All posts by Kate St. John

Fossil in Schenley Park

Closeup #1 of fossil in Schenley Park (photo by Kate St. John)

10 August 2022

Sometime this summer the Department of Public Works placed a large sandstone rock at the base of the stairs behind the Schenley Park Visitors’ Center. The prominent fossil facing the stairs tells a story about life in Pittsburgh 300 to 330 million years ago.

Fossil rock at the base of the WPA stairs, Schenley Park, 6 August 2022 (photo by Kate St. John)

During the late Carboniferous period, while this rock was still sand, a Lepidodendron tree fell on it. Lepidodendron had scales on its branches and trunk that left impressions in the sand, illustrated below in increasingly fine detail.

Lepidodendron artist’s rendering (illustration from Wikimedia Commons)
Lepidodendron trunk or branch and resulting fossil impression (illustration from Wikimedia Commons)

The sand became sandstone and in the early 21st century the rock separated from its fellows thereby exposing the fossil. This rock many have fallen at the Bridle Trail rockslide.

Locations of two closeup photos of the fossil in Schenley Park (photo by Kate St. John)
Closeup #2 of fossil in Schenley Park (photo by Kate St. John)

I have never seen Lepidodendron’s closest living relative, Lycopodium, in Schenley Park …

Lycopodium (ground pine or club moss), Laurel Ridge State park, 30 May 2022 (photo by Kate St. John)

… but I’ll look for it now that I’ve seen its fossil ancestor.

p.s. If this Lepidodendron had fallen in a swamp instead of on a sandy beach, it would have become coal. Read about similar fossils at Ferncliff Peninsula in Ohiopyle State Park in this vintage article: Fossils at Ferncliff

(photos by Kate St. John, illustrations from Wikimedia Commons; click on the captions to see the originals)

Lying in Wait for Aphids

Red aphids coat false sunflowers in Schenley Park, 6 August 2022 (photo by Kate St. John)

9 August 2022

Every August the false sunflowers in Schenley Park become covered in red aphids. My first reaction is disgust, then I look for aphid predators and protectors.

Aphid predators include ladybugs, syrphid flies (hover flies), parasitic wasps and lacewing larvae. Their protectors are the ants who harvest their honeydew.

The ants were out in full force and chased off a ladybug that flew to escape them.

Ants harvesting aphid honeydew, Schenley Park, 6 August 2022 (photo by Kate St. John)

The ladybug found a safer place to munch on aphids. No ants in sight.

Ladybug predator of aphids, Schenley Park, 6 August 2022 (photo by Kate St. John)

Syrphid flies hovered and darted among the leaves, choosing to lay eggs where there would be plenty of aphids for their larvae to feed on.

Syrphid fly on a leaf near the aphids, Schenley Park, 6 August 2022 (photo by Kate St. John)

Larger predators lay in wait to eat the aphid eaters. Can you see the spider inside this flower?

False sunflower with aphid on outer petal, spider lurking inside flower, 3 August 2022 (photo by Kate St. John)

Here’s a hint. His feet are dangling are at the bottom of the circle.

Spider lurking inside the flower (photo by Kate St. John, retouched)

I’m sure there were many more predators lying in wait for aphids. This video shows what to look for.

(photos by Kate St. John)

Common Birds, Exotic Ranges

House sparrow flock in England (photo from Wikimedia Commons)

8 August 2022

Birds move around on their own but some of our most common species came from a different continent or a different habitat and were introduced here by humans. Now you can see both native and exotic ranges in eBird after they made changes this month to the species maps.

House sparrows and pigeons, both introduced from Europe, are a case in point. In the eBird maps below native range is purple, exotic range is orange.

Introduced to cities: House sparrow (Passer domesticus)
Domesticated and introduced: Rock pigeon (Columba livia)
Feral rock pigeon (photo from Wikimedia Commons)
Explore Species Maps: European Starling (screenshot from eBird)

We tend to think that all exotic species were introduced from Eurasia to the Americas. Canada geese made the reverse journey. Europeans actually wanted them. Are they regretting that decision?

Reverse journey to Europe: Canada goose (Branta canadensis)
Canada geese in Hesse, Germany (photo from Wikimedia Commons)
Exotic on its own continent: House finch (Haemorhous mexicanus)

Captured house finches were illegally transported from California to New York City in the 1940s to be sold as “Hollywood finches” in the pet trade. Just before the law caught up to them, the vendors released the birds on Long Island. The “exotic” house finch population has now spread across the continent. eBird shows it on the map below. Click here and scroll down to see how they spread through the decades.

Male house finch (photo by Marcy Cunkelman)
Exotic within its native range: Northern bobwhite (Colinus virginianus)

The northern bobwhite does not do well in urban and suburban habitats but as a game bird it is raised in captivity and released for hunting in gamelands, agricultural fields and open woods. Have you seen a bobwhite in your backyard? It is an escapee within its “exotic” range.

