Susan K Skagen

• United States Geological Survey

Aim Surrogate species can provide an efficient mechanism for biodiversity conservation if they encompass the needs or indicate the status of a broader set of species. When species that are the focus of ongoing management efforts act as effective surrogates for other species, these incidental surrogacy benefits lead to additional efficiency. Assessi...

Avian species endemic to desert grasslands of North America contend with significant ecological challenges, including monsoonal rains, droughts, and variable temperatures. These birds have evolved physiological and behavioral means of coping with such extremes, but ongoing changes to temperature and precipitation patterns are affecting their breedi...

The Prairie Pothole Region, situated in the northern Great Plains, provides important stopover habitat for migratory shorebirds. During spring migration in the U.S. Prairie Potholes, 7.3 million shorebirds refuel in the region's myriad small, freshwater wetlands. Shorebirds use mudflats, shorelines, and ephemeral wetlands that are far more abundant...

As grassland birds of central North America experience steep population declines with changes in land use, management of remaining tracts becomes increasingly important for population viability. The integrated use of fire and grazing may enhance vegetation heterogeneity and diversity in breeding birds, but the subsequent effects on reproduction are...

Species distribution models (SDMs) are commonly used to assess potential climate change impacts on biodiversity, but several critical methodological decisions are often made arbitrarily. We compare variability arising from these decisions to the uncertainty in future climate change itself. We also test whether certain choices offer improved skill f...

Grassland bird populations are showing some of the greatest rates of decline of any North American birds, prompting measures to protect and improve important habitat. We assessed how vegetation structure and composition, habitat features often targeted for management, affected territory and nest site selection by Grasshopper Sparrows (Ammodramus sa...

Small-bodied terrestrial animals such as songbirds (Order Passeriformes) are especially vulnerable to hail-induced mortality; yet, hail events are challenging to predict, and they often occur in locations where populations are not being studied. Focusing on nesting grassland songbirds, we demonstrate a novel approach to estimate hail-induced mortal...

To identify areas on the landscape that may contribute to a robust network of conservation areas, we modeled the probabilities of occurrence of several en route migratory shorebirds and wintering waterfowl in the southern Great Plains of North America, including responses to changing climate. We predominantly used data from the eBird citizen-scienc...

The habitats and food resources required to support breeding and migrant birds dependent on North American prairie wetlands are threatened by impending climate change. The North American Prairie Pothole Region (PPR) hosts nearly 120 species of wetland-dependent birds representing 21 families. Strategic management requires knowledge of avian habitat...

Climate change elevates conservation concerns worldwide because it is likely to exacerbate many identified threats to animal populations. In recent decades, grassland birds have declined faster than other North American bird species, a loss thought to be due to habitat loss and fragmentation and changing agricultural practices. Climate change poses...

Climate change poses major challenges for conservation and management because it alters the area, quality, and spatial distribution of habitat for natural populations. To assess species' vulnerability to climate change and target ongoing conservation investments, researchers and managers often consider the effects of projected changes in climate an...

Sediment accumulation threatens the viability and hydrologic functioning of many naturally formed depressional wetlands across the interior regions of North America. These wetlands provide many ecosystem services and vital habitats for diverse plant and animal communities. Climate change may further impact sediment accumulation rates in the context...

The Prairie Pothole Region (PPR) of the north-central U.S. and south-central Canada contains millions of small prairie wetlands that provide critical habitat to many migrating and breeding waterbirds. Due to their small size and the relatively dry climate of the region, these wetlands are considered at high risk for negative climate change effects...

Disturbed xeric grasslands with short, sparse vegetation provide breeding habitat for mountain plovers (Charadrius montanus) across the western Great Plains. Maintaining local disturbance regimes through prairie dog conservation and prescribed fire may contribute to the sustainability of recently declining mountain plover populations, but these man...

The influence of recent climate change on the world's biota has manifested broadly, resulting in latitudinal range shifts, advancing dates of arrival of migrants and onset of breeding, and altered community relationships. Climate change elevates conservation concerns worldwide because it will likely exacerbate a broad range of identified threats to...

Native grasslands have been altered to a greater extent than any other biome in North America. The habitats and resources needed to support breeding performance of grassland birds endemic to prairie ecosystems are currently threatened by land management practices and impending climate change. Climate models for the Great Plains prairie region predi...

Playa wetlands on the west-central Great Plains of North America are vulnerable to sediment infilling from upland agriculture, putting at risk several important ecosystem services as well as essential habitats and food resources of diverse wetland-dependent biota. Climate predictions for this semi-arid area indicate reduced precipitation which may...

