James W. Rivers

• Ph.D.
• Professor (Assistant) at Oregon State University

The composition of caraboid beetle assemblages can be sensitive to forest structure and disturbance, making them a useful indicator taxon for understanding the effects of forest management. Early seral forests regenerating from even-aged timber harvests share some structural similarities with those regenerating from natural stand-replacing disturba...

Introduction Estimated white blood cell (WBC) counts are a valuable tool for assessing individual and population health in wildlife and domestic animals due to their role in the response to environmental stressors and disease. These measures are infrequently used in the study of wild seabird species, despite their utility when used alongside other...

Parasitism is a known cause of morbidity and mortality in wildlife species and may exacerbate population declines in species threatened by changing landscapes. The marbled murrelet (Brachyramphus marmoratus) is an unusual seabird that forages in the ocean but uses trees in old growth and late successional forests for nesting. Populations have decli...

Forest harvesting can create habitat for wild bees, but with potentially different characteristics from habitats created by natural disturbance such as wildfire. We evaluated how bee communities varied between early seral stands regenerated by wildfire or intensively managed stands regenerated by clearcut harvest up to 20 years post-disturbance, us...

Bee communities often respond positively to wildfire, but little is known about their foraging behavior and pollen use in recently burned forests despite their link to demographic processes. We used palynological analysis to reconstruct how female Osmia lignaria – a native, solitary nesting species – provisioned pollen to offspring in post-fire are...

Context Functional connectivity—the degree to which landscape features facilitate or impede movement among resource patches—affects animal survival, health, and ability to cope with environmental changes. This is particularly important in heterogeneous landscapes prone to rapid change, such as intensively managed forests. Objectives We aimed to qu...

Early seral forests regenerating after stand-replacing disturbance events can provide important habitat for populations of wild bees, an important group of pollinating insects. However, variability in the abundance and diversity of wild bee communities across different types of early seral forests is poorly understood, and can inform pollinator con...

Early seral forests regenerating after stand-replacing disturbance events can provide important habitat for populations of wild bees, an important group of pollinating insects. However, variability in the abundance and diversity of wild bee communities across different types of early seral forests is poorly understood, and can inform pollinator con...

Presence-absence surveys are frequently used to monitor populations of rare and elusive species. Such data may also be used as a proxy for breeding activity, but links between presence-absence data and higher-order processes must be validated to determine their reliability. The Marbled Murrelet (Brachyramphus marmoratus) is a threatened seabird tha...

Purpose of Review Forests play an essential role in conserving pollinating insects and supporting pollination services in mixed-use landscapes and are particularly important to species that require resources restricted to forests. However, some forests provide higher quality habitat for these organisms than others. The primary objectives of this ar...

Although anthropogenic climate change has resulted in significant alterations of ocean environments, the degree to which marine organisms can respond behaviorally to climate effects remains poorly understood, especially for species with increased extinction risk. We monitored marine space use and movement of the threatened marbled murrelet (Brachy...

Understanding how working landscapes can maintain viable wildlife populations is key to evaluating their conservation potential. We assessed the potential of intensively managed conifer forests for supporting healthy, productive bee populations in one of the major timber‐growing regions of the world, the Pacific Northwest. We examined the direct ef...

Large‐scale disturbances such as wildfire can have profound impacts on the composition, structure, and functioning of ecosystems. Bees are critical pollinators in natural settings and often respond positively to wildfires, particularly in forests where wildfire leads to more open conditions and increased floral resources. The use of Light Detection...

Understanding how habitat fragmentation affects individual species is complicated by challenges associated with quantifying species‐specific habitat and spatial variability in fragmentation effects within a species’ range. We aggregated a 29‐year breeding survey data set for the endangered marbled murrelet (Brachyramphus marmoratus) from >42,000 fo...

Despite widespread concerns about the anthropogenic drivers of global pollinator declines, little information is available about the impacts of land management practices on wild bees outside of agricultural systems, including in forests managed intensively for wood production. We assessed changes in wild bee communities with time since harvest in 6...

