ArticlePublisher preview available

Exposure to risk factors experienced during migration is not associated with recent Vermivora warbler population trends

To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

Context Understanding the factors limiting populations of animals is critical for effective conservation. Determining which factors limit populations of migratory species can be especially challenging because of their reliance on multiple, often geographically distant regions during their annual cycles. Objectives We investigated whether distribution-wide variation in recent breeding population trends was more strongly associated with exposure to risk factors experienced during migration (i.e., natural and anthropogenic threats often associated with increased mortality or carry-over effects) or factors associated with breeding and nonbreeding areas in golden-winged warblers (Vermivora chrysoptera) and blue-winged warblers (V. cyanoptera), two Nearctic-Neotropical migrants experiencing regionally variable population trends. Methods We used geolocator data from 85 Vermivora warblers (n = 90 geolocator tracks) tracked from North American breeding locations and Central American nonbreeding locations from 2013 to 2017 to determine variation in space use among populations. We assessed whether differences in space use among populations of Vermivora warblers during migration were associated with exposure to migration risk-factors and whether increased relative exposure to migration risk factors was associated with population declines at regional and subregional scales. Results Regional and subregional populations of Vermivora warblers exhibited variation in space use and exposure to anthropogenic and natural risk-factors. However, we found no evidence that recent variation in population trends of Vermivora warblers was associated with risk-factors experienced by different populations during migration. Instead, factors associated with land cover-types in breeding and nonbreeding areas were more strongly associated with recent population trends. Conclusions Understanding how populations of migratory birds are affected by factors experienced during migration is critical for their conservation. We did not find evidence that variation in exposure to migration risk-factors is associated with recent regional or subregional variation in Vermivora warbler population trends. Consequently, our results suggest that efforts to reverse ongoing population declines of Vermivora warblers may be more effective if directed toward conservation actions targeting limiting factors within the breeding and nonbreeding periods versus those directed at conditions encountered during migration. We caution that geographic variation in projected land-use change may differentially affect areas used by different populations of Vermivora warblers during migration, posing a potential threat to these species in the future.
A Regional population-specific core-use areas (25th percentile) of Vermivora warblers during autumn and spring migration. Blue-winged warblers and golden-winged warblers from breeding sites (triangles) associated with different Bird Conservation Regions (BCRs) are represented by different colors. Geolocator-derived nonbreeding and breeding location estimates are identified by × ’s and + ’s, respectively and colored according to breeding population (i.e., BCR). B The spatial distribution of the mean-adjusted cumulative exposure to migration risk-factors represents the sum of standardized rasters of eight migration risk-factors considered in our analyses. Red cells indicate areas with above-average exposure to migration risk-factors whereas blue cells are associated with below-average exposure. Boxplot shows the scaled exposure of different regional populations (based on the exposure of individuals tracked within each population; colors correspond with the A) of Vermivora warblers to the mean-adjusted cumulative exposure to migration risk factors. Populations that experienced different levels of exposure (based on one-way ANOVA and Tukey HSD; P < 0.05) are denoted with letters. Values inside boxes indicate regional population trend estimates from the Breeding Bird Survey (BBS) for 2000–2015 (BBS Regional Trend Analysis Form). Asterisks specify population trends with 95% confidence intervals that do not overlap zero. Regional populations are defined by BCR and species (blue-winged warbler [BW] or golden-winged warbler [GW]) in boxplot legend: Prairie Hardwood Transition BCR (BW PHT, teal), Central Hardwoods BCR (BW CH, pink), Appalachian Mountains BCR (BW AM, light orange; GW AM, dark orange), and Boreal Hardwood Transition (GW BHT; maroon) BCR
This content is subject to copyright. Terms and conditions apply.
