Peter Marra

Smithsonian Institution · Migratory Bird Center

The impacts of barriers, such as dams, and associated stream effects on the migration of salmon have been well documented, but there is much less information on consequences for terrestrial vertebrates in these freshwater systems. Salmon themselves provide food resources to higher trophic levels and deposit rich marine-derived nutrients (MDN) that...

Climate change is a serious challenge faced by all plant and animal species. Climate change vulnerability assessments (CCVAs) are one method to assess risk and are increasingly used as a tool to inform management plans. Migratory animals move across regions and continents during their annual cycles where they are exposed to diverse climatic conditi...

Our understanding of when natural populations are regulated during their annual cycle is limited, particularly for migratory species. This information is needed for parametrizing models that can inform management and conservation. Here, we use 14 years of data on colour-marked birds to investigate how conspecific density and habitat quality during...

For vertebrates, annual cycles are organized into a series of breeding and non-breeding periods that vary in duration and location but are inextricably linked biologically. Here, we show that our understanding of the fundamental ecology of four vertebrate classes has been limited by a severe breeding season research bias and that studies of individ...

Background Movement behavior strongly mediates species and environment interactions, yet our understanding is constrained by challenges tracking space use at fine spatiotemporal resolutions. Methods Using an automated telemetry array, we quantified variation in and drivers of space use for a nonbreeding population of migratory bird, the American r...

Identifying the drivers of population declines in migratory species requires an understanding of how individuals are distributed between periods of the annual cycle. We built post- (fall) and pre-breeding (spring) migratory networks for the blackpoll warbler (Setophaga striata), a Neotropical-Nearctic songbird, using tracking data from 47 light-lev...

Rarely, is there an opportunity to study and directly observe the same migratory animal across both breeding and nonbreeding seasons. In a rare, documented case, we highlight a live reencounter of a female Setophaga ruticilla (American Redstart) on its nest during the breeding season—an individual that was originally captured and tagged on its nonb...

Giant hummingbirds (Patagona spp.) are extraordinarily large hummingbirds whose taxonomy has been muddled for two centuries. Patagona systematics were recently redefined in a study of migration, physiology, and genomics, revealing two species: the Southern Giant Hummingbird and Northern Giant Hummingbird. Here, we re-evaluate taxonomy and nomenclat...

Museum genomics provide an opportunity to investigate population demographics of extinct species, especially valuable when research prior to extinction was minimal. The Bachman’s warbler (Vermivora bachmanii) is hypothesized to have gone extinct due to loss of its specialized habitat. However, little is known about other potential contributing fact...

The ecoevolutionary drivers of species niche expansion or contraction are critical for biodiversity but challenging to infer. Niche expansion may be promoted by local adaptation or constrained by physiological performance trade-offs. For birds, evolutionary shifts in migratory behavior permit the broadening of the climatic niche by expansion into v...

Predicting how the range dynamics of migratory species will respond to climate change requires a mechanistic understanding of the factors that operate across the annual cycle to control the distribution and abundance of a species. Here, we use multiple lines of evidence to reveal that environmental conditions during the nonbreeding season influence...

The primary threat to biodiversity is habitat loss and degradation. Private residential land (yards) encompass large proportions of urban, suburban, and rural spaces and is among the most rapidly expanding systems on Earth. Yards also represent a conservation opportunity to provide wildlife habitat, support biodiversity, restore ecosystem function...

Understanding the consequences of global change for migratory birds is complex as individuals are exposed to diverse conditions and experiences that interact across their annual cycle. Species distribution models (SDMs) can serve as a powerful tool that help us understand how species distributions respond to global change. However, SDMs applied to...

Jennie Duberstein In 2023, the American Ornithological Society (AOS) ­introduced a Conservation Practitioner Award, which recognizes individuals or groups of biologists at any stage of their career for outstanding work in government agencies (from municipal, state, provincial, federal, or international levels) or nongovernmental organizations to ­f...

Lisa Sorenson Stanley Senner The American Ornithological Society (AOS) Schreiber Award honors extraordinary conservation-related scientific contributions by an individual or small team. Contributions from throughout the world and over any time period are eligible for this award, including applied research, restoration, and educational actions that...

