Nearctic-Neotropical Migratory Songbird Research Articles

The Complete Genome Sequence of Protonotaria citrea, the Prothonotary Warbler.

The Prothonotary Warbler (Protonotaria citrea) is a nearctic-neotropical migratory songbird that breeds in forested swamps and riparian areas in the eastern-central United States and southern Ontario. It is the sole eastern North American wood-warbler that nests in cavities, the only species in the genus Protonotaria, and is one of the few hole-nesting hosts of the Brown-headed Cowbird (Molothrus ater), an obligate brood parasite. We present the whole genome sequence of this wood-warbler species. Illumina sequencing was performed on a genetic sample from a single female individual. The reads were assembled using a de novo method followed by a finishing step. The raw and assembled data is publicly available via Genbank: Sequence Read Archive (SRR19579445) and Assembly (JAOYNP000000000).

Cerulean Warblers exhibit parallel migration patterns and multiple migratory stopovers within the Central American Isthmus

Abstract The Cerulean Warbler (Setophaga cerulea) is a declining Nearctic–Neotropical migratory songbird of conservation concern. Implementing full annual cycle conservation strategies to facilitate recovery has been difficult because we know little about the migratory period or strength of migratory connectivity between North American breeding and South American nonbreeding regions. Between 2014 and 2017, we deployed geolocators on 282 males at 14 study sites throughout the species’ range to (1) evaluate the strength and pattern of connectivity between breeding and nonbreeding regions, (2) identify approximate routes and stopover regions, and (3) document migration phenology. We obtained data from 26 birds and observed moderate migratory connectivity overall but documented strong parallel migration for birds breeding in two longitudinally disparate regions. Most (14 of 15; 93%) Appalachian breeders spent the stationary nonbreeding period in the Colombian/Venezuelan Andes, whereas most (5 of 7; 71%) Ozark-breeders spent the stationary nonbreeding period in Peru/Ecuador. The majority of spring migration (62%) was spent in Central America at multiple stopover locations between Panama and southern Mexico. The 2 migratory periods were approximately equal in duration: 38 ± 2 days (SE) in fall and 42 ± 2 days (SE) in spring. Based on the observed connectivity pattern, conservation of Appalachian-breeding populations during the stationary nonbreeding period should focus on forest conservation and restoration in pre-montane/lower montane forests of Colombia and Venezuela, whereas Ozark-breeding population conservation should focus on forest conservation and restoration efforts in Ecuador and Peru. Further conservation efforts are also needed on the breeding grounds, especially for the most sharply declining populations. And finally, conservation of forests used by Cerulean Warblers during stopover periods throughout Central America and southern Mexico, in southeastern United States coastal areas, and in the Mississippi Alluvial Valley will benefit individuals from multiple breeding locations and populations.

Arrival condition and refueling performance of long-distance migratory songbirds at a spring stopover site in the eastern Gulf of Mexico

Barrier islands along the northern Gulf coast provide critical stopover habitats for Nearctic–Neotropical migratory songbirds using a spring trans-Gulf migration strategy. Islands bordering Apalachicola Bay, Florida, project southward into the Gulf of Mexico providing an opportunity for first landfall. In 2013 and 2014, we studied spring stopover ecology on St. George Island, Florida. We provide a detailed description of the arrival body condition and fuel deposition rates of 8 species of migratory birds. We used 3 approaches to measure fuel deposition rate: (1) estimated an hourly rate of mass change by regressing body mass or scaled body mass by time of day, (2) estimated a daily rate of mass change by examining body mass of recaptured individuals, and (3) for 4 species, measured plasma triglyceride concentrations as a proxy of individual refueling rate. The majority of migratory birds in the eastern Gulf of Mexico arrived in poor body condition with depleted fat and muscle stores. We found no significant changes in body mass or scaled body mass as the day progressed, except for Indigo Bunting (Passerina cyanea), which gained mass throughout the day. Recapture rate was low on St. George Island (<5%), but most recaptured individuals tended to lose mass. Using plasma triglyceride concentration, we found that refueling rate for Gray Catbird (Dumetella carolinensis) declined throughout the day. We found no relationship between body condition and refueling rate in Gray Catbird or Catharus thrushes. Our results suggests that long-distance migratory birds arriving on St. George Island after a nonstop migratory flight may be physiologically challenged due to poor body condition. Our results provide the first quantitative assessment of songbird refueling performance on Florida panhandle barrier islands and reinforce the importance of Gulf of Mexico barrier islands as critical stopover sites for long-distance migrants in poor body condition.

