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Nature Notes: Evolution in the 21st Century

Ed Robinson
August 10, 2023

This has been a year of travel, allowing me to view large numbers of fascinating species, many of them for the first time. It is my habit to make notes when in the field, both to record numbers of creatures but also species I have seen for the first time so I can do my homework later. Sometimes ideas for my next article will pop into my head and I try to write them down before they are gone on the breeze. One of those notations was the genesis of this month’s column.

In early July I had the opportunity to spend a week in gorgeous surroundings in the southwest corner of Montana, sometimes within the boundaries of wonderful Yellowstone Park. My pal Lew Hinman and I were there for a fly fishing extravaganza, but I took the opportunity to do some birding whenever I was not wrangling a large trout to the net. Because of deep winter snows and heavy rains, the rivers were experiencing delayed spring runoff conditions and the birds were quite vocal while defending active nesting territories.

One morning I emerged from our cabin at dawn to hear a new call, a mountain chickadee singing from a tall lodgepole pine. When he finally appeared, I was struck by how close in appearance that bird was to the black-capped chickadees and boreal chickadees I had recently seen in the Rangeley, Maine region. While walking along a large grassy field, I enjoyed the song of the western meadowlark, one of the best songbirds on offer in that part of the country. I could not remember the last time I had encountered an eastern meadowlark in Maine or at our place in New York, a bird that once was quite common here.

yellow chested bird sings while perched on barbed wire

Eastern meadowlark (iStock WMarissen photo)

A few minutes further on and I began to hear the lilting sounds of the song sparrow, a bird you can count on for music across the country. But listen carefully and you will find their songs vary considerably as you move from one region to another. I spent some time considering why a very common bird with an extensive range would end up having such variety in the songs that are key to marking and defending breeding habitat.

Now, I am normally not given to daydreaming about such topics but a February trip to Ecuador’s Galapagos Islands gave us the chance to see one of the world’s best examples of evolution live and up close. If you have the chance to catch my new Ecuador presentation at some point, I discuss this in some detail (mark your calendar for December 14 for a presentation at HHLT’s office). We all learned about Charles Darwin’s journey to the Galapagos Islands in the 1830’s aboard the HMS Beagle, resulting 25 years later in his seminal book “On the Origin of Species.”  One of Darwin’s conclusions was that the wildlife of the Galapagos was so unique because the distant islands and their wildlife had been isolated for thousands of years, allowing those creatures to evolve to their unique habitats without much interference or pressure from outside influences (including mankind).

But now the Galapagos Islands and most other isolated parts of our world are under pressure from a wide variety of factors. Air and water pollution are growing problems and while the global community has made progress on a few fronts, such as eliminating most uses of chlorofluorocarbons to avoid more damage to the ozone layer in our atmosphere, we still dump vast quantities of plastic waste in our seas while China continues to build new coal-fired power plants at a rapid pace. Vital forests are being logged at a high rate in Brazil, Indonesia, and other spots, putting an estimated one million species at risk of extinction. Government-mandated changes to the way we produce and consume energy, and all the minerals we remove from the Earth to accomplish those goals have a huge impact on the environment, often in the most sensitive areas.

From the beginning of mankind’s time on Earth, we have been the dominant species in most ecosystems and all too often, our presence has been anything but benign. In the absence of scientific data and with no regulatory restraints, we harvested and reaped whatever we wished from the environment with little regard to the near or long-term impacts of our actions. Whether we were chasing gold and timber, or hunting animals for our dinner tables, we took whatever we could manage to gather on the assumption that there would be no end to the plenty. Just one example will make the point – today there are over 30,000 recorded mine tailing storage areas around the world holding 220 billion tons of waste, many of them at risk of failure and the release of toxic materials. Growing demand for lithium, copper, gallium, and rare earth minerals results in the processing each year of roughly 100 billion tons of rock and the creation of another eight billion tons of tailings. There is no comprehensive plan in place to clean up even a fraction of this mess.