Woodpeckers often reflect rapid changes to forest health and serve as indicator species to help guide forest management decisions. The Black-backed Woodpecker (Picoides arcticus) is known for its strong association with recently burned forests and is a species of conservation concern due to habitat loss stemming from post-fire management of burned...

Although the importance of natural habitats to pollinator diversity is widely recognized, the value of forests to pollinating insects has been largely overlooked in many parts of the world. In this review, we (i) establish the importance of forests to global pollinator diversity, (ii) explore the relationship between forest cover and pollinator div...

Understanding how pollinators respond to anthropogenic land use is key to conservation of biodiversity and ecosystem services, but few studies have addressed this topic in coniferous forests, particularly those managed intensively for wood production. This study reports on voucher material generated as part of Zitomer et al. (2023), that assessed c...

diet of a threatened seabird, the Marbled Murrelet Brachyramphus marmoratus, using high-throughput sequencing. Marine Ornithology 51: 145-155. Understanding prey consumption patterns is critical to understanding the ways in which seabirds cope with a changing ocean. However, characterizing the dietary habitats of seabirds can be challenging. In thi...

Forage fish are a critical component of marine ecosystems because they integrate energy across trophic levels within marine food webs. Many studies have highlighted the importance of this group, and past research efforts have focused largely on studying forage fish within offshore and estuarine areas. In contrast, limited information is available f...

Understanding how land‐management intensification shapes the relationships between biodiversity, yield, and economic benefit is critical for managing natural resources. Yet, manipulative experiments that test how herbicides affect these relationships are scarce, particularly in forest ecosystems where considerable time lags exist between harvest re...

The value of non‐commodity ecosystem services provided by forests is widely recognized, but intensive forest management practices are increasing, with uncertain consequences for a multitude of these services. Quantitative relationships among biodiversity conservation, timber production and other ecosystem services remain poorly understood, especial...

Ecological, environmental, and geographic factors all influence genetic structure. Species with broad distributions are ideal systems because they cover a range of ecological and environmental conditions allowing us to test which components predict genetic structure. This study presents a novel, broad geographic approach using molecular markers, mo...

Each year hundreds of millions of people intentionally feed wild animals throughout the world. For decades, concerns have persisted regarding the potential for intentional feeding to promote dependency on human‐supplemented food, particularly during energetically demanding periods of the annual cycle. In this study, we evaluated whether individuals...

Habitat selection decisions can impact individual fitness and ultimately scale up to mediate population dynamics. Understanding how birds select habitat is thus critical for discerning the biological processes structuring populations and for developing conservation strategies, particularly for species in decline. Marbled Murrelet (Brachyramphus mar...

Conspecific presence can indicate the location or quality of resources, and animals settling near conspecifics often gain fitness benefits. This can result in adaptive conspecific attraction during breeding habitat selection as demonstrated in numerous terrestrial, territorial birds. There is growing interest in using simulated conspecific social c...

Concerns about long-term pollinator declines have made assessing bee communities a priority in nonagricultural ecosystems, including managed forests. We assessed wild bee communities in Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) stands one to 15 years after clearcut harvest in western Oregon, USA, testing the hypothesis that bee diversity w...

Although ecological disturbances can have a strong influence on pollinators through changes in habitat, virtually no studies have quantified how characteristics of wildfire influence the demography of essential pollinators. Nevertheless, evaluating this topic is critical for understanding how wildfire is linked to pollinator population dynamics, pa...

Theory predicts that species requiring multiple habitat types simultaneously should have heightened sensitivity to anthropogenic pressures, yet tests of this prediction are especially rare. We tested whether breeding site occupancy of the threatened marbled murrelet (Brachyramphus marmoratus) was driven by the synergistic effects of nesting habitat...

