Monthly Archives: August 2015

Bees Can’t See Red

Honey bee at camas (photo from Wikimedia Commons)
Honey bee at camas flower (photo from Wikimedia Commons)

When I wrote about hummingbirds and orange jewelweed last week, some of you wondered if the birds sipped at pale (yellow) jewelweed, too.  While finding the answer I learned a cool fact:  Bees can’t see red.

Hummingbirds are attracted to shades of red so they see the spots on orange jewelweed (Impatiens capensis) as a delicious target and rely on this plant during fall migration.

Over time the spur on Impatiens capensis has evolved to maximize pollination by hummingbirds with a tight cone-shaped entrance that guides the birds’ bills.

Spotted jewelweed, Impatiens capensis (photo from Flora Pittsburghensis)
Orange jewelweed, Impatiens capensis (photo from Flora Pittsburghensis)

Hummingbirds don’t care about yellow so they don’t choose the other jewelweed — the “pale” one — but bees do.

Bees see yellow, purple, blue, and a color called bee’s purple, a mixture of yellow and ultraviolet which we humans can’t see.  Bees can’t see red so they aren’t much attracted to orange jewelweed.

However, pale jewelweed (Impatiens pallida) is designed for bees.  Not only is it yellow but its expandable entrance accommodates both large and small bees, brushing their bodies as they walk in.

Pale jewelweed, Impatiens pallida (photo from Flora Pittsburghensis)
Pale jewelweed, Impatiens pallida, with a bee inside (photo from Flora Pittsburghensis)

Though the two jewelweeds grow near each other, they send different signals.  Red is for birds.  Yellow is for bees.


(Honey bee photo from Wikimedia Commons. Orange and pale jewelweed photos by Flora Pittsburghensis.  Click on the images to see the originals)

p.s. On the subject of bees (in general) here’s a recent article from The Allegheny Front about breeding stronger honey bees:  Building a Better Honeybee

Showy Food For Birds

American spikenard fruit at Schenley Park, August 2015 (photo by Kate St. John)
American spikenard fruit at Schenley Park, 20 August 2015 (photo by Kate St. John)

Here’s a native perennial that produces lots of fruit for migrating birds.

American spikenard (Aralia racemosa) is a showy plant that grows three to five feet tall and wide.  It blooms in airy greenish-white spikes from June to August and ripens its fruit in August and September, just in time for migrating birds. Click here to see it in bloom.

American spikenard, Schenley Park, August 2015 (photo by Kate St. John)
American spikenard, Schenley Park, 20 August 2015 (photo by Kate St. John)

In my opinion, the plant was misnamed. People must have hoped it was similar to the real spikenard, Nardostachys jatamansi, a Himalayan plant in the Valerian family whose root is made into fragrant essential oil (called nard), but American spikenard is not at all like it and isn’t even in the same family. The American plant isn’t valuable to humans; it cannot make perfume.

But Aralia racemosa is valuable to birds. It’s a low maintenance plant that likes full sun or partial shade and spreads slowly by seeds and rhizomes.  In August it offers showy fruit for birds.

Click here for more information at the Missouri Botanical Garden.



(photos by Kate St. John)

Bees Can Monitor Air Pollution

Honeybee at a flower (photo in the public domain vai Wikimedia Commons)
Honeybee at a flower (photo in the public domain vai Wikimedia Commons)

We all know that pollen sticks to bees but did you know that air pollution particles stick, too?  A recent study shows that honey bees can be excellent monitors of local air quality.

Bees have so much static electricity on their bodies that airborne particles stick to their heads, wings and legs as they fly. This includes airborne pollen, salt spray from the sea, soil dust, and industrial pollution.  If you identify the particles, you can identify the pollution source and that’s important if you need to clean it up.

In the study, scientists from the Natural History Museum in London placed eleven beehives near Iglesias, Sardinia, a location known for its legacy pollution of exposed tailings piles from lead-zinc mines in the 19th century.  There are also industries five miles away at the coast: an aluminum smelter, a lead-zinc smelter, and coal-fired and oil-fired power plants.  At a site like this how can you know where the particules comes from?

Scientists captured 10 honey bees at a control site in rural Italy and 20 bees at the Sardinian site, then analyzed the particulate found on their bodies.  The control bees carried natural particles including dust from the local soil.  The Sardinian bees carried sea salt (good) as well as industrial pollution and dust from the lead-zinc mine tailings (bad).

Thanks to the honey bees, the people of Iglesias know more about their air quality.  Honey bees could monitor our quality, too.

Read more here at The Telegraph or the original paper here at PLOS ONE.


(photo from Wikimedia Commons. Click on the image to see the original)

How Fast Do Antlers Grow?

