We should be in that sweet spot on the calendar, too warm to have the heat on and too cool for air conditioning.
Opening the windows is all the climate control you need this time of year, and if a cold snap hadn't chilled Annapolis this week that's what I'd be doing every night.
Instead, I find myself still wrapped in a winter comforter while pining for spring nights of sleep under an open window. That's because the ospreys are back.
There are a dozen nesting pairs circling the creeks around my home, building nests like crazy quilts of twigs, twine and long grasses. Visions of black and white, they soar on the wind, wheeling above the trees and diving into diamond-bright waters before winging their way home with an unfortunate fish clutched in their talons.
Songbirds are nice, but waking to the dawn cry of an osprey is to understand a piece of life on the Chesapeake Bay.
When the ospreys returned to Annapolis last month after a long trip from South America, I started to wonder what the future holds for this favored bird. Climate change is already altering the region. Will it impact this beloved species, too?
The osprey is loved for its looks, but also for its story. It is a symbol of resilience on the Chesapeake. After the widespread use of the synthetic insecticide DDT caused a population plunge, a book by a Maryland author helped wake us to the danger.
Friday is Earth Day, which celebrates that achievement. But this year also is the 60th anniversary of "Silent Spring," by biologist and nature writer Rachel Carson. Her explosive work exposed how pesticides aimed at mosquitoes traveled through the food chain and planted ideas and arguments that still resonate today.
The osprey made a remarkable recovery, directly because of Carson. Everybody wants to borrow that success story, now. There are osprey sports teams, street names, real estate companies; and even those Navy vertical-lift aircraft flying above the city to the Naval Academy are named for them. They inspire painters and photographers, and the Chesapeake Conservancy and other groups run popular web cameras so we can all watch them in their nests.
So I started asking. What I found is reassuring, the osprey appears to be an early success story as a warming climate changes the environment – stoking up storms, reducing seagrass, changing rainfall patterns and increasing flooding.
“So, we know quite a bit about ospreys in the bay, but in terms of climate change we haven’t seen any impact so far,” said Bryan Watts, director of The Center for Conservation Biology at the College of William & Mary in Williamsburg, Virginia.
There are areas of concern. Most have to do with a tiny fish most people know next to nothing about – menhaden.
Are they at risk? Depends on who you ask.
A 2014 study by the National Audubon Society predicted that by 2080, global warming could mean that osprey will lose 79 percent of their current summer range.
While that might not mean the Chesapeake Bay or even the East Coast, the study found that it’s uncertain whether the bird will be able to find enough fish in stable and expanded portions of its range, or how sea-level rise will affect its success in coastal areas.
“I can't give you any definitive final answers, but active monitoring of osprey nest colonies is called for,” ecologist Paul Spitzer, who has been studying osprey in the Mid-Atlantic for five decades, wrote in an email.
First, some numbers. The population of osprey on the Chesapeake is massive, one Watts describes as the largest breeding population in the world.
When dichloro-diphenyl-trichloroethane was developed in the 1940s, it was a synthetic insecticide used to combat mosquitoes that spread malaria, typhus, and other insect-borne diseases that ravaged military and civilian populations in parts of the world.
But a decade later, it had lost much of its effectiveness because the insects were growing immune, and scientists were beginning to question its impact on the environment.
Then in June 1962, New Yorker magazine published excerpts from Carson's upcoming “Silent Spring.” The book explained how the law of unintended consequences was playing out in nature and posed a direct threat to human health through the spread of chemical-induced cancers.
One of her arguments was that DDT bled into the food chain, then worked its way from species to species until it destroyed the survivability of eagle, osprey and other raptor eggs by weakening the shells. Carson wrote that humans had the right to be protected from those kinds of dangers.
"If the Bill of Rights contains no guarantee that a citizen shall be secure against lethal poisons distributed either by private individuals or by public officials, it is surely only because our forefathers, despite their considerable wisdom and foresight, could conceive of no such problem."
It helped launch the modern environmental movement and led a decade later to the creation of the U.S. Environmental Protection Agency, which banned DDT in 1971.
In that year, Watts says there were 1,400 nesting pairs of osprey on the Chesapeake. Fast forward to the 1990s and that population had grown to 3,500.
Today, there are 10,000 to 12,000 nesting pairs in the bay, and they’re continuing to spread out from the main stem up the tributaries where the water is fresher and there hasn’t been a recent history of osprey nests.
“Since 2000, that has been the fasting growing segment of the bay,” Watts said.
If a warming climate, shorter winters and longer summers were affecting osprey, it might show up first in their arrival time or when they lay eggs. Bald eagles are showing signs of that, Watts said, arriving eight to 10 days sooner than before.
There’s some variation in osprey, too, but Watts said it’s the difference between nests in salty parts of the bay and those in freshwater tributaries. Fish grow larger in freshwater, feeding ospreys migrating from South America a little earlier in the year.
The biggest threat to the continued success of the osprey appears to be in its primary food.
Globally, ospreys have a diverse diet. But in specific locations, they focus on one species, maybe two or three. In the main stem of the Chesapeake, that food is menhaden – a small form of herring.
There’s a wonderfully breathless description of an osprey fishing for menhaden in H. Bruce Franklin’s seminal 2007 book, “The Most Important Fish in the Sea.”
