Returns of the Winter Geese

My sons and I have been monitoring birds at Chicago’s Westside parks for almost a decade. Now that Ethan and Aaron are off at college, I still visit Columbus, Douglas, and Riis Parks at least three or four times each month. In each park I walk a route that takes me to most of the places where birds hang out and count every bird I see. I carefully count even the most common species, like American Robin, European Starling, and Canada Goose. We’ve gathered a lot of data over the years, and we’ve learned a lot about the seasonal changes in bird populations in this part of town. (Much of this data is summarized elsewhere on this blog: Columbus Park, Douglas Park, Riis Park.)

One thing that we quickly learned is that Canada Goose populations in the parks fluctuate quite a bit each year, as shown in the following graph of goose count data from Columbus Park, where we have been monitoring since 2007. (Click on the graph to make it larger.)

Seasonal changes in the Canada Goose population at Columbus Park on Chicago’s Westside, April 2007 through October 2015.

During the summer months there are often a few geese at Columbus Park, and some years a pair or two raise a brood of goslings. Other years the resident coyotes and goose-managing humans eliminate all geese from the park, at least during mid summer. Starting in September the park’s goose population begins to increase, and by Christmas Bird Count in mid December we often count 500 or more geese on the lagoon, lawns, and golf course at Columbus Park. During cold and snowy winters the geese may head elsewhere for a month or more, but goose populations usually increase again once the snow and ice melt. Sometime in March northward migration begins, and by April Canada Goose populations have fallen back to their late spring through summer levels. Although it’s not shown on the graph, goose populations in the park also fluctuate during the day, as many geese fly elsewhere at night.

Our monitoring data from Douglas Park is much less complete, since we only started going there regularly in 2012. However, the available data indicate that the yearly cycle at Douglas is similar to Columbus: Lower counts during the spring and summer, sharp increase in fall, drop off mid winter if there are deep snows, and at least a partial recovery before spring migration begins in March.

Seasonal changes in the Canada Goose population at Douglas Park on Chicago’s Westside. Although we visited Douglas several times a year starting in 2007, we only started monitoring there regularly in March, 2012.

We’ve always assumed that the winter Canada Geese in our parks come from somewhere to the north; however, I’ve wondered where, exactly, they spent their summers. Did they nest a hundred miles to the north, in Wisconsin? Or a thousand miles or more from Chicago, in arctic Canada? I’ve also wondered if the winter geese are loyal to one park, returning day after day, month after month, or if they wander from park to park, county to county, state to state, always looking for greener grass? And finally, I’ve wondered if the same Canada Geese return to Chicago, and maybe even to the same park, year after year?

I stumbled on some answers to my questions last December (2014) at Douglas Park. I was following my usual route around the north lagoon when my path was blocked by a small flock of geese. I slowly walked to and through the flock, and as they parted to let me through, I happened to look down. Here’s what I saw:

Canada Geese with leg markers C120 and C105, seen on December 3, 2014, at Douglas Park.

In all my years of monitoring birds, I had never seen markers like these. Of course, I rarely got this close to geese, and when I did I rarely looked at their legs. Looking around online I found a United States Geological Survey (USGS) website where I could submit my marker observations. I completed online forms for these two geese, and a few weeks later I received an email with a certificate of appreciation that looked like this. (I removed the bander’s address to respect his privacy.) :

Certificate of Appreciation for submitting data on the goose with leg marker C120.

Now I had at least a partial answer to one of my questions about Chicago’s winter geese. Both C120 and C105 had been banded the previous summer in Thunder Bay, Ontario, Canada, when they were too young to fly. Intrigued, I started paying much more attention to goose legs as I monitored birds. By slowly walking through goose flocks on the lawns and ball fields, I was able to address another question when I relocated both C105 and C120 at Douglas Park later that month. It seemed that at least some geese were returning to the same park more than once.

By staring at lots of goose legs through the winter and early spring of 2014-2015, I eventually found eight different leg-marked geese at Douglas Park, two at Columbus Park, and six at Steelworkers’ Park on Chicago’s far southeast lakeshore (where my younger son, Aaron, monitors birds). Once the winter’s snows melted, I also started seeing a different sort of marker, a white neck collar with black letter and numbers:

Canada Geese with neck collars 66C and 78A, seen at Columbus Park on Chicago’s Westside, on April 8, 2015.

