In 1992, Fort Polk banded its first juvenile kestrels, which were from a nest located in an enlarged RCW cavity. The kestrel nest tree was within 100 feet of an RCW nest tree, which indicates that RCWs and SAKs prefer the same type of nesting habitat. Both the RCW and kestrel had successful nests and fledged chicks.
The SAK often hunts over large openings in the forest. Fort Polk has a large number of openings in the forest, called firing ranges that are utilized by the SAK for hunting. Our most successful nest boxes are located on the edge or near firing ranges. Another favorite habitat on Fort Polk is Longleaf pine seedtree stands that have approximately 20 mature pine trees per acre. On Fort Polk, we thin our pine stands down to a basal area of 60, sometimes lower, and we have a three-year rotational prescribed fire program. Not only does this habitat management benefit the SAK and RCW, it also benefits other species of concern including Bachman’s and Henslow’s Sparrows, and the rare Louisiana Pine Snake.
Since 1993, we have placed 20-25 SAK nest boxes on Fort Polk. The boxes are placed 20 feet above the ground on pine trees. It is very important that a snag or telephone lines are located near the nest boxes; the SAK uses them for perching and hunting. Our nest boxes usually have 5-6 successful nests a year, producing 3-4 young each. In addition to our nest boxes, we usually find 3-6 nests located in natural cavities each year. Nearly all the nests are found in enlarged RCW cavities located in living or dead cavity trees. All chicks are banded with a U.S. Fish and Wildlife aluminum band and a combination of color bands. There is a lot of competition for the nest boxes from other bird species and squirrels. We usually have more Eastern Screech Owl nests than SAK nests. We have also found Great-crested Flycatchers, Tufted Titmice, and Eastern Bluebirds nesting in our boxes. If we find other bird species using the boxes, we leave them alone, but Fox Squirrels and Southern Flying Squirrels are removed. Flying squirrels are a big problem. It is not uncommon to find 4-8 flying squirrels occupying a nest box. The number one nest predator on nesting SAKs is the Texas Rat Snake, a great tree climber. We have found adults, young, and eggs consumed by the rat snake. To limit predation, we place aluminum sheeting (4 ft. wide) at the base of each nest box tree. The slick aluminum prevents the snake from climbing the trees and reaching the nest boxes.
With proper management, SAK populations should remain stable and possibly increase in the future on federal lands, including Fort Polk and National Forest Service lands. It is critical that regular prescribed fires and timber thinning continue into the future. Not only is this necessary for maintaining healthy populations of SAK, but for other rare species that share its habitat.
Contributed by: Kenneth Moore
Also by Kenneth Moore: Southeastern American Kestrel in Louisiana
Irrigation canals constitute an important nesting site for several aquatic bird species and have slowly transformed into an excellent natural habitat over the passing decades. Several wild aquatic bird species such as Canada geese (Branta canadensis L.; Fig 1) and mallard ducks (Anas platyrhynchos L.; Fig 2) have in particular found such canals as important nesting, resting, breeding and foraging sites across the Canadian Prairies. The lush vegetation that accompanies irrigation canals traversing across the municipalities and rural districts provides excellent nesting and hiding sites for the breeding aquatic species; while the water in the irrigation canal serves as important foraging ground. The dense vegetation protects the nests, eggs and nestlings from a host of predators making their breeding a success story across the Prairies.
The security of the bushes and the abundant supply of food, water, foraging and nesting resources have made certain stretches of the intricate network of irrigation canal a bold success story for several such aquatic bird species. During the breeding season large flocks are seen to be approaching the canal nesting sites in good numbers both by the mallards (Fig 3) and the Canada geese (Fig 4). Although a number of predatory birds and mammals do also nest in nearby trees (Fig 4) and bushes and woods to take advantage of the yearly bounty; particularly the highly vulnerable nestlings and fledglings such as the young and defenseless ducklings and goslings.
However, the greater number and close guards by the caring parents do not actually impact the species population and is in particular nature’s own monitoring in keeping the population under check (Figs 5-6). Hence, in a broader term a healthy and thriving population of the ducks and the geese actually positively contributes towards the stable population of the predatory birds and mammals too; further extending the success of the irrigation canals to other wildlife species. In addition to the mallards and Canada geese or black geese, other species of ducks and geese (such as the grey and white geese) are also known to take advantage of the refuge of the irrigation canal habitats along their annual migration routes. Several other non-aquatic bird species like the different black birds (Fig 5) that inhabit the ecotones between land and water also take advantage of the natural habitats produced by the irrigation canals.
