Archive for March, 2013

On Saturday, I spent about an hour-and-a-half with my three-month-old daughter wandering around a giant shopping center in Roseville, CA.  My wife was spending some time with some friends, and so my daughter and I took the opportunity to have a look around.  As we walked between huge box stores and along expansive parking lots I was impressed, as I often am, at how much animal life was finding a way to live in and amongst all the human impacts that exist in very urban areas.  House Finches were in the bushes all over the place and White-throated Swifts and Lesser Goldfinches were frequently flying and calling over head.

During our rambling, my daughter and I made two particularly exciting discoveries.  The first was finding a bee hive!  The swarm had built their hive in the nooks and crannies of a potion of a wall that have been made to look like pile rocks.  The bees were industriously visiting the wisteria vines, blooming not far away, and also coming in from much greater distances as they foraged for food for the colony.  I was pretty thrilled to find this hive, but was careful not to make too much a big deal about it when people were passing by because I was worried that someone would freak out and that the property managers would find out and spray the colony.  This was weird for me because I usually like to share sightings like this with anyone who is willing to listen, but here I figured that the best thing for the bees would be secrecy.  The second exciting discovery was a Bushtits nest!  The pendulum nest of lichens and spiders web was hanging in a small ornamental tree only about 6 feet above the ground.  The tree was in a little ally way between two humongous stores.  The two adults were very busy searching through the landscaped plant and bringing caterpillars and other insects they found back to the nest to feed their chicks.

Even though this was not a bird walk through some wild place it yielded some wonderful nature experiences, and was a wonderful way to spend some time.  It served as a terrific reminder that there is wildlife to be seen everywhere, and I look forward to continuing to share similar experiences with my daughter.

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Yesterday, I got my 50th species for the yard list I have been keeping since we moved to West Sacramento.  The 50th species was a lovely Red-breasted Sapsucker that  I saw low in the cypress tree that is beside out garage, and then watched as it foraged up into the sycamore tree that overtops of the cypress.  Over the last 7 months or so, the list has grown to include some surprising species.  The Sandhill Cranes that flew over last week were a wonderful treat, and not at all expected by me!  The Orange-crowned Warblers that we saw fairly regularly over the winter were a delight, but now seem to have moved elsewhere, presumably to more suitable breeding habitat.  Another surprise, and delight, has been the Lincoln’s Sparrow that has been a frequent visitor to our yard and also to the bushes just outside my office window.  The list has also grown in taxonomic diversity.  It now not only includes birds, but a few mammals and a just recently added amphibian (a Pacific Tree Frog that has been calling most evenings from the other side of our garden wall)!

The list is also interesting in some of the absences.  While we have had White-crowned Sparrows all winter long, no Golden-crowned Sparrows have visited the yard.  I see and hear them in the area when I am out birding, so I know they are nearby, but none have made an appearance to enjoy the seeds we put out.  Also, a group of Yellow-billed Magpies are always hanging out in a  neighborhood just one block away, but none of them have made the short journey to our place.  One other surprising absence to me is the California Towhee.  When I am out birding, I see them throughout the paths, neighborhoods, and open spaces in the area, but they have not made it onto the yard list.  This despite the fact that our condo has plenty of shrubs and small trees that would seemingly provide excellent cover for them.  I am sure that some of these species will show up eventually, around our yard, but it is interesting to see exactly how ling it takes them to do so.

I have very much enjoyed keeping this list, and I am sure that that enjoyment will continue as the list continues to grow.  I wonder what species number 51 will be!

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Happy Pi Day


Since today is March 14th (3-14), I thought I would take this as an opportunity to learn a bit more about the number π, which is a mathematical constant for the ratio of a circles’ circumference to its diameter (π = C/d), and share what I found.

How this Greek letter came to be used to represent this particular ratio is a bit clouded.  As early as 1647, William Oughtred used it to represent ratios of periphery and diameter.  π ma have been chosen because it is the first letter in the Greek spelling of periphery.  But it was not until 1706 that William Jones first officially used π to mean the ratio of circumference to diameter in his “A New Introduction to the Mathematics,” but in this work he credits many of his equations, possibly including π, to John Machin.  Where Machin got, I have no idea.  Even after 1706, π was not adopted by the mathematics community until Leonhard Euler started using it in 1736.  Euler frequently corresponded with other mathematicians across Europe, and as a result of this, the use of π spread and became universally adopted.

However the symbol came to be used, the concept of π is very old indeed.  The oldest written approximations of π come from Egypt and Babylon where each culture estimated the value of π to within 1%.  In Babylon, a clay tablet was found that dated to 1900-1600 BCE on which was writing on geometry that included a value for π as 25/8 ~ 3.1250.  In Egypt, the Rhind Papyrus, which was written around 1650 BCE but which was a copied from an older document dated around 1850 BCE, includes a formula for the area of a circle which includes a value for π as (16/9)2 ~3.1605.  Further, the Great Pyramid at Giza has a basal perimeter of 1760 cubits and a height of 280 cubits.  This ratio, (1760/280) ~ 6.2857 which is 2π.  Some people believe that this is proof that the architects of the Great Pyramid knew about π and were trying to incorporate the proportions of a perfect circle in the pyramid.

