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Southward Migration (southward + migration)
Selected AbstractsCauses and consequences of post-growth age-dependent differences in small intestine size in a migratory sandpiper (Calidris mauri, Western Sandpiper)FUNCTIONAL ECOLOGY, Issue 1 2006R. W. STEIN Summary 1Calidris mauri Cabanis (Western Sandpiper) exhibits a pronounced post-growth age-dependent difference in small intestine size during southward migration, such that the later-migrating juveniles have larger small intestines than do the adults. Potential causes and consequences of this age-dependent difference are examined. 2Premigrant juveniles of full structural size had small intestines that were 10% longer than those of the premigrant adults, even though the juveniles had not attained asymptotic body mass. The elongated small intestines of premigrant juveniles appear to be growth-related. 3Adults and juveniles exhibited parallel increases in intestinal length (7·0%) and circumference (9·5%) in association with the initiation of migration; these effects are consistent with migratory hyperphagia. 4Refuelling juveniles had small intestines that were 8·5% longer than those of the refuelling adults. Retaining an enlarged small intestine during migration confers increased digestive capacity to the juveniles, which may be under selection to minimize stopover duration. 5Refuelling juveniles had a higher prevalence of cestode infection than refuelling adults in one of two years, and the length-corrected mass of the small intestine was 9·7% heavier in infected individuals. Cestode infection may be an important determinant of migration-related mortality for juveniles, by compromising their health and increasing stopover duration. [source] Robust hierarchical state,space models reveal diel variation in travel rates of migrating leatherback turtlesJOURNAL OF ANIMAL ECOLOGY, Issue 5 2006IAN D. JONSEN Summary 1Biological and statistical complexity are features common to most ecological data that hinder our ability to extract meaningful patterns using conventional tools. Recent work on implementing modern statistical methods for analysis of such ecological data has focused primarily on population dynamics but other types of data, such as animal movement pathways obtained from satellite telemetry, can also benefit from the application of modern statistical tools. 2We develop a robust hierarchical state,space approach for analysis of multiple satellite telemetry pathways obtained via the Argos system. State,space models are time-series methods that allow unobserved states and biological parameters to be estimated from data observed with error. We show that the approach can reveal important patterns in complex, noisy data where conventional methods cannot. 3Using the largest Atlantic satellite telemetry data set for critically endangered leatherback turtles, we show that the diel pattern in travel rates of these turtles changes over different phases of their migratory cycle. While foraging in northern waters the turtles show similar travel rates during day and night, but on their southward migration to tropical waters travel rates are markedly faster during the day. These patterns are generally consistent with diving data, and may be related to changes in foraging behaviour. Interestingly, individuals that migrate southward to breed generally show higher daytime travel rates than individuals that migrate southward in a non-breeding year. 4Our approach is extremely flexible and can be applied to many ecological analyses that use complex, sequential data. [source] Use of wetlands at the mouth of the Yangtze River by shorebirds during spring and fall migrationJOURNAL OF FIELD ORNITHOLOGY, Issue 4 2006Zhen-Ming Ge ABSTRACT The mouth of the Yangtze River is an important stopover site for migratory shorebirds using the East Asian-Australasian Flyway. From 1984 to 2004, we censused and banded shorebirds and monitored hunting activities at the mouth of the Yangtze River to understand how shorebirds used the study area. Counts and banding data revealed greater numbers of shorebirds at the mouth of the Yangtze River during northward migration (spring) than during southward migration (fall), with ratios varying from 1.5:1 to 7.2:1 at different sites from 1984 to 2005. The most common species observed during spring (northward) migration were Great Knots (Calidris tenuirostris), Red Knots (Calidris canutus), Bar-tailed Godwits (Limosa lapponica), Sharp-tailed Sandpipers (Calidris acuminata), and Red-necked Stints (Calidris ruficollis). During spring 2003,2004, 96.98% of the shorebirds observed were adults (ASY or older) and 3% were after hatching-year and second-year birds (AHY or SY). In contrast, almost all (94.73%) birds counted during the fall were hatching-year (HY) birds. These results indicate that adult shorebirds either use a different migration route during fall migration or use the same route, but do not stop at the mouth of the Yangtze River. HY birds, however, may depend on the coastal stopover sites for feeding during their first southward passage. SINOPSIS La desembocadura del Rio Yangtze es un importante punto de parada de playeros migratorios que utilizan la vía del Este-Asiático-Australásico. De 1984 to 2004 anillamos playeros y se condujeron censos para monitorear las actividades de cacería en la desembocadura del Yangtze y ademásdeterminar como los playeros utilizaban dicha área. Los conteos de aves anilladas revelaron un mayor número de playeros durante la migración hacia el norte (primaveral) que durante la migración hacia el sur (otoñal) con una tasa de 1.5:1 a 7.2:1 en diferentes localidades. Las especies que se observaron con mayor frecuencia durante la primavera (moviéndose hacia el norte) fueron Calidris tenuirostris, C. canutus, C. acuminata, C. ruficollis y Limosa lapponica. Durante la primavera del 2003,2004, el 96.98% de las aves observadas fueron adultos y el 3% fueron aves de segundo año o juveniles del primer año. En contraste el 94.73% de las aves contabilizadas durante el otoño fueron juveniles del primer año. Estos resultados indican que los adultos utilizan otra ruta durante la migración otoñal o una ruta similar pero que no paran en la desembocadura del Yangtze. Sin embargo, las aves de primer año muy bien pudieran depender de los recursos alimentarios de los puntos de parada costaneros durante su primer viaje hacia el sur. [source] Cross-cutting moraines reveal evidence for North Atlantic influence on glaciers in the tropical Andes,JOURNAL OF QUATERNARY SCIENCE, Issue 3 2010Jacqueline A. Smith Abstract Surface exposure dating of boulders on an exceptionally well-preserved sequence of moraines in the Peruvian Andes reveals the most detailed record of glaciation heretofore recognised in the region. The high degree of moraine preservation resulted from dramatic changes in the flow path of piedmont palaeoglaciers at the southern end of the Cordillera Blanca (10° 00, S, 77° 16, W), which, in turn, generated a series of cross-cutting moraines. Sixty 10Be surface exposure ages indicate at least four episodes of palaeoglacier stabilisation (>65, ca. 65, ca. 32 and ca. 18,15,ka) and several minor advances or stillstands on the western side of the Nevado Jeulla Rajo massif. The absence of ages close to the global Last Glacial Maximum (ca. 21,ka) suggests that if an advance culminated at that time any resulting moraines were subsequently overridden. The timing of expanded ice cover in the central Peruvian Andes correlates broadly with the timing of massive iceberg discharge (Heinrich) events in the North Atlantic Ocean, suggesting a possible causal connection between southward migration of the Intertropical Convergence Zone during Heinrich events and a resultant increase in precipitation in the tropical Andes. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||