Archive for April, 2012

Each year at the High Plains Environmental Center we await the return of the Ospreys…


In 2006,  a group of volunteers built this nesting platform and has been inhabited by a successfully breeding pair of ospreys ever since. This osprey platform is a great example of how what we do at HPEC is not conservation (preserving what exists already) but rather restoration (creating new opportunities for nature in the midst of development).

Our friend Bill Miller (President of the Fort Collins Audubon Society) wrote the following  history of ospreys in this area.

Ospreys were relatively common on the west slope of Colorado but were mostly migrants passing through on the east slope.  At the time the only known nesting pair was found up at Parvin Lake, east of the community of Red Feather Lakes.  Ospreys are slow to pioneer into new territory but, even though the northern Front Range of Colorado had lots of suitable habitat as a result of more than a century of irrigation projects, there was not a breeding population east of the mountains.

 In 1988 and 1989 the Colorado Division of Wildlife (CDOW), in cooperation with the Denver Museum of Natural History, the Peregrine Fund1, and interested members of the public, joined forces to establish the Peregrine Partnership with the intent to introduce peregrine chicks into the Denver urban setting using a process called ‘hacking.’  Five peregrine chicks per year were provided by the Peregrine Fund and released into a hack box on about the 20th floor of what was the Denver Post building.

 The hack box allowed volunteers to feed the chicks without being seen, thus preventing the chicks from imprinting on humans.  After reaching a certain maturity the chicks were ready to ‘fledge,’ or instinctively take flight.  Instinct would once more take over as the peregrines would take to capturing and feeding on Denver’s numerous pigeons.  Unfortunately, due to the low numbers of peregrines released to the wild through this process, relatively low survival rates in the wild for young birds, and tendencies to disperse from their fledge sites, only one of the ten chicks released in this manner was ever documented to have returned.  It defended the hack site vigorously, rendering unusable for any further releases.

 Buoyed by the enthusiastic public interest and participation in the peregrine project the CDOW determined to have another public-participation release project and assigned it the NE Regional Office in Fort Collins.  The project was assigned to Lisa Evans, NE Regional Education Coordinator.  She garnered support and participation from a variety of organizations.  A Steering Committee was formed, consisting of: members of the Fort Collins Audubon Society and the Colorado Wildlife Federation, the environmental education coordinator for the Poudre School District, the director of the Rocky Mountain Raptor Program, a retired CSU wildlife biology professor, the director of the City of Fort Collins Cultural, Library and Recreational Service,  a representative of the Fort Collins Parks and Recreation Department, other employees of the CDOW,  and interested members of the public.

 The first task undertaken by the Steering Committee was to identify a bird species to be released in the Fort Collins area using the hacking process.  At this point in time reintroduction of peregrines in Colorado was being de-emphasized as the species had been released into the wild with great success.  Bald Eagles were also discussed but the Steering Committee was cautioned against them by several committee members who knew that Bald Eagle chicks can be quite difficult to work with.  Finally, Alex Cringan, recently retired CSU Wildlife Biology professor and who had grown up in Ontario and was quite familiar with the species, suggested that we consider Osprey as the species to be introduced.  The Steering Committee concurred.

 Another major detail that had to be considered was the construction of two hack towers.  These would be the first home in Fort Collins for the osprey chicks.  So the scramble was on to purchase, acquire through donation, or otherwise ‘scrounge’ materials for the two towers.  Public Service Company of Colorado, as it was called at the time, donated six long wooden power poles.  Each tower would be supported by two poles connected by two heavy 4” x 4” timbers commonly used as the cross arms on power poles.  These would provide the base structure for a cage that would be constructed about 20’ to 25’ up in the air, supported by the 4” x 4” timbers.  The cage would be about 4-ft. square, with a plywood floor and top.  The back wall, located where the ladder came up, would have a small door hinged so that volunteers could throw fish into the cage.  The other three walls would consist of electrical conduit mounted vertically in holes drilled through the upper and lower 2” x 4” boards.  The conduit was vertical because there was less chance for a chick which was testing its wings to get caught and break its wing.  The front wall was pivoted at its bottom so that it could swing outward into a horizontal position, supported by a rope.  This would be the launch pad from which the chicks would first take flight once they were ready.

 By the time we were ready to construct the two hack towers we had a sizeable body of volunteers who came with a broad set of skills.  The first tower to be built was along the Poudre River at the southern end of the CSU Environmental Learning Center (ELC).  Constructed in December of 1989 and January of 1990, it was surrounded by a chain link fence to keep ELC visitors off of it.  The second tower was constructed in the spring of 1990 on an island on the west side of the largest water-filled gravel pit that is part of the Riverbend Ponds complex north of East Prospect Street and east of the Poudre River.

