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.
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.
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.
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:
Tall trees for roosting
Warmth when it’s cold
No great horned owls!
Safety in numbers
Night lights. Lots of them.
White noise at the roost
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.
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.
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.
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.
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.
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.
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.
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.
Visit one (or more) of the >2,500 count circles in North America. Each circle has its own compiler who coordinates the count for a single scheduled day within the 15-mile radius. No experience is necessary. The only prerequisite is that you must contact the circle compiler in advance to reserve your place.
Go birding outdoors or, if you live in a Count Circle, stay home and count birds at your feeder. Click here and enter your home address to find out what circle you’re in. (If you’re within a circle, click on the colored bird icon to see date, time and contact information.)
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.
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.
On the tree, horse chestnut husks are spiny.
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.
In winter horse chestnuts are easy to identify by their large, sticky end buds.
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 …
… while Ohio buckeye husks are slightly spiny. The narrow leaves also indicate a native buckeye. (Yes, the leaves looked sick that year.)
Their flowers are pale yellow (not white) and narrower than the horse chestnut’s. (*)
Yellow buckeye buds are large but not sticky. They’re one of the first to leaf out in the spring.
Back in early September I urged us all to start paying attention and Be Careful Out There! Deer in the Road. Deer were restless in the run-up to the rut and had started to move around. From late October through November they mindlessly crossed in front of traffic, but now in early December the bulk of the rut is over and soon (if not already) there are fewer deer in the road. We can almost relax our vigilance because …
Chasing each other: During the rut — October and November — bucks roam in search of mates and chase does on the move. Driven by hormones, all of them ignore vehicles in the heat of sexual pursuit.
Not running from hunters: Some people say that deer run into traffic to get away from hunters but studies have shown that the animals use a completely different strategy.
Since 2013 Penn State’s Deer-Forest Study has tagged and tracked more than 1,200 white-tailed deer around 100 square miles of Pennsylvania forest. In the process they’ve learned that successful deer, the ones that survive hunting seasons, actually know when hunting is about to start and search for a good hiding place in advance. Then each day before dawn (hunters cannot hunt until after dawn) deer go to their hiding places and wait quietly until the afternoon when the hunters have left the woods.
One tracked doe’s hiding spot was incredibly hard for people to reach and impossible to sneak up on. Read about a family’s visit to Hillside Doe’s Hiding Spot.
Watch Hillside Doe’s movements during hunting season. She didn’t have to cross roads to get there.
Lots of animals don’t sleep for long periods like we do but a new study has found a polar opposite in Antarctica (pun intended) where chinstrap penguins (Pygoscelis antarcticus) take 10,000 4-second naps each day during the breeding season. In this way they accrue 11 hours of daily sleep.
For us, the micronaps would be a form of sleep torture since we cannot enter restorative deep sleep in such a short time. But the chinstrap penguins do.
Peregrines are the fastest animal on earth when they dive at 200 mph to catch their prey in flight. In fact they dive even faster when they’re hunting an evasive bird. The higher speed increases turning force so they’re more accurate at catching prey.
In 2005 Ken Franklin went sky diving with a peregrine to clock its maximum freefall speed at 242 mph (389 km/hr). In 2018 scientists wanted to study the details of the peregrines’ dive, but it was too hard to do in real time, so they created 3D simulations of a stooping peregrine pursuing a European starling.
The simulations showed that optimal speed for catching a bird in straight flight is 93 mph but if the prey is zig-zagging in the sky the best speed is 225 mph.
You’d think that the higher attack speeds would make it more difficult for falcons to adjust to a moving target. But the opposite turned out to be true: The predators were more maneuverable at higher speeds because they could generate more turning force; only then were they able to outmaneuver the highly agile starlings. So stoops don’t just help falcons quickly overtake prey—they also help the predators change directions.