Solitary Eagle’s Nest Discovered in Belize:Part 2
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,