Vol.: (0123456789)
1 3
Landsc Ecol (2023) 38:2357–2380
Exposure torisk factors experienced duringmigration
isnotassociated withrecent Vermivora warbler population
GunnarR.Kramer· DavidE.Andersen· DavidA.Buehler· PetraB.Wood· SeanM.Peterson·
JustinA.Lehman· KyleR.Aldinger· LesleyP.Bulluck· SergioHarding· JohnA.Jones·
JohnP.Loegering· CurtisSmalling· RachelVallender· HenryM.Streby
Received: 25 October 2022 / Accepted: 4 June 2023 / Published online: 21 June 2023
© The Author(s), under exclusive licence to Springer Nature B.V. 2023
Context Understanding the factors limiting popu-
lations of animals is critical for effective conserva-
tion. Determining which factors limit populations
of migratory species can be especially challenging
because of their reliance on multiple, often geograph-
ically distant regions during their annual cycles.
Objectives We investigated whether distribution-
wide variation in recent breeding population trends
was more strongly associated with exposure to risk
factors experienced during migration (i.e., natu-
ral and anthropogenic threats often associated with
increased mortality or carry-over effects) or fac-
tors associated with breeding and nonbreeding areas
in golden-winged warblers (Vermivora chrysop-
tera) and blue-winged warblers (V. cyanoptera), two
Supplementary Information The online version
contains supplementary material available at https:// doi.
org/ 10. 1007/ s10980- 023- 01701-2.
G.R.Kramer(*)· H.M.Streby
Department ofEnvironmental Sciences, University
ofToledo, Toledo, OH43606, USA
Present Address:
Department ofOrganismic andEvolutionary Biology,
Harvard University, 26 Oxford Street, Cambridge,
MA02138, USA
U.S. Geological Survey, Minnesota Cooperative Fish
andWildlife Research Unit, University ofMinnesota,
St.Paul, MN55108, USA
D.A.Buehler· J.A.Lehman
Department ofForestry, Wildlife andFisheries, University
ofTennessee, Knoxville, TN37996, USA
U.S. Geological Survey, West Virginia Cooperative Fish
andWildlife Research Unit, West Virginia University,
Morgantown, WV26506, USA
Department ofEnvironmental Science, Policy,
andManagement, University ofCalifornia, Berkeley,
CA94720, USA
West Virginia Cooperative Fish andWildlife Research
Unit, West Virginia University, Morgantown, WV26506,
Center forEnvironmental Studies, Virginia
Commonwealth University, Richmond, VA23284, USA
Virginia Department ofWildlife Resources, Henrico,
VA23228, USA
Department ofEcology andEvolutionary Biology, Tulane
University, NewOrleans, LA70118, USA
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
ResearchGate has not been able to resolve any citations for this publication.
Full-text available
We present comments on an article published by Confer et al. (Ecology and Evolution, 10, 2020). Confer et al. (2020) aggregate data from multiple studies of social pairing between Vermivora chrysoptera and V. cyanoptera, two wood warblers in the family Parulidae that hybridize extensively where they co‐occur. From analysis of these data, they conclude there is near‐complete reproductive isolation between these two species. In our reply, we show that this finding is not supported by other lines of evidence, and significant drawbacks of their study design preclude such strong conclusions. In our critique, we show that (a) coarse‐scale plumage classifications cannot be used to accurately estimate hybrid ancestry in Vermivora; (b) extra‐pair paternity is very high in Vermivora and is likely facilitating hybridization, yet was not considered by Confer et al. (2020), and we suggest this will have a substantial influence on the interpretation of reproductive isolation in the system; and (c) the central finding of strong total reproductive isolation is not compatible with the results of other long‐term studies, which demonstrate low isolation and high gene flow. We conclude with a more comprehensive interpretation of hybridization and reproductive isolation in Vermivora warblers. Vermivora warblers—golden‐winged and blue‐winged warblers—hybridize extensively where they co‐occur. We discuss concerns regarding recent suggestions that this extensive hybridization takes place in the face of near complete pre‐mating isolation, which we suggest is not consistent with other data.
