This unusual advice about pruning was given at a seminar called Preserving Pittsburgh’s Trees on February 17 where we learned about the threats facing Pittsburgh’s urban forest and what we can do about them.
The threats are huge. All of our ash trees will die of emerald ash borer in the next decade (15% of Pittsburgh’s trees). Our new seedlings can’t grow because of deer overbrowsing (in the city!). And oak wilt may kill many oaks, as it did in Frick and Highland Parks last summer.
Oak wilt disease is serious stuff! It’s caused by a fungus to which the red oak group is particularly susceptible. The fungus spreads rapidly underground because the roots of oaks growing near each other touch and graft, allowing an exchange of nutrients. The disease travels from tree to tree through these grafts and can kill an entire stand in 30 days!
Leaves like this — green turning brown — are the only warning you get that a tree is ill. By the time you see this there is no cure and the only way to stop the disease from spreading is to trench a perimeter (cut the roots) 50 feet around the affected stand, then chop down the oaks and remove the stumps where they once stood. This drastic measure had to be applied to two places in our parks last summer. [Note: This leaf coloration can be caused by several diseases so call an arborist to diagnose the problem before you start to solve this on your own.]
So what does pruning have to do with oak wilt?
The disease is not spread easily by insects but that’s the only way it can travel above ground. The fungus can only enter the trees’ bark at a wound running with sap. In late spring and during the summer there are sap-loving beetles, nicknamed picnic beetles, who travel from tree to tree licking sap. If a beetle gets the fungus on its feet it will spread the disease as it visits other trees.
Pruning inevitably creates sap-running wounds. If you prune your oaks while the beetles are active, they may lick the sap on a diseased oak and accidentally infect your oaks with the fungus.
So don’t prune your oaks from late April through the summer.
Read more about oak wilt in this brochure by Iowa State University where I found this photo.
(photo from Iowa State University Plant Disease Clinic. Click on the photo to see the original in context.)
Courtship is well underway among Pittsburgh’s resident birds.
On sunny days red-tailed hawks seem to be everywhere, soaring to claim territory and court their mates. Sometimes you can’t tell the difference between courtship and chasing. Is he driving away an intruder or impressing his mate? And, my heavens, his scream sounds scary! (Read more about red-tail courtship here.)
Because I love watching peregrines and hawks, I often pay attention to their favorite food: pigeons. That’s how I noticed that rock pigeons make courtship flights, too.
Most of pigeon courtship occurs on the ground but there are two flight behaviors that tell you they’re courting.
The first is wing clapping in which a pigeon takes off from the flock making a loud snapping sound as he claps his wings together at the top of his upstroke. This behavior is usually initiated by a male to advertise his sexual maturity. His action often prompts other members of the flock to take off and clap their wings as well.
The other display occurs when a pair breaks off from the flock in flight. Eventually one or both will soar with their wings held upright in a stiff V.
I’ve sometimes seen a trio break away and fly together but only two of them do the V flight. I’ll bet these trios are one female with two males and the guys are trying to impress her. It certainly looks less dangerous than what red-tails do!
(photo from Shutterstock)
We had great fun at Celebrate Pittsburgh’s Peregrines at WQED on Monday night. Here are some pictures from the event.
To put them in context for those who could not attend, I did most of the talking but my visuals were slides and a video (of a peregrine stooping!) both of which look pretty boring in photographs.
The real paparazzi star was Horace the lanner falcon from the National Aviary, pictured here on Cathy Schlott’s glove. Lanner falcons are slightly smaller and paler than peregrines. He showed us what a live falcon looks like.
Horace is one of the birds Cathy is training for the National Aviary’s new outdoor flight show called Sky Deck which will open on Memorial Day weekend. She chose lanner falcons for the show instead of peregrines because lanners maneuver closer to the ground than peregrines and will be easier for the audience to see. I can hardly wait to see him fly this summer!
And here are some pictures of my lecture showing me, the size of the crowd, and part of my presentation.
I talked about the history of Pittsburgh’s peregrines, their lifestyle during the nesting season, and our favorite webcam stars: Dorothy and E2 at Pitt’s Cathedral of Learning, and Louie and Dori at the Gulf Tower.
Thanks to everyone who attended and especially to the National Aviary for introducing us to Horace.
It was really fun. Let’s do this again some time!
(Photos of Horace and me by Sharon Leadbitter. Photos of the lecture by Kristine Masta and Amanda Morgan).
Providing food for his lady is an important part of male peregrine courtship.
At least six weeks before his mate lays eggs, the male begins to bring her food. At first he may seem reluctant to hand it over or she may snatch it by force, but as egg-laying time approaches she stops hunting on her own, he supplies all her needs, and they add ritual to the food exchange.
One ritual that many male peregrines engage in, and that E2 insists on doing for Dorothy, is an exaggerated plucking display.
When E2 brings food back to the Cathedral of Learning he won’t give it to Dorothy right away, even if she flies out to meet him. He makes her wait until it’s properly prepared.
He takes the prey to a cache area, removes the head and wings and makes an elaborate show of plucking it. The feathers fly! And he probably takes a few bites to sustain himself while he’s at it.
When he’s done, he presents the food to Dorothy with a bow. In the photo above from last Friday, she is bowing in return.
The photo makes me chuckle because E2 and Dorothy are breaking the assumptions people make about peregrine behavior. Ten years ago when I began watching nesting peregrines at Pitt I learned that “The male peregrine will not bring food to the nest until the eggs hatch. When you see him bring food to the nest you’ll be able to estimate the hatch date.”
E2 doesn’t care about those rules. There are no eggs yet, but he’s got a job to do and he likes to present the food at the nest.
“For you, my dear,” he says.
