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Avian species are in rapid decline worldwide, with 1 in 8 species facing extinction, and in North America shorebird species are declining at a higher proportion than other groups. The nearshore ecosystem in Maine (USA) supports several bird species that rely on intertidal and subtidal zones, including high densities of migratory shorebirds and wintering waterfowl. Additionally, Acadia National Park (ANP) includes some of the country's highest densities of declining populations of Purple Sandpipers (Calidris maritima) and state threatened Harlequin Ducks (Histrionicus histrionicus). We investigated whether the distribution of candidate umbrella species overlapped with the distribution of 5 waterfowl taxa (Common Eiders [Somateria mollissima], Long-tailed Ducks [Clangula hyemalis], Black Scoters [Melanitta americana], Bucephala spp., and Mallards [Anas platyrhynchos]), thereby examining whether conservation actions (e.g., conservation closures) taken to preserve these 2 species of high conservation concern might also benefit the larger taxonomic groups to which they belong, a concept known as umbrella species conservation. To answer this question, bird abundance surveys were conducted within ANP during 2021 and 2022, and detection and occupancy were compared among the focal groups using a hypothesis-driven model. The occupancy distributions of our 5 waterfowl taxa revealed that sites with the highest occupancy estimates for Common Eiders, Long-tailed Ducks, and Black Scoters included sites occupied by Purple Sandpipers and Harlequin Ducks. Bucephala spp. and Mallard occupancy, however, only weakly overlapped with our candidate umbrella detections, occurring in sites with the lowest and mid-range occupancy estimates. Thus, any positive effect of conservation closures based on these 2 species of concern might impact some, but not all, species we surveyed. Including more survey locations occupied by Purple Sandpipers and Harlequin Ducks would be necessary to see if this pattern is generalizable across the region. Our low sample size for umbrella species detections, however, also highlights the limited utility of using rare species as umbrellas. Received 12 August 2023. Accepted 2 March 2024. Key words: coastal ecosystem, Harlequin Duck, Purple Sandpiper, rockweed harvesting, single-species occupancy. (Spanish)-Las especies de aves estan en un declive rapido en todo el mundo, con 1 de cada 8 especies en riesgo de extincion y en Norteamerica las especies de aves costeras estan declinando a una mayor proporcion que otros grupos. El ecosistema litoral en Maine (EEUU) sostiene a varias especies de aves que dependen de zonas intermareal y submareales, incluyendo altas densidades de aves playeras migratorias y aves acuaticas invernales. Adicionalmente, Acadia National Park (ANP) incluye unas de las densidades mas altas del pais de las poblaciones en declive de correlimo Calidris maritima y de pato Histrionicus histrionicus, amenazados a nivel estatal. Estudiamos si la distribucion de especies sombrilla candidatas sobrelapaba con la distribucion de 5 taxa de aves acuaticas (eider Somateria mollissima, pato Clangula hyemalis, pato negro Melanitta americana, Bucephala spp. y pato Anas platyrhynchos), por tanto examinando si las acciones de conservacion (como cierres de conservacion) tomadas para preservar esas 2 especies en peligro critico tambien podrian beneficiar a los grupos taxonomicos mas amplios a los que pertenecen, un concepto conocido como conservacion de especies sombrilla. Para responder a esta pregunta, se realizaron reconocimientos de abundancia de aves en ANP durante el 2021 y el 2022, y se comparo la deteccion y la ocupacion entre grupos focales usando un modelo guiado por hipotesis. La distribucion de ocupacion de nuestras 5 taxa de aves acuaticas mostraron que los sitios con los mayores estimados de ocupacion para eider S. mollissima, pato C. hyemalis y pato negro Melanitta americana incluian sitios ocupados por correlimo C. maritima y pato H. histrionicus. Sin embargo, la ocupacion de Bucephala spp. y de pato A. platyrhynchos solo tuvo un debil sobrelapamiento con la deteccion de nuestras candidatas a especies sombrilla, en sitios con estimados de ocupacion de rango medio y bajo. Entonces, cualquier conclusion positiva del efecto de conservacion basada en estas 2 especies de interes puede tener algun impacto sobre algunas, pero no todas, las especies del reconocimiento. Seria necesario incluir mas localidades de reconocimiento ocupadas por correlimo Calidris maritima y pato H. histrionicus para ver si este patron es generalizable en toda la region. Nuestro bajo numero de reconocimientos para la deteccion de especies sombrilla, sin embargo, tambien recalca el uso limitado de usar especies raras como especies sombrilla. Palabras clave: correlimo Calidris maritima, cosecha de algas, ecosistemas costeros, ocupacion de una sola especie, pato Histrionicus histrionicus., During the Maine winter, the coastal areas of Acadia National Park (ANP) include some of the continental United States' highest densities of both Purple Sandpipers (Calidris maritima) and Harlequin Ducks [...]

