Long-tailed ducks, common eiders and surf scoters eat crustaceans and mollusks that they pull from the ocean floor. Their populations are in steep decline, in part because hundreds of thousands of them die as bycatch in gillnets.
The diagram below shows a gillnet used for cod fishing in Newfoundland. Though no one fishes for cod anymore, gillnets are still used for other fish where ducks are diving.
Federal fishing laws solved the bycatch problem for dolphins and whales by requiring pingers to warn the mammals away. Fish can’t hear the pingers but dolphins can. Is there a sound that will work for ducks?
University of Delaware grad student Kate McGrew tested long-tailed ducks, common eiders and surf scoters and found out they can hear 1-3 kHz underwater.
Though this arctic seabird doesn’t eat algae it will starve if marine algae is not abundant. On Throw Back Thursday we’ll learn more with the help of two vintage articles.
Dovekies eat small invertebrates and fish but the majority of their diet is made up of copepods. A single dovekie eats 60,000 of them per day. Quadrillions(*) fall prey to dovekies during the breeding season. So … What the heck is a copepod?
Copepods eat microscopic marine algae called phytoplankton that contain chlorophyll and need sunlight to live and grow. In the high arctic, the summer sun makes phytoplankton bloom, as seen below in the Barents Sea. It takes quadrillions phytoplankton to feed billions of copepods to feed the dovekies.
Phytoplankton is really tiny, so small that you need an electron microscope to see it. The Barents Sea bloom above is thought to be Emiliana huxleyi, shown below. The disks are made of calcium carbonate which is also the primary component of seashells. The calcium in phytoplankton makes its way up the food chain.
Thus if phytoplankton is scarce, copepods are scarce and the dovekies starve. That’s how a seabird relies on algae.
(photos from Wikimedia Commons; click on the captions to see the originals)
(*) How many copepods? Here’s a back of the napkin calculation: Suppose there are 50 million dovekies, each one eating 60,000 copepods/day. Dovekies live in their breeding range for four to six months, so there have to be quadrillions of copepods available during that period. Dovekies aren’t the only animal that eats copepods. The numbers are staggering! (My original calculation had a power-of-10 problem. See Tom Brown’s correction.)
By now our sewers are over 100 years old and too small to handle heavy rain. In some places it takes only a 1/4 inch to cause a sewer overflow, sending toilet paper to the rivers. Meanwhile climate change has brought frequent heavy downpours that flood some valleys with sewage, including the neighborhood below Schenley Park.
That neighborhood, called The Run, is located at the base of Four Mile Run’s watershed where all the old sewers converge before reaching the Monongahela River (highlighted in red on the 3D map below).
Sewage floods The Run, 28 Aug 2016 (photo by Justin Macey)
People are sometimes trapped by the floods in The Run. On 28 August 2016 a father and son had to crawl through the sunroof when their car was swamped on Saline Street. Click here for photos of the flood and rescue.
Father and son waiting for rescue, escaped through the sunroof of their flooded car, The Run, 28 Aug 2016 (photo by Justin Macey)
The less rainwater that enters the sewer system the better it is for The Run. Toward that end the Pittsburgh Water and Sewer Authority (PGH2O) is working in Schenley Park for the next several months, building detention swales along Overlook Drive and the Bridle Trail to channel stormwater away from the sewer system.
When the project is done they’ll plant more trees than they removed.
Pitted shell found at Chesapeake Bay, Virginia Beach, 28 Nov 2019 (photo by Kate St. John)
Last month I found this pitted shell at Chesapeake Bay in Virginia Beach and assumed the holes were made by sand and waves. But that can’t be true. If it was, most shells would look like this. So what happened here?
Boring sponges make their homes by boring holes into the calcium carbonate shells and skeletons of animals like scallops, oysters and corals. Using chemicals, they etch into the shell and then mechanically wash away the tiny shell chips, slowly spreading holes within the skeleton or shell and sometimes across its surface. Eventually, these holes and tunnels can kill their host, but the sponge will continue to live there until the entire shell has eroded away.
Cliona celata is a common boring sponge that lives on oyster reefs in Chesapeake Bay and around the world. It’s considered a major pest by Bay oyster harvesters. Here’s what it looks like underwater and in two closeups.
Interestingly, a 2013 study of scallops and boring sponges found that the sponges thrive in the warmer more acidic seawater that results from climate change. This spells bad news for oysters, corals and other shells.
When European starlings are frightened by an aerial predator they fly in tight formation in a giant shimmering blob called a murmuration. If you’ve never seen it, check out these two examples: Murmurations in Lorain by Chad+Chris Saladin and Murmuration a 2011 film on Vimeo.
Starlings aren’t the only ones who fly like this. Shorebirds are masters at staying in formation, flying high and low and sweeping between the waves when threatened from above.
In the video below, a shorebird flock flashes black and white at Ocean Shores, Washington in November 2018. Their backs are dark, their bellies are white, so they change color as they turn in the air.
The flock is doing this for a reason.
Watch a predator dive in at the 0:13 time mark. It looks like a peregrine falcon to me. 🙂
November is courtship time for one of the rarest seabirds on earth.
The Bermuda petrel (Pterodroma cahow) or cahow (pronounced ka-HOW) ranges across the Atlantic Ocean, returning to land only once a year to court and breed at Bermuda.
Cahows nest in dark burrows which they access only at night, so secretive that they were presumed extinct until 1951 when the last 17-18 pairs were discovered on an isolated Bermuda island.
Every year the odds are against an egg becoming an adult. However the birds’ long breeding lives, 30-40 years, ensure the species will survive as long as there are safe places to nest — and that’s the rub. Rats were eradicated from their breeding colonies but many of the burrows are on islands threatened by hurricanes and sea level rise.
Since 2001 the Cahow Recovery Program has been setting up safe breeding burrows on Nonsuch Island and translocating a few pre-fledgled birds to the burrows in hopes they will return there to breed when they reach maturity at 3-6 years of age. So far so good. There are now 15 pairs on Nonsuch, two of which use burrows equipped with live streaming Cahow cams under infrared light.
November is the time to watch the cameras at Cornell Lab’s Bermuda Petrel Cams. The pairs return to their burrows, prepare the nest, court and copulate. In the video below a pair touches beaks and preens in the courtship behavior called allopreening.
Watch the Cahow cams this month, especially at night. The birds are most active on the darkest nights of the New Moon.
Cahows leave their burrows in December, then the female returns in January to lay her single egg. If all goes well a chick will fledge in July.
The long process of creating and raising a single cahow chick has just begun.
p.s. Here’s an amazing fact about cahows: Notice that the birds have tube-like noses. These structures take the salt out of saltwater so they can drink it. They sneeze the salt out of their noses. There are more amazing cahow facts here.
