More Great Horned Owl Pellets at Columbus Park

It’s been a busy month at work, but this morning, for the first time in two weeks, I monitored birds at Columbus Park. I saw 13 species of birds, including a Red-tailed Hawk whose tail was a mix of banded juvenile feathers and bright red adult feathers. However, I did not see the on-again-off-again Great Horned Owl who sometimes roosts in an oak tree on the west side of the Park. (Read about it here.)

I always enjoy seeing the owl, but when the owl’s gone I’m not too sad, because then I can search for owl pellets under its roosting tree. The pellets I’ve found so far (shown in this post) contained a mix of medium and small mammal bones, but no teeth. So I figured the owl was feeding on squirrel, rabbit, or maybe possum-sized mammals. Since I can’t often identify bones to species, I was really hoping to find some owl pellets with teeth or jar bones, which I often can identify. Today I lucked out:

Pellets spit out by the Great Horned Owl who sometimes roosts in Columbus Park. The large, snow-crusted pellet on the right includes a lower jaw. (Taken with my iPhone.)

Here’s a closer look at the jaw:

I dug the jaw out of the frozen pellet so I could see the teeth. With the front gnawing teeth and grinding cheek teeth exposed, I recognized it as the mandible (lower jaw) of a Cottontail Rabbit. (Taken with my iPhone.)

Go here to see a photo of a complete Cottontail Rabbit skull with mandible.

This fall we had lots more rabbits than normal in Columbus Park, and I’d noticed gnawing damage to shrubs and small trees that was probably the work of rabbits. My neighbors in Oak Park had also noticed more rabbits in their yards this year and complained about damage to their gardens.  So, now there’s evidence that our Great Horned Owl is bringing the rabbit population back to normal.

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Here are links to information and activities about owl pellets:

• Wikipedia on pellets made by owls and other birds of prey

• A virtual owl pellet dissection

• A chart showing the kinds of bones found in owl pellets (pdf file)

A January Walk through Columbus Park

As I monitored birds this morning in Columbus Park, I did an experiment. I took photos with my iPhone and uploaded them live to Facebook. It was kind of like a virtual nature walk!

Here the link to the public Facebook album with this morning’s photos:  A January Walk through Columbus Park.

Please let me know what you think!

A Red-tailed Hawk is Hunting the I-290 Median!

For the past three days a Red-tailed Hawk has been hunting from lamp posts at the end of our block:

The Red-tailed Hawk sits on lamp posts at the end of our block. The posts are in the grassy median between the east- and west-bound lanes of Interstate 290 (also called the Eisenhower Express, the Ike, or the Congress).

I first noticed the hawk on Monday while I was walking to Maze Library across the Ridgeland bridge. I saw the hawk flying from post to post, approaching me from the east. Once it got close enough, I recognized it as the pale-bellied Red-tail that I’ve seen in Columbus Park, about a mile east on the expressway:

The Red-tailed Hawk's chest and belly look distinctively pale compared with other local Red-tails.

A few weeks ago I watched this hawk hunting Mourning Doves behind the Refectory at Columbus Park — it failed rather miserably. On Monday the Red-tail made a pass at Pigeons roosting on the apartment building at the end of our block — another fail. Then it flew directly at the large Red Cedar in our alley where House Finches and Goldfinches roost — the small birds scattered, and the hawk was not even close to scoring a meal.

Since then, every time I see the hawk it’s sitting on a lamp post:

The I-290 Red-tailed Hawk in south Oak Park.

It’s always look down, at least when it’s not looking at me. It’s probably hoping for a glimpse at a potential meal — a mouse, perhaps a rat, maybe a rabbit brave enough to cross three lanes of traffic.

I hope the hawk is more successful with mammals than it is with birds. And I hope it understands the dangers of speeding cars and trucks.

The I-290 Red-tailed Hawk on a distant lamp post.