Full-text available
Archival geolocators have transformed the study of small, migratory organisms but analysis of data from these devices requires bias correction because tags are only recovered from individuals that survive and are re-captured at their tagging location. We show that integrating geolocator recovery data and mark–resight data enables unbiased estimates of both migratory connectivity between breeding and nonbreeding populations and region-specific survival probabilities for wintering locations. Using simulations, we first demonstrate that an integrated Bayesian model returns unbiased estimates of transition probabilities between seasonal ranges. We also used simulations to determine how different sampling designs influence the estimability of transition probabilities. We then parameterized the model with tracking data and mark–resight data from declining Painted Bunting (Passerina ciris) populations breeding in the eastern United States, hypothesized to be threatened by the illegal pet trade in parts of their Caribbean, nonbreeding range. Consistent with this hypothesis, we found that male buntings wintering in Cuba were 20% less likely to return to the breeding grounds than birds wintering elsewhere in their range. Improving inferences from archival tags through proper data collection and further development of integrated models will advance our understanding of the full annual cycle ecology of migratory species.
Full-text available
Extensive, severe wildfires, and wildfire-induced smoke occurred across the western and central United States since August 2020. Wildfires resulting in the loss of habitats and emission of particulate matter and volatile organic compounds pose serious threatens to wildlife and human populations, especially for avian species, the respiratory system of which are sensitive to air pollutions. At the same time, the extreme weather (e.g., snowstorms) in late summer may also impact bird migration by cutting off their food supply and promoting their migration before they were physiologically ready. In this study, we investigated the environmental drivers of massive bird die-offs by combining socioecological earth observations data sets with citizen science observations. We employed the geographically weighted regression models to quantitatively evaluate the effects of different environmental and climatic drivers, including wildfire, air quality, extreme weather, drought, and land cover types, on the spatial pattern of migratory bird mortality across the western and central US during August-September 2020. We found that these drivers affected the death of migratory birds in different ways, among which air quality and distance to wildfire were two major drivers. Additionally, there were more bird mortality events found in urban areas and close to wildfire in early August. However, fewer bird deaths were detected closer to wildfires in California in late August and September. Our findings highlight the important impact of extreme weather and natural disasters on bird biology, survival, and migration, which can provide significant insights into bird biodiversity, conservation, and ecosystem sustainability.
Full-text available
Cerulean Warblers ( Setophaga cerulea ) are among the fastest declining Nearctic-Neotropical migrant wood-warblers (Parulidae) in North America. Despite ongoing conservation efforts, little is known about their non-breeding distribution. In June 2016-2018, we deployed geolocators ( n = 30) on adult male Cerulean Warblers in Indiana, USA, to track annual movements of individuals. Recovered geolocators ( n = 4) showed that Cerulean Warblers occurred broadly throughout northern South America. Autumn migration lasted 44-71 days ( n = 4), whereas spring migration lasted 37-41 days ( n = 3). The average migration distance was 5268 km. During autumn migration, Cerulean Warblers made 1-4 stopovers (i.e., ≥2 days; n = 4) and 1-2 stopovers during spring migration ( n = 3). When crossing the Gulf of Mexico during autumn migration, two birds stopped over after crossing, but not beforehand. Two others navigated through the Caribbean rather than crossing the Gulf of Mexico. During spring migration, one individual stopped after crossing, one individual stopped before crossing, and one individual stopped before and after crossing the Gulf of Mexico. No birds migrated through the Caribbean Islands during spring migration. These results represent novel information describing annual movements of individual Cerulean Warblers and will inform conservation efforts for this declining species.