Following up on information in the Certificates of Appreciation I received for the collared geese, I learned they had been marked the previous summer by a local research project, the Ecology of Wintering Canada Geese in the Greater Chicago Metropolitan Area (more information here and here). Through the spring I found eleven different neck-collared geese: Two at Douglas Park, six at Columbus Park, one at Riis Park, and two at Steelworker’s Park.

Even after local goose populations had decreased in the spring I kept looking for marked geese, but I did not see any after late May. However, in early August I received an email from the Canadian goose bander informing me that C165 had returned to Thunder Bay, Ontario.

As usual, local goose populations started increasing in September, and on September 30, 2015, I found two marked geese at Douglas Park, C120 and C151. I now had a partial answer to another of my questions, since I had seen C120 at Douglas twice before during December, 2014. Additional visits to Douglas Park through mid October located four more geese that I recorded the previous winter. In other words, by October 18, five of the eight leg-marked geese seen at Douglas during the winter of 2014-2015 had returned to the park.

Although I continue to stare at goose legs and necks in Chicago Parks (and plan to do so for years to come), this seems like a good time to tabulate my findings to date. The table for Douglas Park pretty much summarizes what I’ve learned so far:

Table summarizing data on marked Canada Geese at Douglas Park, Chicago, from December, 2014, through October 18, 2015.

Looking back at the questions I asked earlier in this blog post, here are some partial answers. (I call the answers partial because I saw markers on about one-in-a-hundred winter geese.):

• Where did the winter (and spring) geese spend their summers?  My sample includes both geese banded during summers in Canada and geese banded during summer of 2014 in the Chicago area.
• Are the winter geese loyal to one park, returning day after day?  My sample includes five geese that were present at Douglas twice in a month.
• …month after month? Two of the seven geese that were seen at Douglas during December, 2014, returned to Douglas after the winter snows melted, during March, 2015. (Apparently they sought greener pastures when the snow got too deep at Douglas Park.)
• Do the same Canada Geese return to Chicago, and maybe even to the same park, year after year?  Five of the eight leg-banded geese seen at Douglas Park last winter have been seen in the park so far this fall.

One more interesting finding from the age column of the Douglas Park table. The oldest goose in that sample, A657, was at least one year old when it was banded during July, 2008. That means it could have spent seven or more winters in Chicago before I finally saw it. I really wish I knew back then that goose legs could be so interesting!

My Douglas Park sample has more leg-marked geese than collared geese, but that pattern is reversed in my Columbus Park sample, as shown in the following table:

Table summarizing data on marked Canada Geese at Columbus Park, Chicago, from December, 2014, through mid October, 2015.

Of the two leg-marked geese seen at Columbus Park, one returned multiple times, both before and after the winter snows. Also, with a larger sample of neck-collared geese at this park, maybe it’s time to ask, why did I only see collared geese after the winter snows? Hundreds of geese received neck collars in the Chicago area during summer 2014, and even if they migrated south at some point, they could have been in the area for a couple months after banding. Neck collars, unlike leg markers, are pretty obvious when you are counting geese, even if they are too far away to read the numbers. I can make excuses for not seeing leg markers: They can’t be seen when the geese are on water or in the air, and they can’t be seen when the geese are far away or when the grass is too tall. Therefore, absences for leg markers probably don’t mean very much. However, I can’t make excuses for missing neck collars, especially when I was already looking for the much less conspicuous leg markers. There’s got to be an interesting story about the travels of neck-collared geese, but my Douglas and Columbus data are too sketchy to tell it. However, data from two other parks provide a bit more information about the collared geese.

Riis Park, on Chicago’s northwest side, attracts fewer geese than Douglas or Columbus Parks. Perhaps that’s why I only found one marked goose there, neck collar C111:

Table summarizing data on marked Canada Geese at Riis Park, Chicago, from December, 2014, through mid October, 2015.

Like the other collared geese this one did not appear in the park until spring. Unlike the collared geese from Douglas and Columbus, this one stuck around for awhile: I saw it on both April 1 and May 27 at Riis, and I also saw it during the May 9th Illinois Spring Bird Count, at Garfield Park a few miles southeast of Riis. Like the other collared geese, it has not been seen since May, 2014 — at least so far.

