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At least 145 records · Page 8Linked to original sources
USGS2019

Modeling effects of crop production, energy development and conservation-grassland loss on avian habitat

Birds are essential components of most ecosystems and provide many services valued by society. However, many populations have undergone striking declines as their habitats have been lost or degraded by human activities. Terrestrial grasslands are vital habitat for birds in the North American Prairie Pothole Region (PPR), but grassland conversion and fragmentation from agriculture and energy-production activities have destroyed or degraded millions of hectares. Conservation grasslands can provide alternate habitat. In the United States, the Conservation Reserve Program (CRP) is the largest program maintaining conservation grasslands on agricultural lands, but conservation grasslands in the PPR have declined by over 1 million ha since the program’s zenith in 2007. We used an ecosystem-services model (InVEST) parameterized for the PPR to quantify grassland-bird habitat remaining in 2014 and to assess the degradation status of the remaining grassland-bird habitat as influenced by crop and energy (i.e., oil, natural gas, and wind) production. We compared our resultant habitat-quality ratings to grassland-bird abundance data from the North American Breeding Bird Survey to confirm that ratings were related to grassland-bird abundance. Of the grassland-bird habitat remaining in 2014, about 19% was degraded by crop production that occurred within 0.1 km of grassland habitats, whereas energy production degraded an additional 16%. We further quantified the changes in availability of grassland-bird habitat under various land-cover scenarios representing incremental losses (10%, 25%, 50%, 75%, and 100%) of CRP grasslands from 2014 levels. Our model identified 1 million ha (9%) of remaining grassland-bird habitat in the PPR that would be lost or degraded if all CRP conservation grasslands were returned to crop production. Grassland regions world-wide face similar challenges in maintaining avian habitat in the face of increasing commodity and energy production to sate the food and energy needs of a growing world population. Identifying ways to model the impacts of the tradeoff between food and energy production and wildlife production is an important step in creating solutions.

Prairie Pothole Region↗
USGS2020

Genomic identification of intergeneric hybrids in New World wood-warblers (Aves: Parulidae)

The documentation of hybrids between distantly related taxa can illustrate an initial step to explain how genes might move between species that do not exhibit complete reproductive isolation. In birds, some of the most phylogenetically distant hybrid combinations occur between genera. Traditionally, morphological and plumage characters have been used to assign the identity of the parental species of a putative hybrid, although recently, nuclear introns also have been used. Here, we demonstrate how high-throughput short-read DNA sequence data can be used to identify the parentage of a putative intergeneric hybrid, in this case between a blue-winged warbler ( Vermivora cyanoptera ) and a cerulean warbler ( Setophaga cerulea ). This hybrid had mitochondrial DNA of a cerulean warbler, indicating the maternal parent. For hundreds of single nucleotide polymorphisms within six regions of the nuclear genome that differentiate blue-winged warblers and golden-winged warblers ( Vermivora chrysoptera ), the hybrid had roughly equal ancestry assignment to blue-winged and cerulean warblers, suggesting a blue-winged warbler as the paternal parent species and demonstrating that this was a first generation (F 1 ) hybrid between these species. Unlike other recently characterized intergeneric warbler hybrids, this individual hybrid learned to song match its maternal parent species, suggesting that it might have been the result of an extra-pair mating and raised in a cerulean warbler nest.

Biological Journal of the Linnean Society↗
USGS2025

Power source, data retrieval method, and attachment type affect success of dorsally mounted tracking tag deployments in 37 species of shorebirds

