When you’re vulnerable to predators it pays to stick together and have a good lookout to warn you of danger.
The dusky-throated antshrike (Thamnomanes ardesiacus) doesn’t look important but he’s quick to notice the presence of hawks and falcons and has a distinctive alarm call that wakes up the forest to impending danger. It turns out that he’s key to the foraging location and cohesion of his mixed species flocks in the Amazon.
Early this year, a study by San Francisco State University temporarily removed dusky-throated antshrikes from their mixed species flocks in Peru. They discovered that within hours the flocks left their semi-open mid-story locations for denser parts of the forest. Often the flocks without an antshrike completely dissolved.
What does the alarm call sound like? Is it loud? Does it grab your attention? You bet! Here’s the sound of a worried dusky-throated antshrike:
His role in the flock works so well that the same mix of species sticks together for generations. As San Francisco State Professor Vance Vredenburg remarked, “You come back to the same habitat after 20 years, and the same flocks are using the same areas of the forest.”
While you’re out running errands here’s something to do while you wait for the stoplight to change …
Are there birds on a wire near you? What are they doing?
Are they all facing the same way?
Birds face the wind when they’re perched so the air doesn’t ruffle their feathers and make them uncomfortable and cold. They also land and take off facing the wind so they actually arrived in that direction.
The direction the birds are pointing tells you the direction wind is blowing … except …
if the birds are not facing the same way, the breeze is very light or the air is calm.
(photo from Wikimedia Commons; click on the caption to see the original)
Barn swallows (Hirundo rustica) are found on every continent except Antarctica, breeding in the northern hemisphere and wintering in the southern hemisphere with one notable exception: a small population breeds in Argentina.
This behavior was unknown until 1980 when scientists confirmed that northern-born barn swallows had decided to nest during South America’s spring. They’ve even shortened their return migration, traveling only as far as the equator during South America’s winter.
Scientists speculate that the birds are breeding in Argentina because we changed the landscape to their liking. 99% of barn swallows prefer to nest on man-made structures including farm buildings, bridges and boathouses. They found what they like near Buenos Aires.
Because these swallows have flipped their north-south patterns a Cornell University study reports that this could be the first step toward a new species, similar to terns and skuas that have distinct northern and southern species (example: great skua and south polar skua). For now, though, the Argentinian barn swallows still recruit northern-born swallows to join them.
While we’re cold up here in North America, some barn swallows are starting families in November.
In a study conducted in Italy, researchers released racing pigeons fitted with GPS backpacks from sites 20 to 80km from home (12.5 to 50 miles). In over 200 flights, the data showed that experienced pigeons preferred to follow roads and rail lines in the early and middle parts of their trips. As they got close to home they left the road grid and made a beeline for the loft.
On the first trip from each site pigeons didn’t use the grid, but the more they made the same trip the more they used big roads.
Why do they do this? Scientists suspect that easier navigation above major roads makes up for taking slightly longer routes. The birds don’t have to think about where they’re going and can focus on flying fast and watching for predators.
That’s why I take expressways in my home town, even when they’re clogged at rush hour. I know the back roads but I’d rather not think about navigating.
Here’s a bird you’re bound to see this month in southwestern Pennsylvania. Brown creepers live year round north and east of Pittsburgh but only come here in the winter. I saw one last week in Greenfield.
The brown creeper (Certhia americana) is a tiny brown bird with a long tail and down-curved bill. He eats insects and spiders which he gleans from the bark of large tree trunks, spiraling upward and checking under the bark as he goes.
When he sits still he’s hard to see. His colors match the bark.
The video below shows him spiraling upward, clinging to the bark with his large feet splayed. Sometimes he hitches sideways to grab a tidbit. When he reaches the top, he will drop like a leaf to the base of another tree trunk and start again.
If you can identify birds by ear, here’s a challenge for you. List the species singing in the video. I identified five species but I’m unable hear brown creepers anymore. Is the brown creeper singing?
p.s. At backyard feeders, brown creepers don’t eat seeds but they’ll come to suet feeders.
(photos from Wikimedia Commons, click on the captions to see the originals. video by Abnerthewonderdog on YouTube)
Have you ever noticed how many birds turn over fallen leaves to find food? Towhees and sparrows, robins and wrens pick through the leaf litter to find overwintering insects. This food bank of edible insects is one reason why not to clear your garden in the fall.
Did you know…? The red-banded hairstreak (Calycopis cecrops) lays its eggs on fallen oak leaves.
Woolly bear caterpillars burrow into leaf cover to survive the winter.
And the moth version of this brown-headed owlet (Cucullia convexipennis) hides in leaf litter during the day to survive November temperatures. Moths in this family, Noctuidae, are the ones who pollinate witch hazel.
So Leave The Leaves alone. Clear them from the storm drains, sidewalk and driveway, but not off your garden!
In the winter huge flocks of starlings line up on the electric wires. They even perch on un-insulated wires like those shown above. Why don’t they get electrocuted?
Here’s some helpful background: Electricity is the flow of electrons in a complete circle — called a “circuit” — that moves out from the power source, into our appliances, and all the way back to the power station. The electrons flow in the path of least resistance.
In September, Dan Dasynich saw a flightless common merganser at Duck Hollow and posted this photo of her stubby wing in the Duck Hollow Facebook group. Her condition prompted a discussion: Since she couldn’t fly did she need to be rescued?
Common mergansers eat fish that they capture by chasing them underwater. They don’t need to fly in order to eat and they don’t need to fly if they can swim to safety.
In September I remarked that this bird has been at Duck Hollow for at least a year, eating well and staying safe, so she didn’t need to be rescued. Today I found proof that she’s been here for seven years, maybe more.
In a blog post from October 2011, I used Tom Moeller’s photo of her with a hooded merganser and pied-billed grebe.
That was seven years ago when she was relatively new to Duck Hollow. Though she can’t fly she’s done well for a very long time.