Category Archives: Water and Shore

Humpback Whales Love Anchovies

Humpback whales lunge-feeding on anchovies in Monterey Bay (photo by Robin Agarwal via Flickr Creative Commons license)

25 January 2023

Every autumn humpback whales (Megaptera novaeangliae) migrate past California on their way to spend the winter off the coast of Mexico. They will linger, however, if they find lots of anchovies. Humpback whales love anchovies.

The California anchovy population typically rises and falls in 10 to 30 year cycles based on ocean conditions and fishing pressure. It surged in 2013 when the New York Times made this video (click on the image below) …

Screenshot from New York Times article... Click here or on the image to see the video

… and surged again this summer. In June 2022 there were so many anchovies that people reported small fish raining down from the sky in San Francisco, probably dropped by passing seabirds. In July anchovies were trapped in oxygen-poor water and died near shore, making a smelly mess.

There were still lots of anchovies when the whales showed up this fall. Robin Agarwal took a whale watch out of Monterey Bay in early October and captured these scenes of lunge-feeding humpback whales.

The anchovies crowded close as the predators approached. The whales forced them to the surface where the tiny fish leapt out of the water to escape.

Humpback Whales lunge-feeding on Northern Anchovies (photo by Robin Agarwal on Flickr)

The whales opened their mouths and anchovies fell in.

In a surge year for anchovies, people feast too.

Anchovies at Valley Bar + Bottle Shop, Sonoma, California (photo from Wikimedia Commons)

Read more about the 2013 anchovy surge in the New York Times: With Extra Anchovies and Whale Watching.

See more of Robin Gwen Agarwal’s photos here.

(humpback whale photos in Monterey Bay by Robin Gwen Agarwal on Flickr, Creative Commons license, food photo from Wikimedia Commons; click on the captions to see the originals)

Reimagined Maps as Art

U.S. watershed map by Robert Szucs at Grasshopper Geography (image from press kit)

24 January 2023

About ten years into his career as a digital cartographer Robert Szucs decided to experiment with data visualization and learned how to create strikingly beautiful, digitally accurate maps. He calls them “Maps Reimagined” and explains,

While my maps are always scientifically accurate, I think of them first and foremost as works of art.

Robert Szucs, Grasshopper Geography Press Kit

His watershed maps became an Internet sensation a few years ago through digital sales on Etsy and news outlets including the Washington Post and Smithsonian Magazine.

The U.S. watershed map above is so detailed that you can pinpoint Pittsburgh in the Mississippi watershed at the conjunction of the Allegheny, Monongahela and Ohio Rivers.

Grasshopper Geography U.S. watershed map, cropped to highlight Pittsburgh at the conjuction of three rivers

Szucs has also produced collections of elevation, forest and human population maps.

There came a point when I said I can’t look at another green-brown-white elevation map again. I needed some fun. I needed colours. And for not the first or last time, I needed to create the maps I wanted to see.

Robert Szucs, Grasshopper Geography Press Kit

This one dramatically illustrates that even the plateaus in the U.S. West are much higher than anything in the East.

U.S. elevation map by Robert Szucs at Grasshopper Geography (image from press kit)

See more maps and learn more about them at

(All images from press kit)

Winter Birds at the Beach

Sanderlings in December (photo from Wikimedia Commons)

3 January 2023

When we think of the beach in winter it sounds pretty bleak but not if you’re a birder. Shorebirds, sea ducks, loons and gulls leave the icy north to winter on the Atlantic and Pacific coasts where they hang out on beaches or just offshore, especially near jetties.

If you can’t travel far from Pennsylvania, visit the New Jersey shore to see thousands of wintering birds. GetToKnowNature describes what you’ll see in her video “Welcome to the beach in winter.” Click here or on the screenshot below to see it on Instagram (you don’t need an account to see it) or here for YouTube.

Screenshot from GetToKnowNature winter beach video on Instagram

(photo from Wikimedia Commons, screenshot from GetToKnowNature video on Instagram)

Tundra Swans at Their Winter Home

Tundra swans at Mattamuskeet Refuge, NC, Sept 2015 (photo from Wikimedia Commons)

29 December 2022

Tundra swans pass over Pittsburgh in mid November but rarely stop on their way to the Chesapeake and Tidewater North Carolina. I missed seeing them overhead in Pennsylvania so while in Virginia this week I went to visit them at their winter home.

Tundra swans (Cygnus columbianus) breed in the arctic wetlands of Russia, Alaska and Canada and spend the winter in temperate marshes and grasslands, often near the coast.

Tundra swan range map from Wikimedia Commons (orange = breeding, blue – wintering)

Banding and radio-tag studies in the 1980s revealed that North America’s tundra swan population is split east and west with separate breeding and wintering grounds. In 2015 US Fish and Wildlife estimated approximately 117,100 in the eastern population and 56,300 in the west.

