Category Archives: Trees

Seen This Week

Blackpoll warbler, Presque Isle, 12 May 2024 (photo by Charity Kheshgi)

18 May 2024

Best birds this week were seen at Presque Isle State Park on Sunday 12 May while birding with Charity and Kaleem Kheshgi. At Leo’s Landing many of the birds were at eye level including this blackpoll warbler and the barn and bank swallows.

Barn and bank swallows, Presque Isle, 12 May 2024 (photo by Charity Kheshgi)

Even the treetop birds, like this yellow-throated vireo, cooperated for photographs.

Yellow-throated vireo, Presque Isle, 12 May 2024 (photo by Charity Kheshgi)

Was this redstart was looking askance at us? Or eyeing a bug?

American redstart, Presque Isle, 12 May 2024 (photo by Charity Kheshgi)

I had high hopes for the Bird Banding at Hays Woods on Wednesday 15 May but we were in for a surprise. No birds to band! Bummer. 🙁 This restart, banded earlier in the week, shows what we could have seen.

American redstart at Bird Lab banding (photo by Kate St. John)

After we left the banding station we had good looks at a scarlet tanager and found this Kentucky flat millipede (Apheloria virginiensis). It’s colored black and orange because it’s toxic.

  • It secretes cyanide compounds as a defense. Don’t touch it!
  • You might find one perched and dying on top of a twig. That’s because it can host the parasitic fungus Arthrophaga myriapodina which causes infected individuals to climb to an elevated spot before death (per Wikipedia). Eeeew.
Centipede Aphelosia virginiensis, Hays Woods, 15 May 2024 (photo by Kate St. John)

This week there were flowers in the tulip trees (Liriodendron) obscured by thick leaves. This flower came into view when a squirrel bit off the twig and didn’t retrieve the branch.

Tulip tree flower and leaves, 16 May 2024 (photo by Kate St. John)

Instead of rain on Wednesday we had a beautiful sunrise.

Sunrise 14 May 2024 (photo by Kate St. John)

To make up for no rain on Wednesday it’s pouring right now on Saturday.

Putting Fluff to Good Use

Warbling vireo using cottonwood fluff to build its nest in St. Louis, MO, 19 May 2019 (photo by Andy Reago & Chrissy McClarren via Wikimedia Commons)

12 May 2024

Eastern cottonwoods (Populus deltoides) rely on the wind for both pollination and seed dispersal. In the spring the male and female trees each produce an inflorescence.

The males produce catkins which drop off the tree when the pollen is gone. The females produce flowers whose seeds are embedded in fluff to carry them away on the wind.

Eastern cottonwood inflorescences: male and female (photos from Wikimedia Commons)

By the time the cottonwoods have gone to seed warbling vireos (Vireo gilvus) have returned to the trees on the shore of Lake Erie. Though the birds look nondescript their song is the sound that fills the air in the parking lot at Magee Marsh in May.

Yesterday at Presque Isle State Park we watched a warbling vireo building a nest in a cottonwood. The nest is a cup that hangs from the fork of two small branches. Both sexes help build it.

Warbling Vireo on nest, Ruby Mountains, Nevada

In s. Ontario [the region of Lake Erie], nest exteriors fashioned with insect and spider silk and cocoons, paper and string, and bits of birch bark; exterior walls composed of grasses, plant fibers, bark strips, plant down, hair, leaves, fine twigs, lichens, and rootlets. Linings were fine grasses, pine needles, plant fibers, rootlets, feathers, and leaves.

Birds of the World: Warbling vireo account

Warbling vireos put the fluff to good use.

p.s. Here’s a mnemonic to help you remember their song:

 The mnemonic of “If I see you, I will seize you, and I’ll squeeze you till you squirt!” is very useful in identifying and remembering this bird’s song.

While easily heard, the Warbling Vireo can be difficult to spot. They tend to perch themselves high in treetops. When they are seen, this common bird is often described as “nondescript”.

— from Indiana Audubon description of warbling vireo

Spring Update: Where Are We Now?

Oak tree in bloom with dangling pollen flowers (photo by Kate St. John)

1 May 2024

Since our last spring checkup six weeks ago, Pittsburgh has galloped into summer. Last weekend we had July-in-April weather with official highs of 83°F and even higher in town.

Pitt peregrine Carla felt the heat at 10am on 29 April as she shaded her chicks and gular fluttered (panted) to cool herself off.

It’s hot at the Pitt peregrine nest, Carla shades the chicks, 29 April 2024, 10am (photo from the National Aviary falconcam at Univ of Pittsburgh)

Pittsburgh is not alone. In a wide swath of the U.S. from Iowa to New York spring was 20+ days early this year. In Pittsburgh nearly half of April was more than 10°F above normal while we had only one cold day at 12°F below normal.

