San Diego Natural History Museum--Your Nature Connection[San Diego County Bird Atlas Project]

WRENDERINGS
Reports from the Field
Winter 1999

The Story of the Upland Sandpiper
Dove Under Glass
Migrating Swainson's Hawks Take a Rest Stop at Ocotillo Wells
Watching Screech Owls by Day
Willie and Her Commute from Southeastern Oregon to Mission Bay


The Story of the Upland Sandpiper

On Tuesday 19 October 1999, before going home after work, I dropped by the Tijuana River valley to see what birds were frequenting the Am-Sod farm east of Dairy Mart Road (W11). A Chestnut-collared Longspur had been found among the Horned Larks on Sunday, and there were enough pipits to warrant a careful look for a Red-throated. As I was driving along the east-west road that cuts across the sod farm, I saw a medium-sized brownish shorebird on my right and immediately recognized it as an Upland Sandpiper. The time was about 4:30 PM, so I knew birders must be alerted immediately if anyone was to confirm my sighting before dark. I drove directly to the nearest pay telephone and called the San Diego Rare Bird Alert and four birders who would make an effort to see the bird before sunset. I then returned to the sod farm, relocated the sandpiper, and kept it under observation until Doug Aguillard, Elizabeth Copper, Rosanne Rowlett, and Richard Webster arrived. The bird was most cooperative, walking to within a few feet of us, and appearing oblivious of the farm workers. Unfortunately none of us had a camera, so written descriptions were the only documentation. At about 5:30 PM the sandpiper called a couple of times, jumped up into the air, gained altitude, and disappeared from view as it headed north over residential San Ysidro. Knowing the track record of previous Upland Sandpipers in California, I was unable to give Pete Ginsburg much encouragement when he arrived about ten minutes later. Of the fifteen (seven spring and eight fall) previously known to have reached California, only three remained more than one day—single birds at Furnace Creek Ranch in Death Valley in May of 1980 and 1985 each remained two days, and one near Oxnard in Ventura County in September 1990 remained for five days. Fortunately for San Diego and southern California birders, this Upland Sandpiper returned the following day and remained through Saturday, being seen by numerous observers and well photographed. This is the first Upland Sandpiper to be found in San Diego County, the latest ever in fall (previous latest was one in Twentynine Palms in San Bernardino County on 28 September 1994), and equaling the longest stay known. I consider myself most fortunate to have found this delightful and distinctive bird.

--Guy McCaskie


Dove Under Glass

My glass greenhouse here in Borrego Springs is unbearably hot in the summer, so I usually stay out of it until winter. But on 15 June 1999 I happened to find a Common Ground Dove incubating two eggs in a stick nest inside the glass structure. The nest was on a ledge 6 inches below the clear glass roof. The heat was intense, so I set up a cloth on the outside to afford some shade. Ten days later at least one chick fledged. To my surprise, the adult was back on two new eggs on 15 July.

The next day I decided to measure the temperature at the nest in late afternoon, when it's usually the hottest. The min/max thermometer placed next to the nest in the shade read 128 Fahrenheit! The following day it hit the maximum readable temperature of 130 F. The recorded air temperature those days was, for Borrego, a moderate 105 and 106 F, respectively. Imagine how hot the incubating bird would have got if the ambient reading was, say, 115 F, common in July? To help verify the nest temperature I set a dial probe thermometer under the nest. Until hatching on 25 July, the highs at the nest ranged from 115 F to 125 F. One of the parents was sitting high atop two chicks when I left on 30 July. The nest was empty when I returned on 1 August. I'll never know what happened. Fledging, requiring about 24 days, is possible since I didn't know exactly when incubation started.

I am amazed that the adult(s) never showed signs of stress or engaged in normal cooling behavior. One reference notes that doves and pigeons are among the birds that pant to cool themselves, but I never saw any evidence of it. And, during my near daily visits at all hours, the adult was always on the nest, sitting tightly on eggs or young.

