Coquina clams (Donax variabilis) are tiny saltwater molluscs found on sandy beaches from Virginia to Texas. Their variable colors are beautiful and at only 3/4 inch long they are just the right size for collecting. I usually find an empty half shell rather than two joined like butterfly wings (above).
Since I only pay attention to empty shells I never thought about where they live and how they get there until I saw this video. Watch two coquina clams disappear in the sand.
I find it very peaceful to watch coquina clams slipping into the sand where the ocean meets the land. Video from July 2021 near St. Augustine, Florida. pic.twitter.com/wWtp6rhxvE
Though American oystercatchers (Haematopus palliatus) breed on barrier beaches and shelly islands on the Atlantic and Gulf coasts, few of us get to see it. The birds want peace and quiet far from humans when they raise a family.
@GetToKnowNature brings us this video of oystercatchers growing up, thanks to her long lens.
Consequently the Colorado River is running very low and Lake Mead reached a crisis point last month. The Guardian reports:
In June , the level of Lake Mead plunged below 1,075ft, a point that will trigger, for the first time, federally mandated cuts in water allocations next year. …
Should second tier cuts occur, Arizona will lose nearly a fifth of the water it gets from the Colorado River. Nevada’s first-round cut of 21,000 acre-ft (an acre-ft is an acre of water, one foot deep) is smaller, but its share is already diminutive due to an archaic allotment drawn up a century ago when the state was sparsely populated.
The crisis is due to lack of precipitation but we learned in 2014 that loss of rain and snow is dwarfed by the depletion of groundwater.
Using nine years of NASA’s GRACE satellite data from the Colorado River Basin, UC Irvine and NASA scientists made an alarming discovery. From December 2004 to November 2013 the watershed lost 53 million acre-feet of water, an amount almost twice the size of Lake Mead. More than 75% of that loss was from groundwater. No one knows how much water is underground but it’s going fast.
In summer, folks in western Pennsylvania and northern Ohio flock to Lake Erie‘s shore to beat the heat. The water provides a respite but in July the western end is hotter than anywhere else in the Great Lakes. That’s because Lake Erie is shallow and shallow water is quick to take on the temperature of the surrounding air. So how shallow is Lake Erie?
Lake Erie is the fourth in line of the five Great Lakes and happens to be fourth largest by surface area — 9,940 square miles.
But as you can see in this bathymetric map it is also the shallowest (blue is deep, red is shallow). Lake Erie’s average depth is only 62 feet with the deepest spot just 210 feet near Long Point, Ontario.
It’s easier to see how shallow it is in this diagram from Michigan Sea Grant. Even Lake Ontario, the smallest by surface area, is 3.8 times deeper! (Lakes Michigan and Huron are superimposed on each other because they have the same pool level, 577 feet above sea level. Click here to see the complete diagram.)
Since the shallowest water is first to heat and first to freeze, the surface temperatures roughly match the lake depths. As of yesterday, 13 July 2021, the water at the western end of Lake Erie was close to 80 degrees F.
In the middle of summer the male ducks disappear — or so it seems. The males are still present but they look like females because they’ve molted into eclipse plumage.
Let’s take a look at mallards to see how this works.
Mallards (Anas platyrhynchos) replace all their feathers once a year but males and females do it at different times. Females molt while nesting (February–May); males molt after the breeding season (June–August).
The molt begins with a complete loss of remiges (wing flight feathers) that takes only a few days, rendering the bird flightless for 3-4 weeks. Fortunately males simultaneously replace their brightly colored body feathers with dull ones so they can hide in dense marshes. Eclipse plumage keeps them out of danger.
Here’s the transformation.
Notice that the male’s head becomes mottled green (below) and then dull brown (photo at top).
Once the males have made this transition it’s a challenge to tell them apart from females but here’s a clue. Look at their bills. In the summer males have yellow or greenish-yellow bills while females have dull orange-ish bills.
Eventually the male starts to molt back to his typical plumage. Partway there he looks like this.
And by November he’s back to his normal flashy self in time to court his springtime mate.
This summer when you see a mallard, look at the bill. Maybe he’s a male in eclipse.
