Research666 the probability that our method missed peaks (spatial: 0.12, temporal: 0.18) or detected false peaks (spatial: 0.11, temporal: 0.37) due to data gaps and showed that our approach remains useful even for sparse and/or sporadic location data. Our study presents a generalizable approach to evaluating migratory connectivity across the full annual cycle that can be used to focus migratory bird conservation towards places and times of the annual cycle where populations are more likely to be limited.
Wildfire is an important disturbance regime that can structure wildlife communities and their habitats for many years. Using a before-after-control-impact framework, we evaluated the effect of the Quartz Fire on a mixed broadleafconifer forest and associated bird community in southwestern Oregon, USA, over 10 yr. To assess whether fire severity explained changes better than simply whether an area was burned, we used a tiered sampling approach by comparing unburned control points with either all burned points combined (burned) or those same points partitioned by severity level (low, moderate, high). As expected, overall tree cover decreased while cover of shrubs increased in response to greater fire severity. This pattern was most pronounced in high-severity areas, where tree cover declined by 40% and remained depressed, but shrub cover recovered from 10% the year following fire to 75% by year 6. Ordinations of bird species density showed turnover in community composition in all burned areas combined, as well as in moderateseverity areas, shifting to a shrub-associated community 9 yr postfire. For individual species, annual density variations were best explained by fire for 14 of 37 species, with fire severity providing the best-fitting model for 7 species. Of those 7 species, 3 declined and 4 increased with greater severity. When grouped into guilds, flycatching foragers and shrub nesters increased with greater fire severity. Our results illustrate the importance of mixed-severity wildfire in creating diverse vegetation structure and composition that supports distinct bird communities for at least a decade following fire.
Migratory species employ a variety of strategies to meet energetic demands of postbreeding molt. As such, at least a few species of western Neotropical migrants are known to undergo short‐distance upslope movements to locations where adults molt body and flight feathers (altitudinal molt migration). Given inherent difficulties in measuring subtle movements of birds occurring in western mountains, we believe that altitudinal molt migration may be a common yet poorly documented phenomenon. To examine prevalence of altitudinal molt migration, we used 29 years of bird capture data in a series of linear mixed‐effect models for nine commonly captured species that breed in northern California and southern Oregon. Candidate models were formulated a priori to examine whether elevation and distance from the coast can be used to predict abundance of breeding and molting birds. Our results suggest that long‐distance migrants such as Orange‐crowned Warbler (Oreothlypis celata) moved higher in elevation and Audubon's Warbler (Setophaga coronata) moved farther inland to molt after breeding. Conversely, for resident and short‐distance migrants, we found evidence that birds either remained on the breeding grounds until they finished molting, such as Song Sparrow (Melospiza melodia) or made small downslope movements, such as American Robin (Turdus migratorius). We conclude that altitudinal molt migration may be a common, variable, and complex behavior among western songbird communities and is related to other aspects of a species’ natural history, such as migratory strategy.
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