Using Salt to Get Water

Musings & News, Trees
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)

Time’s Running Out: Where Are The Crows?

Bird Behavior, Crows & Ravens
Crows flying to the roost at sunset near Wilkins Ave, Oct 2020 (photo by Joanne Tyzenhouse)

18 December 2023

For the past several years Claire Staples and I have counted crows for the Pittsburgh Christmas Bird Count (CBC). In a good year we count 20,000. In a bad year, 220. Stunning, isn’t it. The difference is not in the actual number of crows. It’s whether we can find them.

Please help. Let me know where you see crows overnight or after sunset, especially next week (after Christmas)!

You would think that 20,000 crows would be hard to miss but in late December they get tricky. Just before the CBC the crows change their roost several times or they split the roost and, suddenly, we can’t find half of them.

Several of you responded to Why Do 1000’s of Crows Roost in Town? with dates and locations. Your reports helped me figure out the crows moved on 11 December.

  • Dec 10: Up until Dec 11 Tom saw them roosting near the VA Hospital in Oakland.
  • Dec 11: Jeff Cieslak saw 1000s flying over the North Side parallel to Allegheny River, heading upstream.
  • Dec 12: I counted 4,000 flying west-southwest over Schenley Park’s golf course at dusk. Where were they going?
  • Dec 13: Sue Faust reported them hanging out on the North Side and flying over the Strip District at dusk.
  • Dec 16: Carol Steytler counted as many as 10,000 roosting upstream of the 16th Street Bridge across from Heinz Lofts (across the river?).
Twilight over the Allegheny River at Pittsburgh. Crows swirl near Heinz chimneys, 6 Feb 2021, 5:50pm, taken at 25th St (photo by Kate St. John)

Carol’s 16 December sighting matches a roost they used back in February 2021 (photo above) but they didn’t stay there long and I fear they won’t stay now. And this is only half of them.

Where will the crows be 12 days from now?

I know I’m going to miss their next move because I’ll be out of town December 21-28. Your help is really crucial. Please let me know where you see crows overnight or after sunset. Let me know where you see a big flock swirling. Claire & I also need to find a good vantage point for counting them.

Fingers crossed that we’ll successfully count the crows on Saturday 30 December.

Goshawks With Orange Eyes

Birds of Prey
Eurasian goshawk compared to American goshawks (images from Wikimedia Commons)

17 December 2023

In case you missed it, the “northern goshawk” disappeared last summer. After only 66 years as a single species, the American Ornithological Union (AOU) split the northern goshawk back into its former status as two: the Eurasian goshawk (Accipiter gentilis) and the American goshawk (Accipiter atricapillus).

They basically look alike. The split was based on DNA and vocal evidence but you won’t note these things in the field and you won’t need to. The ranges do not overlap. This is the classic case of “Where did you see the bird?” In North America? Then “American.” In Eurasia? Then “Eurasian.”

Ranges of American goshawk versus Eurasian goshawk (maps from Wikimedia Commons)

Because I had seen a goshawk in Helsinki, Finland on 6 July 2017, I gained an additional Life Bird by the split. (See my lousy photos taken through binoculars below.)

At the time I marveled that this bird had orange-ish eyes. North American juveniles have yellow eyes (see illustration above) while adults have red eyes. Did the orange eyes mean this Helsinki bird was immature? A Finnish bird guide told me “No. In Finland the adults have orange-colored eyes, not red.”

Eurasian goshawk in Helsinki, Finland, 6 July 2017 (photo by Kate St. John)
Eurasian goshawk in Helsinki, Finland, 6 July 2017 (photo by Kate St. John)

The eye color difference is noted in Wikipedia and Birds of the World as well.

Eurasian goshawk:

 In Europe and Asia, juveniles have pale-yellow eyes [until 3 or 4 years of age] while adults typically develop orange-colored eyes, though some may have only brighter yellow or occasionally ochre or brownish eye color.

— Wikipedia: Eurasian goshawk

American goshawk:

Typical adult American goshawk (A. atricapillus) shows strong supercilium, red eyes, black head, and blue-gray back.

— Wikipedia: American goshawk

Since their eye color changes slowly, perhaps more slowly than their plumage, it may be unreliable to use the color as a diagnostic difference between the two species. However, as a North American birder familiar with goshawks, those orange eyes in Finland made a difference for me.

Merlin at Schenley Park

Birds of Prey, Weather & Sky
Merlin at Schenley Park, 12 Dec 2023 (photo by Charity Kheshgi)

16 December 2023

Nearly every winter since the late 1990’s when Bill Hintze(*) first reported them, you can usually find a merlin or two at Schenley Park golf course at dusk. Charity Kheshgi and I went looking on 12 December and right on time a large merlin, probably female, arrived 20 minutes before sunset.

The temperature was relatively warm but it was very windy and felt quite cold. The merlin didn’t care. As the sun set she flew to the top of a pine tree across the road. (She’s in this photo as a dot.)

