Pigeons (Columba livia) and the raptors who hunt them have evolved together for millions of years. The raptors’ successful hunts leave only the fastest, most maneuverable pigeons. Speedy, elusive pigeons mean only the most skillful raptors can survive. Most of us never get to see this interaction so this dramatic video from Romania is a real treat.
The pigeons stay in a tight flock because raptors can’t pick out a victim in a moving ball of birds. The raptors try to separate one bird from the group by slicing through the flock. If it works, the raptor pursues the lone bird.
The study found mercury in harlequins from both locations but those at Unalaska, midway in the Aleutian chain, had eight times more than those at Kodiak, nestled in the Gulf of Alaska. The study then tested the ducks’ main food at Unalaska — blue mussels — and found it there, too.
Mercury apparently increases westward in the Aleutian chain. A 2014 study found mercury in fish above the human consumption limit at the western island of Agattu.
Where is the mercury coming from? In the continental U.S. airborne mercury comes from coal-fired power plants and is regulated and reduced by the EPA. It can also come from active volcanoes, obviously out of our control.
At this point scientists don’t know where the mercury is coming from, but China’s coal-fired industries are a good bet. The prevailing wind in the Aleutian Islands originates in Asia more than six months of the year.
Unfortunately Alaskans can’t prevent mercury pollution that reaches them from Asia. Meanwhile the harlequins warn of danger.
(photo of harlequin duck from Wikimedia Commons, screenshot of global winds from earthvisualization website; click on the caption links to see the originals)
We don’t have flowers in December but we do have ice and it comes in many forms. Here’s the first in a series on ice, starting with my favorite: Rime.
The word “rime” comes from Old English hrim which meant hoarfrost or a chill mist or fog. Nowadays hoarfrost and rime are not the same thing. Hoarfrost doesn’t form in fog. To get rime there has to be cold fog or the location has to be in the clouds. For that reason, “Rime shouts, Mountains!” It’s easy to find rime at high altitudes.
The best part about rime is that it can form in a light wind. When it does it points toward the wind because each new crystal is deposited on the windward side. This is counter-intuitive; it’s the opposite of rain.
What direction did the wind blow through this fence?
Rime can even coat snowflakes. Graupel, which looks like hail, is actually a rime-coated snowflake. I wonder if these pop when you step on them.
This month is a good time to find rime in the Laurel Highlands. My best experience with it was during an east wind at the Allegheny Front Hawk Watch. No one else was up there to enjoy it. It was way too foggy!
Crows are common in the city but ravens are rare so I was surprised to hear a raven this week in Schenley Park. It called and circled overhead waiting for its companion to arrive. “Brrrock! Brrrock!” When the second raven caught up they flew away together.
I see ravens in town about twice a year but I only hear them make the Brrrock call. If I lived where common ravens (Corvus corax) are common, I’d hear their wide variety of sounds.
This video from Anchorage, Alaska gives you an idea of the ravens’ vocal range. He starts with Brrrock. Then he gets creative.
Seven years ago when my cat alerted me to a mouse under the heat duct, I knew in my head that there’s never just one mouse. But my heart refused to listen and I said to myself, “Of course there’s only one mouse, and when I catch that one I’m done.”
Hah! Every fall I’m reminded that there are victories but in a 111 year old house you’re never done. Thankfully there are so few mice this fall that Emmalina has not noticed them. Does this mean there are none or that she’s too old to care?
We harvest the lac to make shellac and use it on …
… furniture …
… and jelly beans.
The parakeet: When I learned that rose-ringed parakeets (Psittacula krameri), above, are a nuisance in India because they devastate the pigeon pea crops I wondered … What are pigeon peas?
The food: Pigeon peas (Cajanas cajan) are a tropical legume first cultivated in India 3,500 years ago. The peas are used like lentils as a staple food in Asia, Africa and South America. I’m sure I’ve eaten pigeon peas without knowing their English name.
The plant: Cajanas cajan plants are grown for their peas (inside the bean pods) and as the host of a beneficial insect, Kerria lacca.
The insect:Scale insects lead sexually dimorphic lives. The males can fly to find females, but they don’t eat. The females are immobile, permanently attached to their host plant, sucking its sap. To protect themselves the females produce a sticky covering called lac. Kerria lacca females, shown below, use several trees as their host plants including pigeon peas.
We harvest the lac to make shellac.According to Wikipedia, we “infest” the host plants with Kerria lacca females. When the branches are well coated we cut them (sticklac), scrape, sieve and heat to remove impurities (seedlac), then use heat or solvent extraction to create shellac.
Alcohol dissolves shellac and makes it spreadable but the liquid form has a 1-year shelf life. Shellac is stored as flakes and mixed with alcohol at the time of use.
The furniture:Shellac is a superior finish, especially for antiques, but it is fussy. When I was a kid my father refinished furniture in his spare time and at one point tried shellac. We kids quickly learned “Don’t touch that table!” Damp glasses left water rings (which faded), alcohol marred it, and household cleaners damaged it. However, shellac is beautiful.
If you’ve ever gone looking for rails, you know they are usually inaccessible. They live in tall dense marsh grass and won’t come out for anything except the sound of another rail — and then only in the breeding season.
But there is in fact a truly inaccessible rail. The Inaccessible Island rail (Atlantisia rogersi) is the smallest flightless bird in the world, extremely rare, and vulnerable to extinction. He lives only on Inaccessible Island.
He made news in October because he cannot fly yet new DNA studies show that his ancestors, related to black rails, did fly more than 2,300 miles from South America over the South Atlantic Ocean to Inaccessible Island. They arrived 1.5 million years ago.
This was a surprise because the island, which is in the Tristan de Cunha archipelago, is closer to Africa than to South America as shown below. (Click on the map or its caption to explore it on Google Maps.)
The island is called Inaccessible because it is. It’s almost impossible to land on the narrow beach — most attempts fail — and the cliffs are so steep that the top is inaccessible.
The island’s walls dwarf the people exploring the beach, below.
Fortunately this tour group got lucky. They were able to land and they found the rail. A member of the group, Brian Gratwicke, took these photos.
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.”