Text and photos by Bob Grier
Once a rare sight here, migrant ospreys are now common and the state's first confirmed osprey nest has been found in western Nebraska.
The surprising start of Nebraska's first-ever confirmed nesting attempt by osprey (Pandion haliaetus) began slowly but picked up momentum quickly as the two brilliantly plumaged adult osprey began carrying tree branches, corn stalks, dried sunflower stems and other vegetation to the top of a power pole along a county road northeast of Scottsbluff in early May.
This nest represented an exciting step in the expansion of the osprey's breeding range across North America. Historical references to osprey nesting in Nebraska are nearly nonexistent and unconfirmed, and even reports of summer sightings are classified as rare and casual. While the ultimate success of the nest is unknown as this article goes to press, the osprey's future in Nebraska looks promising.
"The nesting attempt in western Nebraska is exciting and is a significant first for the state," said Joel Jorgensen, the nongame bird program manager for the Nebraska Game and Parks Commission, "but the arrival of osprey breeding pairs into Nebraska certainly wasn't unanticipated. We've seen a dramatic expansion of osprey breeding range throughout North America, including Minnesota and the Great Lakes region, as well as across the northeast and Canada. At least some of the bird's increasing population and the expansion of their historical breeding ranges can be attributed to their use of man-made nesting platforms, including power poles, floating buoys, waterfowl blinds and even artificial nesting platforms placed near the birds' prime fishing areas."
Osprey are found throughout the world, inhabiting every continent but Antarctica, and their breeding and nesting range in North America has expanded during the latter part of the last century. Nesting is reported from Alaska eastward across most of Canada, along the Atlantic shore from the Maritime Provinces as far south as Georgia and Florida and along the Pacific Coast from the Yukon, British Columbia and southward into Northern California. Osprey are rare in Hawaii, but migratory transients are seen in almost every state in the continental United States.
Migrant adults and young of the year will often stop in Nebraska for extended periods in the fall, and occasionally in the spring, to take advantage of good feeding conditions in northwest Nebraska's Pine Ridge, along the Niobrara and Platte River drainages and eastward on other rivers, lakes and other suitable fishing waters. Specific locations that seem to attract and hold migrants each fall includes the Chadron State Park (SP) pond, Fort Robinson SP's ponds and nearby Carter P. Johnson Lake. Migrating birds have stopped for several days on an urban park lake in Alliance and at Victoria Springs State Recreation Area in central Nebraska, and the birds are occasionally seen on Oliver Reservoir west of Kimball and Lake McConaughy. Ospreys have also been observed in metropolitan Lincoln and Omaha and along the Missouri River corridor.
According to Jorgensen's research, it is possible that migrants seen across Nebraska represent two distinct populations. "Eastern migrants may be part of the growing breeding population in Minnesota and Manitoba that overwinters in the lower Mississippi Valley and in south Texas, which would account for the higher frequency of records from eastern Nebraska. The second breeding population is found in Wyoming and Montana, and that population is also apparently increasing, which may account for the increasing frequency of reports from western Nebraska during the last few years."
Researchers studying dramatic declines in osprey and other avian populations in the 1960s and 1970s first noted the effect of organochlorine pesticides, including DDT specifically, on osprey reproduction. The pesticide's impacts, which included the thinning of eggshells, were quickly tied to serious declines in nesting success for many other bird species as well. At the top of the food chain, ospreys and other raptors were hit hard by the greater concentrations of pesticides in their diets, and in many parts of North America, osprey populations fell as much as 90 percent before DDT was banned. The reproductive success in ospreys and other species began to rebound after the ban, although the pesticides were still used in Central and South America. By 2000, osprey populations in nearly all of North America had returned to historic levels.
The birds' bold, black-and-white plumage and unusually long, narrow wings are keys for quick field identification, and an osprey differs markedly from similarly sized hawks with its white belly, dark wrist patches and bright, white head with dark eye streak. In flight, the bird's long, narrow wings are easily seen. Adult ospreys weigh between 2½ and 4½ pounds, reach lengths of 24 inches, and their wingspans reach a full six feet in length.
The plumage of young-of-the-year osprey often appears less refined or somewhat dull compared with the adult bird's contrasty, well-defined plumage. Younger birds display buff fringes to the upper plumage, a buff tone to the underparts and streaked feathers on the head. There is very little difference between adult males and females: The male's breast feathers are almost all white, while the female has a "necklace" of darker feathers on its white breast. Females are also approximately 25 percent larger than males.
An osprey's diet is almost exclusively fish, although they are known to take other prey, including aquatic rodents, salamanders, other birds and small reptiles when available. The birds have evolved specialized tools and hunting behaviors to capture submerged fish, including an opposable toe that can face backward or forward - the only raptor with a reversible outer toe. The feet also include sharp spicules (barbs) on the underside of the toes and backward-facing scales on the talons that grip their slippery prey. Ospreys also have closeable nostrils to keep out water during their dives.
Even armed with a long telephoto lens and one of the world's fastest autofocus digital cameras, photographing an osprey dropping swiftly to the water's surface while hunting is more luck than skill. Each fall, Nebraskans across the state are often startled to see and hear one of these strikingly patterned birds diving feet first into ponds, lakes and streams to catch fish. Hitting the water at high speed, talons extended, wings folded in a bend behind the wing wrist and head and eyes directly behind its outstretched feet, a diving osprey creates a splash that can be both seen and heard at great distances, especially during the periods of light wind and calm water surface conditions that favors the bird's normal hunting techniques - diving nearly vertically from hovering flight over water or from an elevated waterside perch to capture fish within several feet of the water's surface.