Animal-borne trackers are commonly used to study bird movements, including in long-distance migrants such as shorebirds. Selecting a tracker and attachment method can be daunting, and methodological advancements often have been made by trial and error and conveyed by word of mouth. We synthesized tracking outcomes across 2745 dorsally mounted trackers on 37 shorebird species around the world. We evaluated how attachment method, power source, data retrieval method, relative tracker mass, and biological traits affected success, where success was defined as whether or not each tag deployment reached its expected tracking duration (i.e. all aspects succeeded for the intended duration of the study: attachment, tracking, data acquisition, and bird survival). We conducted separate analyses for tag deployments with remote data retrieval (‘remote-upload tag deployments') and those that archived data and had to be recovered (‘archival tag deployments'). Among remote-upload tag deployments, those that were a lighter mass relative to the bird, were beyond their first year of production, transmitted data via satellite, or were attached with a leg-loop harness were most often successful at reaching their expected tracking duration. Archival tag deployments were most successful when applied at breeding areas, or when applied to males in any season. Remote-upload tag deployments with solar power, satellite data retrieval, or leg-loop harnesses continued tracking for longer than those with battery power, other types of data retrieval, or glue attachments. However, the majority of tag deployments failed to reach their expected tracking duration (71% of remote-upload, 83% of archival), which could have been due to tracker failure, attachment failure, or bird mortality. Our findings highlight that many tag deployments may fail to meet the goals of a study if tracking duration is crucial. Using our results, we provide guidelines for selecting a tracker and attachment to improve success at meeting study goals.

Journal of Avian Biology↗
USGS2020

A multiscale approach to understanding migratory land bird habitat use of functional stopover habitat types and management efforts

It is hard to believe that many of the small “backyard birds” people see during spring and autumn can make migratory journeys that span thousands of kilometers. In fact, over two-thirds of all land birds (i.e., those not associated with aquatic habitats) and over half of the migratory species in North America move long distances to areas in Mexico, Central and South America, and the Caribbean islands. Some have argued that long-distance migrants experience the best of two worlds by virtue of their migratory strategy: increased reproductive success by breeding in food-rich, competitor-poor temperate areas and increased survival by wintering in warmer tropical areas. However, traveling long distances across areas that vary physiographically comes with considerable risks, and the mortality associated with long-distance migration may be substantial, especially among young, inexperienced birds making the journey for the first time. Although many migratory land birds are capable of making spectacular, nonstop flights over geographic barriers, including the Sahara Desert, the eastern Atlantic Ocean, and the Gulf of Mexico, few actually fly nonstop from their point of origin to their final destination. Rather, they make periodic stops lasting a few hours to a few days before resuming migration. The place where a migratory bird pauses for some length of time between migratory flights is called a stopover site. For birds crossing the Gulf of Mexico that must contend with a 13 to 32 hour nonstop flight, the habitats along the northern Gulf of Mexico coast provide the last possible stopover before autumn migrants make a nonstop flight south and the first possible landfall for birds returning north in the spring.

Gulf of Mexico Avian Monitoring Network (GoMAMN)↗
USGS2010

The impact of conservation on the status of the world's vertebrates

Using data for 25,780 species categorized on the International Union for Conservation of Nature Red List, we present an assessment of the status of the world's vertebrates. One-fifth of species are classified as Threatened, and we show that this figure is increasing: On average, 52 species of mammals, birds, and amphibians move one category closer to extinction each year. However, this overall pattern conceals the impact of conservation successes, and we show that the rate of deterioration would have been at least one-fifth again as much in the absence of these. Nonetheless, current conservation efforts remain insufficient to offset the main drivers of biodiversity loss in these groups: agricultural expansion, logging, overexploitation, and invasive alien species.

Science↗
USGS2018

Research and management priorities for Hawaiian forest birds

Hawai‘i's forest birds face a number of conservation challenges that, if unaddressed, will likely lead to the extinction of multiple species in the coming decades. Threats include habitat loss, invasive plants, non-native predators, and introduced diseases. Climate change is predicted to increase the geographic extent and intensity of these threats, adding urgency to implementation of tractable conservation strategies. We present a set of actionable research and management approaches, identified by conservation practitioners in Hawai'i, that will be critical for the conservation of Hawaiian forest birds in the coming years. We also summarize recent progress on these conservation priorities. The threats facing Hawai‘i's forest birds are not unique to Hawai‘i, and successful conservation strategies developed in Hawai‘i can serve as a model for other imperiled communities around the world, especially on islands.

Hawai‘i↗
USGS2013

American Avocet (Recurvirostra americana)

This large, striking shorebird with long bluish-gray legs, a long recurved bill, and a black-and-white chevron pattern on its back and wings is one of four Avocet species in the world, the only one with distinct breeding and non-breeding plumages -- its grayish-white head and neck feathers become cinnamon in early spring as birds begin to form pairs and migrate to breeding areas.