It will be obvious that we cannot continue this rampant behavior without significant impact on the environment. A recent publication from The Nature Conservancy provides some startling statistics to illustrate the problems around us. The North American Bird Conservation Initiative got our attention a few years back by documenting the loss of three billion breeding birds since 1970. Nearly half the bird species unique to Hawaii are believed extinct and one-third are endangered or threatened. In California, one of the most heavily developed and intensively farmed parts of the US, two-thirds of 1,100 endemic species are increasingly at risk. Maine now lists 26 species of wildlife as endangered and 25 as threatened, and that does not include many species of plants also at risk.

It is enough to make you wonder just how the wild creatures around us can survive but there are some reasons to be positive. In the past I have written about the dramatic recovery of most species of waterfowl thanks to the Migratory Bird Act and ongoing efforts by sportsmen and conservation groups in funding habitat preservation and enhancement. In Ecuador a decision was recently made to protect an area over 250,000 acres to secure sensitive habitats and critical fresh water supplies. On December 19, 2022 a milestone agreement was reached at the United Nations Biodiversity Conference when most of the world’s countries signed on to the Kunming-Montreal Global Biodiversity Framework that commits the signatories to protect at least 30% of their land, ocean, and inland waters by the year 2030. Groups like the Nature Conservancy are working with poor nations like Belize, Barbados, and the Seychelles on innovative financing arrangements to help them fund badly needed conservation initiatives.

One constant in the natural world is change, as nothing ever remains the same for very long. This starts with the change of seasons, but the climate is always changing as the Earth goes through periods of warming and cooling. Major events like hurricanes, earthquakes, floods, and fires force species to move, to adapt or to perish, perhaps opening the door for another species to fill the void left behind. Some species are capable of major adaptations, while others are so dependent upon one food source or one habitat that they are unable to handle dramatic changes in their world. In the West, Rocky Mountain elk used to roam the plains much of the time but development of farms and railroads, along with hunting pressure, caused them to relocate for much of the year to higher, more rugged country. Mule deer used to roam much of the Rocky Mountain states but as residential development continues and white-tailed deer expand their territories in lower elevations, mule deer are being pushed to higher ground where they may not find sufficient food during the cold parts of the year.

We tend to think of evolutionary change as taking place over thousands and millions of years. But some changes occur in relatively short periods of time. I grew up in farm country, with my home surrounded by thousands of acres of corn, alfalfa, wheat, and oats. There were lots of hedgerows separating all those fields and it made perfect habitat for pheasants. It was common to startle a beautiful male pheasant while walking and he generally burst into the air cackling up a storm. Not only have farming practices changed enough to limit those pheasant populations, but the birds have evolved to quieter habits, rarely making the noisy flights I remember. Wild turkey populations have flourished since trap & transfer programs were launched in the 1960’s to rebuild their numbers, but males seem to be much quieter these days than when I first began to study them in the 1970’s.

I recently had the chance to consider the changes that have occurred in our immediate surroundings when my friend Lori Smith was kind enough to loan me a wonderful little pamphlet called “Birds of Brunswick, Maine” by J. Weston Walch, first published in the Maine Naturalist in March 1926. The writer offered a snapshot of roughly 200 birds that migrated through or bred in this area, based upon his own observations and those of his friends, many of them hunters. You may find some excerpts of interest, starting with these on local waterfowl…

Mr. Walch quickly comments on Merrymeeting Bay, a shallow body of water formed by the junction of four rivers — the Kennebec, Androscoggin, Cathance, and Abagadassett. The Indigenous name for the Bay was Quavocook, meaning “the duck water place.” Mr. Walch called it “…one of the finest bodies of fresh water for a resting and feeding place for waterfowl to be found in the State.” He went on to note that “…wild fowl sometimes congregated in…such numbers, and made such a noise in the night, that the settlers were unable to sleep until they had driven the intruders away. It is said that to accomplish this they sometimes had to throw firebrands among them.” No such issues today, I fear.