Ospreys actively perching near feeding areas are often heard before seen, their chirplike alarm calls often used as anglers, hunters, hikers and others intrude near a bird's favored hunting sites. The call is a series of short chirps or whistles, often described as a cheep, cheep or yewk, yewk. The more strident alarm call often heard at nesting sites is a frenzied cheereek.
The osprey's scientific name (Pandion haliaetus) comes from the mythical king of Athens, Pandion, whose daughters were turned into birds, and by the Greek words halos, referring to the sea, and aetos, or eagle. The bird's common name is from the Latin word ossifragus, meaning "a bone breaker." Common names include sea hawk and fish hawk.
Ospreys are the only bird that dives feet first into water, often submerging completely based on the speed of their dive and depth of the prey. Bald eagles often approach fish on or close to the surface feet first as well, but almost always pluck the fish from the water while maintaining their forward flight.
On a successful dive, an osprey may surface immediately, quickly "jumping" from the water's surface with its catch. Other times the bird may pause momentarily with its head and neck above the water surface, possibly changing and firming its grip on the fish before the long wings spread out and powerful wingbeats pull the water-soaked bird and its prey upward. Younger osprey and those with larger fish often have to skim the water's surface for a substantial distance before gaining enough speed to rise over waterside trees or other obstacles. At times successful hunters will fly to a nearby perch to consume nearly all of the fish, while at other times a feeding osprey's pattern includes longer flights to secluded perches before feeding, possibly a defensive pattern to reduce the opportunity for other osprey and large raptors that may try to steal their catch.
An osprey photographed on a small, Pine Ridge pond north of Harrison in 2006 and 2007 maintained about a 50 percent success rate during the first of several days of observation. The bird was first seen perched above the pond before sunrise on a cold, misty, mid-September morning, and stayed there for several hours before beginning to actively feed - intently watching for fish near the surface before diving. Several elevated perches above the pond were used during the daylong observations.
The first dive of the morning resulted in a miss and the bird's flight took it across the length of the pond as it gained speed. After an unsuccessful dive, the osprey would swiftly approach the perch from below, slowing its speed quickly in a nearly vertical climb to the perch with outstretched wings. When its dive was successful, the bird normally flew out of sight to a nearby ridge to feed, carrying the trout headfirst before returning 20 to 30 minutes later to continue hunting. The first day provided optimal hunting conditions - smooth, clear water and full sunlight.
Wind conditions the following day completely altered hunting activities. A gray, overcast sky and wind-whipped waves cut the bird's success almost completely. Several hours would pass between attempts and dives were often interrupted before the bird entered the water.
Whether or not they successfully raise young this year, there's a good chance that the osprey nesting near Scottsbluff will be back next year. Ospreys usually mate for life, becoming sexually mature at approximately three years of age, and often use the same nest year after year. Some osprey nests have been used by different nesting pairs for well over 50 years. The nests can reach large size over long periods of use - nine to 12 feet deep and up to six feet in diameter.
Researchers and biologists studying osprey nesting preferences across North America noted that nesting pairs using man-made structures produced about twice as many young as birds that selected natural nesting sites, and successful breeding pairs readily return to the man-made structures year after year. That research also led to the design and construction of artificial nesting platforms that have been used to encourage osprey nesting across North America. The research also noted that ospreys continue to move away from natural nesting sites with the increase in raccoon and other predator populations.
Clutch size is usually from one to four creamy white to pinkish eggs, spotted with reddish brown and intermediate colors. The first egg in the clutch is the largest, about the size of a chicken egg, and each subsequent egg is slightly smaller. During the one- to four-day period of egg laying, the male aggressively guards the female. Once incubation begins, both birds take turns, although the female is on the eggs for normally about 70 percent of the approximate, 35- to 40-day incubation period. During the female's extended period at the nest, the male brings his catch to the female. The first observed feeding at the Scottsbluff nest was a showy display of acrobatics - the male approached from several hundred feet above the elevated nest, folded its wings and dropped into a nearly vertical dive at high speed. At the last minute, the male's wings extended and its talons were thrust forward with the fish. The female moved to one of the power pole's extended arms to feed. After she was done eating, several minutes passed before the male spread its wings and rose to carefully land on the female's back to breed.
Egg laying hadn't begun by the second week in May as this article was prepared for publication, and both the male and female continued to bring sticks of different sizes to enlarge the nest. The building size of the nest and its location on and near the pole's power lines concerned U. S. Fish and Wildlife Service refuge manager Steve Knode of Scottsbluff and Jorgensen, as well as linemen with the Chimney Rock Power Company, which maintains the power transmission lines.
Knode had been notified of the nest building activities in early May by Game and Parks Commission employees at nearby Minatare State Recreation Area and after confirming the identity of the nest builders, he immediately contacted the power company to see if options were available to reduce the risk of electrical short circuit or electrocution. Even while power company linemen were using insulated fiberglass poles to remove nesting material that was lying across several power lines, they were surprised to see the ospreys continue add nesting material to the growing platform nest from above.
If the Scottsbluff area nesting is successful, the eggs should hatch in mid- to late-June. Chicks normally fledge at about 7 to 8 weeks of age, and the young birds are dependent on the adults until the fall migration occurs from mid-July into early November. Spring migration for the ospreys returning to their breeding sites begins in late-February and continues into May. Breeding pairs do not migrate or winter together and the male generally returns to the established nest site before the female.
Biologists and researchers are hopeful that this year's nesting attempt will be successful and plans are already underway to place a platform under the current nest and also install several artificial nesting platforms elsewhere in the North Platte Valley. The promise of an expanding osprey nesting population in Nebraska has been made and the opportunity to see ospreys and their dramatic dives to catch fish may someday be widespread across Nebraska.