Book chapter↗
USGS2008

Primary production and carrying capacity of former salt ponds after reconnection to San Francisco Bay

Over 6,110 ha of the commercial production salt ponds surrounding South San Francisco Bay, CA, have been decommissioned and reconnected to the bay, most as part of the largest wetlands restoration program in the western United States. These open water ponds are critical habitat for millions of birds annually and restoration program managers must determine the appropriate balance between retention of ponds versus re-conversion to tidal salt marsh, knowing that both are essential ecosystems for endangered bird species. Our study describes the ecological value of the new open water pond ecosystems as feeding habitats for birds. We used the oxygen rate of change method to determine ecosystem metabolic parameters from high resolution time-series of dissolved oxygen concentration. Areal gross primary production (8.17 g O 2 m −2 d −1 ) was roughly double the world’s most productive estuaries. High rates of phytoplankton photosynthesis were balanced by equally high rates of community respiration (8.25 g O 2 m −2 d −1 ). Metabolic equilibrium was delicately poised: sharp irradiance and temperature shifts triggered short term photosynthesis reduction resulting in oxygen depletion. We converted net primary production (NPP) into potential carrying capacity of the forage biota that support targeted pond waterbirds. NPP was processed through both a pelagic food web, resulting in forage biota for piscivorous birds and a benthic food web, resulting in forage biota for shorebirds and diving benthivores. Both food webs included efficient algal-based and inefficient detrital trophic pathways. The result of all primary production being routed through simple food webs was high potential forage production and energy supply to waterbirds, equivalent to 11–163 million planktivorous fish or 19–78 billion small estuarine clams within the 330-ha pond between May and October. Food quantity does not necessarily equal quality and these systems have the potential to produce toxic or inedible algae. Our study provides the first measurement of primary production in the open water ponds of San Francisco Bay and presents a novel approach for transforming primary production into forage production as a metric of an ecosystem’s energetic carrying capacity.

California↗
USGS2020

Social attraction used to establish Caspian tern nesting colonies in San Francisco Bay

Conservation of colonial waterbird breeding populations often includes restoring historic nesting habitat or establishing new nesting habitat in protected areas. However, colonization of new or restored nesting habitat may be hindered by the lack of social cues from nesting conspecifics to attract prospecting birds. Social attraction, whereby decoys and colony sound recordings are used to mimic active nesting colonies, has been used successfully to establish waterbird nesting colonies throughout the world. We constructed islands, modified the substrate so that it was attractive to nesting Caspian terns (Hydroprogne caspia), and then used social attraction to establish nesting colonies within two managed ponds in San Francisco Bay, California where Caspian terns had not previously nested. During the 2015–2017 breeding seasons, we deployed decoys of adult Caspian terns, broadcasted colony sound recordings, and monitored Caspian tern response. Caspian terns formed nesting colonies within weeks of social attraction deployment at each of the two ponds in 2015, and the size of these colonies increased in each subsequent year of the study. In 2017, the final year of the study, we estimated a minimum of 501 breeding pairs between the two colonies, making them two of the three largest Caspian tern colonies in the San Francisco Bay estuary. In total, these two colonies produced 1343 nests and 531 fledglings over the three-year study period. Nest densities were low (mean: 0.29 nests/m2 of active colony area) compared to other studies, and greater than 80% of the modified island habitat remained unused by nesting Caspian terns in 2017, suggesting that there is additional space for future colony growth. The successful establishment of two of the largest Caspian tern nesting colonies in the San Francisco Bay estuary in just three years demonstrates the potential of using island construction and habitat modifications, combined with social attraction measures to establish waterbird nesting colonies.