Sunset at Schenley Park’s golf course, 12 Dec 2023 (photo by Kate St. John)

Charity photographed her as a silhouette.

Merlin in Schenley Park after sunset, 12 Dec 2023

Interestingly she didn’t roost at the golf course. When it got darker she flew away to the south-southeast.

If you’d like to see a merlin, stop by the golf course about 40 minutes before sunset and walk around looking at the treetops. Parking is available at the First Tee parking lot.

(*) Bill Hintze and the merlins: I think Bill was the one who first found the merlins but I might be misremembering. If I’m wrong please leave a comment so I can correct the text.

Reindeer Cyclone

Mammals
Herd of reindeer, Ljungris, Sweden (photo from Wikimedia Commons)

15 December 2023

Reindeer, also known as caribou (Rangifer tarandus), have been hunted by humans for thousands of years. An individual reindeer is vulnerable but the herd has a defense mechanism that protects them from humans, polar bears, grizzlies, wolves and other predators. It’s called a reindeer cyclone.

For another view, see this video excerpt from PBS Nature’s program about Vikings that shows reindeer making a cyclone to evade a hunter and it works.

Wildlife in the Borderlands

Birds of Prey, Mammals, Water and Shore
Ringtail resting on a rock, Phoenix, AZ (photo from Wikimedia Commons)

14 December 2023

Watering holes are places of abundant wildlife in Arizona’s Sonoran desert as captured on this trail cam in the borderlands. One of the night visitors is a ringtail (Bassariscus astutus), a member of the raccoon family, shown above. (There are two embedded videos below; please wait for them to refresh.)

When water crosses political boundaries animals cross, too, back and forth from Arizona to Mexico. But now the Border Wall makes most of that impossible.

This vintage article explains.

The Triple Fence

UPDATE on 15 Dec: Here’s the Border Wall.

Acorns Are Complicated

Nuts, Trees
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.)

Global oak phylogeny (diagram from New Phytologist, Wiley Library)

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)

Getting Ready for More Landslides

Climate Change
Landslide by the Bridle Trail in Schenley Park, July 2019 (photo by Kate St. John)

12 December 2023

Spring is landslide season in Pittsburgh. Winter is a good time to get ready for it and there’s no time like the present. With climate change increasing Pittsburgh’s rainfall and downpours, our dissolve-in-water bedrock is getting wet faster.

This morning the Pittsburgh Post-Gazette reported that, thanks to a $10 million federal grant, the City of Pittsburgh is about to begin two landslide mitigation projects along city streets on Mount Washington and is putting a third one out to bid.

Thankfully there is money, though not a lot of it, for municipalities to prevent landslides on our roads, but if you live above a landslide and you own the land that slid you’re out of luck. The slide eventually takes your house with it.

video embedded from KDKA, April 2022

Pittsburgh is especially prone to landslides because of our geology.

Two natural conditions occurring in western Pennsylvania are most responsible for landslide problems throughout the area. First, in many places the bedrock consists mainly of shales and claystones. The primary culprit is a thick, 40- to 60-foot rock layer called the Pittsburgh red beds.

[Red bed]rock rapidly falls apart in water and tends to lose strength with each seasonal freeze-thaw and wet-dry cycle. Water that collects in the rock has little chance to drain and subsequently helps make the slope unstable from the inside out.

The second naturally occurring condition responsible for landslides is western Pennsylvania’s landscape, which is dominated by steep hills and valleys.

[Hillside] soils normally are stiff but very prone to downhill movement. This movement normally is imperceptibly slow. During the spring, however, the soil often becomes very wet from thawing snow and spring rains and the creeping can accelerate into a full-blown landslide.

— Pittsburgh Geological Society: Landsliding in Western Pennsylvania

It is easy to find red bed outcrops on our hillsides. Here’s one in Schenley Park where there used to be topsoil but the red bed, formerly beneath the surface, eroded and left this tree on stilts.

Pittsburgh redbed rock eroded away from tree roots, Schenley Park (photo by Kate St. John, 2020)

A closer look at the red bed rock shows that it broke into tiny pieces — little crumbles — when it got wet. My foot is in the photo for scale.

Pittsburgh redbed rock crumbles into tiny pieces when wet (photo by Kate St. John, my boot shown for scale)

The location of these photos is marked on a Google topo map of Schenley Park below. Notice how steep the hillside is where the red bed is exposed. Uh oh!

Schenley Park topo map with arrow pointing to location of redbed photos (map screenshot from Google Maps)

Because of the prevalence of Pittsburgh red bed rock there are landslide problems throughout Allegheny County. Click here or on the map image below to see the details. Keep in mind that the colors red and orange are bad. The only safe color is yellow.

screenshot of Allegheny County from the Allegheny County Landslide Portal

And just for emphasis, check out this video of a house that slide down the hill in 2019.

video embedded from WTAE Pittsburgh on YouTube, 22 Feb 2019

Starfish Have No Arms

Fish, Frogs
Common starfish (photo from Wikimedia Commons)

11 December 2023

When you look at a starfish it is obvious that its body is arranged like the five spokes of a wheel. This is also true of its fellow enchinoderms sea urchins and sand dollars.

