Nighthawks and broadwings crowd the skies

Last modified: 9/2/2015 7:19:11 PM
I enjoy learning the vocabulary that comes when you delve into a subject, birds included. I’d thought “gregarious” referred to chatty, social people. I have a most gregarious brother.

Seeing the word applied to birds seemed odd, but dictionaries present that meaning right up front. The word stems from the Latin grex, meaning flock or herd. It’s even used botanically to describe plants that grow in clusters.

The first usage back some 400 years probably did not describe humans.

Anyway, a bird that’s gregarious as a migrant has been grabbing birders’ attention for over a week with totals well in the hundreds in the few late-afternoon hours it prefers for travel.

The bird, common nighthawk, is neither common, a hawk, nor nocturnal. It’s a bird with “crepuscular” habits. That’s another great word and I use it often. Meaning active at dawn and dusk, it derives from the Latin word for twilight, crepusculum.

Carl and I joined a dusk nighthawk watch one week ago at Don and Lillian Stokes’s along the Contoocook River’s Powdermill Pond area. North-south rivers provide migrants navigational help as well as bountiful insects to feed on.

Nighthawk watches surely are the most cushy of all, timed perfectly for ‘the cocktail hour’ of late summer when nighthawks migrate.

From deck chairs we raised binoculars and wine glasses as these elegant, long-winged birds passed by or milled about feeding on the wing.

We counted 136 that night, and chat during the watch raised more questions than answers.

Why do nighthawks stir to activity for a couple hours at day’s end? What do they do the rest of the time?

Why do so many show up in southern New Hampshire, some nights surpassing 1,000? (The Stokes’s count high so far is 749, with 745 a close second, and daily highs in Concord and Henniker reached twice that.)

Breeding nighthawks, once common, have just about disappeared from the state, and are listed as threatened in Canada because of a 50 percent decline over 50 years — and yet the fall migration continues to amaze.

Why do some flights head north, not south? I’d assumed they find huge swarms of ants, their preferred food, and switch directions to feed. But no, their northerly flight is direct, not swerving to catch insects.

As for preferred prey, stomach contents of one nighthawk contained 2,175 winged ants and 500 mosquitoes. Hard to believe.

Nighthawks have huge mouths, and ant swarms can be dense.

As for the phenomenon of swarming ants this time of year, a mature colony responds to overcrowding by creating winged fertile females (virgin queens) and males that disperse from a colony. Other colonies swarm at the same time and they join together.

A fertilized female falls to the ground, breaks off her wings, and sets about creating a new colony with enough stored sperm for a decade’s worth of offspring — if she succeeds in establishing a new colony. That’s a big ‘if.’

Winged males, their one job in life done, die a quick death. Without their sister worker ants to feed them, survival is brief.

Sunday evening, winged ants interrupted a cookout on our son’s deck during ‘the cocktail hour.’ The same ants that drove us indoors are also feeding dragonflies and several bird species this time of year.

That’s perhaps why common nighthawks are most active at dusk, a time when mosquitoes and other edible insects are active.

Phil Brown emailed me Monday morning at 2 a.m.: “Can’t sleep and am puzzled and amazed by nighthawks as I have been each fall since I was a kid.” That evening he’d seen “well over 500” from downtown Peterborough — despite trees blocking a lot of sky viewing.

His search of Internet birding sites confirmed that southern New Hampshire is a prime migration route for nighthawks, and he wrote:

“There is something special about N.H.’s landscape for nighthawks. Clearly it has to do with n-s running rivers, but beyond that? The ‘why’ is still the big question about flight timing, direction, and size . . . Many questions, few answers, but a little deeper digging and coordinated observations is needed. Nighthawk migration watches as a pre-season activity to the hawkwatch? Next year, for sure.”

Phil coordinates N.H. Audubon’s annual fall hawkwatch on Pack Monadnock that runs Sept. 1 through Nov. 15 — and features perhaps the most gregarious migrant of all.

I’m giving a hawkwatch workshop Sept. 14, 7 p.m. at Shieling Forest in Peterborough, in preparation for the spectacular flights of broad-winged hawks due that week. Broadwings get a lot of attention for their swarming, crowd-pleasing flight formations, but eagles and ospreys and another 10 or so raptor species please for different reasons.

I hope to borrow a slide from Eric Masterson’s recent hawk migration talk at the Amos Fortune Forum. It’s a photo of pepper flakes on paper. That’s how kettles of broadwings are described when flight conditions are perfect and thermal lift carries a group high before they set their wings for a long coast south to the next free ride high.

Katrina Fenton returns as Audubon’s hawkwatch staffer. Drive or hike to the summit and follow the path north a bit to where her eagle eyes don’t miss much. Gregarious watches are the goal: many people looking north and many exclamations of wonder stirred.

Eric described the fall hawk migration as the most spectacular event of many spectacular events in the natural world. Join in and see if you agree, and join the Sept. 14 hawkwatch workshop, too.

Backyard Birder by Francie Von Mertens appears every other week in the Monadnock Ledger-Transcript.


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