The writer then references an 1876 publication called “Wheelers’ History of Brunswick” which noted that at the time of settlement Brunswick was thick with old growth forest: oak, beech, and pine. By 1820 there were 25 sawmills in the area including Topsham, and by 1839 Brunswick alone had thirty sawmills. With each sawmill cutting an estimated 500,000 board feet of lumber for a growing country, imagine the rapid changes to the local forests and environment with the inevitable impact on wildlife. Of interest is a note that passenger pigeons were still common in 1876, although far fewer were observed than in the 1820’s when they were thick in the forests and skies. Passenger pigeons were gone by 1914.

In 1926 Mr. Walch described black ducks as the most common duck in this region, with up to 15,000 observed in one flock off White Island in Middle Bay. At that time, ducks were still hunted in the spring with an obvious effect of limiting nesting success and lists of ducks harvested by local hunters show black ducks making up roughly 75% of the bag. Another common duck in the fall was the northern pintail. The observation went on to say that mallards were uncommon in those days but that is certainly not the case now, with mallards being one of the most common ducks and considered one cause of the decline in black duck numbers due to hybridization.

Canada geese were described as a common migrant in spring, but uncommon in the autumn. One report showed 4,500 geese in the Bay in April of 1924. Things have changed, with Canada geese having established residency in large numbers and spending the winters here in open water. I found it surprising to read that the raven was considered an unusual bird all those years ago, certainly not the case today.

Red-tailed hawks were described as comparatively rare during migrations. In recent years, thanks to the protections offered by the Migratory Bird Act, red-tails and other raptors are showing up in much higher numbers during migrations and some over-winter in our area. On the other hand, the black-billed cuckoo was described as a common summer resident but Cornell’s eBird app lists them now as rare in our area.

Whip-poor-wills, nighthawks and chimney swifts were all considered common birds 100 years ago but spotting them or hearing them is a more difficult task these days. Those of us of a certain age well remember the delight in watching purple martins soaring around their clustered bird boxes but these days it is unusual even to spot one of those condo-style homes on a tall pole.

It will be interesting to see the results of the five-year long Maine breeding bird survey when the final report is published next year. Preliminary results showed about the same number of birds breeding in the state as in the previous survey done three decades earlier, but the species mix will certainly change. Population estimates will inevitably show some birds as thriving but others struggling in the face of change. I plan to share the highlights of that study when it becomes available.

In closing I will refer to a long-standing scientific principle known as Bergmann’s Rule. Carl Bergmann was a German biologist who noticed distinct differences among and within species living in cold or warm climates. He also noted differences among animals living at northern and more southern latitudes. In summary, Bergmann postulated around 1847 that species in colder environments will be larger in size than the same species living in warmer climates. For an example, consider the white-tailed deer of hot scrub country in Texas with mature bucks averaging around 100 pounds, compared to the bruisers of Maine that are regularly recorded over 250 pounds.

Bergmann commented upon such diversity not only with large-bodied mammals but also with birds, and other scientists later found evidence of this in insects and plants. Clearly there are exceptions to Bergmann’s Rule, but scientists have found evidence that during periods of warming climate conditions, animals seem to have diminished in size. They have pointed to the reversible dwarfing of some species documented by examining skeletal remains from two distinct periods of global warming roughly 55 million years ago. During the Paleocene-Eocene Thermal Maximum average temperatures on Earth were believed to rise 5-8 degrees centigrade for a period of 55,000 years. During the later Eocene Thermal Maximum 2 period, thought to be as long as 100,000 years, temperature rise was similar. In both cases, the cause of the events is thought to have been massive releases of carbon into the atmosphere and the oceans.

Climatologists are increasingly focused on changes in our world with a warming climate. In recent decades we have recorded vast amounts of carbon entering the ocean via thermal vents and the atmosphere has been similarly impacted as a result of industrial activity and massive forest fires. Higher annual average temperatures are causing problems with glacial retreat, rising oceans and disruptive weather events. Regardless of the causes of these changes, it appears that our climate is in a warming phase that will have significant impacts on our environment and our wildlife. One can only wonder what our heirs will find in the Maine of 2123.

If you like Ed Robinson’s writing, check out his two Nature Notes books! Click here for more information.