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Red-tailed Hawks often hunt along highway right-of-ways. Here are some links that discuss this aspect of Red-tail natural history:

• Chesapeake Bay Journal: Red-tailed hawk haunts nation’s highways, fields in quest for prey
• Perch and Habitat Use by Red-Tailed Hawks and American Kestrels (Kansas; scientific journal)
• Red-tail hawk nearly plucked on Highway 17 (South Carolina)

Our Chicago Urban Christmas Bird Count Data 2009

The boys and I spent the entire day conducting our part of the Chicago Urban Christmas Bird Count. Nationally, Christmas counts are organized by the National Audubon Society. The Chicago Urban count circle is sponsored by Evanston North Shore Bird Club and Chicago Audubon Society, with Jeff Sanders as the compiler.

Our part of the count covers the following areas in Chicago and Oak Park: Birding on foot in Columbus Park, Douglas Park, and south Oak Park residential areas; feeder watching at our home on South Elmwood in Oak Park; and driving through industrial and residential areas in between these sites.

This year, birding from sunrise to sunset, we found a total of 26 species. The highlights of our day included:

• Four species of hawks, including a MERLIN at Columbus Park (photo below), 2 AMERICAN KESTRELS, 2 COOPER’S HAWKS, and 2 RED-TAILED HAWKS.
• A WINTER WREN beside the Columbus Park lagoon (where we saw this species often through the fall — photo below).
• An AMERICAN PIPIT at Columbus Park, in the same field where we saw a Pipt on December 11 (photo below).
• A SWAMP SPARROW at Columbus Park (photo of its rump, below), plus 20 AMERICAN TREE SPARROWS (15 at Douglas, 5 at Columbus).

We were also pleased that WHITE-BREASTED NUTHATCHES put in 2 appearances, since we’ve been seeing them much more frequently this year. We also were happy to see a BLUE JAY, because they were common this summer, then mostly disappeared within the last few weeks. We were disappointed that overall sparrow numbers were down at Douglas Park, where the golf-course sanctuary often holds 50 or 60 sparrows this late in the year. And we were very sad that we did NOT see the Great Horned Owl that had been roosting near Austin in late November and early December. (We still hope it returns in time to be registered as a count-week species!)

Here’s our entire list for today, with count numbers:

Canada Goose    280

Cooper’s Hawk     2

Red-tailed Hawk     2

American Kestrel     2

Merlin     1

Herring Gull     1

Ring-billed Gull     5

Rock Pigeon     115

Mourning Dove     45

Downy Woodpecker     4

Hairy Woodpecker     3

Blue Jay     1

American Crow     9

Black-capped Chickadee     9

White-breasted Nuthatch     2

Winter Wren     1

American Robin     55

European Starling    350

American Pipit     1

American Tree Sparrow    20

Swamp Sparrow     1

Dark-eyed Junco     25

Northern Cardinal     21

House Finch     14

American Goldfinch  30

House Sparrow     180

We also have two count-week species so far for our areas:

1 Red-bellied Woodpecker  (seen in Douglas Park 12/17/09)

2 African Collared-Dove and/or African X Eurasian Collared-Dove (seen in south Oak Park 12/18/09).  We are soliciting input on these photos, taken on Dec. 18th — what do you think they are?

• http://www.flickr.com/photos/36234902@N00/4196043460/in/set-72157623026500738/
• http://www.flickr.com/photos/36234902@N00/4196043362/in/set-72157623026500738/
• http://www.flickr.com/photos/36234902@N00/4195286623/in/set-72157623026500738/

Here are some of Aaron’s photos from today:

The Merlin roosted in several trees around the lagoon, but it was tough to get a good photo because of the distance and overcast skies. Note the back color, streaking on the side of the breast, and minimal patterning on the head (all of which we could see much better through our binoculars). Photo by Aaron Gyllenhaal.

This shot, from even further away, gives another view of the Merlin's head. Photo by Aaron Gyllenhaal.

Although it was hard to get a clear shot at the Winter Wren, a few times it hopped into the open, possibly to get a better look at us! Photo by Aaron Gyllenhaal.

There was a large, if late, migration of American Pipits to inland parts of Chicago earlier in December. We were happy that one stuck around Columbus Park for the Christmas Count! Photo by Aaron Gyllenhaal.

Here's a front-on view of the American Pipit. It was hanging out at the north end of the large ball field that fills the southeast corner of Columbus Park, sometimes visiting a seepage area that has some unfrozen water. Photo by Aaron Gyllenhaal.

Although we got good binocular views of the Swamp Sparrow's gray-patterned head, Aaron only got photos of its butt! Photo by Aaron Gyllenhaal.