Ecological correlates of North American bird declines

Species declines and extinctions characterize the Anthropocene. Determining species vulnerability to decline, and where and how to mitigate threats, are paramount for effective conservation. We hypothesized that species with shared ecological traits also share threats, and therefore may experience similar population trends. Here, we used a Bayesian...

Animal tracking has become an effective way to identify where and when migratory species encounter threats throughout their annual cycle. Yet, untracked or poorly tracked species and undiscoverable or inaccessible data for the species that have been tracked mean that gaps in the knowledge of where and when species occur are still an issue for conse...

Understanding the geographic linkages among populations across the annual cycle is an essential component for understanding the ecology and evolution of migratory species and for facilitating their effective conservation. While genetic markers have been widely applied to describe migratory connections, the rapid development of new sequencing method...

Exponential increases in anthropogenic noise and light pollution have accompanied growth of the built environment. Noise and light cause negative consequences for birds, such as disrupted navigation during migration, mortality from collisions with windows and other infrastructure, and reduced reproductive success, as well as some positive consequen...

Understanding the geographic linkages among populations across the annual cycle is an essential component for understanding the ecology and evolution of migratory species and for facilitating their effective conservation. While genetic markers have been widely applied to describe migratory connections, the rapid development of new sequencing method...

Background Each spring and fall billions of songbirds depart on nocturnal migrations across the globe. Theory suggests that songbirds should depart on migration shortly after sunset to maximize their potential for nightly flight duration or to time departure with the emergence of celestial cues needed for orientation and navigation. Although captiv...

Background Weather can have both delayed and immediate impacts on animal populations, and species have evolved behavioral adaptions to respond to weather conditions. Weather has long been hypothesized to affect the timing and intensity of avian migration, and radar studies have demonstrated strong correlations between weather and broad-scale migrat...

Migratory birds that experience poor overwintering conditions are often late to arrive at the breeding grounds, which is known to depress individual fitness. Despite the importance of this carryover effect, few studies have investigated how individuals can modify migratory behaviors en route to reduce delays on arrival and whether accelerating migr...

Context Brown-headed cowbirds (Molothrus ater), through brood parasitism, can exert extrinsic population growth pressures on North American songbirds. Cowbird removal programs may reduce parasitism rates on host species but can be expensive and difficult to implement throughout a host species’ breeding range. Aim We estimated cowbird abundance and...

Migratory tracking of genetically distinct populations can be used to develop conservation strategies that prioritize the protection of unique genetic lineages across the annual cycle. In North America, the island of Newfoundland harbors populations of numerous species that are genetically differentiated from populations in mainland North America....

The onset of spring migratory behavior in birds is thought to be controlled by a rigid endogenous schedule as a result of selection to time migration with environmental conditions on breeding grounds. Recent field studies, however, have revealed flexibility in spring departure schedules and suggest a role for environmental factors such as weather a...

Improving our understanding of migratory behaviors and connectivity is fundamental for identifying limiting factors and drivers of population decline. With advances in miniaturized tracking technology, we are now able to study these critical aspects of avian ecology, which, for secretive species, was once an exceptional challenge. Here, we identify...

Free-roaming domestic cats (i.e., cats that are owned or unowned and are considered ‘at large’) are globally distributed non-native species that have marked impacts on biodiversity and human health. Despite clear scientific evidence of these impacts, free-roaming cats are either unmanaged or managed using scientifically unsupported and ineffective...

For many avian species, spatial migration patterns remain largely undescribed, especially across hemispheric extents. Recent advancements in tracking technologies and high‐resolution species distribution models (i.e., eBird Status and Trends products) provide new insights into migratory bird movements and offer a promising opportunity for integrati...

Protecting biodiversity while sustaining agricultural production is one of our greatest modern challenges. The dominant conservation paradigm in tropical coffee-growing regions involves land-sharing, wherein wildlife-friendly shade trees are integrated into plantations. Meanwhile, the value of land-sparing approaches that combine intensified farmin...

As wind energy rapidly expands worldwide, information to minimize impacts of this development on biodiversity is urgently needed. Here we demonstrate how data collected by weather radar networks can inform placement and operation of wind facilities to reduce collisions and minimize habitat‐related impacts on nocturnally migrating birds. We found ov...

