Author Archives: Wayne Petersen

About Wayne Petersen

Wayne Petersen is Mass Audubon's Director of Important Bird Areas Program.

Wings over the Water: a seasonal parade

It was gray and overcast, the sea was churning, and the wind was fresh from the Southeast – perfect conditions for watching a parade in early November….and watch we did!  Our viewing location was North Beach on Cape Cod’s back side, all the way from East Orleans to Chatham.

“Marching” in this winged parade were over 40,000 sea ducks and seabirds, all headed southward in a more or less continuous passage emanating from destinations as far away as Alaska, western Canada, James Bay, Labrador, the Gulf of Saint Lawrence, and Newfoundland.  This timeless event was part of the annual migration of vast numbers of waterbirds, all originating in nesting grounds far to the north, and all bound for winter destinations well to the south.

The departure of waterbirds escaping the rigors of sub-arctic and boreal winter is part of a great migratory cycle that has evolved through the millennia into one of the most magnificent autumn spectacles to be witnessed on the Atlantic Coast of North America.  When migration conditions are ideal, the number of birds involved may exceed extravagant!

Common Eiders © Peter Flood

And so it was on November 5, 2017.  Between 8:30 a.m. and 3:30 p.m. my companion and I tallied approximately 12,000 Common Eiders, 18,000 Black Scoters, 5000 Great Shearwaters, 3000 Northern Gannets, 100 Razorbills, 400 Black-legged Kittiwakes, and 550 Bonaparte’s Gulls.  When combined with lesser numbers of numerous other species recorded that day, we estimated we had seen over 44,000 waterbirds in approximately seven hours of more or less continuous watching!

The dynamics and precise timing of such movements varies from species to species, but the net effect is unequivocal—the birds moving under such conditions are singular in their purpose, and all are taking advantage of weather frontal conditions and wind directions in ways that will maximize their migratory efficiency.

On November 5,

  • The sea ducks (e.g., Common Eiders) were flying in linear or loosely organized groups, often numbering in the dozens or low hundreds, sometimes flying low over the wave troughs, and sometimes well above the sea surface.
  • The powerful gannets on the other hand tended to fly high, often more than 50 meters above the sea, occasionally turning abruptly and plunging into the sea to catch a fish during their journey.
  • The shearwaters scaled like skipping stones over the sea as far as the eye could see, alternately using the wind between the wave troughs to carry them upward well above the waves, and rapidly gliding downward between the waves to catch another updraft that would carry them skyward again.
  • The more delicate and tern-like Bonaparte’s Gulls stroked along in small parties relatively close to the beach, while further off shore, football-shaped Razorbills would periodically rocket southward between the wave troughs on stubby wings that reminded one of flying penguins.

All this motion, and all headed in the same direction, even though few were bound for the same precise destinations.

Razorbills and Black Scoters © Peter Flood

Where are they headed?

Many of the Black Scoters and Common Eiders are likely headed for the shallow shoals off Monomoy or Nantucket where great submarine beds of blue mussels will sustain them through the winter. Other scoters however might not stop until reaching New Jersey or shoal waters off the Mid-Atlantic Coast for the winter.

The Northern Gannets will likely precipitate out along the continental shelf all the way from Cape Cod to the Gulf of Mexico.

Northern Gannets and gulls off Diamond Shoals, NC © Peter Flood

Most of the Bonaparte’s Gulls will no doubt spend the winter from North Carolina’s outer banks to Florida and the shores of the Gulf of Mexico.

The Great Shearwaters, however, will not stop until they arrive at their austral summer destination on the Patagonian shelf off Argentina, or the remote archipelago of Tristan de Cunha.

So many birds and so little time to accomplish these epic migrations!  However, for land-bound observers privileged to live in a region where these avian parades are seasonally visible from shore, these great waterbird movements represent one of the most dramatic natural parades to seasonally be observed in Massachusetts.

So the next day a brisk east wind is blowing on the heels of a cold front, grab a pair of binoculars and head for the nearest coastal headland!  You won’t be disappointed.

 

 

Hoots, Toots, and Who Cooks For You

Great Horned Owl © Phil Sorrentino

Halloween is typically marked by creepiness—creepy creatures, creepy people, and often creepy sounds.  While it could be true that some of the creepy Halloween sounds are uttered by ghosts, ghouls, and goblins, it’s also true that most are not!  In fact, some mid-autumn night sounds are actually produced by several of our most popular, if not enigmatic birds: owls!

Massachusetts regularly hosts five nesting owl species: Barn Owl, Eastern Screech-Owl, Great Horned Owl, Barred Owl, and Northern Saw-whet Owl.  Other Bay State owl species are either rare or only seasonal visitors.  Because most owls are active at night, much about the lives and activity patterns of owls often goes undetected or unobserved, and frequently it is only the voices of owls that give us a clue about their presence, sometimes without our even knowing which species is making a particular sound.

