Landbird Migration in the American West: Recent Progress and Future Research Directions

Our knowledge of avian behaviors during the non-breeding period still lags behind that of the breeding season, but the last decade has witnessed a proliferation in research that has yielded significant progress in understanding migration patterns of North American birds. And, although the great majority of migration research has historically been conducted in the eastern half of the continent, there has been much recent progress on aspects of avian migration in the West. In particular, expanded use of techniques such as radar, plasma metabolites, mist-netting, count surveys, stable isotopes, genetic data, and animal tracking, coupled with an increase in multi-investigator collaborations, have all contributed to this growth of knowledge. There is increasing recognition that migration is likely the most limiting time of year for migratory birds, and this places increasing importance on continuing to decipher patterns of stopover ecology, identifying critical stopover habitats, and documenting migration routes in the diverse and changing landscapes of the American West. Here, we review and briefly synthesize the latest avian migration findings and advances and consider research needs to guide future research on migration in the West

Lenalidomide in combination with dexamethasone at first relapse in comparison with its use as later salvage therapy in relapsed or refractory multiple myeloma

This subset analysis of data from two phase III studies in patients with relapsed or refractory multiple myeloma (MM) evaluated the benefit of initiating lenalidomide plus dexamethasone at first relapse. Multivariate analysis showed that fewer prior therapies, along with β2-microglobulin (≤2.5 mg/L), predicted a better time to progression (TTP; study end-point) with lenalidomide plus dexamethasone treatment. Patients with one prior therapy showed a significant improvement in benefit after first relapse compared with those who received two or more therapies. Patients with one prior therapy had significantly prolonged median TTP (17.1 vs. 10.6 months; P=0.026) and progression-free survival (14.1 vs. 9.5 months, P=0.047) compared with patients treated in later lines. Overall response rates were higher (66.9% vs. 56.8%, P=0.06), and the complete response plus very good partial response rate was significantly higher in first relapse (39.8% vs. 27.7%, P=0.025). Importantly, overall survival was significantly prolonged for patients treated with lenalidomide plus dexamethasone with one prior therapy, compared with patients treated later in salvage (median of 42.0 vs. 35.8 months, P=0.041), with no differences in toxicity, dose reductions, or discontinuations despite longer treatment. Therefore, lenalidomide plus dexamethasone is both effective and tolerable for second-line MM therapy and the data suggest that the greatest benefit occurs with earlier use

Data from: Carry-over effects of winter habitat quality on en route timing and condition of a migratory passerine during spring migration

We examined how conditions prior to migration influenced migration performance of two breeding populations of black-and-white warblers (Mniotilta varia) by linking information on the migrant's winter habitat quality, measured via stable carbon isotopes, with information on their breeding destination, measured via stable hydrogen isotopes. The quality of winter habitat strongly influenced the timing of migration when we accounted for differential timing of migration between breeding populations. Among birds migrating to the same breeding destination, males and females arriving early to the stopover site originated from more mesic habitat than later arriving birds, suggesting that the benefits of occupying high-quality mesic habitat during the winter positively influence the timing of migration. However, male warblers arriving early to the stopover site were not in better migratory condition than later arriving conspecifics that originated from poor-quality xeric winter habitat, regardless of breeding destination. The two breeding populations stopover at the study site during different time periods, suggesting that the lower migratory condition of early birds is not a function of the time of season, but potentially a migrant's migration strategy. Strong selection pressures to arrive early on the breeding grounds to secure high-quality breeding territories may drive males from high-quality winter habitat to minimize time at the expense of energy. This migration strategy would result in a smaller margin of safety to buffer the effects of adverse weather or scarcity of food, increasing the risk of mortality. The migratory condition of females was the same regardless of the timing of migration or breeding destination, suggesting that females adopt a strategy that conserves energy during migration. This study fills an important gap in our understanding of the linkages between winter habitat quality and factors that influence the performance of migration, the phase of the annual cycle thought to be limiting most migratory bird populations

Data from: Connecting the dots: Stopover strategies of an intercontinental migratory songbird in the context of the annual cycle

The phases of the annual cycle for migratory species are inextricably linked. Yet, less than five percent of ecological studies examine seasonal interactions. In this study, we utilized stable hydrogen isotopes to geographically link individual black-and-white warblers (Mniotilta varia) captured during spring migration with breeding destinations to understand a migrant's stopover strategy in the context of other phases of the annual cycle. We found that stopover strategy is not only a function of a bird's current energetic state, but also the distance remaining to breeding destination and a bird's time-schedule, which has previously been linked to habitat conditions experienced in the preceding phase of the annual cycle. Birds in close proximity to their breeding destination accumulate additional energy reserves prior to arrival on the breeding grounds, as reflected by higher migratory condition upon arrival, higher refueling rates measured via blood plasma metabolites, and longer stopover durations compared to birds migrating to breeding destinations farther from the stopover site. However, late birds near their breeding destination were more likely to depart on the day of arrival (i.e., transients), and among birds that stopped over at the site, the average duration of stopover was almost half the time of early conspecifics, suggesting late birds are trying to catch-up with the overall time-schedule of migration for optimal arrival time on the breeding grounds. In contrast, birds with long distances remaining to breeding destinations were more likely to depart on the day of arrival and primarily used stopover to rest before quickly resuming migration, adopting similar strategies regardless of a bird's time-schedule. Our study demonstrates that migrants adjust their en route strategies in relation to their time-schedule and distance remaining to their breeding destination, highlighting that strategies of migration should be examined in the context of other phases of the annual cycle