By combining all available banding and tracking data, we found that Willets (Tringa semipalmata) have a strong migratory connectivity between breeding and nonbreeding locations at the range-wide and subspecies levels, exposing two subspecies to varying threats such as hunting for the eastern subspecies (T. s. semipalmata) and climatically-altered c...

Behavioral flexibility of individuals is essential if organisms are to ultimately adapt to climate change. As environmental conditions, such as precipitation patterns become increasingly variable, fine-scale spatiotemporal flexibility in space use may allow for individuals to track resources during periods of adverse or atypical conditions. Individ...

Tissue samples are frequently collected to study various aspects of avian biology, but in many cases these samples are not used in their entirety and are stored by the collector. The already collected samples provide a largely overlooked opportunity because they can be used by different researchers in different biological fields. Broad reuse of sam...

FULL TEXT HERE: https://www.degruyter.com/document/doi/10.1515/ami-2020-0116/html The Olive-sided Flycatcher ( Contopus cooperi ) is a steeply declining aerial insectivore with one of the longest migrations of any North American passerine. We deployed light-level geolocators and archival GPS tags on breeders in boreal Alaska to determine migratory...

Migratory animals experiencing substantial change in diet and habitat across the annual cycle may have corresponding shifts in host‐associated microbial diversity. Using automated telemetry and radio tags to recapture birds, we examined gut microbiota structure in the same population and often same individual of Kirtland's Warblers (Setophaga kirtl...

To meet the growing demand for chocolate, cocoa (Theobroma cacao) agriculture is expanding and intensifying. Although this threatens tropical forests, cocoa sustainability initiatives largely overlook biodiversity conservation. To inform these initiatives, we analyzed how cocoa agriculture affects bird diversity at farm and landscape scales with a...

Vulture populations are in severe decline across Africa and prioritization of geographic areas for their conservation is urgently needed. To do so, we compiled three independent datasets on vulture occurrence from road-surveys, GPS-tracking, and citizen science (eBird), and used maximum entropy to build ensemble species distribution models (SDMs)....

Identifying environmental correlates driving space-use strategies can be critical for predicting population dynamics; however, such information can be difficult to attain for small mobile species such as migratory songbirds. We combined radio-telemetry and high-resolution GPS tracking to examine space-use strategies under different moisture gradien...

Free-ranging domestic cats are a detriment to wildlife and humans by preying on native species and transmitting disease. As a result, removing free-ranging cats from the landscape has become a conservation and public health priority. Estimating cat population size with an unbiased sampling design, however, especially in human-dominated areas, is lo...

Birds experience a sequence of critical events during their life cycle, and past events can subsequently determine future performance via carry-over effects. Events during the non-breeding season may influence breeding season phenology or productivity. Less is understood about how events during the breeding season affect individuals subsequently in...

Birds exhibit a remarkable array of seasonal migrations. Despite much research describing migratory behaviour, the underlying forces driving how a species’ breeding and wintering populations redistribute each year, that is, migratory connectivity, remain largely unknown. Here, we test the hypothesis that birds migrate in a way that minimises energy...

en An understanding of the full annual cycle distributions of bird populations is a prerequisite to elucidating the drivers of differing trends among breeding populations. In the United States, Black-crowned Night-Herons (Nycticorax nycticorax) are listed as threatened or endangered in some states where they breed, but populations are stable in oth...

South America is home to the highest diversity of birds on the planet, yet we still understand relatively little about their seasonal movements, or even which species are migratory. During two consecutive years, we used satellite transmitters to study the movement ecology of 10 individual Snail Kites (Rostrhamus sociabilis) captured in southern Bra...

Understanding spatial and temporal movement patterns of migratory birds throughout the annual cycle can help identify potential population threats. The behavior and habitat use of birds during migration and stopover periods is particularly understudied in many species. In this study, we used high spatial resolution archival GPS tags to track Rusty...

Aim Conservation planning for migratory species requires knowing how populations are connected throughout the annual cycle. We measured migratory connectivity for five migratory songbird species by combining stable‐hydrogen isotopes in feathers (δ²HF) with citizen science data on breeding range abundance. Location Caribbean Basin and North America...