Historically, the Prairie Pothole Region (PPR) of North America was characterized by myriad semi-permanent, seasonal, and temporary wetlands interspersed among rivers in a context of prairie uplands. These wetlands have supported millions of en route and breeding wetland-dependent birds. Today, expanses of the PPR landscape are dominated by intensi...

We investigated the functions of perch relocations within a communal night roost of wintering bald eagles (Haliaeetus leucocephalus) along the Nooksack River, Washington, during two winters. We tested seven predictions of two nonexclusive hypotheses: (1) bald eagles relocate within roosts to assess foraging success of conspecifics and (2) bald eagl...

Effective conservation metrics are needed to evaluate the success of management in a rapidly changing world. Reproductive rates and densities of breeding birds (as a surrogate for reproductive rate) have been used to indicate the quality of avian breeding habitat, but the underlying assumptions of these metrics rarely have been examined. When birds...

The major forces of food and predation shape fitness-enhancing decisions of birds at all stages of their life cycles. During the breeding season, birds can minimize nest loss due to predation by selecting sites with a lower probability of predation. To understand the environmental and social aspects and consequences of breedingsite selection in pra...

Recent changes in global climate have dramatically altered worldwide temperatures and the corresponding timing of seasonal climate conditions. Recognizing the degree to which species respond to changing climates is therefore an area of increasing conservation concern as species that are unable to respond face increased risk of extinction. Here we e...

El conocimiento sobre el comportamiento de las aves durante el periode no reproductivo aún es menor que el del periode reproductivo, a pesar de que durante la ultima década ha habido una proliferación considerable de investigaciones que han producido un progreso significativo en el entendimiento de los patrones de migracion de las aves de Norteamér...

Many North American prairie bird populations have recently declined, and the causes of these declines remain largely unknown. To determine whether population limitation occurs during breeding, we evaluated the stability of a population of prairie birds using population-specific values for fecundity and postfledging survival. During 2001-2003, we ra...

Conservation challenges enhance the need for quantitative information on dispersed bird populations in extensive landscapes, for techniques to monitor populations and assess environmental effects, and for conservation strategies at appropriate temporal and spatial scales. By estimating population sizes of shorebirds in the U.S. portion of the prair...

Potential responses to human disturbance at breeding colonies of waterbirds include reproductive failure, population declines and displacement from activity areas. Several additional factors, including species interactions and environmental change, can either mask or intensify the effects of human activity. This study highlights the importance of c...

We quantified post-fledging pre-independence behavior and survival in Lark Buntings (Calamospiza melanocorys) using radio-telemetry. Brood division was recorded in six broods and was maintained throughout the observed fledgling care period. Chicks were capable of short flights (up to 25 m) by fledgling day 6 and longer flights (to 100 m) by fledgli...

Reliable estimates of nest survival are essential for assessing strategies for avian conservation. We review the history of modifications and alternatives for estimating nest survival, with a focus on four techniques: apparent nest success, the Mayfield estimator, the Stanley method, and program MARK. The widely used Mayfield method avoids the know...

We examined the effects of habitat fragmentation and vegetation structure of shortgrass prairie and Conservation Reserve Program (CRP) lands on predation rates of artificial and natural nests in northeastern Colorado. The CRP provides federal payments to landowners to take highly erodible cropland out of agricultural production. In our study area,...

Resumen. Para evaluar los cambios potenciales en las poblaciones de aves que anidan en la tundra relacionados con un aumento en la herbivoría causado por el crecimiento de las poblaciones de Chen caerulescens caerulescens y C. rossii, estimamos las densidades poblaciones de aves en la tundra costera cerca de Cabo Churchill, Manitoba, en junio de 19...

Depressional wetlands in agricultural landscapes are easily degraded by sediments and contaminants accumulated from their watersheds. Several best management practices can reduce transport of sediments into wetlands, including the establishment of vegetative buffers. We summarize the sources, transport dynamics, and effect of sediments, nutrients,...

Determining population size and long-term trends in population size for species of high concern is a priority of international, national, and regional conservation plans. Long-billed curlews (Numenius americanus) are a species of special concern in North America due to apparent declines in their population. Because long-billed curlews are not adequ...

Many North American prairie bird populations have recently declined, and the causes of these declines remain largely unknown. To determine whether population limitation occurs during breeding, we evaluated the stability of a population of prairie birds using population-specific values for fecundity and postfledging survival. During 2001-2003, we ra...