 First to be constructed was a footbridge to the island, using a crane that placed the two longest of the six donated power poles across between the shore and the island.  Once that had been constructed volunteers were able to carry the shovels, scoops and other tools necessary to dig two holes for the support poles.  A helicopter was used to lift the poles into the air and transport them to the island where they were guided into the holes.  Once earth and rock were tamped around the poles the superstructure was constructed as per above, followed by the hack cage.

 In July of 1990 my wife and youngest son took a vacation trip to Lake Coeur d’Alene in Northern Idaho.  The CDOW had worked out a wildlife exchange whereby Idaho Game and Fish Department received some Bighorn Sheep in return for giving up some of their plentiful Osprey chicks.  There are numerous saw mills located along the northern end of the lake where it empties into the Spokane River.  Logs harvested from the hills around the lake are dumped into the lake, chained up to form rafts and then towed to the saw mills.  There they are corralled using more chains suspended on floating logs and extending between log pilings set into the lake bottom.  Osprey took to the pilings as nesting sites and the saw mill personnel had fitted each piling with a 4’x4’ sheet of plywood and two hay bales.  After adding a few token sticks to the hay bales and calling it a nest, Osprey were raising two to four chicks on each piling.  Needless to say, there was no shortage of osprey chicks!

 On July 10th the Idaho Game and Fish staff provided two small boats, one being equipped with an extension ladder.  Then, while other members kept that boat from drifting away from the piling, one brave soul climbed the ladder and took one or two chicks out of their nests, always leaving a minimum of two chicks in the nest.  I was able to video this operation from the second boat on the water while a CDOW cinematographer filmed the process from the Denver Channel 9 News helicopter.  A total of 10 chicks were obtained in this fashion.  It was humorous to see a motel room that night filled with osprey chicks.  Following a supper attended by all participants, my wife, son and I drove home to Colorado later that night, arriving in Fort Collins late in the afternoon of July 11th.  On July 12th the CDOW staff flew the chicks home in a fixed-winged Otter aircraft piloted by a CDOW pilot, and the chicks were released into the two hack cages on the 13th.  And then the fun started!

 For the rest of the summer it was all hands on deck.  The chicks were taken from their nests approximately four weeks before they would have fledged.  Now they had to be fed twice daily atop the wiggling hack towers.  Other volunteers would monitor and record the birds’ behaviors.  And when the birds first started to fly one would occasionally land in the water and have to be rescued by a volunteer who would swim out after the downed bird.

 Ospreys migrate south to Central and South America for the winter.  Adults will return north the following spring but the young of the previous summer will spend another full year in the south before making their first journey north.  Ospreys are found on all of the world’s continents with the exception of Antarctica.  Their diet consists of about 97% fish with the rest being snakes, lizards and amphibians.  Osprey feet and talons are unique in the world of raptors.  All raptors have four talons; all other raptors, however, have three talons facing to the front and one facing to the rear.  Osprey talons are arranged so that one of the three forward-facing talons can be turned so that they have two facing to the rear.  This enables them to gain a better grip on fish which they will then carry back to the nest or a feeding perch slung like a torpedo under them for greater aerodynamic efficiency.  Ospreys usually plunge feet first into the water to capture a fish seen from the air, and then use their powerful wings to rise above the water and fly off carrying their prey.  (See http://www.care2.com/causes/osprey-gives-amazing-fishing-lessons-video.html for how Osprey go fishing)


In 1991 a third hack tower was built along the Poudre River west of North Taft Hill Road.  This was called the Olander Site because students from Olander Elementary School had raised part of the funds for the hack tower’s construction.


Osprey chicks were obtained from Lake Coeur d’Alene in Idaho in the summers of 1990, 1991, and 1992.  In 1993 the chicks were taken from along the Spokane River in Washington.  Collectively approximately 57 osprey chicks were hacked at the three tower locations during the four summer hacking periods.  Since all chicks were banded at the time they were removed from their nests it was possible to determine that some of the introduced osprey had survived their first three or four years and were successful in bringing mates back to Fort Collins.  Currently there are about four or five active osprey nest sites in Fort Collins and one at Equalizer Reservoir in Loveland.  I guess one could conclude that the efforts of two decades ago were successful.

 1)      http://en.wikipedia.org/wiki/The_Peregrine_Fund




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