Finally, here’s some data about marked geese seen at Steelworkers Park on the far southeast side of Chicago. My son, Aaron, and I visited this area once or twice a week until Aaron left for college.  Aaron monitors birds in and around the entire South Works steel mill property, but all our marker sightings were on the lawn Steelworkers Park, on Lake Michigan just north of the mouth of the Calumet River:

Table summarizing data on marked Canada Geese at Steelworks Park, Chicago, from December, 2014, through mid October, 2015.

There was one day in March when we saw a lot of marked geese at Steelworks Park: Six with leg markers and one with a neck collar. Those geese then disappeared, perhaps flying north or maybe just deciding that the grass at nearby Rainbow Beach and Calumet Park was more tasty. A second collared goose (24C, a male) was seen at least four times during April and May (April 2 and 16, May 2 and 21). Sometimes 24C was seen with other geese, and sometimes he was all alone. By May there were many goose nests on the old ore retaining walls near Steelworkers, so it’s possible 24C was the male in a mated pair. However, we never saw him with goslings, so we will never know for sure.

That’s where things stand as the end of October approaches. I’ve begun to answer some of my long-standing questions about wintering Canada Geese by piggy-backing on other people’s efforts. (Banding Canada Geese in July must be hot and dirty work!). I find the results amazing, but not surprising. Amazing things happen in goose brains to make them return time and again to the Westside parks. But they’re birds, after all, and birds do even more amazing things every migration season.

My findings are at most a few pixels in a much larger picture of Canada Goose yearly cycles, but they are a start, and they are the pixels I’m going to value most. Of course the two-year Ecology of Wintering Canada Geese in the Greater Chicago Metropolitan Area is going to fill in a lot more pixels in the Chicago area, and I look forward to reading their reports.

Until then, I’ll keep looking at goose legs and goose necks everywhere I go. If you do the same, and you find any of “my” geese, please report them on the USGS website. I’d also appreciate it if you send me a message about your sighting.

And now they are eating…caterpillars!

Almost two weeks ago we solved the mystery of what warblers were eating in the streets of south Oak Park: Beetle larvae!

Well, the beetle larvae are not longer tumbling from our elm trees, but the warblers and thrushes and Indigo Buntings keep coming, along with tanagers and orioles and more! So, to find out what the birds are eating now, I grabbed a white plastic box lid, held it under some low elm branches, and started shaking:

Here’s what I found: Little green caterpillars! (I put the dime there. Money doesn’t grow on trees in our neighborhood.)

Just in case someone out there can identify what type of moths or butterflies these become, here are some closer views:

I can’t identify the caterpillars, but I do know they taste good to birds. During the past week, we’ve seen 23 kinds of warblers feeding in and under our elm trees:

Golden-winged Warbler

Tennessee Warbler

Orange-crowned Warbler

Nashville Warbler

Northern Parula

Yellow Warbler

Chestnut-sided Warbler

Magnolia Warbler

Cape May Warbler

Yellow-rumped Warbler

Black-throated Green Warbler

Blackburnian Warbler

Palm Warbler

Bay-breasted Warbler

Blackpoll Warbler

Black-and-white Warbler

American Redstart

Ovenbird

Northern Waterthrush

Mourning Warbler

Hooded Warbler

Wilson’s Warbler

Canada Warbler

Feeding along with the warblers we’ve seen:

Yellow-throated Vireo, Warbling Vireo, and Red-eyed Vireo

Veery, Gray-cheeked Thrush, and Swainson’s Thrush

Gray Catbird

Summer Tanager and Scarlet Tanager

Rose-breasted Grosbeak

Indigo Bunting

and Baltimore Oriole

These birds are all spring migrants. The Catbird is the only one who’s likely to stay and nest in our neighborhood. The caterpillars in our elm trees have helped them survive and refuel before the next night with southerly winds to speed them on their journey north.

Did I mention that last week we found thousands of tiny caterpillar poops on our cars each morning? The polite term for caterpillar poop is frass. This morning our cars were almost frass-free, although there was lots of bird poop on our windshields.

We’ll finally get some southerly winds later this week, so we expect most migrant birds to continue north. In their wake we expect our elms to enjoy an almost caterpillar-free summer.