Some of the properties that make π such an interesting ratio include that it is one of the irrational numbers.  This means that it cannot be represented as the exact ratio of two integers.  For example 6/2 = 3.  Instead, π must be represented as a complex fraction, which is one that never resolves, but instead goes on for infinity getting ever more accurate, but never exact.  This infinite, non-repeating property of π is another reason it is interesting. The numbers in π seem to be truly random.  This makes π a sort of natural random number generator which makes it useful in statistics and also in internet security.  The value of π is used in astrophysics where π, to 39 decimal points, has been shown to calculate the volume of the universe to within one atom!  Yet another use of π is in Heisenberg’s Uncertainty Principal.  This principal states that it is not possible to know both the change an atoms position and the change in that atoms momentum simultaneously to an infinite degree of precision.  Heisenberg’s Uncertainty Principal is usually stated as: Δχ Δp ≥ h/4π

So go out, enjoy a slice of pie, think about some math, and have a great Pi Day!


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As I was driving to U.C. Davis yesterday evening, I saw two White-tailed Kites chasing each other above an open field just south of campus.  As I watched, they came together, grappled with each other briefly, and then locked talons and started to drop and spin.  This behavior, also called cartwheeling, is pretty famous in birds of prey.  Eagles are especially well known for talon grappling and dropping and spinning from impressive heights and only letting go just above the ground or tree tops, if then (some injuries and even fatalities have been reported).  Somewhat surprisingly, after looking into what is known about this spectacular behavior, I found very little.  The most interesting information I did find was that most interpretations of this behavior seem to wrong!  This behavior has usually been though to be associated with courtship rituals; however, Simmons and Mendelsohn (1993; see below for complete citation) reviewed accounts of this behavior from around the world that included detailed behavioral observations and found that 82% of them were actually aggressive interactions. Courtships that included this behavior have only been recorded in three species of eagle and one species of vulture and represent only 11% of accounts.  To an even lesser extent, cartwheeling may be used in play behaviors as well.

Personally, I have seen this behavior performed by Golden Eagles, Red-tailed Hawks, and Swainson’s Hawks, but this was the first time I have seen White-tailed Kites perform it.  With their bright, high contrast plumage of white, black and grey they were really quite spectacular!

Simmons, R.E. and Mendelsohn, J.M. 1993. A critical review of cartwheeling flights of raptors. Ostrich 64: 13-24

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A new book is just hitting the shelves from UC Press.  It is call “Birds of the Sierra Nevada: Their Natural History, Status and Distribution” by Ted Beedy, Ed Pandolfino with Illustrations by Keith Hansen.  Here is a link to the official announcement: Beedy, Pandolfino, Hansen

This is a must have book not only for those interested in the Sierra Nevada, but also for anyone who is interested in the birds of California, or North America in general.

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Over the past couple of weeks spring has been becoming ever more evident in central California.  For one, large flocks of American Robins have been showing up.  These are likely groups of Turdus migratorius propinquus, large and pale subspecies, that are migrating from their wintering grounds in central Mexico, through central California on their way to their breeding grounds which could be anywhere from northern California to British Columbia or Montana.  I saw another sign that spring is in the air Tuesday as I was walking across campus.  Near one of the large lecture halls, I heard and saw a male Cooper’s Hawk kekking from the top of a large tree.  This was the first Cooper’s Hawk breeding behavior that I have seen this year, and two day later I saw and heard him again in almost the same spot.  Hopefully he will attract a female and set up a nesting territory here.  It would be a lot of fun to watch.  Another breeding behavior that I have just seen starting is that the male House Finches have stated mate-guarding the females.  I watched one particular male as he followed a female around as she foraged, and repeatedly chased off other males that approached too close to the female.  A final sign from the birds that the seasons are changing was a male Nuttall’s Woodpecker checking out cavities as potential nesting sites.  He was moving through a couple of dead trees in West Sacramento, and stopping at any hole he could find.  he would take a few moments at each to look at the external hole, and then stick his head in to take a look at the interior.  He rejected all the contenders save for one, which he poked his head into, and apparently liked.  He climbed all the way in, and over the next 10 minutes or so that I stayed to watch, he did not come out.  Apparently that was a good spot!  To add to these avian signs of spring is one of my favorite plant signs.  The fruit trees that fill the orchards and line many of the streets in the West Sacramento and Davis areas are all in bloom!  I do love the beauty of trees covered in small white or pink blossoms.

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