Hawks
Aloft, Inc.
Conservation, Avian Research,
and Education
PO Box 10028 - Albuquerque, NM 87184 -
(505) 828-9455
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Raptor use of the riparian woodland (Bosque) and adjacent habitat in Middle Rio Grande Valley, New Mexico
The Middle Rio Grande valley provides valuable summer and winter habitat for many species of raptors, including Cooper's Hawk, Great Horned Owl, Swainson's Hawk, Red-tailed Hawk, Western Screech-Owl, American Kestrel, and Mississippi Kite. Some raptors, such as Cooper's Hawk, Great Horned Owl, Western Screech-Owl, and American Kestrel are resident in the Bosque year-round. During the winter months, the Bosque and particularly the adjacent agricultural lands are home to other raptors, including Bald and Golden Eagle, Red-tailed Hawk, Ferruginous Hawk, Northern Harrier, and Prairie and Peregrine Falcons. Hawks Aloft has conducted driving surveys along the levee to document raptor use of the riparian woodland and the adjacent lands. Surveys were conducted during the winter and breeding seasons over a two-year period, from December 2002 through June 2004. These surveys have been completed, and the data are being analyzed. The data will be compared to numbers detected in the Middle Rio Grande Biological Study, conducted in 1981-1982. Additional comparisons of our current study will include the number of raptors detected in urban versus rural areas, effects of disturbance, and detection rates between different survey methods. Preliminary results indicate that our highest abundance of raptors occurred on transects adjacent to agricultural lands. Therefore, we consider that the presence of agriculture adjacent to bosque habitat attracts a greater number of raptors than urban areas. Differences in habitat within the riparian corridor, e.g., native versus exotic vegetation, also could influence raptor numbers, particularly species such as Cooper’s Hawk and Great Horned Owl. Our study has been designed to examine multiple factors influencing raptor abundance in the Middle Rio Grande Valley. In addition to the raptor survey method detailed here, we also locate and monitor active raptor nests. We hope that continuing studies and further analyses will help us unlock some of the mysteries of how raptors use these habitats, including the true value of agricultural land and large stands of native vegetation. Nesting raptors of the Middle Rio Grande Bosque
The riparian cottonwood forest, known as Bosque, that borders the Middle Rio Grande provides important habitat for wildlife, including many species of raptors that use the woodlands for nesting. Diurnal raptor species known to breed in the Rio Grande Bosque and adjacent lands include Cooper’s Hawk, Swainson’s Hawk, Mississippi Kite, and American Kestrel. Owls that nest within this riparian corridor include Great Horned Owl, Long-eared Owl, Western Screech-Owl, and Barn Owl. The dominant stick nest builder, and the most numerous nesting raptor in the Bosque is the Cooper’s Hawk. Great Horned Owls, Swainson’s Hawks, and Mississippi Kites nest in smaller numbers in the Bosque. The American Kestrel, a cavity nesting falcon, nests in high concentrations in areas with standing dead trees, particularly where fire has occurred in the previous five years. A dedicated team of 6-8 Hawks Aloft staff comb the Bosque from Bernalillo, south to Belen, searching each tree for evidence of stick nests, likely documenting more than 90% of the nests that are present. To date, we have mapped more than 800 stick and cavity nests along 50+ river miles. Each nest is visited three times during the nesting season to determine occupancy, nest improvement, and construction of new nests. Of these nests, 100-150 become active annually (12%-18%). Active nests are monitored throughout the nesting season to determine success and productivity. Each nest is visited at least once every ten days until the young fledge, or the nest fails. The intensity of this search effort allows us to document nest densities for many species.
The data collected through this study document raptor nesting preferences and productivity relative to vegetation, and might provide additional evidence that agriculture adjacent to the bosque supports higher numbers of raptors. For instance, the nesting study has shown that one area of the bosque, in the village of Corrales, has nearly twice the number of active Cooper’s Hawk nests than other areas. In fact, the nesting density of this reach, might be higher than that reported anywhere else in North America. The adjacent land use there is a combination of agriculture and homes located on large properties, many of which contain horses or other livestock. Several management issues, ranging from development and fire protection to water conservation and removal of exotic vegetation, impact the bosque and the adjacent lands. A variety of habitat restoration initiatives also may have short or long-term effects on the wildlife dependent upon this habitat. Because of the potential conflict between raptor conservation and management issues, it is important to monitor raptor use of the bosque and the urban and rural land use adjacent to the riparian woodland that affect raptor populations. Our long-term monitoring could provide insight on how land use and management affects nesting New Mexico raptors.
Raptor Use of the Rio Grande and Estancia Valleys: An All Volunteer Study
The agricultural lands of the Rio Grande and Estancia Valleys support high concentrations of raptors during the nesting and wintering periods. The Estancia Valley has been identified by the National Aududon Society as an Important Bird Area due to its high number of nesting Ferruginous and Swainson’s Hawks and wintering raptor populations of several species. Likewise, the Rio Grande Valley hosts high numbers of raptors, particularly during the winter months, when numerous buteos, harriers, falcons, and eagles reside here. In 1994, we established several driving survey routes on secondary roads and levees. The route length varies somewhat, according to access, but is between 18-20 miles. Each route is surveyed once a month during the winter period of December, January, and February, and during the summer period of June, July, and August. Highly skilled and trained volunteers conduct all surveys using point count methodology.
