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Florida’s four rarest and most distinctive raptors, strikingly different in their ecology and movements, pose severe management and conservation challenges. The Crested Caracara, a grassland-dependent species listed as Threatened by the U. S. Fish and Wildlife Service, is a year-round resident on well-defined home ranges in central and southern Florida that are constantly at risk from development. The semi-nomadic Snail Kite, federally listed as Endangered, depends on a very narrow range of prey species for which availability is driven by unpredictable hydrologic conditions, in turn, influenced by competing water-delivery schedules for agriculture, urban development, and Everglades restoration. The Short-tailed Hawk, a genuine but short-distance migrant within peninsular Florida, preys mainly on birds, very unusual among Buteo hawks, and suffers high mortality from human activities that include shooting. Swallow-tailed Kites are actual long-distance neotropical migrants that winter in southern Brazil but rely on highly diverse habitats, including mature hydric forests for nesting and various wetland mosaics for feeding. Dr. Meyer will present ARCI’s telemetry and demography studies results, which have produced exciting data that are helping shape management and conservation plans for these fascinating, imperiled species.
During the late 1800s to early 1900s, Northern Goshawks (Accipiter gentilis) was driven to near destruction in the northeastern United States by excessive timber harvesting and persecution as a robber of game. Over the past 50+ years, as forests recovered and human attitudes changed, the Goshawk population in this area increased, and the breeding range expanded back southward into West Virginia. Since 1994, the Central Appalachian Goshawk Project has monitored 187 Goshawk nesting attempts, banded 86 nesting adults, and investigated winter movements of breeding adults from NW Pennsylvania down the Appalachian Mountains into the high country of West Virginia. The positive population trend and range expansion during the late twentieth century abruptly reversed in the twenty-first century. Breeding Bird Atlas declines have been recorded in all northeastern states that have completed second atlas projects. After recovering the breeding range in Maryland and West Virginia, Goshawks no longer breed south of central Pennsylvania. Eastern hawk watch data document the virtual cessation of irruptive movements and significant declines at most important sites, including the two lowest counts of Goshawks at Hawk Mountain Sanctuary since the establishment of routine counts in 1970. Banding data from nest sites show frequent reproductive failure and poor female survival vs. male survival. Possible factors causing the declining trend include changes in nest predation pressure, prey population decline, and West Nile Virus.
The 2019 Raptor Population Index (RPI) analyses build on past RPI efforts to assess the status of migrant raptors using data from watch sites across North America. The latest studies utilize data from 73 watch sites (3 that count in spring and fall) to estimate trends in counts for 28 species. In all, we evaluated 1009 trends across all areas using data from 2009-2019. During this time, 22 percent of trends indicate declining counts, 67 percent stable counts, and 11 percent had increasing counts. We identify raptors at risk or species with widespread or regional declines as well as raptors on the rise. To increase understanding of migration trends, we also examine RPI trends alongside winter trends for some species using Christmas Bird Count (CBC) data.
Birds play an essential role as environmental sentinels, and migratory birds of prey are precious because of their very demanding ecological needs. The habitats they use during their migrations need to be in an excellent state of conservation. Long-term monitoring of migration patterns through standardized programs can provide valuable information about these bioindicator groups and help assess the real impact of human activity on ecosystems.
More than 2 million diurnal raptors of 30 species regularly migrate through Palaearctic-African migratory system, breeding in Europe and wintering around the Mediterranean Sea or tropical Africa. In this region, the Mediterranean Sea and the Sahara Desert play an essential role in delimiting soaring birds’ migratory routes. Several places work as significant bottlenecks for bird migration, concentrating thousands of raptors every year. The strait of Gibraltar is one of the most critical points for migratory birds, particularly for soaring birds. Strategically situated in the Palaearctic-African migratory system’s western route, this 14-km funnel-shaped strait acts as a natural bridge between the continents of Europe and Africa. In total, 425,000-500,000 soaring birds across the Strait of Gibraltar every season, including 290,000-380,000 prey species (28 species regularly observed). Data collected in the Strait of Gibraltar allows us to study changes in migration patterns at different timeframes in a context of global change, showing a generalized increase in the number of raptors crossing, mainly in the last decade, and some changes in time schedules and species composition, including the incorporation of species coming from Africa and raptors that used to follow an eastern migratory route.