U.S. Daily Spring Index Leaf Anomaly, 1 May 2024 (map generated by USANPN Visualization Tool)

So what temperature should we expect if we’re only 20 days ahead of schedule? April 29th ought to have been like a normal 19 May but it was way beyond that.

The heat prompted the trees to leaf out early and flowers to bloom ahead of schedule. Maples and buckeyes are in full leaf now and our oaks are at flower+leaf stage as shown at top. The leaves are hosting food for birds in the form of tiny caterpillars, so …

Migratory birds are taking advantage of the south winds and early leaf out. Since 27 April we’ve seen our first scarlet tanagers, rose-breasted grosbeaks, Baltimore orioles, indigo buntings and warblers.

Charity Kheshgi has been documenting our good luck with warblers at Frick Park. Notice the size of the leaves in her photos!

p.s. And where am I? Right now I’m at Magee Marsh a week ahead of The Biggest Week in American Birding. I don’t expect to see the swarms of migratory birds that will be here next week (I’m leaving on 3 May) but I’ll learn what happens before the people show up and why everyone waits until next week. 😉

(credits are in the captions)

Seen This Week: Ducks, a Swan and Leaf Out

Blue-winged teal, Moraine State Park, 27 March 2024 (photo by Charity Kheshgi)

30 March 2024

A Wednesday trip to Moraine State Park was cold and gray but quite worthwhile. We saw 300(!) red-breasted mergansers, many ring-necked ducks, blue-winged teal and a rare bird — a trumpeter swan. Charity Kheshgi’s photos show off the teal and swan.

Trumpeter swan, Moraine State Park, 27 March 2024 (photo by Charity Kheshgi)

Trumpeter swans (Cygnus buccinator) are “the heaviest living bird native to North America and the largest extant species of waterfowl.” They were nearly extinct in 1933 — only 70 remained in the wild — but several thousand were then found in Alaska. “Careful re-introductions by wildlife agencies and the Trumpeter Swan Society gradually restored the North American wild population to over 46,000 birds by 2010.” The trumpeter at Moraine is one of their descendants. (quotes from Wikipedia)

Spring is 20 days early in Pittsburgh this year. To prove it the yellow buckeye trees were in near-full-leaf on Thursday 28 March in Schenley Park.

Yellow buckeye leaves open and green, Schenley Park, 28 March 2024 (photo by Kate St. John)

They are 8 days later than the astoundingly early spring of March 2012. Click here to read about that year.

Comparing two springs, yellow buckeyes’ early leaf-out, Schenley, March 2012 and 2024 (photos by Kate St. John)

Early spring is the hungriest time of year for deer in Pennsylvania because they’ve already eaten all the easy-to-reach food. When the deer population is greater than the area’s carrying capacity they seek out food in unusual places. Thus I was amazed but not surprised to see a deer browsing the bushes next to our highrise at 5:30am. There is nothing to eat down there. There is nothing to eat anywhere near here.

A deer browses at a highrise in Pittsburgh, 5:30am 24 March 2024 (photo by Kate St. John)

American Chestnuts Too Rare to Roast

American chestnut leaves, nut husks and nuts (photo from Wikimedia Commons)

20 December 2023

The Nutty Series: American chestnut

‘Chestnuts roasting on an open fire / Jack Frost nipping at your nose / Yuletide carols being sung by a choir / And folks dressed up like Eskimos.’

NPR: The Story Behind the Christmas Song

Despite the popularity of The Christmas Song, you’ll never find nuts of the American chestnut in the wild. By the time The Christmas Song was written in 1945 mature American chestnuts were nearly gone from North America. Today there are so few surviving mature trees that Wikipedia lists only 25 locations though people are always searching.

American chestnuts (Castanea dentata) used to be more abundant than oaks within their native range.

Former range of the American chestnut (map from Wikimedia Commons)

Then in the late 1800s someone imported Japanese chestnut trees that had chestnut blight. Asian chestnuts are immune, American trees are not. First noticed at the Bronx Zoo in 1904, chestnut blight spread quickly and nothing could stop it. By 1950 mature American chestnut trees were gone throughout their range.

Chestnut blight is caused by a fungus that kills the above-ground portion of the tree by getting under the bark and girdling the trunk.

Chestnut blight on an American chestnut (photo from Wikimedia Commons)

The stump lives and sends up seedlings though they die as saplings. The process repeats — seedlings, sapling, death. Most stumps are at least a hundred years old.