Northern bobwhite (photo from Wikimedia Commons)
Northern bobwhite range map from eBird; Checkmark in the blue circle to remove escapees from map

Learn more about the new eBird maps at Important Changes to Exotic Species in eBird.

(photos from Wikimedia Commons and Marcy Cunkelman, screenshot maps from eBird; click on the captions to see the originals)

Scallops on the Move

Atlantic bay scallop shell (photo from Wikimedia Commons)

7 August 2022

Scallops travel by opening and closing their shells but the direction they move seems counterintuitive. They don’t lead with their hinges. Instead the open edge goes first as they use their eyes to guide themselves.

Scallops’ eyes look like bright beads at the shells’ front edge.

Slightly open live Atlantic bay scallop; eyes look like bright beads (photo from Wikimedia Commons)

Watch scallops on the move in this Twitter movie.

(photos from Wikimedia Commons; click on the captions to see the originals)

Flowers and Seeds

Wingstem from bud to seed, Schenley Park, 3 August 2022 (photo by Kate St. John)

6 August 2022

By early August many flowers have already produced seeds. Wingstem (Verbesina alternifolia) above displays every step in the process: buds, new flowers, fading flowers and seed packets.

The three-flanged seed pods of American wild yamroot (Dioscorea villosa) are as distinctive as its pleated leaves.

American wild yamroot leaves and seeds, Jennings 29 July 2022 (photo by Kate St. John)

Greater celandine (Chelidonium majus) now has both seed pods and flowers (seeds in shadow at left). This alien plant is easy to find in Schenley Park because it is toxic to deer.

Greater celandine with seeds in the background, Schenley Park, 3 August 2022 (photo by Kate St. John)

Yellow jewelweed (Impatiens pallida) is much harder to find because it is ravaged by the large deer herd.

Yellow jewelweed. no seed in the picture, Schenley Park, 30 July 2022 (photo by Kate St. John)

If this flower evades the deer it will turn into a seed pod that bursts explosively when ripe.

Seed pod on yellow jewelweed, Schenley Park, August 2019 (photo by Kate St. John)

(photos by Kate St. John)

Variably Cloudy

Sunrise on 31 July 2022 (photo by Kate St. John)

5 August 2022

This week the clouds at sunrise varied from brooding horizontal stripes to dramatic ragged puffs.

Sunrise on 4 August 2022 (photo by Kate St. John)

This tall stack presaged scattered thunderstorms though none had been predicted.

Cloud stack on 4 August 2022 (photo by Kate St. John)

Twice this week isolated rain clouds created spectacular rainbows half an hour before sunset. This one on 4 August has a faint second rainbow above it.

Rainbow(s) on 4 August 2022 (photo by Kate St. John)

On 1 August the pot of gold was in Shadyside.

Rainbow on 1 August 2022 (photo by Kate St. John)

(photos by Kate St. John)

Orange String on Everything

Vine on a vine: Dodder on porcelain berry, 26 July 2022 (photo by Kate St. John)

4 August 2022

By the end of July in western Pennsylvania, there are patches of orange string draped over plants in moist locations on the edge of the forest. The orange strings are dodder (Cuscata), a native annual parasitic vine that blooms from July to October.

Dodder wraps itself around its host and inserts tiny haustoria to suck out water and nutrients. Last week I found it parasitizing invasive porcelain berry — Go, dodder! — but dodder won’t beat back the grapevine. Dodder doesn’t kill its host.

Orange string on everything: Dodder wrapped on invasive alien plants, 26 July 2022 (photo by Kate St. John)

Look very closely and you can the haustoria clinging and dodder’s tiny flowers that are pollinated by wasps.

Dodder in bloom (photo by Esther Allen)

Dodder will die at the end of the growing season yet you may find it in the same spot every year. Find out why this happens and other interesting tidbits in this vintage article.

(photos by Kate St. John and Esther Allen)

The Traveling Nest

The Rivers of Steel Explorer (photo from Ryan O’Rourke)

3 August 2022

What do you do when your nest and babies sail away without you? A house finch couple on Pittsburgh’s North Shore have learned to wait for the boat to come home.

Male and female house finches, Nov 2010 (photo by Steve Gosser)

This spring a pair of house finches (Haemorhous mexicanus) were very quick to build a nest atop a loud speaker on the aft deck of the Rivers of Steel Explorer, docked behind the Carnegie Science Center. By the time the crew caught up with them the female had finished the nest and laid eggs, so the nest had to remain undisturbed until it was empty.

House finch nest on top of loud speaker on Rivers of Steel Explorer vessel, 29 July 2022 (photo by Ryan O’Rourke)

When would it be empty? Not yet. In August? In September?

House finches are masters at back-to-back nesting, raising three to six broods per year. As the young approach fledging the male takes charge of them while the female starts the next round of egg laying. On the Explorer the female doesn’t pause between one brood and the next.

When I met the Explorer finch family on 26 July they had already raised several broods and were caring for young approximately two days old. While our tour waited on deck for the boat to depart the father fed three tiny nestlings. They are growing fast! Here they are three days later on 29 July.