Land management may combine with air temperature to influence the persistence of animal populations, so both must be evaluated in concert to understand how populations respond to increased forest management intensity and projected climate change. We used a large-scale study that experimentally manipulated herbicide application intensity within rege...

Land management may combine with air temperature to influence the persistence of animal populations, so both must be evaluated in concert to understand how populations respond to increased forest management intensity and projected climate change. We used a large-scale study that experimentally manipulated herbicide application intensity within rege...

Natural disturbances are critical for supporting biodiversity in many ecosystems, but subsequent management actions can influence the quality of habitat that follow these events. Post-disturbance salvage logging has negative consequences on certain components of forest biodiversity, but populations of some early seral-adapted organisms may be maint...

this publication provides data about voucher specimens deposited in the museum in conjunction with a research project on pollinators.

Early-successional forest birds, which depend on disturbance events within forested landscapes, have received increased conservation concern because of long-term population declines. Herbicides are often used to control vegetation within early-successional forests, with unknown effects on avian vital rates. We used a large-scale experiment to test...

As wildfire activity increases in many regions of the world, it is imperative that we understand how key components of fire-prone ecosystems respond to spatial variation in fire characteristics. Pollina-tors provide a foundation for ecological communities by assisting in the reproduction of native plants, yet our understanding of how pollinators su...

Climate and land‐use changes are expected to be the primary drivers of future global biodiversity loss. Although theory suggests that these factors impact species synergistically, past studies have either focused on only one in isolation or have substituted space for time, which often results in confounding between drivers. Tests of synergistic eff...

Purposeful provisioning of food to wild animals is a widespread and growing activity that has the potential to impact populations and communities. Nevertheless, studies assessing use of recreational feeders by free‐living birds during winter are surprisingly rare and largely limited to regions with continental climates characterized by freezing tem...

Managed conifer forests in temperate regions are critical for supplying wood products, but little is known about their potential for pollinator conservation. We hosted a workshop for Pacific Northwest managers and biologists to identify perceived information gaps regarding pollinators in managed conifer forests; we also undertook a literature revie...

The use of timber harvest residue as an energy source is thought to have environmental benefits relative to food‐based crops, yet the ecological impact of this practice remains largely unknown. We assessed whether the abundance and diversity of wild bees (Apoidea) were influenced by the removal of harvest residue and associated soil compaction with...

Ecosystem modification driven by anthropogenic land-use and land-cover change is one of the leading drivers of global biodiversity declines. Simultaneously, ongoing climate change is modifying ecosystems and will have far-reaching impacts on the structure and function of ecological communities. Rising surface temperatures are predicted to have nega...

Rearing environments can shape offspring phenotype across taxa, yet little is known about how brood size influences hypothalamic–pituitary axis functioning, whether its expression trades off with growth, and the degree to which these relationships vary between species. We evaluated how brood size influenced nestling physiological (glucocorticoids)...

Understanding movements of small seabirds has been particularly challenging due to limitations in tracking technology. As tracking devices become smaller and more powerful, and are deployed on smaller bird species, they need to be evaluated. We assessed whether small, platform terminal transmitters (PTTs; 5 g) could be used to study the nesting, mo...

Snags provide essential habitat for numerous organisms and are therefore critical to the long-term maintenance of forest biodiversity. Resource managers often use snag creation to mitigate the purposeful removal of snags at the time of harvest, but information regarding how created snags change over long timescales (>20 y) is absent from the litera...

Many species that use or require early-successional forest are of conservation concern, including a number of songbirds that have experienced long-term population declines. In this study, our initial goal was to test whether herbicide application intensity was linked to offspring sex ratio in the White-crowned Sparrow (Zonotrichia leucophrys), a sp...

Snags are important habitat features for many forest‐dwelling species, so reductions in the number of snags can lead to the loss of biodiversity in forest ecosystems. Intentional snag creation is often used in managed forests to mitigate the long‐term declines of naturally created snags, yet information regarding the use of snags by wildlife across...