We’ll post links to Ethan’s photos once he gets them online.

No Owl Today, Just Fast-Frozen Owl Pellets

The neighborhood crows and I were both disappointed that we didn’t find the Great Horned Owl in its usual roosting tree in Columbus Park. Here’s what the owl looked like yesterday afternoon — the third day in a row we had seen it in exactly the same spot in a White Oak tree:

Yesterday at 2:15 p.m. the Great Horned Owl was in its usual White Oak roost in Columbus Park.

This morning I looked at the same tree from every angle — and every tree around it — for 10 minutes and couldn’t find the owl. Then five minutes after I gave up a flock of Common Crows flew into the roosting tree and landed in its upper branches. These were tough crows! I had earlier seen them harassing first an American Kestrel and then a Red-tailed Hawk. I figured they knew something I didn’t — after all, crows first found this owl for me on November 24th. So, once the crows flew off, I went back to the roost tree and looked again.

Still, no owl.

I should have been disappointed, but I looked at the bright side. If the owl was in its roost, I would have backed off and left it alone. Since there was no owl to scare off, I could go look for owl pellets under its roost. (Owl pellets are the remains of animals that the owl ate — whole or in really big chunks. The pellet is the regurgitated remains of the owl’s meal, after the flesh and guts have been digested.)

Here’s what I found:

The owl pellets are the fuzzy-looking gray things on top of the leaves. The gray fuzz is fur from whatever the owl ate. The white and yellowish bits embedded in the fur are bones from prey animals.

The more I looked, the more I found:

This pellet -- about two inches across -- had more and bigger bones. When I picked it up, I saw ice crystals among the fur. When the owl spit out the pellet, it was still wet with stomach fluids. After the moist pellet hit the leaves, it froze solid.

The last pellet I found was the biggest and the boniest:

The longest bone in this pellet is about two and a third inches long. It's a humerus, the upper bone from a front leg. I'm guessing it came from an animal bigger than a squirrel, maybe a rabbit or a small opossum or raccoon.

I saw one rodent or rabbit front tooth in a pellet, but the rest of the visible bones were from legs, feet, hips, shoulders, or backs.  I’m not good at identifying animals from their limb bones — I need to see teeth.

I guess we’ll go back at some point and dissect some of the pellets. If we find some jaws or skulls, we’ll know better what our urban owl was eating in Columbus Park.

Then we’ll wash our hands really well. After all, we’ll be handling owl vomit!

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We found more owl pellets on January 31st, including one containing a rabbit jaw. You can see them here.

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Here are links to information and activities about owl pellets:

• Wikipedia on pellets made by owls and other birds of prey

• A virtual owl pellet dissection

• A chart showing the kinds of bones found in owl pellets (pdf file)

First Hard Freeze for Our Jars of Water

Back on November 29th we started an experiment on our front porch, with four plastic jars filled with water. At the start of the experiment, the jars looked like this:

Here's what the experiment looked like five days ago, before the temperature hit the freezing mark.

Now, here’s what the experiment looked like on Friday, December 4th, after the air temperature went below freezing, hitting 24 degrees Fahrenheit overnight:

Here's what the water jars looked like after a hard freeze. Three of the five jars had frozen overnight: A, B, and D. Also, we had added a fifth jar: In Jar E, the water that had been BOILED first, then cooled, put in the jar, and sealed with a lid that had NO holes in it. (Thanks to J of Science Museum of Minnesota for suggesting this addition to the experiment.)

Three of the jars had frozen water in them, including the jar with SALTY water. No one predicted that! The two jars that did not freeze were both sealed tight — there were no holes in their lids.

Here’s a closer look at Jar A, which started out as cold, fresh tap water, and was covered by a plastic lid with holes drilled in it:

A closer look at Jar A shows intersecting sheets of ice, more densely frozen closer to the top of the jar.

Jar B showed a similar pattern, although the sheets of ice were more horizontal than vertical:

Jar B also had sheets of ice, more densely frozen towards the top of the jar -- but the ice sheets were more horizontal than vertical.