(photo from the National Aviary webcam at the University of Pittsburgh’s Cathedral of Learning)
A big thank you to everyone who attended last night’s event, Celebrate Pittsburgh’s Peregrines, and especially to Steve Sarro, Cathy Schlott, and Horace, the lanner falcon, from the National Aviary.
I had a great time and enjoyed catching up with old friends and meeting so many of you who read this blog.
I’ll post more pictures from the event as I have time to prepare them. Here’s one from Sharon Leadbitter.
Again, thank you. It was great fun!
(photo by Sharon Leadbitter)
…not everything nice.
On my walk to work Tuesday morning I witnessed a territorial battle between female northern cardinals that was fierce and possibly bloody.
My attention was drawn by three cardinals chasing, chipping and wing flashing in a thicket. Two females were fighting and a male was keeping up with them.
One of the females was clearly stronger than the other but the weaker one would not give up. I could see she was frightened but even as she avoided her attacker she sometimes sang the cardinal song.
Unlike most female birds, female cardinals can counter-sing with their mates. Was she singing for the territory? Was she asking the male for help? I could tell there was not much he could do.
The group chased through the thicket, then both females dropped out of sight into deep ivy. I thought the fight was over. Instead it was more intense. When they emerged from the ivy the stronger female was biting the weaker one on the neck. Ow! Ow!
By now the weaker cardinal had had enough. She broke away and flew low across Forbes Avenue in front of traffic. I watched with horror as she nearly was hit by a Port Authority bus.
But she made it. She was safe.
I felt like a limp dishrag. She nearly died! I didn’t know how much I cared about the drama until my adrenaline was gone.
Little girls may be “sugar and spice and everything nice” but that’s not what this bird is made of.
(photo by Cris Hamilton)
Back in January I posted a photo by Marcy Cunkelman in which a female cardinal stood with one wing straight up as a male cardinal flew toward her. Here’s a cropped version of that photo. (Click on the photo to see the original.)
Many of us wondered what this wing message meant. Well, I just found out.
Donald and Lillian Stokes call this behavior the “lopsided pose” in their Guide to Bird Behavior. It’s a courtship display(!) in which a male or female cardinal tilts one side of its body up, raises its wing and exposes its belly.
According to Stokes, this is usually done within sight of the mate who is only a few feet away. Sometimes they both do it together but it happens so fast we don’t normally see it.
So, despite appearances this doesn’t mean “Back off, buddy.”
She’s saying “I love you!”
(photo by Marcy Cunkelman)
This is not your average woodpecker. It’s an endangered red-cockaded woodpecker.
Though he resembles a downy or hairy woodpecker, a close inspection shows how different he is. His wings and flanks are spotted instead of striped and he has a large white cheek patch instead of a black face with an eyebrow stripe. The cheek patch is the big clue.
He’s called “red cockaded” because the males have a tiny red stripe at the black-white border behind their eyes but this stripe is not always visible — and the ladies don’t have it at all — so you can’t use it as an easy field mark.
Red-cockaded woopeckers require open stands of mature southern pine forests for their livelihood. They hammer a nest hole in longleaf pines with softened heartwood and the trees ooze resin around the opening that protects the nest with a sticky goo. This also makes the woodpecker’s nest easy for birders to see.
Much of the red-cockaded woodpecker’s habitat has been chopped down to create commercial forests, the mono-cultures of soft pine that become wood or paper. That habitat doesn’t work for this bird so if you want to find him you’ll have to visit a southern National Forest. This one was photographed by Chuck Tague in the Ocala National Forest in Florida.
(photo by Chuck Tague)
Last week I wrote about willow beaked-galls. Today it’s galls in trees.
This is a shingle oak, a member of the red oak group that grows in the Midwestern U.S. from Missouri to western Pennsylvania, from Lake Erie to central Tennessee.
Shingle oaks have laurel-like leaves whose edges are not lobed, but they are rumpled. It’s often easy to identify shingle oaks in winter because some of the leaves persist on the tree and the tree is prone to Gouty Oak Galls(*), those dark woody masses you see on the branches above.
Gouty oak galls are caused by a tiny wasp who lays its eggs on the leaves and twigs of oaks. The wasp’s eggs and larvae contain a chemical that causes the tree to grow malformed balls around the larvae. Since the wasp prefers not to travel far from its host, succeeding generations lay eggs in the same tree and thus this tree has many galls.
The galls don’t hurt the tree unless they overwhelm it, but that doesn’t usually happen. And since shingle oaks are not commonly cultivated, people don’t feel obligated to solve the gall problem — which insecticide cannot solve anyway.
As you look for migrating birds in the bare trees, take a look at the branches. You never know what you’ll find.
(photo by Dianne Machesney)
(*) p.s. If you are an oak gall expert and these are not gouty oak galls, please correct me!
Now that the birds are singing again I’m intrigued by news of birdsong.
Just this week I learned that a study found that teenage male birds sing better when the “girls” are around.
Songbirds learn their songs as they mature. They babble as babies and improve as they get older.
Scientists at University of California San Francisco decided to find out how birds learn this skill by recording teenage male zebra finches singing under a variety of social conditions.
As expected the “boys” could sing, but not very well. When alone they sounded immature. But the researchers were surprised that in the presence of a female the boys sang much better, almost like adults.
“The birds picked the best version of the song that they could possibly perform and they sang it over and over again,” said senior author Allison Doupe, MD, PhD in Science Daily.
The study found that social cues improved the birds singing skills faster than when they practiced alone. Ultimately, this finding may provide new ways to improve speech therapy for humans.
It also shows that teenagers are the same the world over. Even among birds, the boys show off for the girls.
Read more about the study here in Science Daily.
(photo of zebra finches from Wikimedia Commons. Click on the photo to see the original.)