The more time I spend in nature, the clearer it becomes that the four seasons are a myth. At the very least, they are too simplistic: how can we look at the blustery cold days in late March, when chipmunks emerge from semi-hibernation and arctic waterbirds court in the harbors, and the hot days in early June, when cicadas buzz and warblers sing in the trees, and call them both spring?
The truth is that our year is made of dozens of short seasons, each bleeding into the next like runny watercolors. One such micro-season comes in early August. I like to think of this time as invisible fall: the weather still looks like summer, and the diversity of birds is mostly the same as it was a month earlier, but if you watch closely, these birds’ behaviors start changing, and it becomes clear that summer is largely over.
By now, shorebirds have been acting like they are deep into fall for a while. Go out to any mud flat or salt marsh at low tide and you’ll surely see scores of these small, long-legged birds scurrying around the flats, probing the muck with their bills. Shorebirds are weird, though. Being high arctic breeders, their breeding season is short, so their fall migration begins on the Cape around the end of June when most birds are still incubating eggs.
The big recent changes here are happening with land birds. I saw one such change on Aug. 1 at the wetland at Bayberry Hollow Farm in Provincetown: a flock of brown-headed cowbirds were there, marching around the horse paddocks.
These flocks, it seems, tend to form primarily in the fall and are composed of both juvenile and adult birds. These juveniles have spent the first weeks of their lives being raised by other birds whose nests they got dumped in by their parents — this flock probably represents the first cowbirds the juveniles have ever met.
Driving to Wellfleet that evening, I saw that flocking in the lead-up to fall is not restricted to cowbirds. A swarm of a few hundred tree swallows danced overhead as they gathered to roost at the east end of East Harbor in Truro, a roost that will continue to grow through the fall. Farther along, a river of grackles appeared in the sky near Wellfleet’s Herring River, also gathering at a roost that will grow during the fall.
August and September are also peak heron season on the Outer Cape, when the year’s crop of young birds join their adult counterparts in the marshes. It’s a good time of year to find uncommon herons, such as the juvenile yellow-crowned night heron that I came across at Herring Pond in Eastham earlier in the month.
This speckled brown bird probably didn’t hatch on Cape Cod, since yellow-crowned night herons are quite rare breeders in the state. Young herons are prone to wandering at this time of year, though. Something about the Outer Cape attracted this young bird from its nesting ground, perhaps in Connecticut or New York.
In the forests, the behavior of warblers makes fall’s approach apparent. During the summer, these tiny songbirds lead rather antisocial lives. The males fiercely defend territories from encroachers, and parents focus on raising their young. But the young fly the coop by late July, leaving these birds free to form flocks.
I was taking an early morning walk along the Herring River in Wellfleet with another local birder when we came upon one of these warbler flocks. It was full of many of the most common breeders in the region: yellow warblers, ovenbirds, black-and-white warblers. But fall flocks like these have far more than just warblers. This one was loaded with chickadees, cardinals, gray catbirds, and even a pair of skulky hermit thrushes. A lot of these birds were juveniles, too, from right along the Herring River.
As we combed through this flock, I caught sight of a strange-looking warbler flitting through the brush. It had a pink bill, a short tail, a buff body, and black stripes on its head. I blurted out, “Worm-eating warbler!” This is a rare bird on the Outer Cape, typical of more southern forests. It flushed, zipping farther down the trail and diving into a bush. We followed it, maneuvering to get better looks and a photo.
There is no better time to spot rarities than the fall. There are lots of adult birds wandering around looking for food on their slow journey south and plenty of young birds still learning the ropes of what being a bird is like.
After about 10 minutes, the bird popped back out, and my friend snapped a photo for proof. Proof is needed, since outside of a tiny population around Falmouth and Mashpee, worm-eating warblers are a true rarity on Cape Cod. Our sighting was only the fourth fall record north of Orleans on the species, according to the citizen science database eBird.
As we continued to walk, there was one change that stood out from the others: the quiet. A month ago, our forests had a rich soundscape of cardinals, pine warblers, tufted titmice, and other local breeders. Now, those birds are mostly just calling — save for the songs of a few loud males, birdsong is notably absent.
Even with the heat of August still blazing, watching the birds I know that, before long, cold winds will sweep through the northeast and herald the end of summer — for humans, at least. For birds, summer’s been over for a while.