Bull elk with large velvet antlers, late July (photo by Paul Staniszewski)
Bull elk with large antlers in velvet, 22 July 2015 (photo by Paul Staniszewski)

When you see elk antlers and realize they’re shed and regrown every year, it makes you wonder, “How fast do these antlers grow?”

Antlers are a key component of the elk’s (Cervus canadensis) reproductive cycle.  Only males have them and they use them to fight over mating rights.  Sometimes a bull’s body and antler size are enough to intimidate a smaller male but if no one backs down they fight head to head — and can be seriously injured in the contest.

Bulls shed their antlers in early winter so every male starts with a bare head in the spring and grows a complete set by mid August when the rut begins.

Here’s a typical bull on May 30 with short antlers in thick velvet, photographed by Paul Staniszewski in Elk County, Pennsylvania.  The velvet is a soft layer of highly vascularised skin that protects the growing bone.

Bull elk with velvet antlers, 30 May (photo by Paul Staniszewski)
Bull elk with growing antlers, 30 May 2015 (photo by Paul Staniszewski)

Only 53 days later, on July 22, the antlers are still in velvet but nearly done growing as shown at the top of this article.

Just before the rut begins the antlers stop growing and the males rub off the velvet against shrubs and trees to shed the dead skin.  Below, a bull has shed all his velvet except for a bit hanging from the tip.

Velvet is nearly gone, 22 August 2015 (photo by Paul Staniszewski)
His antler velvet is nearly gone as this bull elk reaches to eat a pear, 22 August 2015 (photo by Paul Staniszewski)

When complete the rack weighs 25 to 40 pounds and can be 3.9 feet long with a span 5 feet wide.  To reach this size the bone grows nearly an inch a day!

And now, in mid-August, the rut begins.

Bull elk sparring (photo by Paul Staniszewski)
Two bull elk sparring (photo by Paul Staniszewski)

If you’d like to see elk sparring visit Elk County, PA from mid-August to October.  Learn more here at the Elk Country Visitors’ Center website.


(photos by Paul Staniszewski)

On Time For Jewelweed

Ruby-throated hummingbird in Schenley Park, August 2015 (photo by Soji Yamakawa)
Ruby-throated hummingbird in Schenley Park, August 2015 (photo by Soji Yamakawa)
Click on this photo to see a slideshow.

Though many people have hummingbird feeders they aren’t enough to support the birds on migration.  What do ruby-throated hummingbirds eat on their way south?

A study by R.I. Bertin in 1982 found that their primary food source is orange jewelweed (Impatiens capensis) shown in the photo above.  Birds of North America online says:

“Overland migration in North America is nearly synchronous with peak flowering of jewelweed (Impatiens capensis), suggesting this flower is an important nectar source during this time and may influence the timing of migration.”

This month orange jewelweed is thriving by the creek and wetland in Schenley Park.  That’s where I found Soji Yamakawa with his camera last week, spending many hours photographing hummingbirds before his work resumes at Carnegie-Mellon’s Mechanical Engineering Department this fall.   Click on the photo above to see a slideshow of his favorite shots.

Soji and I chatted about the birds and noted there were no adult males in the group. Most adult males have left our area by the second week of August but look closely at the throats of these birds and you’ll see faint stippling or a small patch of red feathers.  They’re immature males, just hatched this spring.

If you want to see hummingbirds in the wild this month, stake out a patch of orange jewelweed and watch for movement among the flowers.  You’ll get a bonus, too.  Rose-breasted grosbeaks forage among the stems, eating the jewelweed seeds.


p.s.  That white patch just above the hummingbird’s bill is jewelweed pollen.

(photos by Soji Yamakawa)

The Tuliptrees Respond

Tuliptree responds to anthracnose by growing new leaves, August 2015 (photo by Kate St. John)
Tuliptree responds to anthracnose by growing new leaves, August 2015 (photo by Kate St. John)

In June’s wet weather, Pittsburgh’s tuliptrees were attacked by anthracnose, a fungus that turned most of their leaves brown.  Click here to see.

July and August were very dry so the fungus died.

The tuliptrees responded.  They’ve grown new leaves!  It doesn’t matter that August is so close to autumn.  They need leaves to make food.

Photosynthesis is restored.


p.s.  The first time I saw trees grow new leaves in the fall was after Hurricane Bob stripped the leaves from the trees on Cape Cod on August 19, 1991.  It was very odd to see spring-like trees on the Cape in early October.

(photo by Kate St. John)

Confused About The Season

Crabapple tree blooming in Frick park in August (photo by Kate St. John)
Ornamental tree in bloom at Frick Park, 16 August 2015 (photo by Kate St. John)

Last Sunday I found several ornamental trees blooming at Frick Park near the Blue Slide playground.

The branches held both flowers and green, unripe fruits.

I don’t know why they’re blooming.

Have you seen trees this month that are confused about the season?


(photos by Kate St. John)