Axanthism Gives Green Frogs the Blues

Among the Green Frogs in the ponds at susquehannawildlife.net headquarters, a specific recessive allele is present among the population of these native amphibians.  On occasions when male and female carriers of this particular recessive allele get together to produce offspring, about one quarter of the progeny will receive a copy of this mutated version of a gene from each parent.  The rare recipient of this pair of recessive alleles that happens to survive the process of hatching from its egg and metamorphosing through the tadpole stage to adulthood will reveal the uncommon appearance of an amphibian with the condition resulting from this inheritance—axanthism.

Axanthic Green Frog
Axanthic Green Frogs and other amphibians do not produce yellow pigment, therefore the normally yellow surfaces of their bodies appear white, the green surfaces blue.  Axanthism is expressed only in individuals possessing a pair of specific recessive alleles for a gene that affects the cells that produce the yellow pigment.  For the trait to be expressed, a frog must receive one copy of the recessive allele from each parent.
Axanthic and Typical Green Frogs
The last axanthic Green Frog we saw in the headquarters ponds was this male (seen here with a typical male Green Frog) found back in July, 2008.  Green Frogs that receive two copies of a dominant allele or a copy of a dominant and a recessive allele from their parents will not express the recessive trait for the axanthism gene.  Making observation of cases of axanthism even rarer is the fact that blue coloration can make these frogs exceptionally susceptible to predation.  Few live long enough to reproduce and thus increase the occurrence of the mutation in a population of frogs*.  This cyanic individual was present during a time when “outdoor” Domestic Cats were killing frogs to take home to their misguided humans.  After this brief sighting and single photograph, this blue Green Frog was never seen again. 

*The incidence of axanthic frogs can increase when a blue parent, which has a pair of the recessive alleles and is therefore said to be homozygous recessive, mates with a typical-looking frog that carries both a dominant and a recessive allele for the axanthism gene and is therefore said to be heterozygous.  Approximately 50% of the young from this pairing will express axanthism.  By comparison, a pair of frogs that are both heterozygous will produce 25% axanthic young, and a pair of frogs that are both blue (homozygous) will yield 100% axanthic young.  A pair of frogs that includes an individual that is herterozygous and a mate that is homozygous dominant for the gene will produce no axanthic frogs, but 50% of the young will be carriers of the recessive allele.  A pair of homozygous dominant frogs produces no axanthic young and no carriers of the recessive allele. 

Photo of the Day

Green Frog on Christmas
It’s been a green Christmas at susquehannawildlife.net headquarters.  Among thick growth of Lesser Duckweed and other aquatic plants in the garden ponds, the Green Frogs and their tadpoles remain active.  The water’s open…still no ice here.

The Best Sneakers

When you were young, you may have selected your tennis shoes because they promised to make you run faster and jump higher.  Remember those?  Then as you got a bit older, you may have really wanted the brand that would get you noticed—those overpriced status-symbol athletic shoes.  As the years went by and you put on the extra pounds in all the wrong places, maybe it occurred to you that it might be a really good idea to get some exercise.  So you went out and bought some stylish and expensive fitness footwear that promised to help you run faster and jump higher—and wore that pair to go shopping at the grocery store.  Then you finally realized…

Green Frog in Cheap Sneakers
…that the best sneakers are just something comfortable to loaf around in.
Green Frog in Cheap Sneakers
Wisdom does come with age.

These Geese are Outta Here!

Flies?  Cabbage White butterflies?  Can it really be a late-February day?  It certainly is.  Here are a few more signs of an early spring.

Green Frog
Green Frogs were out and about on this balmy February day trying to latch on to one of those flying insects.  Their long winter’s nap lasted just over six weeks.
Common Grackle
Approximately two hundred Common Grackles passed by susquehannawildlife.net headquarters today.  This one stopped to have a look around before continuing its northbound expedition.
Migrating Canada Geese
Difficult to spot, hundreds of high-flying Canada Geese were seen in the hazy sky above the headquarters garden during the late morning.  These migrants are working their way north from Chesapeake Bay and won’t be seen again in our region until fall.