Although the brown-headed cowbird (Molothrus ater) is the most intensively studied brood parasite in the world, much of the research on cowbirds has focused on the negative effects of parasitism. Here, we argue that negative attitudes toward the cowbird have overshadowed opportunities this species provides for advancing our understanding of social...

Glucocorticoid steroid hormones play a central role in regulating the metabolic state of animals, especially when they cope with unanticipated stressors in their environment. The cort‐adaptation hypothesis predicts that baseline concentrations of glucocorticoids are adjusted upward to match energetic needs and promote fitness when individuals are f...

Virulence, the amount of harm a parasite inflicts on its host, is integral to elucidating the evolution of obligate avian brood parasitism. However, we lack information regarding how relatedness is linked to changes in behavior and the degree of harm that brood parasites cause to their hosts (i.e., virulence). The kin competition hypothesis combine...

Vocalizations produced by developing young early in life have simple acoustic features and are thought to be innate. Complex forms of early vocal learning are less likely to evolve in young altricial songbirds because the forebrain vocal-learning circuit is under-developed during the period when early vocalizations are produced. However, selective...

Condors and vultures comprise the only group of terrestrial vertebrates in the world that are obligate scavengers, and these species move widely to locate ephemeral, unpredictable, and patchily-distributed food resources. In this study, we used high-resolution GPS location data to quantify monthly home range size of the critically endangered Califo...

Condors and vultures comprise the only group of terrestrial vertebrates in the world that are obligate scavengers, and these species move widely to locate ephemeral, unpredictable, and patchily-distributed food resources. In this study, we used high-resolution GPS location data to quantify monthly home range size of the critically endangered Califo...

Obligate brood parasites must obtain food from unrelated host parents during the developmental period, and this may be especially difficult when parasitic nestlings are raised alone. Unlike specialist brood parasites, generalist brood parasites use a single begging display for a range of host species. In this study, we 1) tested whether the begging...

Lead (Pb) is a metabolic poison that can negatively influence biological processes, leading to illness and mortality across a large spectrum of North American avifauna (>120 species) and other organisms. Pb poisoning can result from numerous sources, including ingestion of bullet fragments and shot pellets left in animal carcasses, spent ammunition...

Large‐scale poisoning events are common to scavenging bird species that forage communally, many of which are in decline. To reduce the threat of poisoning and compensate for other persistent threats, management, including supplemental feeding, is ongoing for many reintroduced and endangered vulture populations. Through a longitudinal study of lead...

Condors and vultures are distinct from most other terrestrial birds because they use extensive soaring flight for their daily movements. Therefore, assessing resource selection by these avian scavengers requires quantifying the availability of terrestrial-based habitats, as well as meteorological variables that influence atmospheric conditions nece...

Glucocorticoids are thought to be related to habitat quality and may provide information about the relative health of individuals. We used a model selection approach to test whether plasma glucocorticoid levels of the Swainson’s thrush (Catharus ustulatus) were associated with two attributes that may reflect breeding habitat quality in coniferous p...

Aerial insectivores have undergone marked population declines in recent decades, including members of the Hirundinidae (swallows), which have long served as sentinels of environmental change. In contrast to other swallow species that breed in North America, we have a poor understanding of most aspects of the basic ecology and life history of the vi...

Aerial insectivores have undergone marked population declines in recent decades, including members of the Hirundinidae (swallows), which have long served as sentinels of environmental change. In contrast to other swallow species that breed in North America, we have a poor understanding of most aspects of the basic ecology and life history of the vi...

Offspring signalling models predict that the begging displays of obligate brood parasites are more intense than nonparasitic species because parasitic young are never reared by their genetic parents and often compete against unrelated host young during development. The brown-headed cowbird, Molothrus ater, has been described as having exaggerated b...

Glucocorticoids are thought to be related to habitat quality and may provide information about the relative health of individuals. We used a model selection approach to test whether plasma glucocorticoid levels of the Swainson's thrush (Catharus ustulatus) were associated with two attributes that may reflect breeding habitat quality in coniferous p...

