Explore the vast range of titles available.

Microsatellite loci in non‐coding regions of nuclear DNA provide an important tool for genetic diversity research, particularly when comparing relatedness between individuals. While microsatellites have been developed for several species within the Blackbird family (Icteridae), no species‐specific microsatellite primers for genetic analysis of Bobolinks (Dolichonyx oryzivorus) exist. Like many grassland songbirds, Bobolink populations are in decline, and accessible genetic analysis tools are therefore critical for understanding population dynamics. This paper introduces ten new, polymorphic microsatellite loci, at least eight of which should provide a reliable tool for the future study and monitoring of Bobolink genetics. These hypervariable and thus highly informative loci were amplified in 152 adult individuals from a well‐studied population in Shelburne, Vermont, USA. This paper introduces ten new polymorphic microsatellite loci for genetic analysis of Bobolinks (Dolichonyx oryzivorus, Family Icteridae), which, like many grassland songbirds, are declining across their native range in North and South America. The informativeness of these hypervariable loci was confirmed based on the genotyping of 152 adult individuals from a well‐studied population in Shelburne, Vermont, USA. These loci will provide an important tool for assessing relatedness between individuals and monitoring population dynamics over time.

Heritability and evolvability estimates of adult traits from free-living bird populations can be used to gauge the ability of populations to respond to selection, but are rare due to difficulties in gathering detailed pedigree information. The capacity to respond to selection is particularly important for species occupying managed habitats such as agricultural grasslands because of the potential for humans to accidentally influence traits. We calculated heritability and evolvability of six morphological traits in a population of Savannah Sparrows (Passerculus sandwichensis) breeding in a large agricultural landscape. We used microsatellite analysis to determine a genetic pedigree, revealing a high level of extra-pair paternity (63%) within a relatively philopatric population. For the entire population, heritabilities varied from low to high (bill width: 0.160±0.182 to tarsus length: 0.651±0.155), while evolvabilities were low across all traits (wing length: 0.035±0.013 to body mass: 0.066±0.106). Our results indicate that any directional selection from agricultural management practices will produce negligible changes in basic morphometrics of Savannah sparrow populations occupying the Champlain Valley of Vermont, USA.

Migratory birds time their migration based on cues that signal resource availability for reproduction. However, with climate change, the timing of seasonal events may shift, potentially inhibiting the ability of some species to use them as accurate cues for migration. We studied the relationship between phenological shifts and reproduction by long‐ and short‐distance migratory songbirds—Bobolinks (Dolichonyx oryzivorus) and Savannah Sparrows (Passerculus sandwichensis). Our study population breeds in hayfields and pastures in Vermont, USA, where farmers are also changing management activities in response to climate change. From 2002 to 2019, we monitored nest initiation dates to quantify correlations with environmental factors and the timing of nest initiation. We collected historical and projected precipitation and temperature data for the breeding grounds, and their respective wintering and stopover sites, the North Atlantic Oscillation (NAO) and the El Niño Southern Oscillation (ENSO). We predicted that winter conditions experienced by the short‐distance migrant, the Savannah Sparrow, but not the long‐distance migrant, the Bobolink, would explain the timing and success of nesting, however that this timing would be misaligned with changes in agricultural practices by hay farmers. Nest initiation dates did not show significant directional change for either species, but did vary among years. Interannual variation in Savannah Sparrow nest initiation dates was best explained by the interaction between precipitation on the breeding grounds and average wintering site (Wilmington, North Carolina). For Bobolinks, interannual variation in nest initiation dates was best explained by the interaction between breeding ground precipitation and average temperature in their fall stopover site (Barquisimieto, Venezuela). However, first haying dates in Vermont advanced by ~10 days over 18 years. These results suggest that the conflict between the timing of hay harvests and grassland songbird reproduction will increase, further threatening population processes for these species, as early harvests notably decrease annual productivity. Nest initiation date (Julian date) of Savannah Sparrows and Bobolinks (A) and first hay harvest dates (B) from 2002‐2019 in the Champlain Valley of Vermont.