Migratory Waterfowl on Local Ponds and Lakes

Following the deep freeze of a week ago, temperatures soaring into the fifties and sixties during recent days have brought to mind thoughts of spring.  In the pond at susquehannawildlife.net headquarters, Green Frogs are again out and about.

Green Frogs
A pair of Green Frogs seen today alongside the headquarters pond.  A sign of spring?

But is this really an early spring?  Migrating waterfowl indicate otherwise.  Having been forced south from the Great Lakes during the bitter cold snap, a variety of our tardy web-footed friends belatedly arrived on the river and on the Susquehanna Flats of upper Chesapeake Bay about ten days ago.  Now, rising water from snow melt and this week’s rains have forced many of these ducks onto local lakes and ponds where ice coverage has been all but eliminated by the mild weather.  For the most part, these are lingering autumn migrants.  Here’s a sample of some of the waterfowl seen during a tour of the area today…

Snow Geese
Like other late-season migrants, Snow Geese take advantage of open water on area lakes until ice forces them south to the Atlantic Coastal Plain.  In a little more than a month from now, they’ll begin working their way north again.
Tundra Swans and American Black Ducks loafing on an ice-free lake.
Tundra Swans and American Black Ducks loafing on an ice-free lake.
Mute Swans
The non-native Mute Swan has become an invasive species.  Because they are predominantly non-migratory, groups of Mute Swans congregating in valuable wetland habitat can decimate these aquatic ecosystems with their persistent year-round feeding.  Their long necks help them consume enormous quantities of benthic foods that would otherwise be available to migratory diving ducks during their autumn and spring stopovers.
Gadwalls
Small flocks of Gadwalls will sometimes spend the winter on ice-free vegetated ponds in the lower Susquehanna region.
A mixed flock of diving ducks on a small lake.
A mixed flock of diving ducks on a small lake.  Let’s take a closer look!
Redheads, Lesser Scaup, and Canvasback
Six Redheads, three Lesser Scaup (top row left), and a Canvasback (upper right).
Redheads
Redheads.
Buffleheads
Buffleheads.
An adult male Lesser Scaup.
An adult male Lesser Scaup.
Lesser Scaup
A female (right) and a first-winter male (left) Lesser Scaup.
Canvasbacks and a Ruddy Duck
Canvasbacks and a Ruddy Duck.

With the worst of winter’s fury still to come, it’s time to say farewell to most of these travelers for a little while.  With a little luck, we’ll see them again in March or April.

Striped Skunk
Our official susquehannawildlife.net prognosticator climbed out of its winter hideout today to have a look around.   Then, without hesitation, the forecast for 2023 was issued, “Winter Stinks!”

A Springtime Quiz

The mild winter has apparently minimized weather-related mortality for the local Green Frog population.  With temperatures in the seventies throughout the lower Susquehanna valley for this first full day of spring, many recently emerged adults could be seen and, on occasion, heard.  Yellow-throated males tested their mating calls—reminding the listener of the sound made by the plucking of a loose banjo string.

Here’s a gathering of Green Frogs seen this afternoon along the edge of a small pond.  How many can you find in this photograph?

If you venture out, keep alert for the migrating birds of late winter and early spring.

Yellow-bellied Sapsuckers are moving through on their way north.  Look for them in mature trees in woodlands, suburbs, and city parks.
The Fox Sparrow (Passerella iliaca), our largest sparrow, is a thrush-like denizen of shrubby forest understories and field edges.  It is an early spring and late autumn transient in the lower Susquehanna valley.
While stopping to rest and feed during their northbound spring journey, Ring-necked Ducks and other diving duck species visit wetlands and flooded timber along the Susquehanna River as well as clear ponds and lakes elsewhere in the watershed.
Eastern Bluebirds are presently migrating through the area.  Some will stay to breed where nest boxes or natural cavities are available in suitable habitat.
Tree Swallows are now arriving.  In open grasslands, pastures, and adjacent to almost any body of water, they will nest in boxes like those placed for bluebirds.
Keep that bird bath clean and fill it with fresh water, the American Robin flights are peaking right now.  Breeding males like this one are starting to sing and defend nesting territories.
Red-winged Blackbirds, like other native blackbirds, are moving through in a fraction of the numbers that were seen in the lower Susquehanna valley during the latter decades of the twentieth century.  They remain a common breeding species in pastures and cattail wetlands.
And of course, keep an eye to the sky.  There are still thousands of Snow Geese in the area.