California↗
USGS2025

Habitat features influencing waterbird use of managed wetlands enrolled in a public-private partnership for land conservation: The California Waterfowl Habitat Program

Draining, water diversion, and development have greatly reduced the availability of freshwater wetland habitat around the world, and many remaining wetlands are on private lands. Public–private partnership programs can be an important means for promoting habitat conservation and management on private lands. We investigated bird use of 117 wetlands enrolled in the California Waterfowl Habitat Program in California's Central Valley, where two-thirds of wetlands are under private ownership and management. Specifically, we quantified the influence of wetland habitat features and surrounding land cover on waterbird density and diversity in late winter and early spring and during the waterfowl breeding season. Dabbling duck and shorebird densities were highest in wetlands that had water depths < 20 cm, and waterbird densities decreased with water depth. Greater amounts of emergent vegetation, especially tall and dense emergent vegetation, had a negative effect on total waterbird density but a positive effect on species richness and secretive marsh bird density. Shorebird and breeding duck densities were lower in wetlands with a large number of trees and other potential perch sites, and waterbird densities decreased with the amount of nearby wetland habitat on the landscape. Overall, we estimated that during late winter and early spring, private properties that were enrolled in the California Waterfowl Habitat Program (8000–8500 ha each year) supported 480,000 birds per day during extreme drought conditions in 2022 and 280,000 birds per day in more normal, non-drought conditions in 2023. Over the 76-day winter and early spring survey period, this amounted to more than 20 million bird use days on wetlands enrolled in the California Waterfowl Habitat Program during late winter and early spring. These results demonstrate the value of public–private wetland conservation partnerships, the influence of wetland habitat features and surrounding land cover on waterbird abundance, and the benefits of habitat features that could be incorporated into management plans and wetland selection criteria for enrollment into public–private conservation programs.

California↗
USGS2022

Collateral damage: Anticoagulant rodenticides pose threats to California condors

Anticoagulant rodenticides (ARs) are widespread environmental contaminants that pose risks to scavenging birds because they routinely occur within their prey and can cause secondary poisoning. However, little is known about AR exposure in one of the rarest avian scavengers in the world, the California condor ( Gymnogyps californianus ). We assessed AR exposure in California condors and surrogate turkey vultures ( Cathartes aura ) to gauge potential hazard to a proposed future condor flock by determining how application rate and environmental factors influence exposure. Additionally, we examined whether ARs might be correlated with prolonged blood clotting time and potential mortality in condors. Only second-generation ARs (SGARs) were detected, and exposure was detected in all condor flocks. Liver AR residues were detected in 42% of the condors (27 of 65) and 93% of the turkey vultures (66 of 71). Although concentrations were generally low (<10 ng/g ww), 48% of the California condors and 64% of the turkey vultures exposed to ARs exceeded the 5% probability of exhibiting signs of toxicosis (>20 ng/g ww), and 10% and 13% exceeded the 20% probability of exhibiting signs toxicosis (>80 ng/g ww). There was evidence of prolonged blood clotting time in 16% of the free-flying condors. For condors, there was a relationship between the interaction of AR exposure index (legal use across regions where condors existed) and precipitation, and the probability of detecting ARs in liver. Exposure to ARs may complicate recovery efforts of condor populations within their current range and in the soon to be established northern California experimental population. Continued monitoring of AR exposure using plasma blood clotting assays and residue analysis would allow for an improved understanding of their hazard to condors, particularly if paired with recent movement data that could elucidate exposure sources on the landscape occupied by this endangered species.

California↗
USGS2006

Disease emergence and resurgence—the wildlife-human connection

In 2000, the Global Outbreak Alert and Response Network (GOARN) was organized as a global disease watchdog group to coordinate disease outbreak information and health crisis response. The World Health Organization (WHO) is the headquarters for this network. Understandably, the primary focus for WHO is human health. However, diseases such as the H5N1 avian influenza epizootic in Asian bird populations demonstrate the need for integrating knowledge about disease emergence in animals and in humans. Aside from human disease concerns, H5N1 avian influenza has major economic consequences for the poultry industry worldwide. Many other emerging diseases, such as severe acute respiratory syndrome (SARS), monkeypox, Ebola fever, and West Nile fever, also have an important wildlife component. Despite these wildlife associations, the true integration of the wildlife component in approaches towards disease emergence remains elusive. This separation between wildlife and other species’ interests is counterproductive because the emergence of zoonotic viruses and other pathogens maintained by wildlife reservoir hosts is poorly understood. This book is about the wildlife component of emerging diseases. It is intended to enhance the reader’s awareness of the role of wildlife in disease emergence. By doing so, perhaps a more holistic approach to disease prevention and control will emerge for the benefit of human, domestic animal, and free-ranging wildlife populations alike. The perspectives offered are influenced by more than four decades of my experiences as a wildlife disease practitioner. Although wildlife are victims to many of the same disease agents affecting humans and domestic animals, many aspects of disease in free-ranging wildlife require different approaches than those commonly applied to address disease in humans or domestic animals. Nevertheless, the broader community of disease investigators and health care professionals has largely pursued a separatist approach for human, domestic animal, and wildlife rather than embracing the periodically proposed concept of “one medicine.” We especially need to embrace this concept as the human population increases because there will be more contact, direct and indirect, among humans, domestic animals, and wildlife. An “Ecology for a Crowded Planet” will be an even more pressing concern, and that includes increasing our understanding of disease ecology, especially that of the zoonoses.