Our understanding of the full life cycle of most migratory birds remains limited. Estimates of survival rates, particularly for first-year birds are notably lacking. This knowledge gap results in imprecise parameters in population models and limits our ability to fully understand life history trade-offs. We used eleven years of field data to estimate first-year apparent survival (ϕ1st) for two species of migratory grassland songbirds that breed in the same managed habitats but have substantially different migration distances. We used a suite of life-history, habitat and individually-based covariates to explore causes of variation in ϕ1st. The interaction between fledge date and body mass was the best supported model of apparent survival. We found differential effects of fledging date based on nestling body mass. Overall, lighter nestlings had greater apparent survival than heavier nestlings; average or heavy nestlings within-brood had greater apparent survival when they fledged earlier in the summer. We hypothesize that heavier birds that fledge earlier in the season have a longer window of opportunity to evaluate potential breeding sites and are more likely to disperse greater distances from the natal region, thus confounding survival with permanent emigration. Lighter birds, particularly those fledged late in the breeding season may spend more time on self-maintenance and consequently have less time to evaluate potential future breeding sites, showing greater fidelity to their natal region. We found no support for management treatment (timing of mowing), sex, brood size, or species as important covariates in explaining apparent survival. Our results suggest that differential migration distances may not have a strong effect on first-year apparent survival.

To better understand the dynamics of avian populations and their role in population trends, we require an in‐depth understanding of the factors influencing the survival of adults and juveniles. However, assessing survival in juveniles is often challenging, especially in small, migratory species where individuals typically disperse from the study area and are not available for recapture in subsequent years. Bobolinks (Dolichonyx oryzivorus) are a long‐distance migrant that exhibits natal philopatry in at least one population, allowing for more comprehensive juvenile survival analyses than in many other long‐distance avian migrants. Using a 17‐yr dataset from two sites representing a Vermont population of Bobolinks, we used Program MARK to assess factors influencing apparent juvenile survival, including factors related to nesting timing, nest attempt number, the philopatric behaviors of relatives, body mass, brood size, and agricultural management scheme. Our top models indicated that nest attempt number and whether or not a nest mate also survived and returned to breed locally were important factors explaining variation in apparent survival in juvenile Bobolinks. Specifically, juveniles from first nest attempts that fledged earlier in the season, with siblings that did not survive and return to breed locally, showed higher apparent survival. Factors such as site and the philopatric behavior of females associated with nests also appeared in top‐ranking models, while factors such as body mass and brood size did not. These results indicate the importance of providing high‐quality breeding habitat to birds early in the season when juvenile survival is greatest and indicate that individuals may be utilizing inbreeding avoidance strategies. These results provide new insight into the ecological and agricultural management factors influencing survival in migratory species that use managed habitats and underscore the importance of integrating juvenile survival data into current management schemes to better support this and other declining species.

In some species, habitat edges (ecotones) affect nest-site selection and nesting success. Openness, or how visually open a habitat is, has recently been shown to influence grassland bird density and may affect nest-site selection, possibly by reducing the risk of predation on adults, nests, or both. Because edge and openness are correlated, it is possible that effects of openness have been overlooked or inappropriately ascribed to edge effects. We tested the roles of edges and visual openness in nest-site selection and nesting success of two grassland passerines, the Bobolink (Dolichonyx oryzivorus) and Savannah Sparrow (Passerculus sandwichensis), in the Champlain Valley, Vermont. We also evaluated the sensitivity of our results to alternative definitions of edge on our landscape. Bobolink (n = 580) and Savannah Sparrow nests (n = 922) were located on seven hay fields and three pastures from 2002 to 2010. Both species avoided placing nests near edges and in less open habitat compared with expectations based on random placement. When the effects of openness and edge were separated, less open habitats were still avoided, but edge responses were less clear. These results were robust to different definitions of habitat edge. We found no strong relationships between either openness or edges and reproductive success (numbers of eggs and fledglings, percentage of eggs producing fledglings, and nest success), although there may be an edgespecific openness effect on timing of reproduction (clutch completion date). Our results support openness as an important factor in nest-site selection by grassland birds.

Three North American passerines are known to perform transoceanic flights during their fall migration, with open-water flights ranging in length from 1,700 to 3,400 km. However, little is known about within-population variation of these flights. From 2013 to 2017, I used geolocators to study variation in the fall migratory track of the Bobolink (Dolichonyx oryzivorus) from a population that bred in agricultural grasslands of Vermont, USA. Thirteen of seventeen birds took transoceanic flights during fall migration, ranging in length from 1,098 to 3,536 km (mean ± SD = 1,969 ± 640); five of these flights were nonstop from North to South America. Bobolinks initiated transoceanic flights between Nova Scotia, Canada, and the central coast of North Carolina, USA, an orthodromic distance of 2,500 km. Mean arrival to 12° latitude in South America was October 17 ± 17 days (range: September 26–November 26). Neither sex, morphological measurements, nor age significantly explained variation in nonstop flight length.