We evaluated the influences of several ecological, biological, and methodological factors on post-fledging survival of a shortgrass prairie bird, the Lark Bunting (Calamospiza melanocorys). We estimated daily post-fledging survival (n = 206, 82 broods) using radiotelemetry and color bands to track fledglings. Daily survival probabilities were best...

Ornithologists who regularly witness the breathtaking influx of songbirds at stopover sites during spring or fall migration know that birds are tremendously adaptable. Migration encompasses a range of actions distinct from permanent residency but includes altitudinal movements, sporadic irruptions, short-distance flights, as well as obligate long-d...

Migration stopover resources, particularly riparian habitats, are critically important to landbirds migrating across the arid southwestern region of North America. To explore the effects of species biogeography and habitat affinity on spring migration patterns, we synthesized existing bird abundance and capture data collected in riparian habitats o...

Migration stopover resources, particularly riparian habitats, are critically important to landbirds migrating across the arid southwestern region of North America. To explore the effects of species biogeography and habitat affinity on spring migration patterns, we synthesized existing bird abundance and capture data collected in riparian habitats o...

Understanding, the influences of habitat fragmentation on vertebrate Populations is essential for the protection and ecological restoration of strategic sites for native species. We examined the effects of prairie fragmentation on avian reproductive success using artificial and natural nests oil 26 randomly selected, privately owned patches of shor...

Reliable estimates of nest survival are essential for assessing strategies for avian conservation. We review the history of modifications and alternatives for estimating nest survival, with a focus on four techniques: apparent nest success, the Mayfield estimator, the Stanley method, and program MARK. The widely used Mayfield method avoids the know...

LBCUs are a species of special concern throughout much of their breeding range in North America, with both the U.S. and Canadian Shorebird Plans listing them as “Highly Imperiled” (Brown et al. 2001). LBCUs are also listed in the U.S. as a Bird of Conservation Concern, at the National level, within FWS Regions 1, 2, 4 and 6, and for many Bird Conse...

Avian conservation in riparian or bottomland forests requires an understanding of the physical and biotic factors that sustain the structural complexity of riparian vegetation. Riparian forests of western North America are dependent upon flow-related geomorphic processes necessary for establishment of new cottonwood and willow patches. In June 1995...

2003. Monitoring the shorebirds of North America: towards a unified approach. Wader Study Group Bull. 100: 102-104. The Program for Regional and International Shorebird Monitoring (PRISM) has recently developed a single blueprint for monitoring shorebirds in Canada and the United States in response to needs identified by recent shorebird conservati...

Several aspects of a developing program to monitor shorebirds in the western hemisphere are pertinent to migration monitoring of landbirds. Goals of the Pro-gram for Regional and International Shorebird Moni-toring (PRISM) include estimating population size and population trends of 74 species, sub-species and dis-tinct populations of North American...

We examined the effects of habitat fragmentation and vegetation structure of shortgrass prairie and Conservation Reserve Program (CRP) lands on predation rates of artificial and natural nests in northeastern Colorado. The CRP provides federal payments to landowners to take highly erodible cropland out of agricultural production. In our study area,...

We quantified post-fledging pre-independence behavior and survival in Lark Buntings (Calamospiza melanocorys) using radio-telemetry. Brood division was recorded in six broods and was maintained throughout the observed fledgling care period. Chicks were capable of short flights (up to 25 m) by fledgling day 6 and longer flights (to 100 m) by fledgli...

Estimates are presented for the population sizes of 53 species of Nearctic shorebirds occurring regularly in North America, plus four species that breed occasionally. Population estimates range from a few tens to several millions. Overall, population estimates most commonly fall in the range of hundreds of thousands, particularly the low hundreds o...

We investigated the functions of perch relocations within a communal night roost of wintering bald eagles (Haliaeetus leucocephalus) along the Nooksack River, Washington, during two winters. We tested seven predictions of two nonexclusive hypotheses: (1) bald eagles relocate within roosts to assess foraging success of conspecifics and (2) bald eagl...

Estimates are presented for the population sizes of 53 species of Nearctic shorebirds occurring regularly in North America, plus four species that breed occasionally. Shorebird population sizes were derived from data obtained by a variety of methods from breeding, migration and wintering areas, and formal assessments of accuracy of counts or estima...

Transcontinental shorebird migrants are dependent upon dynamic freshwater wetlands throughout the interior of North America for stopover resources. Because of the tremendous energy demands of these long distance migratory flights, stopover habitats and resources for rest and refueling are critical to the survival and successful reproduction of this...