Circular↗
USGS2006

Investigations of the Effects of Synthetic Chemicals on the Endocrine System of Common Carp in Lake Mead, Nevada and Arizona

Introduction: Lake Mead is the largest reservoir by volume in the United States and was created by the construction of the 221-meter high Hoover Dam in 1935 at Black Canyon on the lower Colorado River between Nevada and Arizona (fig. 1). Inflows of water into the lake include three rivers, Colorado, Virgin, and Muddy; as well as Las Vegas Wash, which is now perennial because of discharges from municipal wastewater treatment plants (Covay and Leiker, 1998) and urban stormwater runoff. As the population within the Las Vegas Valley began to increase in the 1940s, the treated effluent volume also has increased and in 1993 it constituted about 96 percent of the annual discharge of Las Vegas Wash (Bevans and others, 1996). The mean flow of Las Vegas Wash into Las Vegas Bay from 1992 to 1998 was about 490,000 m3/d (Preissler and others, 1999) and in 2001 increased to 606,000 m3/d (U.S. Bureau of Reclamation, 2001). The nutrient concentration in most areas of the lake is low, but wastewater discharged into Las Vegas Bay has caused an increased level of nutrients and primary productivity (aquatic plant and algal production) in this area of the lake (LaBounty and Horn, 1997). A byproduct of this increase in productivity has been the establishment of an important recreational fishery in Las Vegas Bay. However, concentrations of chlorophyll a (a measure of algal biomass) have also increased (LaBounty and Horn, 1997). In the spring of 2001, parts of Lake Mead experienced massive algal blooms. In addition to nutrient loading by wastewater, the presence of numerous synthetic chemicals in water, bottom sediments, and in fish tissue also has been reported (Bevans and others, 1996). Synthetic chemicals discharging into Las Vegas Bay and Lake Mead (fig. 1) originate from several sources that include surplus residential-irrigation water runoff, stormwater runoff, subsurface inflow, and tertiary treated sewage effluent discharging from three sewage-treatment plants. Chemicals detected in Las Vegas Wash and Bay environments include polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (including DDT and DDE), and 'emerging contaminants' such as fragrances/musks, flame retardants, triclosan and its breakdown products, personal care products, and pharmaceuticals (Bevans and others, 1996; Boyd and Furlong, 2002; Leiker and others, in press). Many of these compounds are able to interact with the endocrine system of animals and potentially cause reproductive impacts. The National Park Service (NPS) manages Lake Mead National Recreation Area (LMNRA) with about 8 million yearly visitors including 500,000 anglers drawn to its world-class recreational fishery. The U.S. Fish and Wildlife Service (FWS) provides management for the federally designated, endangered razorback sucker (Xyrauchen texanus) and for more than 180 species of migratory birds that utilize LMNRA surface waters. These multiple uses of surface water in the area demonstrate their vital importance to the LMNRA as well as the need to maintain the quality of water at levels that are adequate for these uses.

Fact Sheet↗
USGS2014

Historic and recent nesting records of Turkey Vultures in South Dakota

Present-day vultures are generally classified into two distinct groups: Old World vultures and new World vultures. The two groups share morphological and behavioral characters (e.g. scavenger diet, energy-efficient soaring, mostly featherless head), but historically the two groups were considered phylogenetically distant with long and independent histories (Rich 198., Wink 1995, Zhang et al. 2012). Old World vultures occur in the family Accipitridae and are closely related to hawks and eagles. New World Vultures occur in the family Cathartidae but their taxonomic placement has been controversial. New World vultures were previously allied with storks (Ciconiidae) but were usually placed within the order Falconiformes. Recent phylogenomic analyses using DNA sequencing suggest that new World vultures show no affinity with storks and support placement of New World vultures with other landbirds (in the order Accipitriformes, near Accipitridae) rather than with waterbirds (Hackett et al. 2008). Old World vultures presently are confined to Europe, Asia, and Africa, and New World vultures presently occur in North and South America.