Hybrids with different combinations of traits can be used to identify genomic regions that underlie phenotypic characters important to species identity and recognition. Here, we explore links between genomic and plumage variation in Blue-winged Warbler x Golden-winged Warbler (Vermivora cyanoptera x V. chrysoptera) hybrids, which have traditionally been categorized into 2 discrete types. “Lawrence’s” hybrids are yellow overall, similar to Blue-winged Warblers, but exhibit the black throat patch and face mask of Golden-winged Warblers. “Brewster’s” hybrids are similar to Golden-winged Warblers, but lack the black throat patch and face mask, and sometimes have yellow on their underparts. Previous studies hypothesized that (1) first generation hybrids are of the Brewster’s type and can be distinguished by the amount of yellow on their underparts, and that (2) the throat patch/mask phenotype is consistent with Mendelian inheritance and controlled by variation in a locus near the Agouti-signaling protein (ASIP) gene. We addressed these hypotheses using whole genome re-sequencing of parental and hybrid individuals. We found that Brewster’s hybrids had genomic hybrid index scores indicating this phenotype can arise by majority ancestry from either parental species, that their plumage varied in levels of carotenoid pigmentation, and individuals captured in multiple years grew consistently less yellow over time. Variation in carotenoid pigmentation showed little relationship with genomic hybrid index score and is thus inconsistent with previous hypotheses that first generation hybrids can be distinguished by the amount of yellow in their plumage. Our results also confirm that variation near ASIP underlies the throat patch phenotype, which we refined to an ~10–15 Kb region upstream of the coding sequence. Overall, our results support the notion that traditional categorization of hybrids as either Lawrence’s or Brewster’s oversimplifies continuous variation in carotenoid pigmentation, and its inferred underlying genetic basis, and is based primarily on one discrete trait, which is the throat patch/mask phenotype.
Migration strategies in the avian world are often compared at the species level and evaluated relative to general ecology and constraints such as molting and breeding timetables. The advancement of tracking technology provides an opportunity to explore variation in more specific migration tactics within species and their populations as it relates to demographic and environmental factors throughout the annual cycle. We compare migration timing among 4 populations of Bobolink (Dolichonyx oryzivorus) from across the breeding range using data from light-level geolocators. The date of departure from the breeding grounds and the duration of southbound migration differed among breeding populations, and were more variable for eastern breeding populations compared to western populations farther from the main migration corridor. Despite variation in both timing and distance from the corridor among breeding populations, date of arrival at the major southbound stop in the Llanos of South America remained synchronous, but less so than previously described. Weekly flight distances were highly variable and did not differ among populations. Duration of northbound migration did not differ among populations and was half as long as the southbound migration. Our findings show Bobolink populations breeding near the species' relatively narrow migration corridor in the southeastern United States were more variable in terms of how they reached the first lengthy stop in the Llanos, suggesting more flexibility in migration tactics. Breeding locations were not associated, however, with the timing or duration of the remainder of their migratory schedule. Our findings support the hypothesis that food resources, both historical and present, drive and also modify the endogenous migration schedule of this flocking species with a split migration.
Male and female animals often segregate spatially among habitats and landscapes outside of breeding seasons, but it is unclear to what extent conservation efforts account for sexual segregation. Overlooking this phenomenon may result in conservation plans that don't meet the needs of both sexes, especially when resources or threats vary spatially. We assessed the prevalence of sexual segregation and degree to which current conservation efforts account for it with a review of nonbreeding ecology and conservation planning literature for 66 North American migratory landbirds of conservation concern. Sexual segregation was common in the group-reported for one-third of all species and two-thirds of those with published nonbreeding sex ratios-and did not differ with dimorphism or conservation status. Despite this, only 3% of species distribution models and 8% of conservation recommendations considered sexual segregation, indicating the pattern is widely overlooked. Next, we used the declining Golden-winged Warbler (Vermivora chrysoptera) as a case study to test for sex-bias in habitats prioritized by current conservation efforts. By modeling nonbreeding occupancy and forest cover loss for males and females, we show that females lost twice as much nonbreeding habitat as males from 2000 to 2016, yet existing conservation focal areas remain heavily biased towards male-dominated landscapes. Furthermore, female-dominated habitats face higher rates of conversion than male habitats for multiple species of Neotropical migrants, suggesting the failure to address sexual segregation may compromise the effectiveness of migratory landbird conservation. We recommend greater effort to report sex ratios and create sex-specific habitat assessments and distribution models.