What are they saying?

Like most birds, owls vocalize to communicate information important to locating or communicating with their mate, their offspring, or other owls intruding into their territory.  And for these different functions, owls regularly use a variety of calls, some of which are the creepy sounds potentially heard by little trick-or-treaters during their nocturnal Halloween walks.

Great Horned Owls and Barred Owls Hoot

If you happen to live where there is good mix of deciduous (broad-leaved) trees and large white pines interspersed with open areas practically anywhere in Massachusetts, especially if the trees border a lake or pond shore, the deep, resonant hoo, hoo-hoo-hoo, hoo, hoo at dusk or dawn in the autumn is a clear indication that your neighborhood is occupied by a pair of Great Horned Owls.

Alternatively, if you should be awakened in the middle of the night by a rhythmic hooting that clearly sounds like who-cooks-for-you, who-cooks-for-you, allll, and if it has the quality of a distant barking dog, then the neighboring woodland is almost certainly home to a pair of Barred Owls.

Barred Owl © Derek Allad

Northern Saw-whet Owls Toot

While most of our local owl species are relatively sedentary throughout the year, the tiny Northern Saw-whet Owl is highly migratory in varying numbers during October and November.  Impressive numbers are annually captured and banded at several different owl-banding stations in eastern parts of the state—including Drumlin Farm.

Generally silent, territorial saw-whets typically give a long series of mellow, mechanical, whistled toot-toot-toot-notes that sometimes may continue for many minutes.  Primarily a denizen of coniferous forests in western Massachusetts, but also in the pine barrens of southeastern parts of the state, including on Cape Cod where it is probably second only to the much larger Great Horned Owl.  In fact, the Northern Saw-whet Owl is undoubtedly far commoner than most folks suppose.

Northern Saw-whet Owl © Heather Demick

Barn Owls Shriek

For the keen listener abroad at night on Martha’s Vineyard or Nantucket, one can occasionally hear the raspy shriek of a Barn Owl as it leaves its daytime roost, or forages for mice over open moorland.

Barn Owl © USFWS

Eastern Screech-Owls Whistle

At dusk on Halloween evening it would also not be surprising to hear the soft descending whistle (or whinnying sound) of the little Eastern Screech-Owl, the species which is undoubtedly the most common owl in Massachusetts.  Screech-owls also have a low, hollow, monotone whistle that can sometimes be heard throughout the night.

Eastern Screech-Owl (grey morph) © Nathan Goshgarian

Listen carefully and don’t fear!

So don’t be overly fearful of things that hoot or toot at night!  Indeed, go to the window or door and listen more carefully, or take an evening stroll with a flashlight and see if you can spot one of these fascinating creatures for yourself after dark.

 

A Plethora of Pirates: Jaegers rule at Provincetown

First it was shearwaters—now it’s jaegers!

Earlier this fall the waters off Provincetown made news when an unprecedented concentration of thousands of Great Shearwaters was attracted inshore by a superabundance of small menhaden fish (a.k.a. peanut bunker) that were driven ashore by foraging mackerel. This influx afforded birders, fishermen, and the general public a unique opportunity to see these normally open ocean seabirds at practically arm’s length.

Now, several weeks later, exceptional numbers of jaegers have taken center stage in these same waters.  Dusky-colored and predatory, jaegers are gull-like seabirds that in North America nest on high latitude arctic tundra from Alaska to Labrador. Taking several years to mature and exhibiting high variability and a complexity of plumages, jaeger identification can confound even the most experienced observers.

Parasitic Jaeger (dark morph) © Peter Flood

Meaning “hunter” in German, the word “jaeger” (pronounced “yay-ger”) is well-suited to three closely related species—Pomarine, Parasitic, and Long-tailed—all distinctive in adult plumage because of two, long, pointed or twisted central tail feathers.  But far more exciting is the kleptoparasitic lifestyle of jaegers.  Kleptoparasites are species that obtain much of their food by stealing it from other species, which in the case of jaegers usually means smaller seabird species such as terns.

A Parasitic Jaeger pursues a Common Tern © Peter Flood

Parasitic Jaegers are the new rulers of the waters off Provincetown

In Provincetown it is Parasitic Jaegers that have been maintaining dominion over the hapless terns lingering off Race Point in recent weeks.  Literally dozens of jaegers are currently tracking the hard-working terns off Race Point, the ever vigilant pirates constantly on the lookout for terns carrying fish in their beaks.  Upon spying a fish-laden victim, a plundering jaeger will at once give aggressive chase. With fighter plane-like precision, one or more jaegers will pursue a target with aerial gymnastics hardly seen in any other bird species.  So skillful at piracy are jaegers that they are often able to catch a falling fish relinquished by an intimidated tern before the fish hits the water!