Jar D was most surprising. I was expecting the salty water wouldn’t freeze, but the top part of the jar was frozen fairly solid. However, the bottom of the jar was not frozen, but had a bunch of bubbles sticking to the side of the jar:

In Jar D, notice the clear division between frozen water above and unfrozen water below.

So, that leaves us with two mysteries to solve:

• Why did most of the water in the salty jar freeze?
• Why did the water in the sealed jars not freeze?

I have some ideas, but I won’t tell you about them yet. However, I will give you one hint about the second mystery. Here’s what the lower part of salty Jar D looked like on December 2, 2009 — three days after the experiment started, but before the temperature dropped below freezing:

Here's what Jar D looked like three days after I had mixed in several handfuls of sidewalk salt, but before the first hard freeze. How can this help us understand why the top of the jar froze, but the bottom did not?

Feel free to tell us your ideas in the comments section (below) or on Facebook.

An Experiment with Freezing Water

The weather forecast says we’re headed into an extended spell of cold weather, with freezing temperatures predicted for the end of the week. So, it’s time to put some water jars on the front porch to see what happens. This year we’re going to be a bit more organized than usual and set up the jars as an experiment. There are reasons we’re setting it up this way, but we’ll let you try to figure out what those reasons are (with a few hints at the end of this post).

First, here’s our experimental setup: Four PLASTIC jars of water set on our front porch rail this afternoon, here in Oak Park, Illinois:

Here are our four experimental jars of water (all made of plastic). Read the descriptions to see how they differ from one another. We started this experiment on November 29, 2009.

Jar A, on the far left, was filled with cold, fresh tap water. It’s lid has holes in it, so air can get in.

Jar B, just left of center, was filled with warm, fresh tap water. It’s lid also has holes in it, so air can get in.

Jar C, just right of center, also was filled with warm, fresh tap water. It’s lid has NO holes in it, so NO air can get in.

Jar D, on the far right, was filled with cold tap water, then a couple of handfuls of rock salt were added — the same kind of salt you may put on your steps or sidewalk when it snows. It’s lid has holes in it, so air can get in.

So, we are experimenting with the following variables:

• Does the water start out cold or warm?
• Is the water exposed to the air or not?
• Is the water fresh or salty?

Why do we want to experiment with those variables? Maybe you can guess if you check out these blog posts from last winter:

• Imported Water Turns to Ice

• Hurrah! The Ice and Snow Are Back!

• Salty, Super-Cooled, Heat-Sucking Slush — and Homemade Ice Cream

And now, here’s the big challenge:

What do you think will happen to each jar once the weather gets really, really cold?

You will need a separate guess — or “hypothesis” — for each jar, A through D. You can list your hypotheses in the comments section, below, or send them to me by e-mail (eric@saltthesandbox.org) or Facebook.

Think hard, and good luck! (Or should I say, “good skill”?)

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Note: I revised this post later the same day to make it clear that the jars are made of plastic. (Although it might be fun to try it with glass some day. Fun in a Mythbusters kind of way….)

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To find out what happened on December 4th, when the air temperature dropped below freezing, please go here: https://neighborhoodnature.wordpress.com/2009/12/07/first-hard-freeze-for-our-jars-of-water/

Look What the Crows Found: A Great Horned Owl!

Late this morning I saw at least 14 American Crows in Columbus Park. To me that’s really great — I love crows, but their local population was decreased a few years ago by West Nile Virus. Now that they’re coming back, there’s reason for excitement — you never know quite what’s going to happen when crows are around.

The first crows I saw — a group of nine — were foraging in the woods by the lagoon. Two of them were tearing up a hornet nest. (I’ll post about that later.) They took off when they saw me, heading east and out of the Park.

The next group of crows was only five in number, but they were making lots of noise when I encountered them in the woods along Austin. At first I figured they might be looking for hornet nests — they were in the same trees where I found the nests in this blog post. But they just landed in the trees, took off again, circled over the golf course, then returned to the same trees — calling constantly. The second time they landed it was obvious that they weren’t just calling — they were calling at something. It seemed that they might be “mobbing” a hawk, so I scanned the trees with my binoculars. I thought I might find a Red-tailed or Cooper’s Hawk, which are common in the Park. Instead, this is what I saw:

The crows had located a Great Horned Owl -- the first owl I had ever seen in Columbus Park.