Space Use by Prairie Warblers in Regenerating Mixed-oak Forests of Central Pennsylvania

Setophaga discolor (Prairie Warbler) is a Nearctic–Neotropical migratory songbird that is experiencing long-term population declines. A potentially important driver behind these decreases is the loss of shrubland and early successional forest communities in the eastern United States. Central to conservation for species like the Prairie Warbler is an understanding of breeding habitat requirements at the scale of the home range. Despite the Prairie Warbler being identified as a species of continental conservation concern, few studies have explicitly quantified habitat conditions within its home ranges. We used radio telemetry to quantify Prairie Warbler use of space during the breeding season as well as associated vegetation data across 3 study sites in north-central Pennsylvania from May to June 2016. We radio-tracked 11 adult male Prairie Warblers. Using the telemetry locations, we estimated kernel densities and classified minimum convex polygons around kernel densities to define males' home ranges and core-use areas. The average home range (95% kernel) was 6.4 ha, and the average core-use area (50% kernel) was 0.73 ha. Prairie Warbler core-use areas contained more shrubs and lower tree count than peripheral portions of home ranges. To this end, management activities that promote a dense shrub layer across early successional communities should benefit Prairie Warblers. Results from this study serve as baseline data that can be used to help direct future studies at the home-range scale of Prairie Warbler breeding-season ecology.

Migratory birds as vehicles for parasite dispersal? Infection by avian haemosporidians over the year and throughout the range of a long‐distance migrant

AbstractAimThe role of migratory birds in the spread of parasites is poorly known, in part because migratory strategies and behaviours potentially affecting transmission are not easy to study. We investigated the dynamics of infection by blood parasites through the annual cycle of a long‐distance Nearctic–Neotropical migratory songbird to examine the role of this species in dispersing parasites between continents.LocationThe Americas.TaxonGrey‐cheeked Thrush (Catharus minimus, Aves, Passeriformes, Turdidae), Birds.MethodsWe used molecular and microscopy screening of haemosporidian parasites (Plasmodium, Haemoproteus, and Leucocytozoon) to examine the prevalence, distribution, and diversity of lineages through the annual cycle (breeding, migration, and wintering) of the grey‐cheeked thrush in North and Central America, Santa Marta mountains, the Andes, and the Amazon. We aimed to identify transmission areas, to examine the degree of sharing of haemosporidian lineages with resident birds in various areas and to assess the potential role of immunologically naïve juvenile individuals in parasite transmission.ResultsPrevalence and lineage diversity of haemosporidians varied significantly over time, being higher during breeding and fall and spring migration, and declining during wintering. Grey‐cheeked thrush shared few parasite lineages with tropical resident birds and slightly more lineages with other migratory and resident boreal species. We detected gametocytes in blood during spring migration stopover, but these were of lineages not found in resident tropical birds, indicating relapses of parasites transmitted elsewhere. Transmission likely occurs mostly on the breeding grounds, where juveniles and adults carried lineages restricted to closely related species of thrushes and other species of boreal birds.Main conclusionsLong‐distance migratory songbirds are likely not important dispersers of blood parasites because there are ecological and evolutionary barriers to the interchange of parasites across vastly separated areas. Further work with thorough spatial and temporal sampling across other species, and considering the role of vectors, is necessary to understand the ecological and evolutionary factors explaining the distribution of parasites over broad scales.

Modeling spatial variation in winter abundance to direct conservation actions for a vulnerable migratory songbird, the Bicknell's Thrush (Catharus bicknelli)

ABSTRACT The winter range of the Bicknell's Thrush (Catharus bicknelli), a globally vulnerable Nearctic–Neotropical migratory songbird, is restricted to the Greater Antilles. Most birds occur on Hispaniola, where the species exhibits sexual habitat segregation, and where the loss of its preferred wet broadleaf habitats has been severe. Conservation of female-dominated habitats has been identified as a top priority for the species' preservation. During 2010, we conducted standardized field surveys for the Bicknell's Thrush in forests of the Dominican Republic's Cordillera Septentrional, an area of high importance for females. We combined occurrence data with environmental variables to create a model of thrush distribution and habitat selection in the region. Elevation (densities peaked at ∼600 m), aspect (northeastern slopes), the amount of forest cover within 1 km, and forest density best described thrush presence and abundance. As an example of how predictive models of abundance can inform conservation, ...