Nest predation, the major cause of nest failure in passerines, has exerted a strong influence on the evolution of life history traits of birds. Because human disturbance during nest monitoring may alter predation rates, we investigated whether human scent affected the survival of artificial ground nests in shortgrass prairie. Our experiment consist...

The relative importance of cottonwood‐willow riparian corridors and isolated oases to land birds migrating across southeastern Arizona was evaluated during four spring migrations, 1989 to 1994, based on patterns of species richness, relative abundance, density, and body condition of birds. We surveyed birds in 13 study sites ranging in size and con...

The overviews of prairie vertebrates thus far in this book focus primarily on resident or breeding species of several taxa. A myriad of avian species, including warblers seeking the boreal forests and waterfowl flying to northern wetlands, temporarily inhabit the central Plains as they rest and refuel for their long journeys. This chapter spotlight...

Regional patterns of shorebird diets were examined by reviewing 75 papers reporting prey of 43 shorebird species throughout the western hemisphere. Collectively, shorebirds consumed a wide variety of invertebrate taxa, including 12 phyla, 22 classes, 72 orders, 238 families, and 404 genera of invertebrates. The most widely represented invertebrate...

Arctic-nesting shorebirds require several refueling stops during their long migrations between breeding grounds and Central and South American wintering areas. The protection of stopover habitats for transcontinental migrants depends on whether birds fly long distances between a few select sites or fly short distances and stop at several wetlands....

ABSTFCAC~. - We examined the responses of migrating shorebirds to habitat dynamics in a wetland complex on the Great Plains during 1989-1992. Availability of habitat was variable within and between seasons, but fluctuations in habitat were dampened when wetlands were considered as a complex rather than individually. Shorebirds exhibited an ability...

Estimation of lean mass and lipid levels in birds involves the derivation of predictive equations that relate morphological measurements and, more recently, total body electrical conductivity (TOBEC) indices to known lean and lipid masses. Using cross-validation techniques, we evaluated the ability of several published and new predictive equations...

Shorebirds represent a highly diverse group of species, many of which experience tremendous energy demands associated with long-distance migratory flights. Transcontinental migrants are dependent upon dynamic freshwater wetlands for stopover resources essential for replenishment of lipid reserves and completion of migration. Patterns of shorebird m...

In order to investigate the effects of human activities on relationships within foraging guilds, we examined inacanus dynamics of eagles, crows, and gulls scavenging on spawned salmon in the Pacific Northwest. We examined several hypotheses that postulate the asymmetric foraging relationships of the three guild members and that reveal the influence...

Large Haliaeetus leucocephalus feeding on chum salmon Oncorhynchus keta carcasses on the North Fork of the Nooksack River, Washington, were more successful in pirating than smaller eagles. Small pirating eagles were usually unsuccessful unless they were adults attempting to supplant other small eagles. Feeding eagles were more successful in defeati...

Lack's (1954, 1968) hypothesis that asynchronous hatching of altricial birds is an adaptive response to unpredictable food shortages during the breeding season was examined in the highly granivorous Zebra Finch (Poephila guttata). I compared growth and survival of nestlings in asynchronous and artificially created synchronous broods reared under fo...

I examined Lack's (1954, 1968) hypothesis that asynchronous hatching is an adaptive response to food shortage during the breeding season by comparing growth and survival of nestlings in asynchronous and artificially created synchronous broods of American Goldfinches (Carduelis tristis). I also examined the effects of seasonal and environmental fact...

We studied Red-winged Blackbird (Agelaius phoeniceus) behavior in marsh and prairie habitats to determine whether courting males provide cues of their nest defense, whether females prefer males that defend nests vigorously, and whether male nest defense affects nest success. We found no evidence that courtship behavior provides cues of male nest de...

Multivariate analyses are put in the context of more usual approaches to phycological investigations. The intuitive common-sense involved in methods of ordination, classification and discrimination are emphasised by simple geometric accounts which avoid jargon and matrix algebra. Warnings are given that artifacts result from technique abuses by the...

Shorebird migration strategies vary by species, migra- tion distance and route, time of year, and resources at staging and stopover sites. The Western Hemisphere Shorebird Reserve Network has been highly successful in the identification, designation, and protection of im- portant migration habitats for many species that stage in traditional areas....

Riparian forests have long been considered important habitats for breeding western landbirds, and growing evidence reinforces their importance during the mi- gratory period as well. Extensive modification of natu- ral flow regimes, grazing, and forest clearing along many rivers in the western U.S. have led to loss and simplification of native ripar...