By BILL CHAISSON
By Bill Chaisson
Because I have not been going out for walks at midday rather than in the mornings and evenings, I have not been seeing big flights of migrants. Most birds other than raptors migrate at night, so the best time to see them is first thing in the morning, when they descend to some likely spot in order to feed, often ravenously. The birding community of New Hampshire posts their sightings at NHBirds, while eBird (maintained by the Cornell Laboratory of Ornithology) provides this service for the whole country.
As yet I have not seen anyone in New Hampshire post having seen hundreds or even dozens of warblers or other migrants at a single go. Migration is still building to a peak, but as I have lamented in this column in the past, the number of migrating birds has simply declined over the last several decades. There are several factors driving this phenomenon. As I noted in my last column, early 20th century legislation to protect wildlife was primarily aimed at regulating or stopping the hunting and trapping of birds. In the late 20th century and early 21st century it is the environment on which birds depend for food and shelter that needs protecting.
One of the 20th century stories involves the coffee-growing regions of Colombia. This country sits at the top of the Andes and the northern edge of the Amazon rainforest and has the highest bird diversity in the world. It is the destination of many North American species that are members of families with Neotropical origins.
Once upon a time Colombia was called a “Third World” country, which merely indicated it was not part of the First World (Western industrialized countries) or the Second World (the Soviet bloc). Now countries like Colombia are referred to as “developing countries” because economic changes tend to happen in desperate surges to catch up with the “developed countries.”
Gustave Axelson, the editorial director at the Cornell Lab of Ornithology, went to Colombia in 2018 to report on the changes in the coffee plantations there.
“From the 1970s to the 1990s,” he wrote by way of background, “more than 60% of Colombian coffee lands were cleared of forest as new varieties of sun-grown coffee were planted. During that same period, populations for many Neotropical migrant species plummeted—a drop many scientists say is related to deforestation of the birds’ wintering areas across Central and South America.”
Forty-two migrants are known to winter in coffee plantations, 22 of which are in decline, but the cerulean warbler was the poster child for this phenomenon; its numbers decreased 70% after clearing for coffee began. Since the 1990s, however, there has been a move toward shade-grown coffee. “That’s not to say shade coffee is better habitat than primary forest,” wrote Axelson, “rather, it’s a vital addition to what’s left. More than 75% of Colombia’s mountain forests are gone. Some species may rely on shade-coffee farms in the absence of forest.” Shade-growing is also sustainable and produces better coffee.
The widespread wildfires in the western third of the country are a threat to migrants in the present. The ash from these fires is now visible (especially near sunset) here in New Hampshire, but a map at birdcast.info, a website that covers bird migration, shows a huge swath of smoke and ash in an arc from the Southwest north to Alberta and then sweeping eastward. Several studies have shown that “normal” air pollution negatively affects bird health. This unusual pollution is deadly. The biggest die-off was discovered at White Sands, New Mexico and reported by CNN on Aug. 20; hundreds of thousands of dead birds were found, many of them migrant species, and then hundreds more were found at other localities across the state. Other sites of mass death have been reported in Texas, Colorado, and in Mexico.
Birdcast.info is not primarily doom and gloom, however. They post a daily map of the U.S. showing “migration intensity.” The map generated for Sept. 18 showed high intensity predicted in the east would be in two broad areas that parallel both sides of the Appalachians, starting in upstate New York. According to the site, “these forecasts come from models trained on the last 23 years of bird movements in the atmosphere as detected by the US NEXRAD weather surveillance radar network.” The model predicts moderate to high intensity across much of New England, diminishing somewhat over the next two days.
You can join eBird free of charge. The site includes a map of the whole country filled with “pins” at the site of individual checklists. A recent checklist from Mount Kearsarge tallied 22 species. It included eight species of warbler, but another bird has been making a big splash this year: red-breasted nuthatches are everywhere in good numbers.
Over the past two weeks I have encountered them several times, always in groves of evergreens, their preferred habitat. This species is not a migrant per se, but instead is prone to periodic southward irruptions. This is apparently one of those years. I have seen groups of up to five, and 10 were counted on Mount Kearsarge on Sept. 12.
Raptors migrate during the day, so you can watch them en route rather than when they stop to feed. The Pack Monadnock Raptor Migration Observatory at Peterborough posts their counts daily at NHBirds. On Sept. 17 they observed 2,195 broad-winged hawks, a species that always migrates in large flocks, with 4,776 for the season so far. The broad-winged hawk family I was watching in Sutton departed its nesting area in mid-August. I do not know whether they wander locally before heading south. The other raptor that is regularly seen in flocks is the sharp-shinned hawk. Thirty-six were seen on Sept.17 in Peterborough and 202 have been counted so far this season.
Bill Chaisson, who has been a birdwatcher since age 11, is a former editor of the Eagle Times. He now works for the Town of Wilmot and lives in Sutton.
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