A Nearctic-Neotropical Migratory Songbird\u2019s Nesting Phenology and Clutch Size are Predictors of Accumulated Cyclone Energy

The breeding season phenology of Nearctic-Neotropical migratory songbirds is constrained by subsequent seasons resulting in single-brooded behavior (one successful clutch per year) in some species. Early cessation of the nesting season prior to an active hurricane season will allow for behavioral plasticity during a physiologically challenging migration. Hurricane activity shows a high degree of inter-annual variability. I show that a single-brooded Nearctic-breeding species’ (Catharus fuscescens) nesting phenology and clutch size are significant predictors of Accumulated Cyclone Energy. The most skilled predictive model includes both mean clutch initiation date and mean clutch size (R2 = 0.84). Spearman rank correlation coefficients for both predictors with subsequent major hurricanes (1998–2016) are −0.55 and 0.52, respectively. Therefore, May and June clutch initiation and clutch size showed stronger correlations with subsequent hurricanes than early season (prior to August) meteorological predictions widely publicized by CSU, NOAA, and TSR (≤0.45, 2003–2014). Rainfall anomalies in the southern Amazon basin associated with ENSO cycles are a possible proximate cue affecting phenology and clutch size. This discovery potentially has far-reaching ornithological, meteorological, and social implications and shows that tropical storms significantly constrain breeding season behavior providing renewed evidence that hurricane activity is a primary factor regulating Nearctic-Neotropical migratory songbird populations.

Population trends in Vermivora warblers are linked to strong migratory connectivity

Migratory species can experience limiting factors at different locations and during different periods of their annual cycle. In migratory birds, these factors may even occur in different hemispheres. Therefore, identifying the distribution of populations throughout their annual cycle (i.e., migratory connectivity) can reveal the complex ecological and evolutionary relationships that link species and ecosystems across the globe and illuminate where and how limiting factors influence population trends. A growing body of literature continues to identify species that exhibit weak connectivity wherein individuals from distinct breeding areas co-occur during the nonbreeding period. A detailed account of a broadly distributed species exhibiting strong migratory connectivity in which nonbreeding isolation of populations is associated with differential population trends remains undescribed. Here, we present a range-wide assessment of the nonbreeding distribution and migratory connectivity of two broadly dispersed Nearctic-Neotropical migratory songbirds. We used geolocators to track the movements of 70 Vermivora warblers from sites spanning their breeding distribution in eastern North America and identified links between breeding populations and nonbreeding areas. Unlike blue-winged warblers (Vermivora cyanoptera), breeding populations of golden-winged warblers (Vermivora chrysoptera) exhibited strong migratory connectivity, which was associated with historical trends in breeding populations: stable for populations that winter in Central America and declining for those that winter in northern South America.

An experimental examination of the influence of energetic condition on the stopover behavior of a Nearctic–Neotropical migratory songbird, the American Redstart (Setophaga ruticilla)

ABSTRACT Late arrival on the breeding grounds has been associated with reduced fitness in migratory birds. Because migratory stopover accounts for the majority of time spent on migration, how individuals respond to both exogenous and endogenous factors associated with stopover will influence the pace of migration and arrival timing on the breeding grounds. Among the most important endogenous factors, body condition (i.e. fat stores) is expected to influence both movement behavior and departure decisions of individual migrants during stopover. In a novel experiment, we manipulated the condition of after-second-year (adult) male American Redstarts (Setophaga ruticilla) captured during spring migratory stopover and radio-tracked all individuals after release using a passive automated telemetry array and conventional hand tracking. After accounting for the positive effect of tailwind and capture date on departure probability, we demonstrated that body condition influenced both the movement behavior of individ...