Bird migration in South America is a complex phenomenon, with masses of birds moving on several axes—latitudinal, altitudinal, and longitudinal—during a given season. Given this complexity, there is still much to learn about bird migration in the continent. Diurnal raptors represent an excellent model group to investigate South America’s migration because of the 96 species found in the continent, 44 exhibit seasonal movements. Migratory raptors have been sorted into three migration systems: the Nearctic-Neotropical system includes species that breed in the Nearctic region and overwinter in the Neotropics reaching South America via the Mesoamerican Land Corridor (the principal flyway) or the Caribbean Sea (making landfall mainly in the Venezuelan coast); the Neotropical–Intra-tropical system includes species that breed in tropical and subtropical latitudes and overwinter within the equatorial belt. However, there is no evidence of any significant flyways in this system; the Austral-Neotropical system includes species that breed in the austral temperate zone and overwinter north of the breeding range within South America, and the principal flyways appear to be the western and eastern slopes of the Andes, central Pampas, and the Atlantic coast.
Studies to map the significant migration flyways and breeding and wintering ranges of migratory raptors in South America remain fertile research grounds. Therefore, in this talk, I will (1) review the current knowledge of raptor migration within South America and (2) present novel systematically collected data on the wintering distribution and seasonal abundances (summer vs. winter) of raptors. Finally, I will present suggestions concerning future research lines to better understand raptor migration in South America.
The Hook-billed Kite (Chondrohierax uncinatus) is a specialized Neotropical raptor with a wide distribution that has received little research attention despite local declines occurring. It is considered non-migratory across most of its distribution, but there are scattered records of Hook-billed Kite migration, first documented in the 1990s in Mexico. For the first time, we describe the largest migration of the Hook-billed Kite in Belize and Mexico and model how environmental conditions influence it. Eight years (2013-2020) of count data was collected in Belize and 25 years (1995-2019) in Mexico from three raptor monitoring count sites to compare movements in the different regions. Precipitation on the breeding grounds did not influence the phenology or magnitude of the kites migrating through Belize.
In contrast, in Mexico, with more rainfall north of the count site, the migration was later. Belize is the most critical concentration point and migratory corridor for this Neotropical raptor. This research provides vital ecological information in light of human-caused climate change and habitat loss, identifying potential threats, conservation needs, and population status for Hook-billed Kites and other neotropical raptors.
With 3 billion birds lost in North America since 1970 and a growing awareness that climate change will reshape bird communities worldwide, the future of migratory birds is more uncertain now than ever. As we face this uncertainty, there is an urgent need to understand better how bird populations change and engage people in protecting them. Two efforts at the National Audubon Society provide examples of bringing people together to understand better and protect birds. Climate Watch has mobilized community scientists to test hypotheses about how birds are changing their distributions in response to climate change. Results from the first several years of the program reveal that climate change is already causing a measurable shift in bird species’ ranges during the winter and breeding seasons. The collected data were used as independent observations to validate climate suitability projected range shifts for several bluebirds and nuthatch target species. What was found was that these birds are shifting their distributions as climate change-based models project, with birds moving into areas that are becoming more suitable in the 2020s. These results shed light on the importance of community science programs and how they can aid in our understanding of birds’ responses to broad-scale changes in climate. The Migratory Bird Initiative is focused on protecting North American migratory birds by identifying the places they need to thrive across the Americas, taking actions to protect the sites that matter most, reducing threats, and engaging people in the joy of migration. As one part of this work, we have aggregated tracking and banding data to tell the story of how birds move across the hemisphere. Because raptors are large enough to have supported tracking technology for many years, there is a rich set of data for visualizing migration and telling the story of these unique journeys. These two examples illustrate how birds respond to climate change and what we can do to tell their story and inspire people to act.
At the top of food webs, birds present a diverse suite of predators in many ecosystems. In the Arctic tundra, the snowy owl, the rough-legged hawk, the peregrine falcon, the gyrfalcon, and jaegers and gulls all feed on small mammals such as lemmings, the main herbivores. It has been suggested that predation pressure, especially by irruptive predators, could limit or even regulate herbivore numbers. However, empirical data aiming to answer such questions are rare. Since 2004, we studied movement ecology and monitored numerical (variation in numbers) and functional (variation in diet and consumption rates) responses of avian predators concerning the abundance of prey. Our results provide evidence that predation pressure is substantial and could limit herbivore numbers during the snow-free period. Our results suggest that those birds could determine herbivore numbers on a broad continental scale by tracking raptors with satellite transmitters, given their long-distance post-breeding movements. Furthermore, the satellite tracking allowed us to show that snowy owls, known specialist predators of the terrestrial ecosystem, rely extensively on marine resources during winter. Those observations suggest that allochthonous subsidies from the marine ecosystem could ultimately affect the tundra food web’s functioning by supporting dense populations of predators when terrestrial resources are unavailable.