Acid deposition from fossil fuel combustion caused calcium depletion in eastern North America during the 20th century, and calcium is a critical resource for birds during both the egg laying and nesting periods. The effects of acid deposition on animals have largely acted through trophic relationships, with reduced calcium availability in prey possibly being a limiting factor for forest songbirds. Following 21 years of experimental whole-watershed acidification at the Bear Brook Watershed in Maine, we investigated Ovenbird (Seiurus aurocapilla) territory size and potential prey (leaf litter arthropod) abundance, assemblage, and calcium concentration during one breeding season. We delineated and estimated the area of 8 Ovenbird territories in an acidified and a control watershed, but found that territory size did not differ between watersheds. However, while calcium concentrations of potential prey also did not differ between watersheds, territory size decreased as calcium concentrations of potential prey increased, regardless of watershed. Our results suggest that calcium limitation can be a determinant of territory size in some landscapes, and this provides further support to importance of the role of calcium in the lives of passerines. Received 17 June 2020. Accepted 1 October 2021. Key words: acid deposition, breeding ecology, calcium, nutrient limitation, trophic interactions. La deposicion de acido producto de la quema de combustibles fosiles causo perdidas dc calcio en el este de Norteamerica durante cl siglo veintc y el calcio es un recurso critico para las aves durante los periodos de puesta de huevos y anidacion. En su mayoria, los efectos de la deposicion de acido en animales han operado por medio de relaciones troficas, donde una reduccion en la disponibilidad de calcio en sus presas es posiblcmente un factor limitante para aves canoras de bosque. Siguiendo 21 afios de acidification experimental de toda la cuenca en la Bear Brook Watershed en Maine, investigamos el tamano del territorio y la abundancia, ensamble y concentracion de calcio de las presas potenciales (artropodos de la hojarasca) del chipe Seiurus aurocapilla durante una temporada reproductiva. Delineamos y estimamos el area de 8 territorios dc este chipe cn una cuenca acidificada y una cuenca control, pcro encontramos que el tamano del territorio no difiere entre estas. Sin embargo, aunque las concentraciones de calcio de sus presas potenciales tampoco difieren entre cuencas, el tamano de territorio decrccio mientras que la concentration de calcio de presas potenciales se incremento independientemente dc la cuenca. Nuestros resultados sugieren que la [imitation de calcio puede ser una determinantc de tamano de territorio en algunos paisajes y esto provee mayor soporte a la importancia del calcio en la vida de las paserinas. Palabras clave: calcio, deposition de acido. ecologia de la reproduccion. interacciones troficas. limitation de nutrientes., Effects of acid deposition from fossil fuel combustion on ecosystems came to the forefront of society's ecological consciousness in the latter half of the twentieth century (Lynch et al. 2000). [...]

Eco‐phylogeographic approaches to comparative population genetic analyses allow for the inclusion of intrinsic influences as drivers of intraspecific genetic structure. This insight into microevolutionary processes, including changes within a species or lineage, provides better mechanistic understanding of species‐specific interactions and enables predictions of evolutionary responses to environmental change. In this study, we used single nucleotide polymorphisms (SNPs) identified from reduced representation sequencing to compare neutral population structure, isolation by distance (IBD), genetic diversity and effective population size (Ne) across three closely related and co‐distributed saltmarsh sparrow species differing along a specialization gradient—Nelson's (Ammospiza nelsoni subvirgata), saltmarsh (A. caudacuta) and seaside sparrows (A. maritima maritima). Using an eco‐phylogeographic lens within a conservation management context, we tested predictions about species' degree of evolutionary history and ecological specialization to tidal marshes, habitat, current distribution and population status on population genetic metrics. Population structure differed among the species consistent with their current distribution and habitat factors, rather than degree of ecological specialization: seaside sparrows were panmictic, saltmarsh sparrows showed hierarchical structure and Nelson's sparrows were differentiated into multiple, genetically distinct populations. Neutral population genetic theory and demographic/evolutionary history predicted patterns of genetic diversity and Ne rather than degree of ecological specialization. Patterns of population variation and evolutionary distinctiveness (Shapely metric) suggest different conservation measures for long‐term persistence and evolutionary potential in each species. Our findings contribute to a broader understanding of the complex factors influencing genetic variation, beyond specialist‐generalist status and support the role of an eco‐phylogeographic approach in population and conservation genetics. [ABSTRACT FROM AUTHOR]

The high attrition rate among science, technology, engineering, and mathematics (STEM) majors has long been an area of concern for institutions and educational researchers. The transition from introductory to advanced courses has been identified as a particularly "leaky" point along the STEM pipeline, and students who struggle early in an introductory STEM course are predominantly at risk. Peer-tutoring programs offered to all students in a course have been widely found to help STEM students during this critical transition, but hiring a sufficient number of tutors may not be an option for some institutions. As an alternative, this study examines the viability of an optional peer-tutoring program offered to students who are struggling in a large-enrollment, introductory biology course. Struggling students who regularly attended peer tutoring increased exam performance, expert-like perceptions of biology, and course persistence relative to their struggling peers who were not attending the peer-tutoring sessions. The results of this study provide information to instructors who want to design targeted academic assistance for students who are struggling in introductory courses.