South Dakota↗
USGS1990

The importance of subarctic intertidal habitats to shorebirds: A study of the central Yukon-Kuskokwim Delta, Alaska

A 6-year study of shorebird use of intertidal habitats of the Yukon-Kuskokwim Delta revealed this area to be one of the premiere sites for shorebirds throughout the Holarctic and worthy of designation as a Hemispheric Shorebird Reserve in the Western Hemisphere Shorebird Reserve Network. The study area, which covered 10% (300 km 2 ) of the delta's intertidal flats, regularly hosted 17 species of shorebirds between late April and mid-October. The greatest use was during the postbreeding period (late June-October), when Dunlins ( Calidris alpina ), Western Sandpipers ( C. mauri ), and Rock Sandpipers ( C. ptilocnemis ), each with large local nesting populations, accounted for 95% of the shorebirds recorded. Peak counts during autumn approached 300,000 birds. Considering the seasonal occurrence and turnover of populations, we estimate 1-2 million shorebirds use the central delta each year. The delta supports large fractions of the Pacific Rim or world populations of Bar-tailed Godwits ( Limosa lapponica ), Black Turnstones ( Arenaria melanocephala ), Red Knots ( C. canutus ), Western Sandpipers, Dunlins, and Rock Sandpipers. Densities of shorebirds using the central delta's four major bays and connecting coastal areas peaked at 950 shorebirds/km 2 in early September. Hazen Bay frequently hosted more than 1,200 shorebirds/km 2 . Postbreeding shorebirds used intertidal habitats in three distinct patterns according to age class. For most species (n = 7), there was a period when adults appeared first, followed by a brief interval when adults and juveniles mixed, then by a prolonged period when only juveniles remained. In the second pattern (n = 3 species), adults moved onto the intertidal flats first, were later joined by juveniles for a prolonged staging period, then migrated with them. In the third pattern (n = 3 species), only juveniles used the delta's intertidal habitat. Temporal segregation among species and age groups may minimize competition for food and thereby allow the delta to support high diversity and numbers of shorebirds.

Alaska↗
USGS1990

Notes on longevity and flightlessness in bristle-thighed curlews

Bristle-thighed Curlews ( Numenius tahitiensis ) are among the least-studied shorebirds in the world. They have a highly restricted breeding range in western Alaska and winter exclusively on remote islands in the central and south Pacific (AOU 1983, Kessel 1989). The status of these birds is not known, but they are considered to be rare throughout their range (Johnsgard 1981). We describe two unusual traits of Bristle-thighed Curlews - exceptional longevity and flightlessness during molt-and discuss their significance to the species' migration and nonbreeding ecology.

The Auk↗
USGS2025

Survival of captive-raised light-footed Ridgway’s rails is influenced by release date and time in wild

Captive breeding and translocation programs are an increasingly common conservation tool and management strategy used for some of the rarest and most endangered species in the world. These programs come at a high cost, and many translocation programs fail to monitor animals after release. Light-footed Ridgway’s rails ( Rallus obsoletus levipes ) are federally endangered marsh birds endemic to coastal wetlands of southern California and northern Mexico. Juvenile captive-raised light-footed Ridgway’s rails have been released into marshes within their U.S. range for >20 yr, but little effort has been devoted to post-release tracking of their movement and survival. We used satellite GPS transmitters to track survival of 46 juvenile captive-released and 42 juvenile wild-caught light-footed Ridgway’s rails from 2020–2022. Our results suggest that juvenile captive-released rails had lower initial daily survival probability (0.979) compared with that of juvenile wild-caught rails (0.994). Survival probability of captive-released rails increased with time in the wild, matching that of wild birds at about 100 d post-release. Survival of captive-released birds was most influenced by the date birds were released (releases in early summer had the highest survival). Our study emphasizes the importance of post-release monitoring as part of any captive breeding and translocation program and provides important insight into management strategies that may improve captive-released rail survival in the wild.