Now if we could just find a biological control for the bark beetles that spread Dutch Elm Disease….

Look What’s Falling from Our Elm Trees!

Every spring there are a few days in late April and early May when we see warblers in the streets, feeding on something. Two years ago it happened in late April, as seen in these photos of Yellow-rumped Warblers on our south Oak Park  block:

Well, it’s been happening again the past few days. It’s like a block party for the birds, and it got me wondering–what’s for breakfast, lunch, and dinner? What tasty things are the warblers feeding on?

My best guess was that there was some sort of insect feeding on the opening leaves of the American Elms that tower over many sections of our block. Every spring there are also warblers feeding on something in the treetops, and every year there are tiny holes chewed in the leaves:

So, I was thinking that maybe whatever was feeding on the leaves somehow fell to the ground, where sharp-eyed warblers could spot them on the asphalt and continue their meals.

To test my hypothesis, I placed a white plastic lid where it could catch whatever was falling. I left it there from late afternoon yesterday until early this morning:

Then, this morning, I brought the lid inside to see what I could find. It was covered with tiny, pale yellow grub-like insect larvae!

So, one question answered: That’s what’s falling from the trees, and probably what the warblers are eating. But many questions remain:

• What are these things? Hatchling caterpillars, or some other kind of insect?
• Why are so many falling from the trees? Shouldn’t they be better adapted to hang onto the leaves? Or do they “jump” whenever a bird is picking at their leaf?
• Once they hit the ground, they are still alive–you can see them moving. Can they somehow continue to live on the ground, perhaps feeding on fallen elm leaves and elm seeds? If so, when they are larger and stronger, would they climb back up into the trees?

So, I guess our next challenge is to try to raise a bunch of the larvae until they are large enough to identify. And once they are bigger we can put some of them at the base of an elm tree and see what happens.

I’ll let you know what happens!

—–

A few hours I posted this, a Facebook friend and garden designer made this comment (Thanks, René!):

“I’m no entomologist, but after some research, my best guess is Elm Leaf Beetle. These guys feed on elms and drop to the ground in large numbers as little yellow guys to pupate. Sounds like the yellow-rumped Warblers are doing a good job of natural pest control.”

Here’s a photo of Elm Leaf Beetle damage: http://www.ipm.ucdavis.edu/PMG/X/I-CO-XLUT-CD.004.html
Here’s a drawing of the Elm Leaf Beetle life cycle: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pni7403-2.html
Here’s a photo of some Elm Leaf Beetle pupae: http://www.ipm.ucdavis.edu/PMG/X/I-CO-XLUT-EA.001.html

We’ve put some of our fallen larvae (or whatever) into a plastic box with newly opened leaves–now we’ll see what happens!

—–

Here are links to our earlier blog posts about birds in our streets:

• Block Party for the Birds: Warblers and Sparrows in the Streets

• Warblers on the Rooftops, Thrushes in the Alley

• Front Stoop Birding: Warblers Come to Us

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.

—–

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.

——

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!

—–

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

—–

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)

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.

Cooper’s Hawk in the Brush Pile

For the third day in a row we had a juvenile Cooper’s Hawk trying to pluck House Sparrows from our backyard brush pile. For the third day in a row it came up empty clawed.

Here’s is Monday’s drama. The hawk kept trying to find a route to the very center of the brush pile, where a sparrow cowered on the ground:

As the hawk jumped down to the far south corner of the brush pile, the sparrow scrambled out from the north edge and took off, flying over the fence and through the neighbors’ yards. The Cooper’s Hawk followed as fast as it could, but gave up four backyards north. It flew back to our yard and landed on the fence, were it was greeted by a Gray Squirrel:

Juvenile Cooper's Hawk faces off with a Gray Squirrel. This time the squirrel blinked first, jumping down to forage while the hawk held its perch.

I thought we would be in for another bird-mammal confrontation, which our Cooper’s Hawks always seem to lose. Instead the squirrel calmly jumped into our backyard, where it resumed foraging for stray sunflower seeds.

Since then, we’ve seen the juvenile hawk on our brush pile at least once a day. Each time the sparrows wait until the hawk is on the south edge of the pile, and then they flee to safety.