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Archive for March, 2009

Bird Vocalization of the Month: Mid-March Medley

by ocarmi on Mar. 24th, 2009 5 Comments

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Bird song is often concentrated in the morning. My late ornithology teacher, Dr. Ned Johnson, taught us that one hypothesis as to why birds sing so much in the morning is that it’s useful to them to reaffirm their social status after the long lull of the night. Bird song can give other birds a clue as to how good a mate the singer is likely to be, or how strong a competitor.

These early morning “dawn choruses” change over the year, often increasing in intensity towards spring, as males use song to attract mates. The also change in composition, as wintering birds leave the Bay Area to migrate north, others arrive from the south, and still others remain.

To find out what the local dawn chorus sounds like at this time of year, I stepped out of the Academy early Wednesday morning, March 18, and recorded what I heard in Golden Gate Park. Recording was challenging over the loud hum of early morning traffic, and in-between frequent interruptions by buses and garbage trucks. My recordings are not very refined, but I hope they provide a glimpse as to what may be encountered in our urban environment, within the realistic context of urban noise. Here are some of the birds I heard:

American Robin
American Robin Turdus migratorius
Photo credit: Eric Heupel
American Robins (Turdus migratorius) were some of the earliest risers, announcing themselves with this call. They soon started to sing. Robin song is one of the most frequently asked about vocalizations, with people wondering what bird sings so beautifully early in the morning. They sang in increasing number, peaking around 7:00 am, creating this dreamy, echoey soundscape.
I heard the occasional Song Sparrow (Melospiza melodia) song long before dawn. However, shortly after the robins began singing, Song Sparrows increased their song rate, allowing me to obtain a few recordings. A Song Sparrow will often sing a very similar song over and over for a length of time, and then make a modification and sing a new songtype for a while. Neighbors sound distinctly different from one another. Check out the variety from three individual birds: sparrow #1, sparrow #2, sparrow #3.
Song Sparrow
Song Sparrow, Melospiza melodia
Photo credit: Len Blumin
Song Sparrow song often includes a long, noisy, broadband note (one consisting of broad range of pitches all at once) somewhere in the middle of the song. This sound, and the general pattern of the song—a kind of jumble of various kinds of sounds at extreme pitches—reminds me a great deal of the sound of a fax modem (if any of you can recall what one sounds like)!

I did not manage to record everything I heard, but here are a few more notable vocalizations. Chestnut-backed chickadees (Poecile rufescens) were also among the early risers. Shortly after, and still before light, I managed to catch this pair of Mallards (Anas platyrhynchos) flying overhead. I was confounded by one particular vocalization, which turned out to be one of a Fox Sparrow (Passerella iliaca).

Male Townsend's Warbler
Townsend’s Warbler, Dendroica townsendi
Photo credit: Greg7
I feel very lucky to have obtained a recording of one of my favorite spring songsters—the Townsend’s Warbler (Dendroica townsendi), which sings a thin, buzzy song. Townsend’s Warblers are beautiful, but often difficult to see, since they spend much of their time in the canopy of conifers. They sing with increasing frequency as spring progresses, but eventually leave to breed further north, in the Northwest, from Oregon, as far north as Alaska.

Finally, just before 8:00 am, I was quite surprised to hear several Winter Wrens (Troglodytes troglodytes) singing to each other, by a gully near Fulton Street. Winter wrens are tiny, brown birds which seem to be constantly on the move around fallen logs on the banks of streams in wooded areas. They are very difficult to see. There is a good-sized population of wintering Winter Wrens in the Bay Area, and a smaller one of nesting Winter Wrens. I have no idea if the Winter Wrens I recorded were winterers, spring migrants, or if they’ll end up staying for the summer and breeding!