To find a chestnut in the woods I look for the leaves at knee height. The photo below shows a typical American chestnut stump with seedlings. This one has a dead sapling as well.

American chestnut seedlings sprouting from a stump surrounding a sapling that died of blight (photo by Richard Gardner,

For over 70 years arborists have been searching for a cure for chestnut blight and trying to breed immune American chestnuts. They have crossed the American chestnut with Chinese chestnuts, then back-crossed the hybrid to another American chestnut. These efforts, supported by The American Chestnut Foundation among many others, take decades to realize any success.

There are several experimental orchards in Pennsylvania. All are protected from deer.

American chestnut orchard in PA, 2012 (photo from Wikimedia Commons)

Arborists collect the nuts, not to roast but to plant, so we’ll have more chestnuts some day.

American chestnut nuts in husk (photo by USDA Forest Service – Southern Research Station , USDA Forest Service, SRS,

As potentially successful hybrids become available, they are planted more widely — still in protected areas — to test their immunity and build back the chestnut population.

Planting an American chestnut orchard at Sky Meadows, VA, 2015 (photo from Wikimedia Commons)

At these locations the leaves are above knee height.

American chestnut leaves (photo from Wikimedia Commons)

Perhaps in one to two hundred years the nuts of American chestnuts will be easy to find and we’ll appreciate the first phrase of The Christmas Song again.

(credits are in the captions)

Using Salt to Get Water

Salt shaker (photo from Wikimedia Commons)

19 December 2023

You’ve probably noticed that in humid weather table salt clumps in the salt shaker and sticks to the top. That’s because at the molecular level salt’s ions have a net positive charge that attracts atmospheric water which has a net negative charge. Salt literally pulls water out of the air and builds crystals. This process can make the top of the salt shaker moist or dampen a salted road on a humid day.

Can salt’s natural means of pulling water from the air be used to gather water in a larger way? Researchers led by Marieh B. Al- Handawi investigated Athel tamarisk (Tamarix aphylla), a desert plant native to Africa and Asia that takes up saline water with its roots and secretes excess salt through its leaves.

Tamarisk salt cedar, Tamarix aphylla (photo from Wikimedia Commons)

The tiny leaves are arranged alternately, almost wrapping the branches. The salt crystalizes on the leaves. Look closely and you can see tiny crystals.

Closeup of Athel tamarisk branch (photo from PNAS: Harvesting of aerial humidity with natural hygroscopic salt excretions)

The smaller crystals stay on the plant and attract more water, especially overnight as shown on this branch in the early morning (8 a.m.) with condensed water droplets.

Athel tamarisk: A branch recorded in the early morning (8 a.m.) showed condensed water droplets. (PNAS: Harvesting of aerial humidity with natural hygroscopic salt excretions)

As the sun gets higher it evaporates the water, leaving behind larger salt crystals which fall to the ground.

A branch recorded in the late morning (11 a.m.) was encrusted with salt crystals. (PNAS: Harvesting of aerial humidity with natural hygroscopic salt excretions)

Every day the water cycle repeats: (A) branches attract water overnight, (B) water evaporates during the hot day while salt crystals grow, (C) water is gone and crystals are large, (D) during overnight high humidity the crystals attract water from the air and the plant absorbs the water. — paraphrased from PNAS: Harvesting of aerial humidity with natural hygroscopic salt excretions.

The tree is “drinking” from its leaves.

Researchers observed that at least one type of salt, lithium sulfate, forms small crystals that remain on the leaves and absorb water from the air. When the team added colored water to salty leaves, they watched the liquid stick to the crystal crust, then absorb into the plant’s leaves—evidence that the salty coating acts as a bona fide water collection mechanism.

Science Magazine: Desert trees may pull water from thin, dry air using salt-encrusted leaves

The tree is very salt tolerant so this water collection process won’t translate directly for humans. But perhaps we’ll find a way.

For more information see Science Magazine: Desert trees may pull water from thin, dry air using salt-encrusted leaves or the PNAS publication Harvesting of aerial humidity with natural hygroscopic salt excretions.

(photos are from the Open Access PNAS article: Harvesting of aerial humidity with natural hygroscopic salt excretions)

Acorns Are Complicated

Red oak acorns on the branch (photo by Kate St. John)

13 December 2023

The Nutty Series: Acorns and the Quercus genus

Every day I try to bring you answers about nature and birds, sometimes to questions we never thought to ask, but today I have more questions than answers about acorns.

Acorns are complicated because oaks are extremely diverse. There are about 500 species in the Quercus genus (oaks) plus about 180 hybrids, all of them native to the Northern Hemisphere and Asia.