“Hovering high above the other birds, a male osprey scans for targets beneath the surface, then suddenly folds its gull-shaped wings and power-dives through the aerial tunnels, extends its legs and raises its wings high over its head an instant before knifing into the water in a plume of spray, emerges in another plume and laboriously flaps its four-foot wingspan as it slowly climbs and soars away with a writing menhaden held headfirst in its talons.”
When there are more menhaden, there is more food for osprey. Less fish equals fewer osprey.
It's not just a meal.
Menhaden are oily, high-lipid fish. Osprey nestlings can convert lipids to "metabolic water." So, in addition to serving as a primary food source for bay osprey, Spitzer said those fish also are the only water source for young birds in those open nests on long, hot, full-sun summer days.
“Things get hot and the nestlings are in that exposed nest, shaded by the female, but with no water source except their prey,” he wrote.
At some nesting sites, menhaden are not that abundant, and there are few prey alternatives – such as Broad Creek near St. Michaels. In 2018, Spitzer said a June heatwave resulted in larger numbers of dead nestlings.
In the Chesapeake, the largest drain on menhaden is Omega Proteins. This Virginia fishing company uses long seine nets to harvest tons of the small fish every year for products like chicken feed and vitamin supplements.
Near those fishing Virginia grounds in Mobjack Bay, Watts and his research team have been watching how the osprey copes with Omega, which he called a "resource depletion" fishery. In observations back to the 1970s, menhaden historically served as 70% to 80% of the osprey diet. Today, it’s 20%.
Regional and state officials have both cut the quota for menhaden fishing in recent years. But there just isn’t a substitute for the birds that provides the same benefits.
“There is no question that the osprey that nest in Mobjack are not breaking even demographically,” Watts said.
As the planet continues to warm, there could be an impact on menhaden. Fish are affected by a variety of environmental changes, such as increased stormwater runoff caused by clearing forests.
Research on the Severn River has shown the existence of small dead zones, areas with little or no dissolved oxygen in the water, in creeks and bays previously undocumented, said Tom Guay, a spokesman for the Severn River Association.
That can force changes in the behavior of small fish, pushing them to the top of the water column and making them susceptible to mass die-offs known as fish kills.
Richard O. Bierregaard Jr., a distinguished visiting research professor at the University of North Carolina, Charlotte, is optimistic about the ability to adapt as climate change affects the bay. He said that despite the 2014 Audubon forecast, Ospreys can switch to new food where it is available.
The fastest-growing populations in freshwater streams aren’t dependent on menhaden; instead eating catfish and gizzard shad.
“They eat pretty much whatever fish is around. So, water temps may change and that may well change what fish are available (this is already happening in the Gulf of Maine), but ospreys won’t care,” he wrote in an email. “In fact, in coastal areas, they switch fish they feed on several times during the breeding season as some fish migrate into their hunting range and others drop out.”
The stress on osprey in Maryland is less because there is no commercial fishery focused on menhaden like the one in Virginia. But there are areas, like the one Spitzer described on Broad Creek, that have fewer menhaden and consequently lower osprey populations.
“Local osprey nest abundance and reproductive success is tied to menhaden prey base abundance in this region,” Spitzer wrote.
There are other pressures, too.
Spitzer said that ospreys are social raptors, living in “exploded colonies,” with the nest sites spread over as much as 40 square miles.
“These are often beautiful, exciting places,” he wrote in a five-year study of the Broad Creek colony. “So I poetically term them ‘Osprey Gardens.’”
These gardens are usually over bodies of water or salt marshes and augmented by humans who put up nest platforms. On Broad Creek, Spitzer recommends establishing the area he observed as a sanctuary.
It’s too late for a similar unspoiled area in Talbot County, where the owner of two headwater streamside forests is having the mature trees harvested.
“These are lost opportunities for neighborhood sanctuary and recreation,” Spitzer wrote. “And, of course, forest protection is a measure to mitigate climate change. Regulations did not protect these remnant forests, 50 and 35 acres, which were sold for paltry sums… Private property, perfectly legal.”
After her book was published in September 1962, the chemical industry sued Carson, the magazine and her book publisher. It was an era when criticizing government policy carried real risks, especially for a woman.
The lawsuit failed, but attacks on her work live on. Critics have blamed her as recently as a few years ago for millions of deaths caused by malaria, without acknowledging that DDT was already ineffectual by the time Carson wrote about it.
She died of breast cancer a year after her book was published, and there is some speculation that she may have been willing to suffer the attacks sure to come from industry sources because she knew she didn't have much time left.
Some of the science she used for her arguments was flawed, based as they were on scientific understanding in her time. But her central idea still rings true.
We almost daily read about how the seas are overflowing with microplastics and forever chemicals. Her work led to the creation of cancer registries that can be used to link the illness to sources of chemical pollution, such as the death of Anne Arundel County firefighter George "Walter" Taylor in 2020.
He worked with perfluoroalkyl and polyfluoroalkyl, "PFAS" commonly used in firefighting foam. The Maryland General Assembly banned them in a law named for Taylor and adopted this spring.
If Carson's message on DDT was heeded, her idea that there has to be a balance hasn't always been – and climate change and overzealous fishing are just more examples.
For osprey, however, Carson's final, and most famous work has been a success. It's just not an absolute.
“They’ve re-colonized portions of the bay,” Watts said. “But there are some of these places that do give us concern.”