Hence, the construction and development of the large network of irrigation canals across the Prairies have been an excellent natural resource that has been helping in building the population of local birds and in directly contributing towards establishing a sustainable environment. However, it will be important in future to do extensive bird surveys in and adjacent to such artificial habitats for monitoring the bird population and in better understanding the nature and behaviors of different species that have been intelligently using such available resources to their advantage. It is often interesting to note that anthropogenic activities that impact wildlife species so negatively could also have positive impacts in some other ways. It will be therefore important for us to learn from the experience and develop our future technologies in a pro-nature or environment friendly fashion so that we could effectively curb our foot prints on the nature and also successfully reduce our impacts on the population of different wild species of birds.
Prime nesting and foraging habitats of Canada geese adjoining irrigation canals are pictured below (Fig 7-8).
Article contributed by Saikat Kumar Basu
To travel horizontally, a static soaring bird must descend and subsequently ascend using convective currents as an elevator, often in a slow cyclic pattern. The bird will enter a rising column of air at the bottom, ascend to the upper limits of the thermal, and then set its wings in a shallow, descending glide slope to move a linear distance. When the bird exhausts the momentum of its descent or nears the ground, it must intersect the bottom of another thermal to gain height and repeat the process. A bird that travels in this manner may have to work many thermals in succession in order to travel great distances across the landscape. Thus, soaring birds are keenly aware of the location, timing and prospect of air currents in their home territories; they will often use the same geological features or localities known to produce such currents and exploit them as “aerial highways”.
Two primary air currents used by the male Solitary Eagle–one an updraft and the other a downdraft–straddled the Orange-breasted Falcon hack site on opposite sides. The hack site was positioned on a peninsular, highland ridge, directly overlooking an unnamed river at the height of 2,000+ vertical feet, not far from Thousand Foot Falls, a popular tourist attraction. The eagle would ascend from the north, often carrying prey, soar directly over the hack site, and then descend the opposite side to the south in order to intersect another thermal further down the river valley. This initial descent, so near to the observation blind, gave one the impression that the eagle was “landing” in the forest directly below the hack site. Such a conclusion would be a mistake and is precisely the reason this particular Solitary Eagle’s nest went undiscovered for nearly a decade. Previous raptor biologists had erroneously searched for the nest in the forested slopes of this southern drop zone.
Only a person who could correctly interpret the eagle’s flight patterns would be able to ascertain a final descending glide into a nest. When a soaring bird is truly landing, it will stiffly set its wings, rotate the feet forward, angle the head and body toward the intended perch and glide in a fast, direct fashion. It will not ascend lazily into the air again. Once the general landing area of the food-carrying male eagle was defined, it was a simple matter of setting up surveillance points along its route of travel to pinpoint the nest location. The Peregrine Fund attendants manned three observation points that intercepted the eagle’s trajectory for four days before locating the actual nest tree.
The male Solitary Eagle was first seen at the hack site on 7 June 2011, the day the attendants arrived to prepare the hack tower for the Orange-breasted Falcon release. Regular sightings occurred at the hack site every two- three days thereafter between 1000 and 1500 hours, when wind and thermal activity was at its peak. After two weeks of continuous observation, surveillance points were marked along the eagle’s known flight path by 27 June 2011, and sightings began to occur daily, as the attendants drew closer and closer to the nest. Roni Martinez was invited by the author at that time to assist in the search–after the general nest location and flight path were known–to help the hack site attendants monitor surveillance points with an “extra set of eyes”. As a native conservation officer, Roni was also needed to negotiate passage through a military weapons training area adjacent to the suspected nest site, as it was decidedly foolish for American foreigners to be caught trespassing across this dangerous, and possibly restricted, zone without permission.
Continued in Part 3
Article contributed by Stacia A. Novy
Photo: The Peregrine Fund Crew
Caption: The “Solitary Eagle Search Team” employed by The Peregrine Fund,
On the morning of discovery, Stacia, Matt, Audrey and Roni hiked across the military exercise area, northwest of Baldy Beacon, to access a new observation point that was closest to the predicted nest location. Roni brought along a spotting scope, while Stacia draped a trusted, high-powered 10 X 50 Swarovski binocular about her neck. The Peregrine Fund owned a Zeiss spotting scope, but theirs was needed for observations back at the Orange-breasted Falcon release site, which Camille and Jon were scheduled to manage that day. Therefore, Roni had to bring his own scope for use in the field, as the attendants’ scope was not available. The three hack site attendants indicated the hillside of greatest interest to Roni: a thickly forested slope that had shown the greatest amount of eagle activity while under observation and, thus, most likely to contain the nest. Roni scanned the slope with the spotting scope and just happened to see the male Solitary Eagle swoop in carrying a yellow snake at that precise moment. Roni later exclaimed that he “never would have seen the eagle against the dark backdrop of trees if the snake hadn’t been so brightly colored”.