There are five species of parasitic cowbirds ( Molothrus) and the Brown-headed Cowbird (M. ater) is the only widespread species in North America. The Brown-headed Cowbird is a host generalist and is typically found in open habitats and forest edges. The cowbirds are of a more recent origin than many other brood parasites and perhaps as a result, co...

Avian brood parasitism is a model system for studies of coevolution and ecological interac- tions between parasites and their hosts. However, recent work may have led to misconceptions con- cerning the Brown-headed Cowbird (Molothrus ater), the most widely studied brood parasitic bird in the world, and its effects on host species. Potential misconc...

The brown-headed cowbird Molothrus ater is a brood-parasite that lays eggs in nests of a wide range of host species, including the closely-related red-winged blackbird Agelaius phoeniceus and the dickcissel Spiza americana. Although cowbird eggs have accelerated development and hatch sooner than similar-sized host eggs, this development takes place...

Multiple parasitism of host nests by generalist brood parasites reflects the decisions of laying females and may influence the development and behavior of parasitic young. We used microsatellite and mtDNA control-region haplotype data to examine the relatedness of Brown-headed Cowbird (Molothrus ater) offspring in multiply parasitized nests sampled...

1. Glucocorticoid hormones are an integral part of the vertebrate stress response, and theoretical models argue for a link between glucocorticoid levels and individual fitness. The cort‐fitness hypothesis posits that elevated levels of baseline glucocorticoids are reflective of an individual in poor condition and with a reduced likelihood of surviv...

To examine regional variation in strontium (Sr), which at high concentrations may reduce eggshell quality, increase egg breakage and reproductive failure, we analyzed Sr, and calcium (Ca) concentrations and Sr/Ca ratios in eggshells from 20 avian species from California, Texas, Idaho, Kansas, and Michigan. In addition, we included data previously r...

Despite the critical role of fat in providing energy for large-scale seasonal movements, little is known about the fatty acid composition of shorebird depot fat. Fatty acid composition is important because it may impact flight performance and seasonal migratory movements. We analyzed the fatty acid composition of depot fat of 12 species of shorebir...

Alarm calling by parents is widespread among animals and has strong implications for parent and offspring fitness, yet it is virtually unknown whether parental alarm calls can initiate a corticosterone response in offspring. We investigated whether parental alarm calls of the white-crowned sparrow, Zonotrichia leucophrys, activated the corticostero...

The outcome of sperm competition (i.e. competition for fertilization between ejaculates from different males) is primarily determined by the relative number and quality of rival sperm. Therefore, the testes are under strong selection to maximize both sperm number and quality, which are likely to result in trade-offs in the process of spermatogenesi...

Recent declines in broadleaf-dominated, early-seral forest globally as a function of intensive forest management and/or fire suppression have raised concern about the viability of populations dependent on such forest types. However, quantitative information about the strength and direction of species associations with broadleaf cover at landscape s...

Quantifying community-level host use by generalist brood parasites is important because it provides a measure of the resources that parasites need for reproduction. During the 2002-2007 breeding seasons, we quantified host use by the Brown-headed Cowbird (Molothrus ater) at Konza Prairie Biological Station in northeast Kansas. Overall, 54.4% of nes...

Military training activities are known to impact individual species, yet our understanding of how such activities influence animal communities is limited. In this study, we used long-term data in a case study approach to examine the extent to which the local small landbird community differed between a site in northeast Kansas that experienced inten...

Avian brood parasites typically depress the fitness of their hosts by reducing the number of host offspring produced, yet little is known about how parasitic nestlings influence the behaviour of host parents and host offspring. In this study, we used three hosts of the brown-headed cowbird, Molothrus ater, that varied in size (i.e. smaller, similar...

The Northern Harrier (Circus cyaneus) is a widespread raptor that preys mainly upon small mammals and, to a lesser extent, birds. Most published accounts of harrier food habits report the majority of avian prey items are passerines with few large (> 500 g) birds taken. In fall 1999, I observed a Northern Harrier that appeared to have attacked and k...