Close up of house finch nest, 29 July 2022 (photo by Ryan O’Rourke)

Our tour pulled away from the dock and I forgot about the house finches for 90 minutes while we traveled Pittsburgh’s three rivers. Mother and father house finch were absent but they had not forgotten. Waiting on shore they were so attuned to the habits of the Explorer that when the vessel maneuvered to dock they raced across the channel to the aft deck. “The kids are home!”

The Traveling Nest is one of many birding highlights on Rivers of Steel Explorer tours. Captain Ryan O’Rourke explained, “In addition to hosting a bird-watching cruise with the National Aviary, part of our educational program for students includes a lesson in birding and how birds can be indicators of the health of our rivers.”

And then there are rare birds that the Explorer is first to see. On 26 April 2022 O’Rourke reported 13 American avocets on the Monongahela River at Station Square. I chased these birds and missed them. Wish I’d been on the boat!

Next month you can join Rivers of Steel and the National Aviary for Riverboat Birding on the Explorer, 3 September 2022. Sign up below or click here.

(photos by Ryan O’Rourke and Steve Gosser)

Carnivorous Teasels?

Teasel in bloom, Schenley Park, 26 July 2022 (photo by Kate St. John)

2 August 2022

This flower head is so spiny and eye catching that we rarely look at the leaves though they’ve been studied intensely at least three times since the 1870s.

Teasel’s (Dipsacus fullonum) paired perfoliate leaves collect rainwater in the cup where they clasp the stem and unwary insects drown in the puddle. Notice the water in the leaf cups below. (Click the first photo to see a marked-up version showing the water line.)

Same teasel showing water trapped in a leaf cup, Schenley Park, 30 July 2022 (photo by Kate St. John)
Teasel leaves showing with water cup (photo from Wikimedia Commons)

In the mid 1870s Francis Darwin, son of Charles Darwin, hypothesized that teasel digests the decaying insects, then studied and published about the digestive mechanism. Not everyone was convinced. Teasels were studied again and again.

A 2011 study published in PLOS ONE found that teasels with dead insects in the leaf cups set more seed than those without, thus a nutrient benefit of carnivory. But a 2019 study in Canadian Science Publishing found that seed production had more to do with soil nutrients.

Teasels obviously use spines to defend themselves, but do they play offense, too? Are they carnivorous? It would be nice to think so but we don’t know.

Read more in this 2017 article In Defense of Plants, published before the 2019 study.

(photos by Kate St. John and from Wikimedia Commons)

Yesterday at Schenley Park on 7/31

Pileated woodpecker, May 2020 (photo by Chad+Chris Saladin)

1 August 2022

Twelve of us met in Schenley Park yesterday morning and walked East Circuit Road in search of birds. As expected in late July the birds were quiet, though we did manage to see or hear 27 species. Our checklist is here and listed at the end.

Best Bird was a pileated woodpecker hammering on a fallen log in the darkest woods. The photo above is not from our walk. Chad+Chris Saladin had better light for their photo in May 2020.

I forgot to take a picture of the group. 🙁 Here is my one photo from the walk: Yellow hawkweed (Pilosella caespitosa) blooming in the grass.

Hawkweed blooming at Schenley Park, 31 July 2022 (photo by Kate St. John)

eBird checklist: Schenley Park, Allegheny, Pennsylvania, Jul 31, 2022 8:30A – 10:30A
Mourning Dove (Zenaida macroura) 2
Chimney Swift (Chaetura pelagica) 8
Red-tailed Hawk (Buteo jamaicensis) 2
Red-bellied Woodpecker (Melanerpes carolinus) 4
Downy Woodpecker (Dryobates pubescens) 1
Hairy Woodpecker (Dryobates villosus) 2
Pileated Woodpecker (Dryocopus pileatus) 1
Northern Flicker (Colaptes auratus) 5
Eastern Wood-Pewee (Contopus virens) 1 Heard
Red-eyed Vireo (Vireo olivaceus) 1
Blue Jay (Cyanocitta cristata) 4
American Crow (Corvus brachyrhynchos) 7
Carolina Chickadee (Poecile carolinensis) 6
Tufted Titmouse (Baeolophus bicolor) 1
White-breasted Nuthatch (Sitta carolinensis) 1
House Wren (Troglodytes aedon) 3 Young with obvious gape-beak
Carolina Wren (Thryothorus ludovicianus) 1
European Starling (Sturnus vulgaris) 2
Gray Catbird (Dumetella carolinensis) 1
Wood Thrush (Hylocichla mustelina) 1 Heard one making agitated call
American Robin (Turdus migratorius) 15
House Finch (Haemorhous mexicanus) 2
American Goldfinch (Spinus tristis) 3
Chipping Sparrow (Spizella passerina) 1
Song Sparrow (Melospiza melodia) 2
Common Grackle (Quiscalus quiscula) 1
Northern Cardinal (Cardinalis cardinalis) 5

(pileated woodpecker photo by Chad+Chris Saladin; hawkweed photo by Kate St. John)