(photos from Wikimedia Commons; click on the captions to see the originals)
In early summer Pittsburgh birders tire of searching among dense leaves so we travel to Clarion County’s recovered strip mines for grassland birds. Yesterday five of us drove 90 minutes to look for open country birds we’ve found there in the past.
Dickcissels (Spiza americana) are back again this year and easy to find singing on the wires at Concord Church Road. These rare nomads were a Life Bird for me in 2012. Read this vintage article, Dickcissels, for the reason why they to come to western Pennsylvania.
Feathers wear out so birds molt to replace them. Most species molt their flight feathers one pair at a time, losing a matching feather on each side, so they can continue to fly. Not so with swans, geese and whistling ducks. They replace all their feathers shortly after the breeding season in a single annual synchronous molt. During the molt they cannot fly.
Though it seems crazy to lose the ability to fly these large heavy birds are safe on water and unsafe in flight if missing a few feathers. It works for them to lose these flight feathers all at once.
Geese rarely display their stubby wings but you can tell when they’re molting by looking at their tails. Most of the year their flight feathers cover their rumps (left). When molting (right) you can see a white rump patch.
Right now in Pittsburgh Canada geese are in their flightless period that lasts six weeks from mid-June to August. You’ll see them flock in or near large bodies of water, feeding on land and walking to the water to swim to safety. You might even notice they are absent from favorite feeding places, such as Flagstaff Hill, which don’t have bodies of water nearby. Such sites are unsafe when they cannot fly.
Have you seen any Canada geese flying lately? No. Because they can’t.
Whenever we see this sandpiper species he’s up to his ankles(*) in water and is poking with his long bill to eat insects, crustaceans, mollusks and amphibians.
Solitary sandpipers (Tringa solitaria) are distinguished from other shorebirds by a white eye ring, white spots on dark back, and the fact that they’re usually alone. We see them on migration as they travel between their wintering grounds in Central and South America and breeding grounds in the muskeg bogs and boreal forests of Canada and Alaska.
Everywhere they go they land on the ground and walk in water. I have never seen one in a tree and yet …
When solitary sandpipers reach their breeding grounds they nest in trees.
Solitary Sandpipers use old nests of songbirds in trees, especially those of American Robins, Rusty Blackbirds, Canada Jays, and Cedar Waxwings, which are usually near the trunks of small trees a few yards above the ground, but may be higher. [that’s 9 ft or higher]
Males identify old songbird nests that have potential, and females apparently make the final selection. Females modify the nest by removing old lining and often relining with fresh materials.
One of the joys of early spring is finding the first Louisiana waterthrush (Parkesia motacilla) of the year as it forages along a stream and sings its loud distinctive song. The bird is so loud that we hear him first then look for movement along the water’s edge. He stands out because he constantly bobs his tail. In fact he bobs the entire back end of his body!
Just half a minute of this video illustrates what I mean.
A few weeks later the spotted sandpiper (Actitis macularius) arrives to walk the water’s edge bobbing the entire back end of his body, too.
Same habitat, same movement. Is there some advantage in drawing attention to one’s back end? Why do these birds wag their tails? I found a partial answer at All About Birds:
… waterthrushes don’t actually wag the tail, they dip (or teeter) the entire rear of the body by moving their ankle joints. This motion is very much like the bobbing of Solitary and Spotted Sandpipers, which share their wetland habitats. It’s been suggested that this habit might either help them avoid scaring off their prey or possibly startle their prey into motion.
There’s plenty of time to watch them teeter in the weeks ahead. My first Louisiana waterthrush of 2021 was at Cedar Creek Park in Westmoreland County on 30 March. I expect the first spotted sandpiper next week.
Bonus! Here’s a closeup of a Louisiana waterthrush singing:
(photos from Wikimedia Commons; click on the caption to see the originals)
p.s. Others birds pump their tails including eastern phoebes, palm warblers, hermit thrushes, wagtails and pipits. It is not quite the same motion.
When Europeans explored the Pacific they sometimes named islands for the day they found them. Thus Easter Island (Rapa Nui) was named by Dutch explorer Jacob Roggeveen who encountered it on Easter Day 5 April 1722 and Christmas Island (Kiritimati) was given its English name by Captain James Cook on Christmas Eve 1777.