We report the first record of Bronzed Cowbird (Molothrus aeneus) parasitism on the Great-tailed Grackle (Quiscalus mexicanus), which represents the 96th known host for this cowbird species. The record is based on a parasitized clutch, collected from Sinaloa, Mexico, in the collection at the Western Foundation of Vertebrate Zoology. The clutch conta...

Great Blue Herons (Ardea herodias) typically prey upon fish and other aquatic organisms, and they occasionally take small mammals and birds. We observed a Great Blue Heron attack, kill, and attempt to consume an Eared Grebe (Podiceps nigricollis). The heron was unable to swallow the grebe, and it abandoned the carcass after approximately 30 min. An...

Sperm morphology varies considerably across taxa, and postcopulatory sexual selection is thought to be one of the main forces responsible for this diversity. Several studies have investigated the effects of the variation in sperm design on sperm function, but the consequences of variation in sperm design on testis morphology have been overlooked. T...

El pájaro gato gris (Dumetella carolinensis) ha sido documentado visitando y rompiendo los huevos de nidos artificiales, pero las implicaciones de dichas observaciones no son claras porque hay poco costo por depredar un nido sin defensa. Durante el verano de 2001 en Konza Prairie Biological Station en Kansas, filmamos un pájaro gato gris que rompió...

Playa wetlands contribute to the biological diversity of the southern Great Plains, yet many are modified by current farming practices. We surveyed 12 farmed playa wetlands from 1998–99 to (1) document seasonal avian use of these habitats and (2) assess the performance of two rapid assessment techniques, the Habitat Assessment Technique and the Wet...

Although it is well-established that nestlings of many altricial species beg when parents are away from the nest, we have a poor understanding of parent-absent begging in brood parasites, including the proximate factors that may influence begging frequency and intensity. In this study, I examined how parent-absent begging was influenced by competit...

Identifying the natal origins of brood parasites is a major challenge that usually requires labor-intensive searching for nests of host species. Stable isotope analysis of feathers and other body tissues of parasitic young could be a possible tool for determining natal origins if tissues reflect the isotopic composition of the diet fed to nestlings...

Hosts of generalist brood parasites often vary with regards to their life-history traits, and these differences have the potential to influence the competitive environment experienced by brood-parasitic nestlings. Although begging by brood parasites is more exaggerated than their hosts, it is unclear if generalist brood parasites modulate their beg...

Military installations provide important native habitat for songbirds, including many species that have experienced population declines in recent decades. As part of the Land Condition Trend Analysis (LCTA) program to monitor animal populations on military lands, we surveyed small (<250 g) breeding landbirds on 60 permanent plots on the Fort Riley...

ABSTRACT. The gray catbird (Dumetella carolinensis) has been documented visiting and breaking the eggs of artificial nests, but the implications of such observations are unclear because there is little cost in depredating an undefended nest. During the summer of 2001 at Konza Prairie Bio- logical Station, Kansas, we videotaped a gray catbird that b...

Many features appear to influence avian nest success, and nest concealment and distance to habitat edge are among the most influential. We placed simulated bird nests baited with House Sparrow (Passer domesticus) eggs in two riparian grasslands to document the influence of these two habitat characteristics on nest depredation rates. Over three tria...

Birds nesting at high latitudes may copulate during migration to arrive on the nesting grounds ready to breed. We surveyed 12 species of shorebirds during spring migration to determine whether (1) males produced abundant sperm and (2) females harboured functional sperm storage tubules (SSTs). Sperm production by males on migration was rare. Only fo...

Intensive monitoring of bird nests to measure reproductive success is time-consuming and may influence the fate of nests. Reproductive indices that do not require searching for and visiting nests may be reasonable alternatives to nest monitoring if they provide results similar to nest-searching efforts. We evaluated the reproductive index of Vicker...