A Favorite Pin Oak Tree: 19th Century Origins

The Pin Oak tree at the edge of the road in Eliza Howell Park is one of my favorite trees. It stands alone, with enough room for its branches to spread. 

At this time of the year, the leaves are fallen and the branches are bare.

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I first started paying close attention to this oak because the birds are attracted to it. Warbling Vireos have nested here twice in recent springs and both Red-bellied Woodpeckers and Blue Jays are all over it in late September and early October, collecting acorns.

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Photo by Margaret Weber

This is a quite large – and old – Pin Oak, a species that does not live as long as some other oaks. After having been asked several times how old it is, I decided to try to find the answer. There is no exact method of knowing the age of a living tree, but there is a widely used method of estimating the age.

The steps in estimating tree age are these:

  1. Measure the circumference of the tree at 4 ½ feet from the ground.
  2. Divide the circumference by pi (3.14) to get the diameter.
  3. Multiply the diameter (in inches) by the “growth factor” that has been identified for the specific species, based on how fast growing it is. (Different organizations have published the growth factors for different species.)
  4. The resulting number is the approximate age of the tree, in years.

Pin Oaks are moderately fast growing and have been given a growth factor of 3.0.

It is difficult to measure the circumference of a large tree by oneself so recently, when accompanied by Charon, another Eliza Howell enthusiast, we undertook the measurement.

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At 4 ½ feet high, the tree measured exactly 12 feet in diameter (144 inches).

144 divided by 3.14 = 45.86.

45.86 times 3.0 = 137.58

Using this method to estimate age, the tree is about 137 or 138 years old.

137 years ago was 1883. This is just an estimate, but it is probably safe to say that this tree began to grow before the twentieth century, long before this property was donated to Detroit for parkland.

It was already over 100 years old when I started enjoying it, appreciating it in all seasons. On hot summer days, when someone else has not claimed the spot, I park the car in its welcome shade as I take my walk.

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Across the road is the prairie flower field and the Pin Oak sometimes makes a lovely background for a flower picture — Joe Pye Weed in this case.

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Pin Oak leaves turn late in the Fall, in November in Eliza Howell. The bronze (?) shade is not as striking as the leaves on some other trees, but there is something very attractive about it.

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As oak trees go, Pin Oak trees do not have a long lifespan. This one is perhaps older than average. I hope it continues to provide beauty, food, shade, and nesting habitat long after my nature walk days are over.

The Strange Case of Blue Jay Migration

Blue Jays have been a major presence in Eliza Howell Park during the last month, the time of their fall migration. Each year I anticipate their acorn harvesting frenzy (see “Blue Jays Harvesting Acorns,” August 27, 2018) and this year they again worked the oak trees in great numbers.

Note: All bird photos by Margaret Weber

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Their month-long period of intense activity in Detroit is exciting to observe, but I am increasingly aware of their unusual – and not fully understood – migration behavior.

Most birds that migrate through our area in the fall leave all or much of their breeding ground for the winter. Blue Jays, by contrast, are found in the very same areas all year round. It is interesting to compare the following two range maps. The first is White-throated Sparrow, also moving through here in September, and the second is Blue Jay. (These maps are taken from the Cornell Laboratory of Ornithology website.)

White-throated Sparrow range

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White-throated Sparrows leave almost their entire breeding area in the fall.

Blue Jay range

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Blue Jays are found throughout winter in the very same areas in which they breed. A few scatter to the west, but the entire breeding area remains occupied.

Such a range map usually suggests that a species is non-migratory. Blue Jays, however, migrate and do so in great numbers. Every fall the raptor counters at the two locations by Lake Erie (Detroit River Hawk Watch at Lake Erie MetroPark and Holiday Beach Conservation Area in Amherstburg, Ontario) count Blue Jays as well as raptors. As of October 10 this year, Holiday Beach watchers had reported over 350,000 Blue Jays moving through since early September. And the migration wasn’t fully over yet.

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This is what is known (and/or thought likely) about Blue Jay migration, based on my review of some of the published research:

  • The species is partially migratory; only some migrate
  • Most that migrate go only a few hundred miles south in the fall
  • It is estimated that fewer than half migrate
  • Those that migrate (and those that don’t) include both young birds and older birds
  • Individual birds might migrate one year and not the next and then migrate again in the following year
  • The migration number in a particular year is suspected to be related to food sources

The jay numbers will soon decline in Eliza Howell as the migrants move on. But I do not know whether individual birds like this one, seen in an oak tree in September, will stay for the winter.

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I do not know whether this one, nesting here in June, will be around in the coming winter

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I had assumed, if I thought about it much at all in the past, that the same birds (the non-migrants) were present in summer and winter and the migrants all passed through. Now I doubt that.

One of my other questions, not addressed in the limited research I have reviewed, is whether some of the individual jays harvesting acorns in the park leave/migrate before the winter and do not ever go back to eat the acorns they hid. Is acorn harvesting possibly community and not just individual food-gathering?

The Blue Jay is a common bird, so it is tempting not to give it a second thought. But I rarely see jays these days without thinking about what I do not know about them.

“Acornucopia”— and Wildlife Benefits

“Cornucopia” being abundance or profusion, vast numbers of acorns might be called “acornucopia.” Eliza Howell Park is home to many productive oak trees and the acorns seem especially plentiful this year.

There is a great variety of oak trees in the park. On an afternoon walk on September 19, I was noting the varieties of acorns and collected these examples in a very short period of time.

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Acorn production varies from year to year and from species to species. Overall, 2018 is a bountiful year. Some trees have as many acorns as I ever remember seeing.

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One of my favorite oaks, a type of red oak, is a large tree with several low hanging branches filled with acorns that fit my mental image of the archetypal acorn.

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For many wildlife, an abundance of acorns means a valuable food source as winter approaches. Dozens of mammals and birds eat acorns. Acorns make up about 25% of the diet of White-tailed Deer in the fall. An abundant acorn crop often means healthier deer heading into the breeding season.

This stag, which crossed the EHP footbridge right before me one day last fall, may well have been foraging for acorns.

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Rabbits, raccoons, opossums, even foxes, eat acorns. And squirrel consumption of acorns is so well known that I need not comment.

Many of the mammals feed at night, but it is easy to watch the different birds getting their acorns. The greatest in number are Blue Jays (see “Blue Jays Harvesting Acorns,” August 27, 2018). They, along with Red-bellied Woodpeckers and American Crows, pick the acorns in the tree. Grackles, on the other hand, feed on the ground under trees for the fallen ones. Jays crack the acorns open with repeated pecks with their beaks; grackles have a sharp ridge in their beak (keel) which they use to open the shell.

Some birds eat acorns whole and let their gizzards do the work of grinding the food. Wild Turkeys, birds that eat many acorns, have been found in EHP in recent years.

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Wood Ducks also eat lots of acorns. They will be leaving the park soon, heading south for the winter, but they are still around now and are often on the banks of the river, where their nutrient sources include acorns.

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Photo by Margaret Weber

Every year, in late summer and fall, the presence of acorns calls my attention to the number and variety of oak trees in the park and I spend some time trying to get to know them better. It is not easy to identify some of them by species name, since there are so many different species in the eastern U.S. and oaks do hybridize.

I recently collected a few acorns, each with a leaf from its tree, for more leisurely study at a later time.

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We have all heard that “mighty oaks from little acorns grow.”

A few acorns do grow into large trees, but most of the many, many thousands of acorns present in Eliza Howell right now serve other valuable purposes: food for wildlife and an opportunity for me and others to admire, enjoy, and learn.