Since they don't sweat, birds normally cool themselves by panting, fluttering their throat (gular) pouch, or compressing their body feathers. During the desert summer, everything from verdins to ravens can be seen panting—even when it is in the low 90s F. I'm wondering how the ground dove survives these extreme temperatures and, moreover, how do the young keep from suffocating or dying from heat while under the constant cover of the adult? Perhaps the adult dove, with her body temperature of about 107 F, is actually cooling the eggs and young. Any suggestions?

Incidentally, I cannot recall seeing any of our three species of dove (including also the Mourning and White-winged) exhibit normal cooling behavior. The Common Ground Dove ranges all across the southern U.S. down to Brazil, Ecuador, and Venezuela, where I presume humidity is relatively high. How does this species cope with the high temperatures and often very low humidity of Borrego? A cursory search of scientific literature and a few phone calls to researchers haven't turned up any answers yet. The search will continue.

--Paul Jorgensen


Migrating Swainson's Hawks Take a Rest Stop at Ocotillo Wells

Wednesday morning 20 October, at 8:30 AM, a resident of an Ocotillo Wells trailer park, Gary Walker, called to say there was a flock of at least 25 hawks in the trees near his trailer. The only hawk I know that flocks is migrating Swainson's—a declining species that breeds across western North America and winters in Argentina. Gary greeted me across the street from the Iron Door bar as I arrived at 8:50. He pointed out the hawk-filled tamarisk trees among the trailer residences. In searching the park and scoping the surrounding area up to 1/2 mile away, I excitedly counted 140 individual Swainson's Hawks. There could have been many more. Usually, migrating Swainson's don't hang around. Last spring, 74 were reported one morning at Scissors Crossing, and they were gone by late that morning. They apparently roost a night and move on, but two other residents of the trailer park told me that at least part of this recent group had been there for six days. Interested to see what this flock was up to, I hung around. About 9:30 AM, a few birds at a time began flying off to the south. By 10:30 they were all gone. If Gary hadn't called we never would have known they were here.

Back at the office, I hastily checked my reference books and database for the status of this species. The largest flock ever reported for San Diego County, according to my references, was 120 seen in April 1975 in Borrego Springs. In fact, the most recent report I could find of a flock of at least the size of the one at Ocotillo Wells was 20 years ago, when an amazing 500-600 were seen on 26 October 1979 in Kern County. First thing the next morning I drove back and checked Ocotillo Wells and out toward Split Mountain. No hawks.

Swainson's Hawks often feed on insects in alfalfa fields during migration. I wonder if this group was commuting a few miles away to the insect-rich fields of the Imperial Valley during its stay? Or have the birds fattened up enough that they can cross the deserts without feeding for days? Intriguingly, on 24 October Ken Kurland reported a flock of 130 in the trees around his home just southeast of El Centro. How many flocks of Swainson's Hawks this size cross southern California? The flock from Ocotillo Wells must have made its next stop near El Centro.

Now for "The Rest Of The Story." Swainson's Hawk, now listed as threatened by the California Department of Fish and Game, was once a common breeder and migrant in San Diego County, with the last recorded nesting in 1933. The huge migrating flocks were disappearing from California by the early 1900s. The species also declined throughout much of the rest of its range, as a result, it was assumed, of destruction of habitat. While that may be true, it wasn't until very recently that researchers found that another problem was at work; thousands of Swainson's were being killed annually by a pesticide in Argentina—up to 20,000 in one incident!

Let's hope that conservation efforts to reduce pesticide deaths and to preserve habitat will be successful and result in more sightings like this one. Might someday Swainson's Hawk even return to nest here? In the meantime, I look closely at every hawk I see, especially in spring and fall.

--Paul Jorgensen


Watching Screech Owls by Day

Learning how to find Western Screech Owls in the daytime was the nicest surprise for me from the 1999 atlas season and has helped me identify the species' prime habitat. Just play a tape of the owl's territorial call, the same as you would at night. To build your confidence you'll need to be patient because the birds are not as responsive as after dark. When you're owling at night the owl usually flies to you, but in the daytime it usually remains on the day roost, calling. One of the things I have learned from searching for Screech Owls by day is that they usually roost in a broken-off limb that has hollowed out over time by decay, rather than in an old woodpecker hole in a trunk.