Western and Eastern populations of tundra swans (maps from US Fish & Wildlife)

The largest winter concentration of tundra swans is in northeastern North Carolina, deep purple on this eBird map (Dec-Jan occurrences in the past 10 years).

eBird map of tundra swan distribution in the Lower 48, Dec-Jan in the past 10 years (2012-2022)

Virginia’s Back Bay National Wildlife Refuge is close to the North Carolina border and attracts a portion of that large population. On the day after Christmas I stopped by to see them.

The bay view from the boardwalk is vast (see below) and the swans were quite distant. Through my scope I counted only 65 at first.

The bay at Back Bay National Wildlife Refuge (photo by WarriorMare via Flickr Creative Commons license)

But I could hear a lot more swans than I could see. Over the next few hours more than 200 moved out to open water. The loudest ones shouted at each other and leaned in to emphasize their point.

Tundra swans vocalizing (illustration of European subspecies (Bewick’s swan) by Jos Zwarts from Wikimedia Commons

Listen to distant tundra swans at Back Bay NWR, humming, whistling and shouting. Don’t be fooled when they sound like sandhill cranes. These are tundra swans at their winter home.

Tundra swans vocalizing at Back Bay NWR, Virginia, 26 Dec 2022 (recorded by Kate St. John)

(credits are in the photo and map captions; click on the captions to see the originals. Sound converted from .wav to .mp3 using

Bubble Rings, Dolphins and Whales

Diver almost touches a bubble ring he has made (photo from Wikimedia Commons)

11 December 2022

Similar to smoke rings, bubbles rings are vortexes that spin internally while they move through the water.

The internal spinning keeps the core in shape and allows it to continue traveling long after other bubbles have dispersed.

Dolphins and whales purposely produce bubble rings from their blow holes and play with them. They examine and prod the rings, roll them like wheels, speed them up, or nudge them until a smaller ring splits off. They will even bite or swallow the ring or swim through it if it’s large enough.

Beluga whales make bubble rings at Shimane Kaiyokan Aquas (aquarium) in Hamada, Japan (photo from Wikimedia Commons)

Divers familiar with the wild animals probably knew about this long ago. The rest of us saw it for the first time at aquariums. Here are some videos.

Video from 2008:

Video from 2010 at Sea World:

p.s. Though scientists have written about dolphins and bubble rings for at least 50 years, BBC Earth published a video only 8 months ago in which a scuba diver placed a bubble machine underwater and filmed the dolphins’ reactions. The narrated script says the dolphins are afraid of the manufactured bubbles and have to learn to be brave. Apparently, the producer was not aware dolphins already know about bubble rings, so why would they be afraid? Sigh. It’s a good example of why you cannot believe everything you hear on TV. Stay curious!

(photos and animation from Wikimedia Commons; click on the captions to see the originals. videos embedded from YouTube)

Disappearing Islands in Chesapeake Bay

High tide at Tangier Island, Virginia, 16 Sept 2016 (photo from Wikimedia Commons)

7 December 2022

Sea level is rising overall about 3 millimeters (0.1 inches) per year due to climate change but Chesapeake Bay is rising even faster than the ocean — as much as 4.6 millimeters per year — because the area is still subsiding after the last Ice Age. Some Chesapeake Bay islands are disappearing.

NASA’s Landsat images of lower Chesapeake Bay from 1999 and 2019 show how much land has been lost in only 20 years. In 1999 there were white sand beaches on the island edges. By 2019 the beaches are gone and Great Fox Island in the center of the image has almost disappeared.

Satellite imagery from “Great Fox is Disappearing” NASA Landsat Image Gallery

The Chesapeake Bay Foundation used to hold in-residence educational programs on Great Fox (also called Fox Island) but in October 2019, with only 34 island acres left, they declared the end of the program. You can see why in the video below.

Just across the Virginia line (at the bottom of the satellite images) is Tangier Island whose land mass has shrunk 67% since the 1850s. Its population shrank as well. By now Tangier has only 345 acres and a population of about 470.

Residents are routinely flooded during the highest tides, pictured at top and below.

Tide water floods yards on Tangier Island, Virginia, Sept 2016 (photo from Wikimedia Commons)
Tide water floods streets on Tangier Island, Virginia, Sept 2016 (photo from Wikimedia Commons)
Tidewater rising in the yards at Tangier Island, Virginia, Sep 2016 (photo from Wikimedia Commons)

A 2015 analysis by the U.S. Army Corps of Engineers predicted that Tangier Island will become uninhabitable within 25-50 years, about mid-century.

The harbor channel, Tangier Island, Dec 2011 (photo from Wikimedia Commons)

Tangier Island will eventually join Great Fox Island under the bay.

