It’s no coincidence that ospreys return to their nesting grounds just as alewives and blueback herring run up southeastern Massachusetts coastal streams from the ocean. Herring make up 50 to 80 percent of ospreys’ spring diets.
I counted eight ospreys circling above the new wetlands-to-be along the Coonamessett River this week. Two dove and came up with fish.
(I quietly thought to myself get them now, guys, because as vegetation grows up around a new, deeper and wood-filled channel, there will be more places for migrating fish to hide. And it is mostly males that are hunting while females stay at nests to incubate and defend eggs.)
And it’s no coincidence that just as oak leaves emerge—and a diverse and abundant community of leaf-eating insects hatches out—that thousands of warblers and other northward-migrating songbirds arrive to feast and fuel up for their spring journey.
I counted dozens of those migrant species on a near-perfect day last Saturday, May 16, as part of Mass Audubon’s annual spring “Birdathon,” a fun-filled (but solo this year), 24-hour dash to record as many different species as possible.
It’s not much of an overstatement to argue that timing is everything in the natural world. When I stopped my neighbor of 34 years to chat with her about my bird-finding, she said, “It’s been one of those cool, slow springs with lots of birds like we used to have.” She’s right on three counts.
One, this spring has been later than normal. About nine days later than normal, based on models of leaf phenology—or timing—developed from long-term records in forests of New Hampshire. Two, springs are changing. The date of tree bud burst—the best recordable benchmark of spring—now arrives a week earlier in New England than it did 50 years ago. Spring temperatures also fluctuate more. And yes, there really are fewer birds.
The timing of the burst of spring, of floods, wet seasons, plankton blooms—different combinations of light and temperature and water that create the conditions that allow plants to grow—is critical. The animals that eat the plants, and the animals that eat those animals, all follow from that.
That timing is fine-tuned by evolution. If you are a bird, you arrive too early—while it’s still cold and wet—you eat less, you can’t get on with the business of breeding, and in the worst case you die. Play it safe and arrive too late, many of the best breeding territories are already taken, and maybe you also fail to reproduce. So there’s a premium on arriving at exactly the right time.
Climate change—what’s changing our springs—disrupts that timing. Most birds use day length as the primary cue to begin to migrate and prepare to breed. Other factors on the breeding ground—temperature, snow cover, food supply—can adjust the overall timing, but only by a modest amount. Because the triggers to migrate and begin the hormonal and other changes required to breed are hard-wired by evolution, and because climate change does not affect day length but does affect conditions along migration routes and on breeding grounds, large numbers of bird species will have a hard time adjusting to these new mismatches.
Higher climate variability and other human-caused pressures compound the problem.
A whole new field of biology is emerging to examine these mismatches, and not just in birds. For example, a study published last month that documents Cape Cod’s endangered North Atlantic right whales are skinnier and in poorer condition compared with their close kin, southern right whales off of Argentina, Australia and New Zealand. Changes in the abundance and distribution of the North Atlantic right whales’ primary zooplankton prey in their feeding grounds likely contribute to poorer condition—along with the fact that about 15 percent of whales each year expend extra energy when they get entangled in fishing gear.
There’s something magical about animals moving around this planet that we share with them. When asked by a Boston Globe reporter why migrating warblers are so appealing, Chris Wood, director of the Cornell Laboratory of Ornithology’s eBird citizen science bird reporting program responded, “Because they’re awesome!”
I couldn’t agree more. I live for the last three weeks in May. And I think the phenomenon of animal migration is awesome, and worth cherishing and protecting. It’s also worth thoroughly enjoying—right now.
But like many climate change scientists, I struggle watching spring with what I know is coming.
In his book, “Round River,” Aldo Leopold wrote, “One of the penalties of an ecological education is that one lives alone in a world of wounds. Much of the damage inflicted on land is quite invisible to laymen. An ecologist must either harden his shell and make believe that the consequences of science are none of his business, or he must be the doctor who sees the marks of death in a community that believes itself well and does not want to be told otherwise.”
This cuts a little too close to the bone right now, when science finds itself—in far too many high places—kicked to the floor.
Sadly, we live in a world full of increasingly severe wounds. To Leopold, those wounds used to be fixable cuts and abuses like overgrazing, clear-cut logging and misguided hunting of top predators. Today—with climate change—they are growing gashes.
It’s nice to have an old-fashioned spring. But it’s also a reminder about what we are losing.