Dying baby birds are becoming an epidemic

I miss the July days I grew up with. Skies were blue. Winds were fair. Summer seldom became unbearably muggy until the first day of the Bangor State Fair.

This year, May marked the 12th consecutive month of record-breaking temperatures globally. When all the data is in, June will be the 13th. July is on pace to smash that record again, especially after the last couple weeks.

In the more than 12 years I’ve been writing this column, not one reader has asked if hot weather kills nestlings. Readers are asking now.

Yes, it does. In fact, it’s an epidemic. It’s been abnormally hot in Maine, and the rest of the country has been even hotter.

Birds across America’s heartland suffered the most. Species that nest in grasslands and agricultural areas of the Midwest can’t escape the relentless sun by seeking shade. Food supplies wither. Nestlings perish from starvation and dehydration.

Birds in hot areas are better adapted to heat, but not this much. In Arizona, temperatures in Phoenix hit 110 degrees 54 times in 2023, topping 115 degrees 20 times. This year, Phoenix broke an all-time heat record, hitting 118 degrees on Fourth of July.

Three billion birds have disappeared from the planet since 1970. To date, the biggest factors contributing to the steep decline have been habitat loss, outdoor cats and collisions with man-made structures.

Although these losses add up fast, at least the birds die one at a time and avoid a mass loss. Excessive heat can kill off an entire brood at once. Losses mount exponentially.

Dutch physicist Daniel Gabriel Fahrenheit invented the mercury thermometer in 1714. For 310 years, we’ve been able to measure temperatures precisely. We know with certainty that global temperatures are rising even as some politicians deny it.

The birds know it, too. There’s been a lot of attention paid to southern species moving north. We’ve certainly seen it in Maine. I keep an informal list of the birds I find now that I never would have seen in those beautiful July days of my youth.

These include Carolina wren, red-bellied woodpecker, tufted titmouse, northern cardinal, turkey vulture and prairie warbler. Several other southern species are now nesting on this side of the New Hampshire border, or soon will be.

We give less attention to northern species moving south. But several North American bird species that typically winter in the Caribbean are opting to nest farther south, to shorten their spring and fall migration routes.

Georgetown University, in cooperation with several other colleges, institutes and the Smithsonian, released an alarming study in December. Shifting tropical rainfall patterns are disrupting wintering habitat for some North American songbirds.

Researchers focused on the American redstart — a common Maine warbler. They found that tougher weather patterns on their summer nesting grounds, combined with unpredictable and inadequate rainfall on their wintering grounds in Jamaica, was reducing the distance redstarts could migrate successfully. Mortality rose, and there was a southward contraction in their breeding range.

In short, “You can’t get there from here.”

Given this data, politicians claim that this is evidence that birds are adapting to climate change just fine. There’s a flaw in their logic. Most birds have nowhere to go. We’re seeing it in Maine.

As heat bakes the Pine Tree State, mountain birds can move upslope. Eventually, they run out of mountain. Two alpine species Bicknell’s thrush and blackpoll warbler went onto Maine’s Threatened Species list just last year.

As sea level rises, Maine’s salt marshes flood more often, jeopardizing birds that nest there. Soon, they run out of marsh. The salt marsh sparrow went onto Maine’s Endangered Species list last year.

The Gulf of Maine is warming faster than 99 percent of the world’s oceans. Maine’s endearing Atlantic puffin has been on the state’s threatened list since 1997. Every year, researchers hold their breath, hoping the offshore puffin colonies don’t collapse.

During hot summers, Maine’s cold-water fish species are displaced by an influx of inedible warm-water species. Puffin chicks starve. Breeding success has been on a roller-coaster ride for years.

We can always hope that threatened birds will adapt, but hope alone is a doubtful strategy. Adaptation is a slow process, accomplished by accidental trial-and-error. When their habitat changes too quickly, few animals can adapt fast enough.

How much of this am I seeing in my own backyard? Every year, red-breasted nuthatches nest behind my house. This year, for the first time, there are none.