Global distribution of ”Quercus” (oaks). The New and Old World parts are separate clades (map from Wikimedia Commons)

The complete phylogeny diagram is densely packed. (If you’d like to see it up close, click here for the full-size version.)

North America has the largest number of native oak species (160 in Mexico, about 90 in the US), which makes identifying them a challenge. Sibley’s Guide to Trees illustrates 69 native and 7 imported oaks in North America. Pittsburgh is on Sibley’s range maps for these oak species but the list is not exhaustive because they hybridize.

  • Red Oak Group
    • Northern Red Oak
    • Eastern Black Oak
    • Pin Oak
    • Scarlet Oak
    • Bear Oak
    • Shingle Oak
  • White Oak Group
    • Eastern White Oak
    • Swamp White Oak
    • Burr Oak
    • Chestnut Oak
    • Common Chinkapin Oak
    • (non-native) English Oak

The best I can do in the field is divide them into the red oak or white oak group based on buds, bark and leaves. Knowing this, I balk at identifying acorns down to the species level. There is only so much room in my brain and I’m saving it for birds.

So with that in mind here are a few acorns I’ve found in Pittsburgh recently. What exact species are they? The only one I know for sure is the burr oak.

Pin oak acorns found on Devonshire St sidewalk (photo by Kate St. John) — see comments for ID
Bur oak acorn, Schenley Park, Oct 2022 (photo by Kate St. John)
White oak acorn without its cap (photo by Kate St. John)
Red oak acorns and a mix of fallen leaves, Sept 2020 (photo by Kate St. John)

Buckeyes and Horse Chestnuts

Two Buckeyes: Horsechestnut (large) and bottlebrush buckeye (small), photographed three months after harvest by Kate St. John

6 December 2023

The Nutty Series: Buckeyes are the Aesculus genus

Buckeyes have always been one of my favorite objects because their skin is smooth and shiny fresh out of the husk, perfect to carry in my pocket like a worry stone.

In America, the native Aesculus are commonly
called “buckeyes,” a name derived from the
resemblance of the shiny seed to the eye of a
deer [a buck’s eye]. In the Old World, they’re called “horse
chestnuts”—a name that arose from the belief
that the trees were closely related to edible
chestnuts (Castanea species), and because the
seeds were fed to horses as a medicinal treatment for chest complaints and worm diseases.

Arboretum FOundation (in Seattle): The Many Faces of Aesculus

In Pittsburgh we call all of them “buckeyes.”

Let’s go backwards in the growing season from nut to husk, flower and leaf by examining buckeyes planted in Schenley Park more than 100 years ago.

The large nut pictured at top left is from a European horse chestnut (Aesculus hippocastanum) native to Albania, Bulgaria, mainland Greece and North Macedonia. Each husk contains one to three nuts. Sometimes they’re flat on one side. My favorites are the round ones.

Horsechestnut husks and nuts (photo from Wikimedia Commons)

On the tree, horse chestnut husks are spiny.

Horsechestnut fruit on the tree (photo from Wikimedia Commons)

They’re produced from the white flowers that have pink (already fertilized) highlights. Notice that each leaf has seven fat leaflets. The number and shape of the leaflets indicate this is a horsechestnut.

Horse chestnut flowers and leaves (photo by Kate St. John)

In winter horse chestnuts are easy to identify by their large, sticky end buds.

Hose chestnut twig and buds (photo by Paul Wray, Iowa State University,

The yellow buckeye (Aesculus flava) is native to the Appalachians and Ohio Valley and is North America’s tallest buckeye tree at 70 feet. Planted as an ornamental in Schenley Park it can hybridize with its shorter cousin, the Ohio buckeye (Aesculus glabra), making identification difficult for non-botanists like me.

Yellow and Ohio buckeye nuts look a lot like horse chestnuts. Seeing the husk is a big help because yellow buckeye husks are smooth …

Yellow buckeye nuts in the husk (photo by Wendy VanDyk Evans,

… while Ohio buckeye husks are slightly spiny. The narrow leaves also indicate a native buckeye. (Yes, the leaves looked sick that year.)

Ohio buckeye fruits on the tree, Schenley Park (photo by Kate St. John)

Their flowers are pale yellow (not white) and narrower than the horse chestnut’s. (*)

Yellow or Ohio buckeye flowers (I cannot tell which (*)) photo by Kate St. John

Yellow buckeye buds are large but not sticky. They’re one of the first to leaf out in the spring.

Yellow buckeye buds and leaf out at Schenley Park, 5 April 2022

Ohio buckeye buds are strongly keeled.

