall bipeds. Although the song seemed somewhere down the slope, suddenly the bird was just in front of us, skulking around in a sword fern cluster. This wren is a trickster, making his voice appear in places he is not, and sounding oh-so-big! But this bird is tiny and dark brown, with a short cocky tail. Its movement is reminiscent of a mouse. Instead of running on the ground, this wren flies low between clumps of vegetation to investigate upturned roots and decaying logs for food.

We were lucky that day to see the Pacific wren, and we are always delighted to hear its liquid song.

Pacific Wren, November 13, 2019. By Minder Cheng.

Idell:
Near the Channel Island section remains one of my favorite survey spots. The unmistakable cheery calls and twittering of the Lesser Goldfinch fill the air, and on overcast days their bright yellow breasts appear to be tiny globes of sun--but fluttering ones!

Bart (from two email messages):
A huge flock of Cedar Waxwings spent several hours in the garden today (April 27). They seemed to be flying in a large circle–arriving over the Visitor Center and landing in the alders. From there they went down to the flowering Amelanchier (next to the button willow), then off into the aspens and points south. They kept going in this circuit for a few hours. I think there were probably 100 in the flock.

This evening (May 8th), the Cedar Waxwing flock is back. As I am with this, there are a lot of them perched at the top of the alder that is right across from the Visitor Center deck. There are only about a quarter to half as many as last time (probably between 25 and 50 right now) and they don’t seem to be as “flighty” as they were. Most of them just few off toward the southwest, after a small group flew in from the southeast.