Analysis of a 60 km segment of the Alaskan Beaufort Sea coast using a time‐series of aerial photography revealed that mean annual erosion rates increased from 6.8 m a−1 (1955 to 1979), to 8.7 m a−1 (1979 to 2002), to 13.6 m a−1 (2002 to 2007). We also observed that spatial patterns of erosion have become more uniform across shoreline types with different degrees of ice‐richness. Further, during the remainder of the 2007 ice‐free season 25 m of erosion occurred locally, in the absence of a westerly storm event. Concurrent arctic changes potentially responsible for this shift in the rate and pattern of land loss include declining sea ice extent, increasing summertime sea surface temperature, rising sea‐level, and increases in storm power and corresponding wave action. Taken together, these factors may be leading to a new regime of ocean‐land interactions that are repositioning and reshaping the Arctic coastline.
We studied relationships between body size of female Black Brant goslings (Branta bernicla nigricans) late in their growth period and first year survival, eventual adult body size, breeding propensity, and size and volume of clutches they eventually produced to examine the relationship between growth and fitness in this population. We indexed body size by calculating PC1 scores based on either culmen and tarsus, or culmen, tarsus, and mass. Gosling (PC scores based on culmen and tarsus) size was positively correlated with resighting rate (P = 0.005), indicating that larger goslings survived at a higher rate than did smaller goslings. Gosling size was correlated with adult size of the same individuals (P = 0.0004). Larger goslings were more likely to breed as 2— or 3—yr—olds than were medium or small goslings (P = 0.008). Larger adult brant laid more eggs (P = 0.03) and produced clutches with greater total volume (P = 0.03) than did smaller brant. Given the important role of foraging environment in growth of goslings, these data suggest an important role of early environment in determining life—history traits.
The role of migratory birds in the movement of the highly pathogenic (HP) avian influenza H5N1 remains a subject of debate. Testing hypotheses regarding intercontinental movement of low pathogenic avian influenza (LPAI) viruses will help evaluate the potential that wild birds could carry Asian-origin strains of HP avian influenza to North America during migration. Previous North American assessments of LPAI genetic variation have found few Asian reassortment events. Here, we present results from whole-genome analyses of LPAI isolates collected in Alaska from the northern pintail (Anas acuta), a species that migrates between North America and Asia. Phylogenetic analyses confirmed the genetic divergence between Asian and North American strains of LPAI, but also suggested inter-continental virus exchange and at a higher frequency than previously documented. In 38 isolates from Alaska, nearly half (44.7%) had at least one gene segment more closely related to Asian than to North American strains of LPAI. Additionally, sequences of several Asian LPAI isolates from GenBank clustered more closely with North American northern pintail isolates than with other Asian origin viruses. Our data support the role of wild birds in the intercontinental transfer of influenza viruses, and reveal a higher degree of transfer in Alaska than elsewhere in North America.
Background: The global spread of the highly pathogenic avian influenza H5N1 virus has stimulated interest in a better understanding of the mechanisms of H5N1 dispersal, including the potential role of migratory birds as carriers. Although wild birds have been found dead during H5N1 outbreaks, evidence suggests that others have survived natural infections, and recent studies have shown several species of ducks capable of surviving experimental inoculations of H5N1 and shedding virus. To investigate the possibility of migratory birds as a means of H5N1 dispersal into North America, we monitored for the virus in a surveillance program based on the risk that wild birds may carry the virus from Asia.
Condition indices are commonly used in an attempt to link body condition of birds to ecological variables of interest, including demographic attributes such as survival and reproduction. Most indices are based on body mass adjusted for structural body size, calculated as simple ratios or residuals from regressions. However, condition indices are often applied without confirming their predictive value (i.e., without being validated against measured values of fat and protein), which we term 'unverified' use. We evaluated the ability of a number of unverified indices frequently found in the literature to predict absolute and proportional levels of fat and protein across five species of waterfowl. Among indices we considered, those accounting for body size never predicted absolute protein more precisely than body mass, however, some indices improved predictability of fat, although the form of the best index varied by species. Further, the gain in precision by using a condition index to predict either absolute or percent fat was minimal (rise in r 2 50.13), and in many cases model fit was actually reduced. Our data agrees with previous assertions that the assumption that indices provide more precise indicators of body condition than body mass alone is often invalid. We strongly discourage the use of unverified indices, because subjectively selecting indices likely does little to improve precision and might in fact decrease predictability relative to using body mass alone.
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