Ospreys On My Mind

This has been a summer of ospreys.  I am surrounded  by these glorious raptors.  Less than a tenth of a mile from my Long Island summer cottage, a massive osprey nest sits atop a utility pole (a structure replete with electrical lines).

It holds a brood of two, perhaps three young ospreys.  Their mother spends much of her time with them in the nest, guarding, watching, calling for food, and, at times, distributing pieces of the fish caught by their father.  He, in turn, when not out in search of fish, roosts nearby.

Joining the usual sounds of summer at the cottage are crystalline, high pitched, ringing chirrups (well, that’s what they sound like to my ear – descriptions in the literature vary quite widely), often starting slowly and well spaced, then rising in frequency and intensity.  These are primarily the begging calls of the female osprey, pleading with her mate to bring the food needed by their voracious offspring.  Ornithologist Alan F. Poole, in his recent, essential book, Ospreys:  The Revival of a Global Raptor, posits that there are three kinds of osprey calls with many variations:  alarm calls responding to a threatening interloper, guard calls signaling to other ospreys that a strange osprey is approaching, and begging calls voiced by mothers and young.  (Poole, p. 24-25; full citations are provided in the Sources section at the end of this post.)  The begging calls I’ve been hearing are apparently necessary to prompt the adult male to fulfill his biological role of providing for his family.  As with all such relationships, some males are more responsive than others.

Though I know it’s really not, my cottage feels for all the world as if it is at the epicenter of the osprey revival:  within roughly three to four miles of it are three other nests occupied by ospreys.  What an amazing turnaround from a half century ago, when the outlook for these and other beautiful avian raptors was bleak, their numbers devastated by the damage done by DDT and its breakdown products.

A nascent environmental movement in the mid 20th century, sparked by publication in 1962 of Rachel Carson’s Silent Spring, targeted the uncontrolled, widespread use of this and other insecticides.  The story of how the damage from DDT was stopped and reversed centers, in part, on Charles F. Wurster, an organic chemist, who was instrumental in the successful campaign against DDT which involved the filing of a series of lawsuits and much public testimony that galvanized public opinion against the insecticide.  A great deal of credit for the osprey revival that surrounds me must be given to Wurster who, it is sad to note, passed away in early July this year at age 92.  (Diamond, 2023)  He was among those marshalling and presenting evidence in the 1960s and 1970s that the insecticide was spreading uncontrollably worldwide, well beyond the areas in which it was directly applied.  They documented how its breakdown components seriously harmed wildlife, including avian raptors such as osprey who, at the top of the food chain, built up high levels of the insecticide in their bodies by consuming contaminated animals lower in the food chain, a process known as “biological concentration.”  These high levels of the insecticide led the birds to lay eggs with thin, fragile shells which broke under the pressure of the brooding mate.  (See, for example, Ackerman, 1996/2019, p. 46.)  The threat to the survival of these iconic birds (including the bald eagle) was great.  In 1967, Wurster was one of the founders of the Environmental Defense Fund which was instrumental in securing a nationwide ban on the use of the insecticide in 1972.

Poole notes that, although in North America the application of DDT decimated osprey populations (some specific populations declining by as much as 90 percent), once the ban took hold, osprey populations began a striking rebound.  Indeed, in some areas, the successful recovery has led to slowing population growth as available nesting sites are occupied, leading to movement of some birds into new, neighboring areas.  He reports that in Southern New England and Long Island (where my cottage is), there are at present approximately 1,500 breeding pairs of ospreys, primarily near saltwater.  (Poole, p. 43-44)

Ospreys’ scientific name is Pandion haliaetus.  The birds breeding in North America are P. haliaetus carolinensis, one of several subspecies.  They have a wingspan of about 63” and an overall body length of 23”.  Surprisingly, given how commanding they appear, they weigh only some 3.5 pounds.  (Sibley, 2003)  Ospreys’ diet consists nearly completely of fish.  As a result, they are often referred to as fish hawks, though they are not truly hawks.  P. haliaetus is the only member of the family Pandionidae which, in turn, is a member of the Accipitriformes order, a taxon that does include hawks, eagles, vultures, kites.  Ospreys share a number of attributes with hawks and eagles, such as acute eyesight, robust talons, hooked beaks, and reversed sexual dimorphism (females are larger than males).  But their piscatory diet has led to the evolution of a constellation of characteristics distinguishing them from all other birds of prey.  They are singularly constructed to hunt and capture fish.  Their fish-hunting armory includes long, nearly featherless legs well structured to reach into the water for their prey, particularly sharp, deeply curved talons (one of which on each foot can rotate so the bird can hold a struggling fish with two talons on each side), and longer and narrower wings bent at the wrist facilitating hovering and rising from the water after a dive.  (Poole, p. 11-12)  Pictured below is an osprey watching over a marsh near my cottage (this bird is not likely one associated with my nest).

The “M” silhouette of the wings of an osprey in flight and its high speed dive into the water in pursuit of a fish are among the most prominent and visible hallmarks of the bird, along, of course, with their piercing calls and massive nests.  Seen below are two ospreys in flight, quite possibly the pair nesting near me.  Their distinctive wing profile is clear.  Given the tattered wings, the bird in the lower right is a female because only they molt during the nesting season.  Males require a full complement of feathers for their constant hunting.

Nearly all of the osprey populations breeding in the northern hemisphere migrate in the fall to over-wintering areas in the southern hemisphere.  Adults reverse the journey in the spring, many returning to the same mates and same nesting area of the prior spring and summer.  Indeed, they may return to the same nests where they raised broods previously.   Their migrations are staggering feats of physical endurance and navigation, covering thousands of miles, many of those miles over open ocean waters or deserts.  Ospreys migrating from the Northern Hemisphere travel some 2,500 to 3,500 miles on average over the course of 4 to 5 weeks.  Poole offers a detailed look at the migration patterns of these birds.  (Poole, p. 106 et seq.)