Reproductive outcomes determine the timing of arrival and settlement of a single-brooded Nearctic–Neotropical migrant songbird (Catharus fuscescens) in South America

ABSTRACT The breeding seasons of Nearctic–Neotropical migratory songbirds are thought to be constrained by the temporal demands of subsequent seasons. In any population, a subset of adults may fail to fledge young despite repeated attempts, which may prolong reproductive effort. We used geolocators to track the single-brooded Veery (Catharus fuscescens) from a Delaware, USA, breeding site to South America and back, to examine how reproductive failure and the timing of reproduction affected the spatiotemporal aspects of the nonbreeding season. We also considered the effect of additional variables: age, sex, time in population (i.e. experience), productivity, and nutrition via ptilochronology. We found that clutch completion date and reproductive success were significant predictors of South American entry and arrival date at first winter sites, respectively. Reproductive success also influenced the latitude of winter sites. For females only, there was a consequence of reproductive failure: unsuccessful fema...

Effect of fuel deposition rate on departure fuel load of migratory songbirds during spring stopover along the northern coast of the Gulf of Mexico

Migrants are generally assumed to minimize their overall migration time by adjusting their departure fuel loads (DFL) in relation to anticipated and experienced fuel deposition rates (FDRs). We utilized a 21-yr long migration banding station dataset to examine the relationship between FDR and DFL during spring migration in six Nearctic-Neotropical migratory songbird species during stopover along the northern coast of the Gulf of Mexico (GOM) following trans-gulf flight. Estimates of fuel stores, stopover durations, and FDRs from our long term migration data set were combined to determine DFL. We expected and found that migrants across all six species adjust their DFL to the rate at which they deposit fuel reserves. This robust finding suggests that songbird migrants are sensitive to time constraints during spring passage presumably to fine-tune their stopover schedule in relation to experienced and anticipated habitat quality. Two of the species studied showed an effect of age on the FDR–DFL relationship: one was consistent with the expectation that older birds would be less sensitive to changes in FDR, while the second was contrary to our expectations and likely suggesting an age-dependent response to habitat quality. We found sex-dependent differences consistent with male DFL being more sensitive to FDR in only two of six species studied, and argue that both males and females are time constrained during spring passage in relation to arrival at breeding destinations. The positive relationship between FDR and DFL among all species and for age and sex groups in some species reflects a migration strategy sensitive to time.

Multi-Generational Kinship, Multiple Mating, and Flexible Modes of Parental Care in a Breeding Population of the Veery (Catharus fuscescens), a Trans-Hemispheric Migratory Songbird.

We discovered variable modes of parental care in a breeding population of color-banded Veeries (Catharus fuscescens), a Nearctic-Neotropical migratory songbird, long thought to be socially monogamous, and performed a multi-locus DNA microsatellite analysis to estimate parentage and kinship in a sample of 37 adults and 21 offspring. We detected multiple mating in both sexes, and four modes of parental care that varied in frequency within and between years including multiple male feeders at some nests, and males attending multiple nests in the same season, each with a different female. Unlike other polygynandrous systems, genetic evidence indicates that multi-generational patterns of kinship occur among adult Veeries at our study site, and this was corroborated by the capture of an adult male in 2013 that had been banded as a nestling in 2011 at a nest attended by multiple male feeders. All genotyped adults (n = 37) were related to at least one other bird in the sample at the cousin level or greater (r ≥ 0.125), and 81% were related to at least one other bird at the half-sibling level or greater (r ≥ 0.25, range 0.25–0.60). Although our sample size is small, it appears that the kin structure is maintained by natal philopatry in both sexes, and that Veeries avoid mating with close genetic kin. At nests where all adult feeders were genotyped (n = 9), the male(s) were unrelated to the female (mean r = -0.11 ± 0.15), whereas genetic data suggest close kinship (r = 0.254) between two male co-feeders at the nests of two females in 2011, and among three of four females that were mated to the same polygynous male in 2012. To our knowledge, this is the first evidence of polygynandry occurring among multiple generations of close genetic kin on the breeding ground of a Nearctic-Neotropical migratory songbird.