Along the coastal slope almost any riparian or live oak grove will do for the owls. At some point noise and light pollution seem to exclude them. I've not been able to find them in the city, so anyone with knowledge of this species in an urban environment please make sure we have the data.

Let me tell you of my experience on 19 June of this year, in square F22, San Ysidro Mountain. Coming down a canyon, I entered a clearing with 15 to 20 mature live oak trees and began playing my tape. After the second call the bird responded from a tree about 30 feet away, and for the next 45 minutes he sat there calling constantly. During this time he was mobbed by an amazing 21 species of birds. This never seemed to bother him, and no one, not even the Scrub Jays, ever touched him. No bird ever got closer to him than about 18 inches, showing that they all had considerable respect for this small predator. Needing to cover more of the square, I got up to leave, heading down the canyon. Suddenly the owl flew over my shoulder and disappeared down a bend in the creek. I rounded the bend and was heading down the trail when he gave a single call. I stopped, realizing we were quite close to each other, and started looking for him, to no avail. I turned on the tape for one call, and he responded immediately, giving away his location perhaps 9 feet away. He was between 3 and 4 feet off the ground on a small branch with the trunk of an oak tree maybe 3 inches behind him for perfect camouflage. Never will you see a better match of color and pattern. I saw the eyes and bill clearly, but the rest of him blended into the trunk so well that he all but disappeared. The sight was so surreal I felt as though I were within a Dali painting. I knelt down so we could be at the same eye level, and we just sat quietly looking at each other. Another 5 minutes passed, then I very slowly began to crawl toward him until I was about 3.5 feet away. I lay down, and we looked each other over. I'm not sure who was more intrigued with this encounter, the owl or I. I closed my eyes as though I were taking a nap and so did the owl.

I hated to leave my newfound friend but all things must end, so I quietly backed away and headed on downslope, leaving behind one of those wonderful moments we birders are always in search of. Now I wouldn't think of going birding in the daytime without including Screech Owls.

--Dave Seals


Willie and Her Commute from Southeastern Oregon to Mission Bay

I first encountered the Willet four years ago when I was feeding some Mallards at Mission Bay. She (I will explain how I know her sex later) competed for the bread right along with the ducks. The next day, she ran right up to me for a treat. Since then, she has flown or run to me as soon as I start out for my walk. I keep track of when she leaves and returns from migration, but I always wondered where she went.

Imagine my surprise when she returned on 8 July of this year with a 3-color band above her left ankle and a blue tracking device on her right leg with an antenna that follows along on the sand. With an 800 number supplied from Phil Unitt I learned she was banded on her nest site near Lakeview, Oregon, along with other Willets. Her DNA showed she is a female. I will continue to keep track of her here in San Diego.

Jonathan Plissner of the USGS Forest and Rangeland Ecosystem Science Center in Corvallis, Oregon, wrote me with the story on how this bird acquired her accessories:

At last, I have received results of the genetics work we were having done on the Willets we banded this year in Lakeview, Oregon. It turns out that "Willie" is indeed a female ("Wilma"?).... We captured her on her nest at the Lakeview Airport on 31 May 1999, at which time we put on the leg bands and radio unit. Her mate had been banded in 1998 at the same nest site, but we did not catch his mate last year, so we don't know if they were together last year or not. His leg bands consist of a radio band on the upper left leg and the color combination orange/black/orange on the right leg. He was seen in the vicinity of the nest as early as the 19th of May. We found the nest on the 12th or 13th of May. Four eggs were laid, and they were incubated until at least 11 June. But on the 14th, we discovered that the eggs had been eaten by some predator. Willie stayed in the vicinity of the airport until the 23rd, and we monitored her movements daily until she left the area. Her mate stayed on for another week before leaving on the 29th. I hope you are enjoying her presence in San Diego. If I am down that way this winter, I will let you know. Although our Willet project at Lakeview finished this past summer, there may be interest in having someone from here in Corvallis drive down to look for returning birds next spring. If so, we will look for Willie again at her nest site (they don't seem to change much from year to year).

--Linda Johnson

birdatlas@sdnhm.org

Redhead chick sketch by Nicole Perretta

Winter 1999 Wrenderings | Wrenderings Archive | Bird Atlas Introduction