When the young in the nest near me fledge they will undertake the same migration as their parents in the fall, but will remain in over-wintering areas for an additional year.  When they migrate back to the north, they will often return to the areas in which they fledged 18 months earlier.  Their early lives are full of perils, particularly those associated with these migrations.  Fewer than half of the birds that fledge will survive to breed.  (Carpenteri, p. 75)  

Ospreys are singularly adaptable, cosmopolitan birds, found worldwide (on all continents, save Antarctica).  They are clearly very tolerant of humans and human activity.  The various descriptions of where ospreys build their nest testifies to that.  In her lyrical description of nature along the Delaware side of the Delaware Bay (Birds by the Shore), science writer Jennifer Ackerman devotes a chapter to ospreys and recounts:

I have the good fortune to live within a three-mile radius of five active osprey nests.  One sits atop a platform on the double cross-arms of an old utility pole in the marsh at the center of town, hard by a railroad and King’s Highway.  The highway carries the crush of traffic disgorged from the Cape May-Lewes ferry, a steady stream of tourists hell-bent for a seaward peep.  (Ackerman, p. 39)

The nest down the road from me on Long Island also abuts clamorous human activity.  Pictured below is the nest in its full context, situated right next to a railroad bridge over a road, and near a street level railroad crossing (not shown).  All of this means the nest’s occupants endure the dinging railroad crossing bell, the screeching train wheels, and piercing whistle blows as a Long Island Rail Road commuter train makes eight daily trips east and west.

The conditioning of these young birds to this environment certainly expands the range of nesting places they will accept when they are adults.  With the ongoing destruction of the environment near the water along much of the east coast of North America, and with it the reduction in available natural osprey nesting sites, the adaptability of ospreys has stood them in good stead.  They take readily to artificial nesting sites, to wit, the crossbar at the top of a utility pole.  A broadscale effort to construct safe, artificial nesting sites is underway in many areas, and Poole reports that perhaps as many as 60% of osprey now nest on artificial sites.  (Poole, p. 43)

With their dramatic hunting dives, their calls, their open and exposed nests, ospreys cannot be ignored.  They predate the appearance of our species.  The extant osprey species has been around for perhaps fewer than two million years, while two paleontologically accepted, now extinct species of Pandion were present much earlier:  P. homalopteron from the mid-Miocene (some 16 to 13 millions ago) and P. lovensis from the late-Miocene (about 9 million years ago).  (Warter; Becker; Florida Museum of Natural History)

I think it significant that two accomplished nature writers have been moved to suggest that there is an ancestral memory connecting us to ospreys.  Jennifer Ackerman muses that, from the first appearance of humans on water’s edge, ospreys were there, and so we may inherently associate the bird with the seashore.

Perhaps the osprey exists on a mental map of an earlier world passed down from our ancestors, and the birds in its landscape enters us like the parental.  Perhaps it is also the other way around:  Perhaps it contains us as part of its element, having seen us through the ages, through our infancy and whole tumult of civilized man.  (Ackerman, 51-52)

In a strikingly similar vein, Alan Poole has pondered the “parallel lives of humans and Ospreys over the course of our evolution.”  (Poole, p. 15)  At each stage of our movement across the world, as we explored seashores and pursued fish, ospreys were probably part of our lives.  He concludes,

And it’s a good bet that in these early human societies Ospreys were part of nighttime conversations around campfires, woven into myth and culture, much as Ospreys enter the lives and conversations of people who live around them today.  (p. 15)

Yes, when we encounter these raptors, there may well be a natural psychological affinity.  Walt Whitman experienced this, I think, when, one day in June, 1878, he sat on a river bank, watching a bird roosting on dead tree on the opposite shore.  It was, he wrote,

a haughty, white-bodied dark-wing’d hawk – I suppose a hawk from his bill and general look – only he had a clear, loud, quite musical, sort of bell-like call, which he repeated again and again at intervals.

Clearly, this was an osprey, perhaps marking Whitman’s presence with his calls.  The bird then flew repeatedly over the water and left Whitman with an indelible memory: 

Once he came quite close over my head; I saw plainly his hook’d bill and hard restless eyes.  (Whitman, p. 111-112)

Sources

Jennifer Ackerman, Birds by the Shore:  Observing the Natural Life of the Atlantic Coast (previously published as Notes from the Shore), 1995 and 2019.

Jonathan J. Becker, Pandion Lovensis, A New Species of Osprey from the Late Miocene of Florida, Proceedings of the Biological Society of Washington, Volume 98, 1985.

Stephen D. Carpenteri, The Fish Hawk Osprey, 1997.

Dan Diamond, Charles Wurster, Scientist Who Battled to Ban Pesticide DDT, Dies at 92, The Washington Post, July 25, 2023.

Florida Museum of Natural History, Pandion lovensis, Zachary Seth Randall, original author.

Alan F. Poole, Ospreys:  The Revival of a Global Predator, 2019.

David Allen Sibley, The Sibley Field Guide to Birds of Eastern North America, 2003

Stuart L. Warter, A New Osprey from the Miocene of California (Falconiformes:  Pandionidae), Collected Papers in Avian Paleontology Honoring the 90th Birthday of Alexander Wetmore, Smithsonian Contributions to Paleobiology, Number 27, 1976.

Walt Whitman, Specimen Days, Dover Edition published in 1995 reproducing the 1883 publication.