A Parasitic Jaegar prepares to catch relinquished fish © Peter Flood

In the days ahead as the last of the lingering terns head for South America for the winter, the aerial pirates that have been recently harassing them off Provincetown will begin to drift away, shadowing the terns all the way to their South Atlantic wintering quarters.  Although Parasitic Jaegers are capable of capturing fish or scavenging food on their own, during their non-breeding season at sea they generally prefer their criminal life style as a way to obtain food.  Come spring however, the jaegers will head north for their arctic nesting grounds where their diet will shift to small rodents or shorebird eggs and chicks.

Always predatory and always on the move, jaegers are fascinating seabirds that can only be admired when viewed in full pursuit of a fleeing tern, or when observed deftly flying amid the frothy troughs of a storm-tossed sea.

Get to P-town soon to see these spectacular birds for yourself!

Parasitic Jaegers pursue a tern © Peter Flood

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Flight of the Broad-wing: an epic in the sky

Every year, at about this time, dedicated hawk watchers and serious raptor aficionados begin paying particular attention to radar images and weather prognostications on the evening news. Indeed, some devotees even regularly take their vacation in the middle of September. So what’s so special about mid-September? To those in the know with an interest in hawk migration, mid-September is THE time to intercept the peak southward departure of the Broad-winged Hawk (Buteo platypterus).

Adult Broad-winged Hawks are 15 inches-long with a 24 inch wing-spread, a black tail crossed midway with a single wide, white band, a brown back, and rusty-brown underparts.  In flight they are compact, with broad wings that are pale underneath and traced with a thin black border around the edges (as shown in the above photo). Ranging throughout most of the eastern United States and southern Canada west to Alberta, Broad-wings spend much of their summer hunting amphibians, snakes, small mammals, and birds to feed their young.  However in mid-September it is the spectacular autumn migration of this species that annually captivates and mesmerizes hawk watchers, and often even the general public as well.

Unlike other raptors (or most other species of birds for that matter) few have such a telescoped seasonal departure as the Broad-winged Hawk. With seemingly mathematical precision, much of the North American breeding population typically initiates its southward migration sometime between September12–20.  Depending upon weather conditions, in some years this time window becomes even more compressed, occasionally with many thousands of individuals passing favored observation sites literally within a few hours. Here in Massachusetts, Wachusett Mountain in Princeton, Mt. Watatic in Ashburnham, and Mt. Tom in Holyoke are among the better places to witness this phenomenon.

In mid-September Broad-wings across much of their breeding range wait strategically for the passage of cold fronts accompanied by falling temperatures and light winds from the north side of the compass to begin their migration.  Under such conditions the hawks almost simultaneously begin lifting up from the summer woodlands where they nested to search for rising warm air masses called thermals that will help eventually transport them to South America for the winter.

Using such thermals to carry them skyward many thousands of feet, eventually the Broad-wings break out of the thermals and travel to another thermal, often several miles away, by means of long, high-speed power glides that cause them to gradually lose altitude at the same time.  Once they reach another thermal, they then ride the new “escalator” skyward. Because hundreds of Broad-wings are using this same strategy, on a good day for migration, a large thermal often contains many hundreds of tightly soaring individuals all rising upwards at the same time.  In hawk parlance such an aggregation is called a “kettle” (shown below).

On days favorable for migration, many thousands of Broad-winged Hawks make their way southward at the same time using this combination of riding warm air thermals upward for lift, and then power gliding to another thermal so they can regularly cover hundreds of miles a day under ideal conditions. The migration tends to follow the southwesterly leading line created by the Appalachian Mountains. Between the thermal-and-glide strategy, and wind lift created along Appalachian ridgetops, the hawks gradually make their way to the Gulf Coast, where they gradually “turn the corner” in southern Texas to avoid crossing the Gulf of Mexico, and then make their way into Mexico and south through Central America, and finally into northern South American where most will spend the winter.

Not surprisingly there are variations in this strategy along the way, including several world-famous hawk-watching bottlenecks where, with several other species, they pass through Mexico, Costa Rica, and Panama.  While this is by no means the full story, it is the essence of how each year this magnificent raptor accomplishes one of the most amazing autumn migrations in the western hemisphere.

 

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Beachfront Armageddon: A fish tale and a seabird saga

For several weeks the sandy beaches at Race Point and Herring Cove Beach in Provincetown have witnessed a spectacular and practically unique confluence of seabirds and fish.  The players in the P-town saga have been Atlantic menhaden (Brevoortia tyrannus) and Great Shearwaters (Ardenna gravis).