Grassland birds are often affected negatively by habitat fragmentation. Outcomes include greater nest predation and brood parasitism, decreased colonization rates of small, isolated patches, and greater nest density in remnant core habitats. These effects have been well documented in the Midwest, but little is known about fragmentation and edge effects on grassland birds in the fragmented agricultural fields within the forested landscapes of the northeastern United States. From 2002 to 2010, we assessed how edges and edge types affected nest-site location and daily nest survival (DNS) of Savannah Sparrows (Passerculus sandwichensis) and Bobolinks (Dolichonyx oryzivorus) breeding in 11 fields (range: 13.2–38.3 ha; mean = 21.1 ha) within a large agricultural region of Vermont. Mean (± SD) distance to edge was 80.3 ± 39.6 m for Savannah Sparrows (n = 995) and 94.5 ± 56.5 m for Bobolinks (n = 652). Both species nested significantly less than expected within 50 m of the edge. For Savannah Sparrows nesting within 50 m of the edge, DNS increased with increased distance from the edge. Birds initiating nests later in the season nested closer to edges, but renests were farther from edges than first nests. Distance to edge had no detectable consequence for Bobolink nest success. Both species used portions of fields near hedgerows less than expected but used wetland, forest, agricultural, road, and developed edges in proportion to availability. For both species, DNS did not vary among edge types. Although edges were used less than expected, nesting near edges had only minor consequences for nest success.

Natal dispersal by Sciurus carolinensis (Eastern Gray Squirrel) is poorly understood, given so rarely reported, yet dispersal patterns in small mammals can affect seed dispersal and predation, as well as population dynamics of predators. Herein, I document long-distance dispersal by 3 Eastern Gray Squirrels from the suburban coastal campus of the University of New England in Biddeford, ME. Mean dispersal distance was 10.1 km (min–max = 6.3–14.5 km), occurring in random directions (SW, S, NW). These results, combined with the previous studies, better describe the distribution of natal dispersal by Eastern Gray Squirrel—critical information in understanding population processes and potentially developing effective landscape-management strategies.

The Bobolink (Dolichonyx oryzivorus) is a long-distance migratory grassland songbird whose global population is in long-term decline, largely due to habitat loss and intensification of agricultural practices. To better understand the factors affecting their annual cycle, we used a known-age population of male Bobolinks (n = 121) breeding in agricultural grasslands of Vermont and explored how variation in plumage (extent of yellow in cap) and body morphology (body mass and wing length) explained variation in apparent survival. Bobolink body mass and wing length varied between years 2–5. Bobolink cap size did not change with age. However, none of the 3 morphological characters explained variation in apparent survival. Our results highlight the challenges associated with understanding variation in individual quality relative to age, particularly regarding factors that affect demographic processes in declining species. El tordo charlatán (Dolichonyx oryzivorus) es un ave canora de pastizal migratoria de larga distancia cuya población global está en declive a largo plazo, principalmente debido a la pérdida de hábitat y a la intensificación de las prácticas agrícolas. Para entender mejor los factores que afectan su ciclo anual, utilizamos una población con edad conocida de tordos charlatanes machos (n = 121) que se reproducían en pastizales agrícolas de Vermont y exploramos cómo la variación en su plumaje (la extensión del amarillo de su capucha) y la morfología corporal (masa corporal y longitud del ala) explicaban la variación en la sobrevivencia aparente. La masa corporal del tordo charlatán y la longitud del ala variaron entre los años 2–5. El tamaño de la capucha del tordo charlatán no tuvo variaciones con la edad. Sin embargo, ninguno de los 3 caracteres morfológicos explicaba la variación de sobrevivencia aparente. Nuestros resultados resaltan los desafíos asociados a entender la variación en la calidad de los individuos relativa a la edad, particularmente con respecto a factores que afectan procesos demográficos de especies en declive. Palabras clave: ala, Icteridae, masa, morfología, plumaje, Programa MARK, Vermont.