Virtually every species of diurnal raptor known to occur in New Mexico has been detected over the course of this ten-year, ongoing study, making for some very exciting field days. The data enable us to monitor general population trends in these two important areas, as well as trends for individual species. Managed by Gerald Hobart, a volunteer, this project provides an excellent opportunity for individuals that would like the opportunity to view some of the less frequently observed raptors of New Mexico such as Prairie and Peregrine Falcons, Merlin, Rough-legged Hawk, and possibly even a Zone-tailed or Common Black Hawk. Please contact Gail to learn more about how you can become involved in this citizen science project.
Aplomado Falcon Prey Base Study Hawks Aloft is working with the Bureau of Land Management Socorro Field Office to evaluate avian prey base in anticipation of Aplomado Falcon reintroduction in New Mexico. At a casual glance, the desert habitat of central Socorro County appears devoid of avian life, but this habitat supports a variety of birds Common species include Sage Sparrow in the winter and Brewer’s Sparrow in the early spring, as well as Horned Lark and Cactus Wren all year. Raptors specializing in avian prey have been observed during the study, including Cooper’s Hawk and Prairie Falcon. We will compare transect and plot survey data with other regions to evaluate the relative prey base potential of Socorro County for Aplomado Falcons.
Mexican Spotted Owl Monitoring and Inventory in the Lincoln National Forest, Otero County, New Mexico This is a 4 year project which will be complete after the 2005 field season this summer. The purpose of the study is to determine the effects of the Scott Able fire on Mexican Spotted Owl reproduction. This project is divided into two parts: monitoring nine breeding territories and inventory of the entire Scott Able burn area. To monitor the territories, HAI must visit each area at night by hiking to pre-designated call points. At each point we use a vocal imitation of the owl’s 4-note call. The owls typically respond to our calling, which results in revealing their location. We can then conduct a day visit to determine their nesting status. This summer we will be conducting a complete inventory of the Scott Able burn area. This will include calling at call points on roads, ridge tops, and canyons in the survey area. In 2004, we successfully located 6 pairs and three of these nested. Of those, two nested successful, fledging 4 young, while the third nest failed for unknown reasons.
Northern Goshawk Monitoring and Inventory in the Lincoln National Forest, Otero County, New Mexico
Hawks Aloft is currently monitoring six historic Northern Goshawk territories in and around the Scott Able and Cree fires. The purpose is to determine the effects of the fires on Northern Goshawk reproduction. Goshawks are a difficult species to monitor due to their high mobility, secretive nature, and large home-range size. In 2004, we located one active nest in on territory and three individual goshawks on other territories. To complete the inventories of each fire study area, transects with call points will be established. At each call point, the goshawk call will be broadcasted with a tape player and megaphone. If a goshawk is in the area it will respond vocally or will silently come into the call area to investigate. Once a goshawk responds to the broadcasted call the area is searched to determine nesting status.
Raptor Distribution Study, Taos, New Mexico Hawks Aloft, in conjunction with the Taos Field Office, Bureau of Land Management is conducting raptor distribution and productivity surveys in the upper Rio Grande Gorge, Orilla Verde Recreation Area, and the Rio San Antonio Gorge. Raptor species include, Golden Eagle, Red-tailed Hawk, Prairie Falcon, Peregrine Falcon, and Great Horned Owl.
Golden Eagle and Ferruginous Hawk Study, Farmington, New Mexico
Through the Farmington Field Office, Bureau of Land Office, Hawks Aloft is monitoring the distribution, productivity, noise disturbance, and conservation of Golden Eagle and Ferruginous Hawk in the Four Corners area. The project is designed to minimize impacts to breeding Golden Eagle and Ferruginous Hawks in a resource area that is heavily utilized for gas and oil production. Golden Eagle and Ferruginous Hawk Study, Socorro, New Mexico In addition to the Farmington study, Hawks Aloft is monitoring the distribution, productivity, and conservation of Golden Eagle and Ferruginous Hawk through the Socorro Field Office on BLM and non-BLM land. The project is designed to minimize impacts and conserve habitat for breeding populations Golden Eagle and Ferruginous Hawk in a resource area that is heavily utilized for grazing cattle.
Ferruginous Hawk and Swainson's Hawk Study, Estancia Valley, New Mexico Hawks Aloft is undergoing long-term monitoring of distribution and productivity of Ferruginous Hawks in the Estancia Valley. This area is largely composed of private ranches and farmland. We work with private landowners to raise awareness and protect habitat for breeding Ferruginous Hawk and Swainson’s Hawk. This area is notable for the number of breeding pairs that it supports, as well as its high nest success rates.
McKinley Coal Mine, BHP Billiton Navajo Mine, and San Juan Coal Mine Raptor Distribution McKinley Mine, near Gallup, New Mexico is responsible for surveying raptor distribution and productivity as part of the mine's permit requirements. Raptors are monitored within the mine lease area, and a 2 mile buffer zone outside the mine lease. Species found in this area include: Golden Eagle, Cooper’s Hawk, Red-tailed Hawk, Prairie Falcon, Peregrine Falcon, American Kestrel, Great Horned Owl, and Burrowing Owl. Hawks Aloft also conducts raptor distribution surveys for BHP-Billiton Navajo Mine and San Juan Coal Mine in the Farmington, New Mexico area. Summer and winter wildlife surveys are also conducted to monitor wildlife use of reclaimed areas. Species that utilize this habitat include: Golden Eagle, Northern Harrier, Red-tailed Hawk, Prairie Falcon, Peregrine Falcon, American Kestrel, Great Horned Owl, and Burrowing Owl.
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