Adcyap1 polymorphism covaries with breeding latitude in a Nearctic migratory songbird, the Wilson's warbler (Cardellina pusilla)

Understanding the genetic background of complex behavioral traits, showing multigenic control and extensive environmental effects, is a challenging task. Among such traits, migration is known to show a large additive genetic component. Yet, the identification of specific genes or gene regions explaining phenotypic variance in migratory behavior has received less attention. Migration ultimately depends on seasonal cycles, and polymorphism at phenological candidate genes may underlie variation in timing of migration or other aspects of migratory behavior. In this study of a Nearctic–Neotropical migratory songbird, the Wilson's warbler (Cardellina pusilla), we investigated the association between polymorphism at two phenological candidate genes, Clock and Adcyap1, and two aspects of the migratory phenotype, timing of spring migration through a stopover site and inferred latitude of the breeding destination. The breeding destination of migrating individuals was identified using feather deuterium ratio (δ 2H), which reliably reflects breeding latitude throughout the species' western breeding range. Ninety‐eight percent of the individuals were homozygous at Clock, and the rare heterozygotes did not deviate from homozygous migration phenology. Adcyap1 was highly polymorphic, and allele size was not significantly associated with migration date. However, Adcyap1 allele size significantly positively predicted the inferred breeding latitude of males but not of females. Moreover, we found a strong positive association between inferred breeding latitude and Adcyap1 allele size in long‐distance migrating birds from the northern sector of the breeding range (western Canada), while this was not the case in short‐distance migrating birds from the southern sector of the breeding range (coastal California). Our findings support previous evidence for a role of Adcyap1 in shaping the avian migratory phenotype, while highlighting that patterns of phenological candidate gene–phenotype associations may be complex, significantly varying between geographically distinct populations and even between the sexes.

Organophosphate pesticide method development and presence of chlorpyrifos in the feet of nearctic-neotropical migratory songbirds from Canada that over-winter in Central America agricultural areas.

Recent modeling analysis suggests that numerous birds may be at risk of acute poisoning in insecticide-treated fields. Although the majority of avian field studies on pesticides have focused on treated seed, granule, insect or vegetation (oral exposure) ingestion, dermal exposure is an important exposure route when birds come into contact with deposited pesticides on foliage and other surfaces. Some nearctic-neotropical migratory songbirds are likely exposed to pesticides on their non-breeding habitats and include treated crops, plantations or farmlands. In the present study, we developed a method for four environmentally-relevant organophosphate (OP) pesticides (fenthion, fenamiphos, chlorpyrifos and diazinon) in the feet of migratory songbirds (i.e. Common yellowthroat, Gray catbird, Indigo bunting, America redstart, Northern waterthrush, Northern parula, and an additional 12 species of warblers). A total of 190 specimens of the 18 species of songbirds were sampled from available window-killed birds (spring of 2007 and 2011) in downtown Toronto, Canada. The species that were available most likely over-wintered in Mexican/Central American crops such as citrus, coffee and cacao. The feet of the dead birds were sampled and where OP foot exposure likely occurred during over-wintering foraging on pesticide-treated crops. Chlorpyrifos was the only measurable OP (pg mg feet weight(-1)) and in the 2011-collected feet of Black throated blue warbler (0.5), Tennessee warbler (1.0), Northern parula (1.2), Northern waterthrush (0.6), Common yellowthroat (1.0) and the Blue winged warbler (0.9). Dermal contact with OP pesticides during over-wintering in agricultural areas resulted in low levels of chlorpyrifos and long time retention on the feet of a subset of songbirds.

Patterns of testosterone in three Nearctic–Neotropical migratory songbirds during spring passage

Preparation for breeding may overlap extensively with vernal migration in long-distance migratory songbirds. Testosterone plays a central role in mediating this transition into breeding condition by facilitating changes to physiology and behavior. While changes in testosterone levels are well studied in captive migrants, these changes are less well known in free-living birds. We examined testosterone levels in free-living Nearctic–Neotropical migrants of three species during their vernal migration. Testosterone levels increased during the migratory period in males of all three species but significantly so in only two. Testosterone levels in females remained the same throughout their migration. Our results support the extensive overlap between vernal migration and breeding preparation in male songbirds. The pattern of testosterone changes during vernal migration is far from clear in females.

Intratropical migration of a Nearctic-Neotropical migratory songbird (Catharus fuscescens) in South America with implications for migration theory

Abstract:Recent advances in tracking technology have revealed significant intratropical movement of Nearctic–Neotropical migratory songbirds during their non-breeding season. We report the movement of 25 veeries (Catharus fuscescens) over multiple seasons (2009–2013) through equatorial rain forests of South America. Veeries initially settled on the Brazilian Shield geological formation but undertook an intratropical migration to a second South American region in January, February or March. Consequently, our study is the first to track individual forest passerines to document an annual migration from the Brazilian Shield to the Guiana Shield and into lowland regions of Amazonia. The movement and settlement patterns showed no spatiotemporal relationships with Nearctic–Neotropical migration, remained in accordance with the flood pulse of the Amazon basin, and were spatially and temporally complex suggesting relatively ancient ancestral origins. The ability to isolate the migration event from Nearctic–Neotropical migration is an important contribution to the ongoing discourse regarding the evolution of trans-hemispheric migration in the genus Catharus.