For more information see Great Fox is Disappearing at NASA’s Landsat Image Gallery, Wikipedia’s Tangier Island account and this April 2022 NBC News video about Tangier Island.

(photos from Wikimedia Commons and NASA Landsat Image Gallery; click on the captions to see the originals)

Dolphins Just Wanna Have Fun

Northern right whale dolphin, Monterey Bay, Calif. 30 Nov 2022 (photo by Robin Agarwal via Flickr Creative Commons license)

4 December 2022

Dolphins are very intelligent and engage in many kinds of play. Robin Agarwal photographed their antics while on a pelagic tour in Monterey Bay on 30 November 2022. For instance …

The northern right whale dolphin (Lissodelphis borealis) in mid-leap, above, looks super sleek because he has no dorsal fin.

A Pacific white-sided dolphin, below, went way beyond mere jumping. He leapt, turned, and sometimes entered the water tail first. Somersaults!

Dolphin somersaulting! Pacific white-sided dolphin

Here’s a calmer view of this species (Lagenorhynchus obliquidens) with a cape of bubbles from his spout.

Pacific white-sided dolphin surfaces with a cap of bubbles on its back, Monterey Bay, Calif, 30 Nov 2022 (photo by Robin Agarwal via Flickr Creative Commons license)

Another favorite dolphin game is to ride the pressure wave at the front of a fast moving boat. Called “bow riding,” the bow wave pushes dolphins fast forward without any flapping on their part.

Dolphins like this game so much that they rushed toward the whale watch boat. Robin Agarwal says of this photo, “Pacific White-sided Dolphins and Northern Right Whale Dolphins stampeding towards the boat to bow ride – my favorite sight in the world.”

Dolphins stampede toward the whale watch boat in order to bow ride, Monterey Bay, Calif. 30 Nov 2022 (photo by Robin Agarwal via Flickr Creative Commons license)

Here they are bow riding with an “unusual swirl color morph” among them.

Unusual ‘swirl’ color morph Northern Right Whale Dolphin joins the other NWRDs and Pacific White-sided Dolphins at the bow

Dolphins just wanna have fun!

Check out the great photos by Robin Gwen Agarwal on Flickr.

(photos by Robin Gwen Agarwal on Flickr Creative Commons license.)

Greater and White-Fronted

Greater white-fronted geese from Crossley ID Guide to Eastern Birds (image form Wikimedia Commons)

28 November 2022

Over the Thanksgiving weekend 6 greater white-fronted geese (Anser albifrons) showed up in western Pennsylvania — four in Lawrence County and four in Armstrong County.

Though they breed in the arctic around the world, the North American population stays west of the Mississippi. These geese are rare in Pennsylvania.

Range map of greater white-fronted goose embedded from

Their “greater” and “white-fronted” adjectives don’t make much sense unless you know the species they resemble in Europe.

They are “greater” because they are larger than the lesser white-fronted goose (Anser erythropus) that occurs only in Eurasia and is now Vulnerable to extinction.

They are “white-fronted” because they have white feathers on their faces surrounding their beaks, a field mark that distinguishes them from the similar greylag goose (Anser anser), another Eurasian species.

Greater white-fronted goose (detail from the Crossley ID Guide Eastern Birds, arrow added to indicate white front)

Only a handful of greater white-fronted geese are seen in western Pennsylvania in any given year, and then only in late October through early March.

If you see a goose that resembles this one check its field marks carefully. It may be an odd domestic goose, described here:

(images from Wikimedia Commons, map embedded from

Late November Birds at Duck Hollow

Ring-billed gull and common merganser, Duck Hollow, 23 Nov 2022 (photo by Charity Kheshgi)

26 November 2022

This week Charity Kheshgi and I saw ring-billed gulls (Larus delawarensis), a common merganser (Mergus merganser) and a few pied-billed grebes (Podilymbus podiceps) at Duck Hollow. All three species visit the Monongahela River in November when freshwater freezes up north.

Pied-billed grebe in silhouette, Duck Hollow, 23 Nov 2022 (photo by Charity Kheshgi)

The common merganser gave us an opportunity to mentally compare her field marks to a similar bird. Here are some tips.

Female common and red-breasted mergansers are so similar that it takes some practice to tell them apart. Charity’s photos show the common merganser’s two unique field marks:

  • A sharp demarcation between dark head versus white breast / gray back.
  • A sharply defined white under-chin.

Notice the common merganser field marks in three photos.

Common mergansers at Duck Hollow, 16 Nov 2022 (photo by Charity Kheshgi)
Common merganser, not showing its crest, Duck Hollow, 16 Nov 2022 (photo by Charity Kheshgi)
Common mergansers — unique field marks in blue (photo by Charity Kheshgi)

Female red-breasted mergansers (Mergus serrator) lack those sharp lines. The colors blend from one to the other.

