Stopover On Galapagos During Autumn Migration Of Bobolinks (Dolichonyx Oryzivorus)

The Bobolink (Dolichonyx oryzivorus) is the only landbird species that is known to stop every year in Galapagos while migrating; however, its stopover ecology while on the islands is unknown. In October 2015, we searched for and captured Bobolinks in the highlands of San Cristóbal. We found Bobolinks in two fields, separated by 9.15 km, at ∼425 m elevation. Average daily counts of Bobolinks on these two fields were 3.2 ± 1.8 and 4.8 ± 2.3 individuals. We caught nine individuals; body mass and fat reserves varied from 22.5–40.0 g and no fat reserves to 50–100% reserves, respectively. Both fields were dominated by grasses ranging in height from 30 cm to \u3e100 cm, and included purple cuphea (Cuphea sp.). Other habitats we surveyed, where we did not observe Bobolinks, included closely cropped grass (5–10 cm), taller grasses with seed and with scattered to dense guava trees (Psidium guajava), and small (0.1–0.3 ha) corn plantations with seed. Six of the birds we caught had seeds of Drymaria cordata entwined in their feathers; while native to the Galapagos, this plant is highly invasive in other parts of the world

Migration Tactics Of A Long-Distance Migratory Songbird From Across A Continental Breeding Range

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

Haemosporidian Parasite Community In Migrating Bobolinks On The Galapagos Islands

Bobolinks (Dolichonyx oryzivorus) migrate from their breeding grounds in North America to their wintering grounds in South America during the fall each year. A small number of Bobolinks stop temporarily in Galapagos, and potentially carry parasites. On the North American breeding grounds, Bobolinks carry a least two of the four Plasmodium lineages recently detected in resident Galapagos birds. We hypothesized that Bobolinks carried these parasites to Galapagos, where they were bitten by mosquitoes that then transmitted the parasites to resident birds. The haemosporidian parasite community in 44% of the Bobolinks we captured was consistent with those on their breeding grounds. However, the lineages were not those found in Galapagos birds. Our results provide a parasite community key for future monitoring

Bobolink (Dolichonyx Oryzivorus)

Bobolink (Dolichonyx oryzivorus) Order:PASSERIFORMES Family: ICTERIDAE Includes the following information: Introduction, Appearance, Systematics, Distribution, Migration and Habitat, Diet and Foraging, Sounds and Vocal Behavior, Behavior, Breeding, Demography and Populations, Conservation and Management, Priorities for Future Research, Acknowledgments, About the Author(s), Multimedia, Tables and Appendices, Reference

Local Parasite Lineage Sharing In Temperate Grassland Birds Provides Clues About Potential Origins Of Galapagos Avian Plasmodium

Oceanic archipelagos are vulnerable to natural introduction of parasites via migratory birds. Our aim was to characterize the geographic origins of two Plasmodium parasite lineages detected in the Galapagos Islands and in North American breeding bobolinks (Dolichonyx oryzivorus) that regularly stop in Galapagos during migration to their South American overwintering sites. We used samples from a grassland breeding bird assemblage in Nebraska, United States, and parasite DNA sequences from the Galapagos Islands, Ecuador, to compare to global data in a DNA sequence registry. Homologous DNA sequences from parasites detected in bobolinks and more sedentary birds (e.g., brown-headed cowbirds Molothrus ater, and other co-occurring bird species resident on the North American breeding grounds) were compared to those recovered in previous studies from global sites. One parasite lineage that matched between Galapagos birds and the migratory bobolink, Plasmodium lineage B, was the most common lineage detected in the global MalAvi database, matching 49 sequences from unique host/site combinations, 41 of which were of South American origin. We did not detect lineage B in brown-headed cowbirds. The other Galapagos-bobolink match, Plasmodium lineage C, was identical to two other sequences from birds sampled in California. We detected a close variant of lineage C in brown-headed cowbirds. Taken together, this pattern suggests that bobolinks became infected with lineage B on the South American end of their migratory range, and with lineage C on the North American breeding grounds. Overall, we detected more parasite lineages in bobolinks than in cowbirds. Galapagos Plasmodium had similar host breadth compared to the non-Galapagos haemosporidian lineages detected in bobolinks, brown-headed cowbirds, and other grassland species. This study highlights the utility of global haemosporidian data in the context of migratory bird–parasite connectivity. It is possible that migratory bobolinks bring parasites to the Galapagos and that these parasites originate from different biogeographic regions representing both their breeding and overwintering sites

North American Breeding Bird Survey Underestimates Regional Bird Richness Compared to Breeding Bird Atlases

Standardized data on large-scale and long-term patterns of species richness are critical for understanding the consequences of natural and anthropogenic changes in the environment. The North American Breeding Bird Survey (BBS) is one of the largest and most widely used sources of such data, but so far, little is known about the degree to which BBS data provide accurate estimates of regional richness. Here, we test this question by comparing estimates of regional richness based on BBS data with spatially and temporally matched estimates based on state Breeding Bird Atlases (BBA). We expected that estimates based on BBA data would provide a more complete (and therefore, more accurate) representation of regional richness due to their larger number of observation units and higher sampling effort within the observation units. Our results were only partially consistent with these predictions: while estimates of regional richness based on BBA data were higher than those based on BBS data, estimates of local richness (number of species per observation unit) were higher in BBS data. The latter result is attributed to higher land-cover heterogeneity in BBS units and higher effectiveness of bird detection (more species are detected per unit time). Interestingly, estimates of regional richness based on BBA blocks were higher than those based on BBS data even when differences in the number of observation units were controlled for. Our analysis indicates that this difference was due to higher compositional turnover between BBA units, probably due to larger differences in habitat conditions between BBA units and a higher likelihood of observing geographically restricted species. Our overall results indicate that estimates of regional richness based on BBS data suffer from incomplete detection of a large number of rare species, and that corrections of these estimates based on standard extrapolation techniques are not sufficient to remove this bias. Future applications of BBS data in ecology and conservation, and in particular, applications in which the representation of rare species is important (e.g., those focusing on biodiversity conservation), should be aware of this bias, and should integrate BBA data whenever possible

An Interspecific Foraging Association Between Nearctic-Neotropical Migrant Passerines in Bolivia

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