Great Shearwaters are Ring-billed Gull-sized seabirds that maintain their breeding terminus at Tristan de Cunha, a remote archipelago located deep in the southern hemisphere approximately halfway between the tip of southern South America and Cape Horn in South Africa.  Annually most of the world’s population of Great Shearwaters migrates north across the equator to spend the austral winter in the northwest Atlantic Ocean. By late summer most of the adult population has begun the long return journey back to Tristan du Cunha to nest, but the non-breeding sub-adult population regularly remains in North Atlantic waters until late fall.  While in the northern hemisphere Great Shearwaters typically remain on remote fishing banks far off the New England and Atlantic Canadian coasts where they forage on baitfish such as sand lance, capelin, sea herring, or squid and fish bycatch obtained by tracking commercial fishing vessels.

Each high tide left behind a swath of dead menhaden.

Menhaden are a super-abundant forage fish often characterized as one of the most commercially important fishes occurring along the Atlantic coast of the United States, particularly from Massachusetts to the Carolinas (Bigelow and Schroeder’s Fishes of the Gulf of Maine, Collette & Klein-MacPhee, eds., Smithsonian Press, 2002).  Due to their super abundance, immature Menhaden typically less than 2” in length are important fodder for a variety larger predatory fish, marine mammals, and seabirds.  For reasons not always clear, the literature suggests that they are periodically subject to mass late summer stranding and mortality events. These mortality events most often occur in shoal water habitats such as the heads of tidal creeks or small coves like the Herring Cove area in P-town where they may suffer from oxygen depletion or are driven ashore by predators (op.cit.).

Regardless of the explanation, a massive menhaden mortality event took place during the last couple weeks of August and early September.  Most notable however was the fact that unprecedented numbers (i.e., many thousands!) of Great Shearwaters appeared inshore to feast on the abundant fish.  For many days in a row, on each falling tide the voracious shearwaters literally swarmed in the surf picking off the tiny fish like popcorn. For a normally completely pelagic species that spends most of its life out of sight of land, this behavior was most unusual and provided birdwatchers, fisherman, and beach-goers a rare opportunity to observe these interesting seabirds at literally pointblank range!

Check out this video to see what this phenomenon looked like.

 

2016-2017 Christmas Bird Count Summary

Ross’s Geese have been seen more often in Massachusetts in the last few years © Aaron Maizlish

The last issue of The Warbler provided a brief history of the venerable Christmas Bird Count (CBC) – a scheme established in 1900 to monitor winter bird populations during a three-week period around Christmas.  This issue offers a few Massachusetts highlights from the 2016-2017 CBC season.  In checklist order, waterfowl made a big splash this winter with rarities such as Pink-footed Goose, Greater White-fronted Goose, Ross’s Goose, and Cackling Goose variously honking things up on several counts, along with some mega-numbers like 17,629 Black Scoters on the Truro CBC, 33,054 Long-tailed Ducks at Nantucket, and a state-wide total of 2,231 Hooded Mergansers.  Several “chickens” continued a downward trend with only 13 Northern Bobwhites tallied on one count, and a state-wide total of 12 Ruffed Grouse on only 6 CBCs.  Compare these figures with the state total of 2,273 Wild Turkeys!

Vultures continued maintained a northward shift in winter numbers (possibly a climate change signal) with a total of 19 Black Vultures noted on just two counts, and 133 Turkey Vultures on 8 CBCs.  A rare-in-winter Osprey appeared in Truro, and state-wide, 219 Cooper’s Hawks maintained their seasonal dominance over the 138 recorded Sharp-shinned Hawks.  In the unobtrusive category, a Yellow Rail recorded at Nantucket was most unusual, and a total of 255 Lesser Black-backed Gulls on that same island speaks to how rapidly this Old World species is moving into North America.

A heavy fall flight of Northern Saw-whet Owls was no doubt responsible for tallies of 45 Saw-whets on the Concord CBC and 30 in Truro.  Two White-winged Doves in Boston’s Victory Gardens and a hardy Rufous Hummingbird on the Buzzards Bay CBC were unique this CBC season. Falcons reflected varying success, with the beleaguered American Kestrel state total of only 13 individuals continuing a disappointing downward trend, while cumulative totals of 37 Merlins and 34 Peregrine Falcons can only be described as optimistic.

Several bona fide rarities included an Ash-throated Flycatcher on the Mid-Cape Cod CBC, a Sedge Wren at Buzzards Bay, and a Townsend’s Solitaire at Cape Ann.  And for any readers who think that American Robins are only harbingers of spring, consider a total of 35,125 robins on the Mid-Cape CBC and the state-wide total of 53,300!

Late lingering can only explain the occurrence of an Ovenbird, a Northern Waterthrush, and a Black-throated Green Warbler at three different localities.

While this summary speaks only to some of the highlights gleaned from this season’s CBC, full details and more information will soon be available at the CBC website.