Red-breasted merganser (photo from Wikimedia Commons)

Note that the presence of a head crest is not a reliable difference between the two; both can display it.

So here’s a quiz: Which species is in the photo below? Are these common or red-breasted mergansers?

Which merganser is this? (photo from Wikimedia Commons)

p.s. Location, location, location! Of the two species, common mergansers are inland birds more likely in Pittsburgh in November. Red-breasted mergansers concentrate at the coasts and Great Lakes in winter.

(photos by Charity Kheshgi and red-breasted mergansers from Wikimedia Commons)

Eagles Die When We Kill a Weed

Bald eagle portrait (photo from Wikimedia Commons)

6 November 2022

In 1994 dozens of bald eagles were found convulsing, dead or paralyzed near Arkansas’ DeGray Lake. Autopsies revealed the eagles died of a new disease called avian vacuolar myelinopathy (VM) that manifests as brain lesions. The dying spread to Florida, Georgia, the Carolinas and Texas (hashed areas on the map below) and continues to this day. In 2021 scientists discovered what causes VM. It’s a chain of events that begins when we use an aquatic weed killer to control an invasive weed.

VM occurs in watersheds where A. hydrillicola colonizes H. verticillata. Watersheds where VM has been diagnosed (indicated by black crosshatching). Watersheds where H. verticillata has been confirmed to be colonized with A. hydrillicola are shown in red, and watersheds where A. hydrillicola has not yet been observed on H. verticillata are shown in yellow. Watersheds not yet screened for A. hydrillicola, but where H. verticillata occurs, are shown in green. This map, embedded from NIH, is current to fall 2019.

The invasive weed is hydrilla (Hydrilla verticillata) that spreads easily and clogs waterways. It’s a huge problem in many southeastern states, especially in Florida.

Hydrilla at Lake Seminole, Florida (photo from Wikimedia Commons)

Hydrilla hosts a cyanobacteria called Aetokthonos hydrillicola which does not produce toxins by itself(*). However when it comes in contact with bromide-containing aquatic weed killer, meant to kill hydrilla, it produces a neurotoxin.

Cyanobacterium on hydrilla produces a neurotoxin in the presence of bromide weed killers (subimage from diagram below + jug composed from spare parts)

Fish and waterbirds, including American coots, eat the hydrilla and consume the neurotoxin. Soon they develop VM brain lesions.

American coot eating hydrilla (photo from Wikimedia Commons)

Bald eagles and other predators eat the fish and coots, often preying on sick ones because they are easy to catch.

Bald eagle hunting an American coot (photo from Wikimedia Commons)

And so bald eagles develop brain lesions and die of vacuolar myelinopathy.

The AVM cycle begins with a cyanobacteria on hydrilla that develops a neurotixin when treated with bromide weed killer (diagram from Wikimedia Commons)

The way to stop the dying is described in this NIH article Hunting the eagle killer: A cyanobacterial neurotoxin causes vacuolar myelinopathy:

Integrated chemical plant management plans to control H. verticillata should avoid the use of bromide-containing chemicals (e.g., diquat dibromide). [The neurotoxin] AETX is lipophilic with the potential for bioaccumulation during transfer through food webs, so mammals may also be at risk.

— from NIH: Hunting the eagle killer: A cyanobacterial neurotoxin causes vacuolar myelinopathy

Thus if you use a bromide-containing chemical (e.g. diquat dibromide) to control hydrilla you will unintentionally kill bald eagles.

Diquat aquatic weed killer contains bromide which leads to AVM (image constructed by Kate St. John)

Other solutions for controlling hydrilla without herbicide are highlighted in Florida Today (article and video): Melbourne-Tillman harvests hydrilla to avoid herbicides.

Meanwhile bald eagles aren’t out of the woods yet because we don’t know how long it will take for the neurotoxins to clear from infected lakes.

For more information see the article that inspired this topic: Science Magazine: Mysterious eagle killer identified: A new species of cyanobacteria that lives on invasive waterweed produces an unusual neurotoxin.

(photos and diagram from Wikimedia Commons, map embedded from NIH; click on the captions to see the originals)

(*) The mystery was solved when scientists discovered that the toxin came from bromides that did not occur naturally. From NIH, Hunting the eagle killer: A cyanobacterial neurotoxin causes vacuolar myelinopathy: “Laboratory cultures of the cyanobacterium, however, did not elicit VM. A. hydrillicola growing on H. verticillata collected at VM-positive reservoirs was then analyzed by mass spectrometry imaging, which revealed that cyanobacterial colonies were colocalized with a brominated metabolite. Supplementation of an A. hydrillicola laboratory culture with potassium bromide resulted in pronounced biosynthesis of this metabolite. H. verticillata hyperaccumulates bromide from the environment, potentially supplying the cyanobacterium with this biosynthesis precursor.”