Ohio buckeye bud (photo by T. Davis Sydnor, The Ohio State University,

For a summary of nine common buckeyes (Aesculus) used in landscaping see The Spruce: What is a Buckeye?

p.s. The small buckeye nut in the top photo is from the shrub-sized bottlebrush buckeye (Aesculus parviflora), planted in Schenley Park near Panther Hollow Lake. Click here to learn more.

(*) Which Flowers? I could not tell whether the flower photo was yellow or Ohio buckeye. Mary Ann Pike suggests Ohio buckeye in this comment.

Seen at Some Point

Sunrise seems to pierce Central Catholic’s steeple, 28 Nov 2023 (photo by Kate St. John)

2 December 2023

Saturday blogs usually show what I’ve “Seen This Week” but I have only one worthy photo, shown above. For the rest I’ve chosen sights that are timely for the season and seen at some point.

This Wednesday the water was low in the Monongahela River at Duck Hollow, just as it is in this photo from Nov 2020. However the sky was not so blue and it was very cold!

Nine Mile Run outflow at Duck Hollow, 29 Nov 2020 (photo by Kate St. John)

Wednesday’s low was 21°F but today will warm to nearly 60°F. No frost today like the bit shown below from Nov 2021.

Frost on the grass, 4 Nov 2021 (photo by Kate St. John)

The trees are bare now and showing off their silhouettes. Here are three typical sights on the cusp of December.

Bare trees at dusk, Schenley Park, 15 Nov 2012 (photo by Kate St. John)

You can identify young American elm trees by their twig arrangement that look like fish skeletons.

Twigs on young American elms look like fish bones, 2 Dec 2012 (photo by Kate St. John)

Black locust trees are always gnarly but this one was made worse when it was trimmed away from the utility wires in 2012.

Black locust tree looks twisted after powerline cutback, 28 Jan 2012 (photo by Kate St. John)

(photos by Kate St. John)

Shagbark Hickory Nuts

Shagbark hickory fruit (husks), nuts and leaves in October (photo from Wikimedia Commons)

29 November 2023

The Nutty Series: Shagbark hickory

Last month shagbark hickories (Carya ovata) put on a show in Pittsburgh’s parks with bright yellow leaves and fallen nuts.

Shagbark hickory leaves in autumn (photo from Wikimedia Commons)

The thick green husks began to turn brown immediately and peel off in quarter-moon sections. This piece of husk sat indoors for more than a month before I took a photo of its interior. The dark brown exterior is visible at the bottom edge.

Section of a shagbark hickory husk, Nov 2023 (photo by Kate St. John)

If a nut lasts through the winter its husk looks quite worn out by March. This one was probably uneaten for a good reason.

Shagbark hickory nut that overwintered, March 2021 (photo by Kate St. John)

Shagbark nutshells are slightly oval with a remnant stem and four ribs. When I cracked open the nut I collected, it was a dud. Maybe an insect got to it. This Wikimedia photo of a sawed nut shows the meat.

Shagbark hickory nut, sawed open (photo from Wikimedia Commons)

Though shagbark hickory nuts taste good and can substitute for pecans, shagbarks are not cultivated because …

They are unsuitable to commercial or orchard production due to the long time it takes for a tree to produce sizable crops and unpredictable output from year to year. Shagbark hickories can grow to enormous sizes but are unreliable bearers.

C. ovata begins producing seeds at about 10 years of age, but large quantities are not produced until 40 years and will continue for at least 100. Nut production is erratic, with good crops every 3 to 5 years, in between which few or none appear and the entire crop may be lost to animal predation.

Wikipedia Shagbark Hickory account

Interestingly, shagbarks (Carya ovata) and pecans (Carya illinoensis) can hybridize in the wild though the hybrids usually don’t produce nuts.

Shagbark hickories are easy to identify by their shaggy bark. Just look up and you’ll see it peeling from the trunk. Young trees can fool you, though, because they have smooth bark (click here to see young bark).

Shagbark hickory tree, Raccoon Wildflower Reserve, March 2021 (photo by Kate St. John)

Shagbarks are one of the first native trees to leaf out so their sap runs early in the spring. Yellow-bellied sapsuckers (Sphyrapicus varius) take advantage of this and drill the trees as they migrate north. The birds move sideways around the trunk as they drill in a ring around the tree. The trees heal the wounds by producing callus tissue that grows outward, almost like lips. These attract the the sapsuckers who then drill the same rings year after year.

Shagbark hickory with yellow-bellied sapsucker drill-rings, Schenley Park, Oct 2017 (photo by Kate St. John)

(credits are in the captions)