Your homework assignment:

  • Familiarize yourself with the song of the American Robin, one of the most frequently asked about natural sounds.
  • Listen to the recordings of the Song Sparrows, and see whether you can identify the broadband note in the middle of the song. Do you agree with me that the Song Sparrow sounds like a fax modem? What do you think it sounds like?
  • Listen to the other recordings. Choose one you particularly like, and listen to it several times. When you’re walking about in the morning, or anytime during the day, and you hear a bird vocalization, ask yourself if it matches any of the ones you’ve learned.


Field Ecology with Tyveked Teachers

by megan on Mar. 9th, 2009 4 Comments

Field Ecology Participants, February 2009

During a brief break from the torrential rain February brought, 19 teachers from all across the Bay Area joined staff from the California Academy of Sciences for a great day of outdoor ecology. The location: Jasper Ridge Biological Preserve, a 1,189-acre preserve dedicated to research and education, located in the eastern foothills of the Santa Cruz Mountains.

NewtIn the morning, we split up into small groups to explore the amazing diversity of ecosystems available at Jasper Ridge. Each group took charge of one ecosystem — creek, redwoods, oak woodlands, or chaparral — recording both qualitative and quantitative data at their field site. We observed plants, animals, rocks, and soil types; measured the temperature of both the soil and the air; and estimated canopy cover. In some locations, we even saw mortars and pestles, evidence of the Ohlone populations who once inhabited the area.

After plenty of time exploring our ecosystems, we headed back to the field station to share our experiences. Each group shared their data – painting a verbal picture of the environment in which they spent the morning.

HikingThen, we contrasted quantitative data obtained from each field site. It was incredible to see the difference in temperature between ecosystems that were only a few hundred yards apart! What would account for such disparity? Canopy cover certainly plays a role in moderating temperature. Participants also learned how an area with a north-facing slope — which receives less direct sunlight than its south-facing counterpart in the Northern hemisphere, due to the tilt of the Earth on its axis — might be a bit on the cooler, moister side.

In the afternoon, we were joined by Professor Rodolfo Dirzo, an ecologist in Stanford’s Biology Department. In a brief presentation, Rodolfo explained the basics of plant ecology research, and then we headed back outside to conduct our own vegetation transects. By now, you must have noticed our charming Tyvek suits. Although not standard for a field ecologist, we felt it necessary to protect ourselves from the abundance of poison oak in the area. (Even with the attractive neck-to-toe protection, I got a few spots of oak!). I’m not sure whether we look like scientists or like a HAZMAT clean-up crew, but we looked so good we couldn’t help taking many pictures of the group!

Vegetation TransectWe ventured into the forest to learn about the plants that comprise the oak woodland ecosystem. We measured out ten 50-meter transects, crawling on hands and knees to identifyall the woody plants falling within 2 meters of our transects. Back in the classroom, we performed data analysis, working through the statistics to determine the density, frequency and dominance of various species.

Real science. Real fun.

-Jill, Curriculum Developer for the Teacher Institute on Science and Sustainability

Just Published by the Planetarium

by megan on Mar. 2nd, 2009 No Comments

The Morrison Planetarium is proud to present the 2009 Pocket Almanac! Anxiously awaiting meteor showers? Hoping to view an eclipse? Scouting planets in the night sky?

Stop by the Naturalist Center to pick up a hard copy, or download it here. This guide folds to fits nicely in your back pocket!

The Planetarium provides materials for sky watchers through several other outlets. You can call 415.379.8000 to hear monthly skywatching tips, or download a quarterly SkyGuide by downloading our most recent Membership Newsletter. Or, tune in regularly to the “StarDate” radio program on KCBS 740 AM!

Interested in attending an astronomy-themed lecture for your own professional development? The Benjamin Dean Lecture Series presents monthly talks for the general public by noted scientists in the fields of astronomy and space science. Upcoming speakers include planet-hunter Geoffrey Marcy, SETI scientist Jill Tarter, astrobiologist David Morrison, and principal investigators from NASA’s explorations of other planets and deep space. For more information, check out our Events+Lectures calendar.