BAWW Data Set

Data was collected in the field. BirdID is the unique identifier of each black-and-white warbler that was sampled during the study. The study was conducted over 4 years (y1=2008, y2=2009, y3=2010, y4=2011). A bird's breeding destination (North=boreal forest of Canada, South=southeastern U.S.) is based on stable hydrogen isotope values of a bird's tail feather. The timing of migration (Early, Mid, Late) for each individual is based on the range of capture dates for each sex in a given breeding destination and in a given year. Blood plasma metabolite concentrations of triglycerides (TRIG) and β-hydroxy-butyrate (BOH) were collected via brachial vein puncture. A Principal Component Analysis was conducted on plasma metabolite levels and the 1st principal component axis (PC1) was used as a measure of refueling with positive values representing increasing TRIG levels and decreasing BOH levels. The time between blood sampling and sunrise (Day.Time) and capture time (Bleed.Time) were recorded to determine their influence on blood plasma metabolite values. Only a subset of birds captured had TRIG and BOH measurements and therefore some fields indicate NA because plasma metabolite data was not included in analyses. Stopover duration estimates (Stopover) were calculated with program MARK. Condition is a size-specific condition index value. Age and sex of the warbler are also included

Stable isotope analysis of multiple tissues from Hawaiian honeycreepers indicates elevational movement.

We have limited knowledge of the patterns, causes, and prevalence of elevational migration despite observations of seasonal movements of animals along elevational gradients in montane systems worldwide. While a third of extant Hawaiian landbird species are estimated to be elevational migrants this assumption is based primarily on early naturalist's observations with limited empirical evidence. In this study, we compared stable hydrogen isotopes (δ2H) of metabolically inert (feathers) and active (blood plasma, red blood cells) tissues collected from the same individual to determine if present day populations of Hawaiian honeycreepers undergo elevational movements to track areas of seasonally high flower bloom that constitute significant food resources. We also measured stable carbon isotopes (δ13C) and stable nitrogen isotopes (δ15N) to examine potential changes in diet between time periods. We found that the majority of 'apapane (Himatione sanguinea) and Hawai'i 'amakihi (Chlorodrepanis virens) captured at high elevation, high bloom flowering sites in the fall were not year-round residents at the capture locations, but had molted their feathers at lower elevations presumably in the summer after breeding. δ2H values of feathers for all individuals sampled were higher than blood plasma isotope values after accounting for differences in tissue-specific discrimination. We did not find a difference in the propensity of elevational movement between 'apapane and Hawai'i 'amakihi, even though the 'amakihi is considered more sedentary. However, consistent with a more generalist diet, δ15N values indicated that Hawai'i 'amakihi had a more diverse diet across trophic levels than 'apapane, and a greater reliance on nectar in the fall. We demonstrate that collecting multiple tissue samples, which grow at different rates or time periods, from a single individual can provide insights into elevational movements of Hawaiian honeycreepers over an extended time period

all analyses

Data collected in the field. Subject is the unique identifier of each black-and-white warbler that was sampled during the study. The study was conducted over 4 years (y1=2008, y2=2009, y3=2010, y4=2011). Breeding (N=boreal forest, S=southeast) is based on stable hydrogen isotope values. Timing (E=Early, M=middle, L=Late) is based on the range of capture dates for each sex in a given breeding destination and in a given year. rbc represents the stable carbon isotope value based on red blood cells collected from brachial vein puncture. Cond is a size-specific condition index value. Age and sex of the warbler

El Niño-Southern Oscillation Is Linked to Decreased Energetic Condition in Long-Distance Migrants

Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases. We utilized a 17-year migration dataset to examine how El Niño-Southern Oscillation climatic events in geographically different regions of the Western hemisphere carry-over to impact the stopover biology of several intercontinental migratory bird species. We found that migratory birds that over-wintered in South America experienced significantly drier environments during El Niño years, as reflected by reduced Normalized Difference Vegetation Index (NDVI) values, and arrived at stopover sites in reduced energetic condition during spring migration. During El Niño years migrants were also more likely to stopover immediately along the northern Gulf coast of the southeastern U.S. after crossing the Gulf of Mexico in small suboptimal forest patches where food resources are lower and migrant density often greater than larger more contiguous forests further inland. In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas. Birds over-wintering in both regions had consistent median arrival dates along the northern Gulf coast, suggesting that there is a strong drive for birds to maintain their time program regardless of their overall condition. We provide strong evidence that not only is the stopover biology of migratory landbirds influenced by events during the previous phase of their life-cycle, but where migratory birds over-winter determines how vulnerable they are to global climatic cycles. Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in South America