If you’re staying close to home, be sure to check out the changing appearance of the birds you see nearby.  Some species are losing their drab winter basic plumage and attaining a more colorful summer breeding alternate plumage.

European Starlings are losing their spotted winter (basic) plumage and beginning to display a glossy multicolored set of breeding feathers.
An American Goldfinch in transition from winter (basic) plumage to bright yellow, black, and white summer colors.

So just how many Green Frogs were there in that first photograph?  Here’s the answer.

If you counted seven, you did really well.  Numbers eight and nine are very difficult to discern.

Happy Spring.  For the benefit of everyone’s health, let’s hope that it’s a hot and humid one!

Clean Slate for 2020

Inside the doorway that leads to your editor’s 3,500 square foot garden hangs a small chalkboard upon which he records the common names of the species of birds that are seen there—or from there—during the year.  If he remembers to, he records the date when the species was first seen during that particular year.  On New Year’s Day, the results from the freshly ended year are transcribed onto a sheet of notebook paper.  On the reverse, the names of butterflies, mammals, and other animals that visited the garden are copied from a second chalkboard that hangs nearby.  The piece of paper is then inserted into a folder to join those from previous New Year’s Days.  The folder then gets placed back into the editor’s desk drawer beneath a circular saw blade and an old scratched up set of sunglasses—so that he knows exactly where to find it if he wishes to.

A quick glance at this year’s list calls to mind a few recollections.

The 2019 bird list included 48 species, the 47 on the board plus Ruby-throated Hummingbird, which was logged on a slip of paper found tucked into the edge of the frame.

This Green Frog, photographed on New Year’s Day 2019, was “out and about” along the edge of the editor’s garden pond.  Due to the recent mild weather, Green Frogs were active during the current New Year’s holiday as well.
On a day with strong south winds in late February or during the first two weeks of March, there is often a conspicuous northbound spring flight of migrating waterfowl, gulls, and songbirds that crosses the lower Susquehanna valley as it departs Chesapeake Bay.  These Tundra Swans were among the three thousand seen from the garden patio on March 13, 2019.  A thousand migrating Canada Geese, 500 Red-winged Blackbirds, numerous Ring-billed Gulls, and some American Herring Gulls were seen during the same afternoon.
This juvenile Cooper’s Hawk was photographed through the editor’s kitchen window.  From its favorite perch on this arbor it would occasionally find success snagging a House Sparrow from the large local flock.  It first visited the garden in November, the species being absent there since early spring.  Unlike previous years, there was no evidence of a breeding pair in the vicinity during 2019.
Plantings that provide food and cover for wildlife are essential to their survival.  Native flowers including Trumpet Vine (Campsis radicans) and Partridge Pea provide nourishment for the Ruby-throated Hummingbirds that visit the editor’s garden, but they really love a basket or pot filled with Mexican Cigar (Cuphea ignea) too.  The latter (seen here) can be grown as a houseplant and moved outdoors to a semi-shaded location in summer and early fall.  But remember, it’s tropical, so you’ll need to bring it back inside when frost threatens.
A Swamp Sparrow is an unusual visitor to a small property surrounded by paved parking lots and treeless lawns.  Nevertheless, aquatic gardens and native plants helped to attract this nocturnal migrant, seen here eating seeds from Indiangrass.  It arrived on September 30 and was gone on October 2.

Before putting the folder back into the drawer for another year, the editor decided to count up the species totals on each of the sheets and load them into the chart maker in the computer.