However, the scope had so narrow an angle of view that the position of any tree on such a distant hillside could not be determined. All Roni could see was the tree, and the tree was so far away that it could not be seen with the naked eye. Roni wrung his hands and nervously paced back and forth in the field, shouting, “Don’t touch the scope! Nobody touch the scope!” Even the slightest tilt of the lens would have offset the view and the marked tree would have been lost in a fuzzy sea of green. So, the author performed an old falconry trick: she calmly placed her wide-angled binocular on top of the telescope lens barrel to view the nest tree with all the distinctive landmarks around it. With those features in mind, the author was able to lead Matt and Roni through the rough, forested terrain until they got close enough to see the actual nest.
This same method works with trained falconry birds as they will tighten their body conformation and fixate their eyes on quarry before launching an attack, most likely to triangulate a position. Before the hunting hawk flies off the fist, the falconer can place a binocular on the bird’s head to see what it is looking at. Since birds-of-prey possess binocular vision–as do humans and manufactured optics–the technique works. It is commonly used throughout the falconry community both in North America and abroad. Audrey remained behind at the final observation point, but watched the three others progress to the nest tree through the spotting scope. When the nest was finally found, the good news was radioed back to Jon and Camille, as they were a part of the original “Peregrine Fund Solitary Eagle Search Team”, but could not participate on the day of discovery.
As The Peregrine Fund/World Center for Birds of Prey was the first organization to document the presence of Solitary Eagles in the region so long ago, it seems a fitting conclusion that subsequent employees of that same organization confirmed the first breeding record for the country of Belize 22 years later. Following on the heels of this phenomenal find, the South American and North American classification committees of the American Ornithologists’ Union recently agreed to subsume the Solitary Eagle’s old genus Harpyhaliaetus, into the genus Buteogallus. Recent DNA studies have confirmed that the Solitary Eagle is so closely related to the Common Black Hawk (Buteogallus anthracinus) and Great Black Hawk (Buteogallus urubitinga) that reclassification is warranted.
Editor’s Note: This is not the first time the author has located a rare raptor. In 1996, while working for The Peregrine Fund on an Aplomado Falcon repatriation project in Laguna Atascosa National Wildlife Refuge (NWR) in Texas, she discovered a Collared Forest-Falcon (Micrastur semitorquatus). It was the first record of that tropical species for Laguna Atascosa NWR and was documented in their archives.
Article contributed by Stacia A. Novy
Photo Title: Peregrine Fund Vehicle
Caption: “The author returns after a successful day of searching for the
Solitary Eagle’s nest”
It has long been assumed that the nest building skills of birds are instinctive, but new research has revealed that building a nest could very well be a learned skill. Following and filming the activities of male Southern Masked Weavers in Botswana over a period of three months, researchers noted that not all nests are created equal. As the name of the bird suggests, Southern Masked Weavers use a weaving technique when constructing their nests from local grasses. However, the method of nest building varied between birds with some weaving from left to right and others weaving from right to left. It was also noted that they appeared to learn from their mistakes, and while a bird may regularly drop blades of grass when it first starts its nest building process, it soon learns to adjust its technique to prevent this.
The brightly colored African bird was chosen as the test subject for the study for a number of reasons. Their complex nests which hang from trees either as single units or multiple intertwined condominiums are seen as evidence of above average intelligence. Also, a single bird will build several nests in a season, allowing the research team to note the differences in nests built by the same bird.
Working with scientists from Botswana, researchers from the universities of St Andrews, Edinburgh and Glasgow noted that the fact that the Southern Masked Weaver birds displayed marked variations in their approach to nest building reveals that they may learn from experience. At this point, however, it is not clear whether they have the mental capacity to learn, or their improvement in skills can be attributed to repetition of a task. Researchers also pointed out that observing this behavior in one bird species does not imply that it would apply to all birds. One of the scientists taking part in the study, Dr. Patrick Walsh of Edinburgh University’s School of Biological Sciences, noted that if birds built their nests instinctively according to a genetic template, it would follow that all birds would build all their nests in the same way every time, but this has not been the case. Summing it up nicely, Dr. Walsh was reported as saying: “Even for birds, practice makes perfect.”