Understanding patterns of plant population mortality during extreme weather events is important to conservation planners because the frequency of such events is expected to increase, creating the need to integrate climatic uncertainty into management. Dominant plants provide habitat and ecosystem structure, so changes in their distribution

No abstract

Neotropic migratory birds are declining across the Western Hemisphere, but conservation efforts have been hampered by the inability to assess where migrants are most limited-the breeding grounds, migratory stopover sites or wintering areas. A major challenge has been the lack of an efficient, reliable and broadly applicable method for measuring the strength of migratory connections between populations across the annual cycle. Here, we show how high-resolution genetic markers can be used to identify genetically distinct groups of a migratory bird, the Wilson's warbler (Cardellina pusilla), at fine enough spatial scales to facilitate assessing regional drivers of demographic trends. By screening 1626 samples using 96 highly divergent single nucleotide polymorphisms selected from a large pool of candidates (~450 000), we identify novel region-specific migratory routes and timetables of migration along the Pacific Flyway. Our results illustrate that high-resolution genetic markers are more reliable, precise and amenable to high throughput screening than previously described intrinsic marking techniques, making them broadly applicable to large-scale monitoring and conservation of migratory organisms.

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 poorquality 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.