Warm Springs, Early Lay Dates, and Double Brooding in a North American Migratory Songbird, the Black-Throated Blue Warbler

Numerous studies have correlated the advancement of lay date in birds with warming climate trends, yet the fitness effects associated with this phenological response have been examined in only a small number of species. Most of these species–primarily insectivorous cavity nesters in Europe–exhibit fitness declines associated with increasing asynchrony with prey. Here, we use 25 years of demographic data, collected from 1986 to 2010, to examine the effects of spring temperature on breeding initiation date, double brooding, and annual fecundity in a Nearctic - Neotropical migratory songbird, the black-throated blue warbler (Setophaga caerulescens). Data were collected from birds breeding at the Hubbard Brook Experimental Forest, New Hampshire, USA, where long-term trends toward warmer springs have been recorded. We found that black-throated blue warblers initiated breeding earlier in warmer springs, that early breeders were more likely to attempt a second brood than those starting later in the season, and that double brooding and lay date were linked to higher annual fecundity. Accordingly, we found selection favored earlier breeding in most years. However, in contrast to studies of several other long-distance migratory species in Europe, this selection pressure was not stronger in warmer springs, indicating that these warblers were able to adjust mean lay date appropriately to substantial inter-annual variation in spring temperature. Our results suggest that this North American migratory songbird might not experience the same fecundity declines as songbirds that are unable to adjust their timing of breeding in pace with spring temperatures.

A Winter Distribution Model for Bicknell’s Thrush (Catharus bicknelli), a Conservation Tool for a Threatened Migratory Songbird

Conservation planning and implementation require identifying pertinent habitats and locations where protection and management may improve viability of targeted species. The winter range of Bicknell’s Thrush (Catharus bicknelli), a threatened Nearctic-Neotropical migratory songbird, is restricted to the Greater Antilles. We analyzed winter records from the mid-1970s to 2009 to quantitatively evaluate winter distribution and habitat selection. Additionally, we conducted targeted surveys in Jamaica (n = 433), Cuba (n = 363), Dominican Republic (n = 1,000), Haiti (n = 131) and Puerto Rico (n = 242) yielding 179 sites with thrush presence. We modeled Bicknell’s Thrush winter habitat selection and distribution in the Greater Antilles in Maxent version 3.3.1. using environmental predictors represented in 30 arc second study area rasters. These included nine landform, land cover and climatic variables that were thought a priori to have potentially high predictive power. We used the average training gain from ten model runs to select the best subset of predictors. Total winter precipitation, aspect and land cover, particularly broadleaf forests, emerged as important variables. A five-variable model that contained land cover, winter precipitation, aspect, slope, and elevation was the most parsimonious and not significantly different than the models with more variables. We used the best fitting model to depict potential winter habitat. Using the 10 percentile threshold (>0.25), we estimated winter habitat to cover 33,170 km2, nearly 10% of the study area. The Dominican Republic contained half of all potential habitat (51%), followed by Cuba (15.1%), Jamaica (13.5%), Haiti (10.6%), and Puerto Rico (9.9%). Nearly one-third of the range was found to be in protected areas. By providing the first detailed predictive map of Bicknell’s Thrush winter distribution, our study provides a useful tool to prioritize and direct conservation planning for this and other wet, broadleaf forest specialists in the Greater Antilles.

Distribution and abundance of nearctic–neotropical songbird migrants in a forest restoration site in southern Costa Rica

Many ecological relationships that are inherently reciprocal are often studied from one perspective only (Agrawal et al. 2007). One example is the interaction between tropical forests and nearctic-neotropical migratory songbirds (hereafter migrants). Several studies have determined that some migrant populations are limited by conditions at their tropical wintering grounds in Central America, South America and the Caribbean (Marra et al. 1998, Mills 2006); however, the ecological role of migrants in these tropical forests is poorly understood.