Despite the habitat improvements in the garden, the trend is apparent.  Bird diversity has not cracked the 50 species mark in 6 years.  Despite native host plants and nectar species in abundance, butterfly diversity has not exceeded 10 species in 6 years.

It appears that, at the very least, the garden habitat has been disconnected from the home ranges of many species by fragmentation.  His little oasis is now isolated in a landscape that becomes increasingly hostile to native wildlife with each passing year.  The paving of more parking areas, the elimination of trees, shrubs, and herbaceous growth from the large number of rental properties in the area, the alteration of the biology of the nearby stream by hand-fed domestic ducks, light pollution, and the outdoor use of pesticides have all contributed to the separation of the editor’s tiny sanctuary from the travel lanes and core habitats of many of the species that formerly visited, fed, or bred there.  In 2019, migrants, particularly “fly-overs”, were nearly the only sightings aside from several woodpeckers, invasive House Sparrows (Passer domesticus), and hardy Mourning Doves.  Even rascally European Starlings became sporadic in occurrence—imagine that!   It was the most lackluster year in memory.

The Tufted Titmouse was a daily visitor to the garden through 2018.  This one was photographed investigating holes in an old magnolia there during the spring of that year.  There were no Tufted Titmouse sightings in the garden in 2019.  This and other resident species, especially cavity nesters, appear to be experiencing at least a temporary decline.
Breeding birds including Northern Cardinals may have had a difficult year.  In the editor’s garden, a pair were still feeding and escorting one of their young in early October.  The infestation of the editor’s town by domestic house and feral cats may have contributed to the failure of earlier broods, but a lack of food is also a likely factor.

If habitat fragmentation were the sole cause for the downward trend in numbers and species, it would be disappointing, but comprehensible.  There would be no cause for greater alarm.  It would be a matter of cause and effect.  But the problem is more widespread.

Although the editor spent a great deal of time in the garden this year, he was also out and about, traveling hundreds of miles per week through lands on both the east and the west shores of the lower Susquehanna.  And on each journey, the number of birds seen could be counted on fingers and toes.  A decade earlier, there were thousands of birds in these same locations, particularly during the late summer.

At about the time of summer solstice in June each year, Common Grackles begin congregating into roving summer flocks that will grow in size to assure their survival during the autumn migration, winter season, and return north in the spring.  From his garden, the editor saw just one flock of less than a dozen birds during the summer of 2019.  He saw none during his journeys through other areas of the Susquehanna valley.  Flocks of one hundred birds or more did not materialize until the southbound movements of grackles passed through the region in October and November.

In the lower Susquehanna valley, something has drastically reduced the population of birds during breeding season, post-breeding dispersal, and the staging period preceding autumn migration.  In much of the region, their late-spring through summer absence was, in 2019, conspicuous.  What happened to the tens of thousands of swallows that used to gather on wires along rural roads in August and September before moving south?  The groups of dozens of Eastern Kingbirds (Tyrannus tyrannus) that did their fly-catching from perches in willows alongside meadows and shorelines—where are they?

Several studies published during the autumn of 2019 have documented and/or predicted losses in bird populations in the eastern half of the United States and elsewhere.  These studies looked at data samples collected during recent decades to either arrive at conclusions or project future trends.  They cite climate change, the feline infestation, and habitat loss/degradation among the factors contributing to alterations in range, migration, and overall numbers.

There’s not much need for analysis to determine if bird numbers have plummeted in certain Lower Susquehanna Watershed habitats during the aforementioned seasons—the birds are gone.  None of these studies documented or forecast such an abrupt decline.  Is there a mysterious cause for the loss of the valley’s birds?  Did they die off?  Is there a disease or chemical killing them or inhibiting their reproduction?  Is it global warming?  Is it Three Mile Island?  Is it plastic straws, wind turbines, or vehicle traffic?

The answer might not be so cryptic.  It might be right before our eyes.  And we’ll explore it during 2020.

A clean slate for 2020.

In the meantime, Uncle Ty and I going to the Pennsylvania Farm Show in Harrisburg.  You should go too.  They have lots of food there.