California↗
USGS2020

Understanding the golden eagle and bald eagle sensory worlds to enhance detection and response to wind turbines

The objective for this study was to measure the auditory and visual physiology of Golden and Bald Eagles in order to use eagle sensory capabilities to inform the design of potential deterrent stimuli that could be used to reduce eagle/turbine collisions with wind turbines. The rationale for this approach is that sensory systems of any organism will limit the capability of that organism to perceive aspects of the world around it. Moreover, species can differ dramatically in their sensory physiology so it is important to examine these characteristics in the species of concern, rather than relying on data from similar birds. Our project consisted of two main phases. The first phase was the acquisition and analysis of visual and auditory information from Golden and Bald Eagles in rehabilitation centers. This was performed in order to identify light and sound stimuli tuned to sensitive areas in the eagle’s sensory systems. The second phase of the project was to present these stimuli to both species of eagles in a behavioral experiment to identify which stimuli would be the most effective in changing the behaviors of the eagles. Results of phase one indicated that the visual system of the Golden Eagle strongly absorbs ultraviolet light, making it unlikely the Golden Eagle (and most likely the Bald Eagle) will detect ultraviolet light signals. The Golden and Bald Eagles have differences in the sensitivities of their visual systems to light within the eye, but mathematical models indicate that both species are able to detect indigo/blue and orange/red light produced by LEDs (light emitting diodes) very well. We also found that both species of eagles have a blind spot above their head. This blind spot is particularly large in Golden Eagles due to a pronounced brow ridge above the eyes. This blind spot will result in the inability of a Golden Eagle to see something in front of it when its head is pointed down during flight – as might happen while hunting (i.e. searching the ground for prey). As such, the blind spot may increase the chance of collision with wind turbines if the eagle is actively hunting. This problem is less pronounced in Bald Eagles because their blind spot is smaller than in the Golden Eagles and their foraging strategy is different. Results of phase one also indicated that the auditory systems of the Golden and Bald Eagles respond differently to a variety of sounds (static tones, static chords (i.e. stacked tones), and sounds with dynamic changes through amplitude modulation or frequency modulation). Both species’ auditory systems responded strongly to tones across a wide range of frequencies (0.5 – 5kHz ), however the Bald Eagles’ auditory system was much better at processing complex sounds with dynamic rapid changes in amplitude or frequency modulation than the Golden Eagle. All of these sounds were then played with two types of noise in the background (white or pink). White noise more closely resembles the sound of wind and pink noise more closely resembles wind turbines or other sources of anthropogenic noise. Most sounds were more strongly masked by pink noise than by white noise, but several sounds (especially sounds with rapid modulation changes) showed little or no masking, indicating these were good candidate signals. However, even though rapidly changing sounds are less subject to noise masking, they are also less strongly processed by the Golden Eagle auditory system. This tradeoff does not exist in Bald Eagles because individuals of this species are very good at processing rapidly changing sounds. Given that Golden Eagle populations are at greater risk than Bald Eagle populations, we suggest that the most efficient alerting sound stimuli used in deterrent systems should be complex sounds that do not change very rapidly. We identified candidate light (indigo/blue and orange/red LED lights) and sound (sinusoidal frequency modulated sound, linear frequency sweeps, amplitude modulated sound, and a mistuned harmonic stack) stimuli that both eagle species sensory systems are highly sensitive to. Results of phase two, in which we presented these stimuli to eagles in a behavioral experiment, indicated that eagles behaviorally responded to all the stimuli presented, but at varying degrees. The Golden Eagles, especially, elicited higher rates of visual exploratory behavior with a flashing blue light stimulus and all sound stimuli. Our results suggest using these stimuli in field-testing of light/sound eagle deterrent systems on wind turbines. The eagles showed lower rates of behavior over the course of an experiment, suggesting either that they habituated to our stimuli or were initially stressed by the setup of the behavioral tests. These results underscore the need to test for habituation effects. Nonetheless, habitation to the stimuli in these field tests would likely be reduced by the use of random presentations of the four sounds and if possible random presentation of the candidate lights.

Report↗