Sea urchin endoskeleton (photo from Wikimedia Commons)
Sand dollar (photo by Kate St. John)

As larvae starfish are bilateral just like us, but when they grow up they change.

Most animals, including humans, have a distinct head end and tail end, with a line of symmetry running down the middle of their body dividing it into two mirror-image halves. Animals with this two-sided symmetry are called bilaterians.

Echinoderms, on the other hand, have five lines of symmetry radiating from a central point and no physically obvious head or tail. Yet they are closely related to animals like us and evolved from a bilaterian ancestor. Even their larvae are bilaterally symmetrical, later radically reorganizing their bodies as they metamorphose into adults.

— NewScientist: Starfish don’t have a body – they’re just a big squished head

Scientists were curious about how the animal formed five arms so they examined the genes on the body surface of the bat star (Patiria miniata) …

Patiria miniata (photo from Wikimedia Commons)

… and were surprised to find that the the entire animal, from center to tips of the arms, expresses as “head” genes. There are no torso or limb genes. As Science Magazine put it, “Genetically speaking, starfish have no arms — only a head.“

The findings show that “the body of an echinoderm, at least in terms of the external body surface, is essentially a head walking about the seafloor on its lips”, says Thurston Lacalli at the University of Victoria in Canada.

— NewScientist: Starfish don’t have a body – they’re just a big squished head
Starfish – sea star – mosaic showing diversity of the class Asteroidea (photo from Wikimedia)

Read more in NewScientist: Starfish don’t have a body – they’re just a big squished head

Why Do 1000’s of Crows Roost in Town?

Bird Behavior, Crows & Ravens
Three American crows (photo from Wikimedia Commons)

10 December 2023

When 20,000 crows come to Pittsburgh for the winter, they have to sleep somewhere and they inevitably make a mess. Why do they roost near us where the mess will get on our nerves? Why don’t they sleep in the woods? Let’s take a look the reasons crows choose one location over another when it’s time to sleep.

Crows have a few simple requirements for a roost and they all have to come together at the same place. Safety is a big one. Crows want:

  1. Tall trees for roosting
  2. Warmth when it’s cold
  3. No great horned owls!
  4. Safety in numbers
  5. Night lights. Lots of them.
  6. White noise at the roost
  7. No harassment from humans

1. Tall trees for roosting: Crows prefer to roost at the very top of mature trees. They perch on the highest twigs that support their weight.

Crows coming to the roost, Pittsburgh, 2017 (photo by Sharon Leadbitter)

2. Warmth when it’s cold: When the weather is well below freezing trees are too exposed for a good night’s sleep so crows may choose rooftops instead. Cities are warmer than the surrounding countryside due to the urban heat island effect.

Crows on the roof (photo courtesy Crows’ Call at University of Washington, Bothnell)

3. No great horned owls! Crows are terrified of great horned owls who can hunt them in the dark. They prefer places that great horned owls avoid.

Great horned owl (photo by Alan Wolf via Flickr, CC license)

4. Safety in numbers: Crows sleep in a crowd so that someone’s always awake to watch for owls. It also lowers the odds of an individual being eaten.

Crows asleep near Heinz Chapel by the light of the Supermoon, Dec 2017 (photo by Kate St. John)

5. Night lights. Lots of them: Crows like to sleep with the lights on. It’s easier to watch for owls when you can see them coming. There are no nightlights in the woods.

Crows in a tree on Thackeray Ave, Pittsburgh, 2011 (photo by Peter Bell)

6. White noise at the roost: In addition to night lights, crows want white noise at the roost(*), the sound of running water or traffic. This location along Fifth Avenue at the University of Pittsburgh combines all their requirements in one place. Except that the mess bothers humans.

Crows roosting along Fifth Avenue in the trees at Pitt, Dec 2017 (photo by Kate St. John)

7. No harassment from humans: The perfect roost is usually near humans but crows make an enormous mess that people have to clean up. When the crows wear out their welcome, people figure out ways to get them to leave. This includes loud abrupt noises such as clappers and bangers, flashing lights, and harassment by falconers’ birds.

Clappers used to disperse crows (photo courtesy Alex Toner, Univ of Pittsburgh)
screenshot from video Falconry moves the crows in Portland, OR

Now that we know what crows want at a roost we can figure out where they’re likely to be. Convincing them to leave is much easier to do before they land. 😉

(*) p.s. Why do crows want white noise when they sleep? No one has explained it but I have a theory that great horned owls avoid white noise. Owls need to hear their prey when they’re hunting and white noise makes that impossible.