The Great Horned Owl was the very first owl I had ever seen in Columbus Park! A few minutes earlier I had walked right under that tree, scanning the surrounding tree tops as I went, but I had completely missed the owl. Good thing the crows helped me out — the owl was sleeping away the day in a White Oak tree. Oaks hold their leaves longer than the other trees in Columbus Park, and the leaves helped hide the owl from view.

I walked a little closer, taking photos as I went. I got within about 75 feet and took this shot:

This closer view shows the owl's tufts of feathers, which look like horns to some. It also shows the white neck band, which helps distinguish Great Horned Owls from other species with horn-like tufts.

After a few more photos, I backed away. The crows had left, and I decided to do the same. Time to let the owl get back to sleep.

I hope the crows stick around all winter and beyond. Who knows what they’ll find next time! And I hope the owl finds lots to eat tonight in Columbus Park.

Seasons of the Tulip Tree: Almost Full Circle

We’ve been following a neighborhood Tulip Tree as it cycles through the seasons. The last time we posted photos was way back on June 18, when the seeds were green, but ripening. The seeds remained that way through most the summer, then gradually started turning brown. Once the leaves had turned bright yellow in late October, the seeds looked like this:

The Tulip Tree seeds are framed by yellow leaves. Also note the duck-bill shaped bud to the left of the seeds.

Soon the leaves were swept off the tree by a wind-drive rain, and something — probably squirrels — found the ripened seeds to their liking. Here is one of the last remaining seed clusters, photographed in early November:

This was one of the last seed clusters remaining on the Tulip Tree.

Once the seeds have all been eaten or fallen to the ground, the tree will be back to where it started last spring.

You can see our first photos of Tulip Tree buds at the bottom of this post from April 8, 2009.

Go here for our most complete post about Tulip Trees, which starts with the flowers and then goes back in time to how the tree looked as the buds were opening.

Last of the Fall Wildflowers at Columbus Park?

Earlier this year Neighborhood Nature showed the earliest examples of spring flowers we could find. Now that November’s two-thirds gone, I guess it’s time to show the last wildflowers still blooming in Columbus Park. (I’ll do my best to give their names, but bear with me — I’m not a botanist!)

It was sunny and almost warm during this morning’s bird monitoring in Columbus Park. However, some parts of the Park were devoid of birds, so I had time to look down as I listened hard for any birdlike sounds. These nickle-sized flowers caught my eye — I’m pretty sure they’re Daisy Fleabane. (You can see a photo of the entire plant here.)

Although these look like daisies, the flowers are much too small. So I think it's Daisy Fleabane.

The small patch of prairie habitat beside the lagoon held two plants in flower. The first one looked like a very small example of Queen Anne’s Lace (aslo called Wild Carrot) — the flower head was less than two inches across. (You can see a photo that shows the leaves here. Please use the comments, below, to correct me if I’m wrong.)

This one looked like a very small example of Queen Anne's Lace (also known as Wild Carrot).

I’m also uncertain what this plant is called. I’m guessing this might be False Dragonhead, a kind of mint. Another name for this species is Obedient Plant, since if you push the flowers to one side, they stay there until you push them back. However, I forgot the try that test today, so my identification has not been physically confirmed. Also, this flower looked more pinkish in the field — I’m not sure why the photos don’t do justice to the color. (You can see a photo of the entire plant here.)

I'm guessing this is False Dragonhead, a kind of mint. (Again, use the comments, below, to help me out!)

My final flowers were just hanging on — most of the others on this plant had gone to seed. It was a kind of thistle, found in Austin woods — but don’t ask me what kind of thistle, I wouldn’t have a clue. (Again, these looked more pinkish in the field. You can see a photo that shows some leaves here.):

A few thistle flowers remained, but the rest had gone to seed.

“Gone to seed” is where all these flowers are bound. Food for birds, and sometimes a feast for the eyes despite the lack of color. Check out these goldenrod seeds, which may be Showy Goldenrod, one of the most beautiful of its kind. (You can see a photo that shows more of the plant here.)

Even gone to seed, goldenrods are beautiful.

So, are these the last wildflowers I’ll see this year in Columbus Park? I’ll keep looking for more on future visits. (And I’ll also try to tame that possible Obedient Plant.)