The Rough-legged Hawk (Buteo lagopus) breeds throughout arctic and subarctic regions of North America and winters throughout southern Canada and the conterminous United States spatial overlap between breeding and wintering areas. Christmas Bird Count and Migration Site data suggest the species may be declining and shifting winter distributions northwards. Furthermore, winter range shifts influence regional population trends such that careful interpretation of trends is needed for all migratory species. We deployed GPS transmitters on 139 Rough-legged Hawks from 2014 – 2021 to better understand the species’ mobile behavior. We trapped and deployed transmitters on hawks on the wintering grounds, breeding grounds, and migration throughout much of North America. Movement data has provided: invaluable information on Rough-legged Hawk migration ecology, temporal and spatial mortality patterns, and factors influencing how far and how consistently individuals migrate.
We will present preliminary results from our movement ecology study and how they may help inform the continued interpretation of migration count site trends moving forward.
Since the early 1980s, hawk watch site leaders for Pennsylvania and nearby states spend one day together annually to discuss the prior season counts, highlights for different species, and discuss the highs and lows from the previous season. This meeting is known as the Kittatinny Roundtable as some of the group’s longest-running sites align along this landscape. The site with the highest one-day count for a species is usually celebrated and gets bragging rights while together, the counters discuss and commiserate the lows. For one day, all the counters for the sites come together and share their passion for migration. On Saturday, July 31, HMANA hosts part of the Kittatinny Roundtable within its virtual conference and invites all hawk watchers to sit in and possibly participate. We will expand our regional view of prior season results to include sites from Canada south to Virginia and west through the Great Lakes. Laurie Goodrich and David Barber, Hawk Mountain, will host the Roundtable discussion, and Carolyn Hoffman, a long-time participant, and board member. Site leaders will participate in the past season discussion, and other participants invited to comment in the discussion period. Participants should bring their daily count results for fall 2020 and spring 2021 to share. HMANA hopes the Kittatinny Roundtable can serve as a model for future regional conferences of hawk watchers.
Mississippi kites have experienced pronounced changes to their geographic distribution and local abundances over the last century. Co-occurring with these changes has been the colonization of urban areas, first in the Great Plains and then later in eastern regions, by a large number of kites. Today, Mississippi kites represent one of the most abundant urban-breeding raptors in North America. The presence of kites in cities has afforded both opportunities and challenges. The high nesting density achieved by some kites populations has allowed for numerous investigations of their ecology, including studies of relative nesting success, diet, habitat selection, and mate- and site fidelity. It also will enable urbanites to gain a close view and develop an appreciation of a raptor species. However, on rare occasions, kites and urbanites are brought into conflict over parks and other green spaces, with some kites vigorously defending their nesting areas against pedestrians. These conflicts, though proportionally small, often attract the majority of public attention and can engender negative attitudes towards nesting kites and other raptors. Despite their increasing abundance, several aspects of natural kite history remain unknown, including detailed information on population genetic structure and much about their migration and over-wintering ecology. Research into these areas is ongoing, with updates forthcoming.
Conservation of long-lived species requires identifying and protecting the areas and resources they use throughout their life cycle and the year. The Golden Eagle (Aquila chrysaetos) is a long-lived species that exhibits deferred breeding, resulting in a long (i.e., > three years) natal dispersal period. The Natal dispersal of Golden Eagles is poorly documented, and we know little about the areas they inhabit and the resources they use during this period. We have been quantifying the year-round movements of migratory Golden Eagles raised in Denali National Park and Preserved, Alaska, since 1997 using satellite and GSM telemetry. Our study results provide new information on the movements during the natal dispersal period, including during the nesting season. Our study results show that non-territorial golden eagles’ activities are very different from those of territorial golden eagles during the nesting season. From courtship through the dispersal of young, the nesting season for migratory Golden Eagles in interior and northern Alaska extends from mid-February through early October. After returning to Alaska (from mid-February to early April), territorial eagles remain in and near their territories. In contrast, pre-adult non-territorial eagles return to Alaska much later than territorial eagles (i.e., from mid-April through early June). They often exhibit nomadic behaviors for part of the nesting season. In contrast, some settle temporarily (several weeks to several months) in specific areas, including areas on Alaska’s Arctic Coastal Plain in northern Alaska and the vast wetlands of the western Seward Peninsula in western Alaska. The repeated use of these areas by multiple telemetered eagles over many years suggests that they provide essential habitats and resources for Alaska’s migratory Golden Eagles before they enter a breeding population. Our studies also indicate that Alaska’s areas during the nesting season by non-territorial and territorial Golden Eagles are very different. Quantifying these differences can help us identify and hopefully protect the places and resources needed for territorial and non-territorial Golden Eagles in Alaska.