Many migratory species are declining and for most, the proximate causes of their declines remain unknown. For many long-distance Neotropical migratory songbirds, it is assumed that habitat loss on breeding or non-breeding grounds is a primary driver of population declines. We integrated data collected from tracking technology, community science and...

A female Kirtland’s Warbler was observed and captured on 12 February 2019 at the Font Hill Nature Reserve (18°02′ N, 77°57′ W) on the south coast of Jamaica, hundreds of kilometers southwest of the typical nonbreeding range of Kirtland’s Warblers. This is the first report of a Kirtland’s Warbler (Setophaga kirtlandii) in Jamaica. The individual was...

Long‐distance migrations are among the most physically demanding feats animals perform. Understanding the potential costs and benefits of such behaviour is a fundamental question in ecology and evolution. A hypothetical cost of migration should be outweighed by higher productivity and/or higher annual survival, but few studies on migratory species...

Deciphering how environmental heterogeneity affects population dynamics in migratory species is complicated by the redistribution of individuals in time and space across the annual cycle. Approaches that tackle this problem require information about how migratory species respond to ecological factors across time and space, and how they are linked a...

Individuals that disperse long distances from their natal site must select breeding patches with no prior knowledge of patch suitability. Despite decades of theoretical studies examining which cues dispersing individuals should use to select breeding patches, few empirical studies have tested the predictions of these theories at spatial scales rele...

en The size of the pectoral muscle is an important component of body condition in birds and has been linked to indices of fitness and migratory performance. Bauchinger et al. (2011. Journal of Ornithology 152: 507–514) developed, calibrated, and validated an aluminum “muscle meter” device that estimates the size of pectoral muscles noninvasively. T...

Migratory connectivity is the degree to which populations are linked in space and time across the annual cycle. Low connectivity indicates mixing of populations while high connectivity indicates population separation in space or time. High migratory connectivity makes individual populations susceptible to local environmental conditions; therefore,...

The contribution of interspecific competition to structuring population and community dynamics remains controversial and poorly tested. Interspecific competition has long been thought to influence the structure of migrant–resident bird communities in winter, yet experimental evidence remains elusive. The arrival of billions of songbirds into Neotro...

Sexual habitat segregation during the wintering period is a widespread phenomenon and has important implications for the ecology and conservation of migratory birds. We studied Black-and-white Warblers (Mniotilta varia) wintering in second-growth scrub and old-growth mangrove forest in Jamaica to quantify sexual habitat segregation and explore whet...

Throughout much of the world, growing populations of free-ranging domestic cats pose an increasingly serious threat to biodiversity. However, no study has estimated the magnitude of wildlife mortality caused by cats in China, one of the largest and most biodiverse nations on earth. We used a novel, survey questionnaire-based approach to estimate an...

Understanding how migratory animals respond to spatial and temporal variation in habitat phenology is critical for identifying selection pressures and tradeoffs at different life history stages. We examined the influence of breeding habitat phenology on life history timing of the eastern willet (Tringa semipalmata semipalmata) across a latitudinal...

Ecological “big data” Human activities are rapidly altering the natural world. Nowhere is this more evident, perhaps, than in the Arctic, yet this region remains one of the most remote and difficult to study. Researchers have increasingly relied on animal tracking data in these regions to understand individual species' responses, but if we want to...

Migrating birds require en route habitats to rest and refuel. Yet, habitat use has never been integrated with passage to understand the factors that determine where and when birds stopover during spring and autumn migration. Here, we introduce the stopover‐to‐passage ratio (SPR), the percentage of passage migrants that stop in an area, and use 8 ye...

Technology has revolutionized our ability to track animals across the globe, significantly advancing our understanding of animal movement [1, 2]. Technological and logistical challenges, however, have led to non-migratory movements that fall outside of the territory/home range paradigm, receiving less attention. This may have resulted in a widespre...

Although the migration ecology of birds breeding in the Neotropics is still poorly studied relative to that of their counterparts breeding at north-temperate latitudes, studies conducted over the last 2 decades have revealed that migration in the Neotropics is much more common and diverse than previously thought. These studies have identified dozen...