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Seasonal Occurrence (seasonal + occurrence)
Selected AbstractsSEASONAL OCCURRENCE OF SPERM WHALE (PHYSETER MACROCEPHALUS) SOUNDS IN THE GULF OF ALASKA, 1999,2001MARINE MAMMAL SCIENCE, Issue 1 2004David K. Mellinger Abstract An acoustic survey for sperm whales was conducted in the Gulf of Alaska. Six autonomous hydrophones continuously recorded sound signals below 500 Hz from October 1999 to May 2001. After recovery, recordings were processed using an automatic process to detect usual clicks of sperm whales. The detection algorithm equalized background noise, summed the data in a frequency band, and then used autocorrelation to detect the whales' highly regular clicks. Detections were checked manually, revealing that 98% of detections did contain clicks. Results indicate that sperm whales are present in the Gulf of Alaska year-round; this result extends what is known from whaling data, which were gathered principally in summer. Sperm whales were more common in summer than winter by a factor of roughly two, and occurred less often at the westernmost site surveyed (52°N, 157°W) than elsewhere in the Gulf. This is the first study of sperm whales based exclusively on remote acoustic sensing. This methodology is feasible because sperm whale clicks extend to frequencies (,100 Hz) low enough to be recorded by low-sample-rate instruments that operate continuously, and because the detection algorithm has a low false-detection rate. The methodology may be replicated to facilitate comparisons between different time periods and geographic regions. [source] Seasonal occurrence and local movements of the grey-headed (brown-necked) parrot Poicephalus fuscicollis suahelicus in southern AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2003Craig T. Symes Abstract Seasonal movements of grey-headed (brown-necked) parrots were recorded in parts of its range and are likely a response to breeding and availability of specific food sources. Breeding occurred in the northern Kruger National Park and lowveld near the Mutale,Luvhuvhu river confluence from April to August. Aggregations and movements of birds occurred during the post-breeding season (August,December) in response to seasonally abundant food sources. In north-eastern South Africa, grey-headed parrots occurred at Levubu, following the breeding season and their arrival in the area was correlated with the availability of unripe Mabola Plum, Parinari curatellifolia fruit. Similar regional movements occurred in Zimbabwe, the Caprivi of northern Namibia and Zambia. During these movements, flocks of up to 50 individuals were observed, whilst during breeding months singletons and pairs were more frequently seen. This increased abundance in time and space suggests that seasonal migratory movements occur. Résumé Des déplacements saisonniers de perroquets Poicephalus robustus ont été relevés dans des parties de leur aire de répartition, et ils sont vraisemblablement une réponse aux besoins de la reproduction et à la disponibilité des sources de leur nourriture spécifique. La reproduction avait lieu d'avril à août dans le nord du Parc National Kruger et dans le lowveld près du confluent des rivières Mutale et Luvhuvhu. Des rassemblements et des déplacements d'oiseaux avaient lieu dans la saison qui suivait celle de la reproduction (août , décembre) en réponse à l'abondance saisonnière des sources de nourriture. Au nord-est de l'Afrique du Sud, ces perroquets se rencontraient à Levubu, après la saison de reproduction, et leur arrivée coïncidait à la disponibilité des prunes Mabola (Parinari curatellifolia) avant leur maturité. On constatait des déplacements régionaux saisonniers semblables au Zimbabwe, dans le Capríví au nord de la Namibie et en Zambie. Au cours de ces déplacements, on a observé des bandes qui peuvent compter jusqu'à 50 individus, alors que pendant les mois de reproduction, on voyait plus souvent des solitaires ou des couples. Cette abondance accrue à certains moments et à certains endroits suggère qu'il existe des migrations saisonnières. [source] Seasonal occurrence of impetigo: a retrospective 8-year review (1996,2003)CLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 5 2005A. Loffeld Summary Impetigo, a common skin infection, has shown seasonal variation in African, Australian and Indian studies. We investigated seasonal variation of impetigo in a UK paediatric population. A total of 1552 children with impetigo were seen in the Accident and Emergency (A&E) department between 1996 and 2003. The number of impetigo cases was always higher in late summer than in winter, and furthermore, increased year on year. These changes could not be accounted for by variation in total patient numbers seen in A&E, and suggest a correlation between impetigo frequency and climatic temperature. Possible reasons for these findings include exposed skin due to loose clothing in the summer leading to more skin-to-skin contact and minor trauma. [source] Characteristics of wintertime daily and extreme minimum temperature over South KoreaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2004Sang-Boom Ryoo Abstract In South Korea, consecutive positive temperature anomalies have been observed since the mid-1980s. The objective of this study is to assess the recent trends in, and variability of, daily minimum temperature over South Korea with particular emphasis on its extremes. Temporal characteristics of wintertime daily and extreme minimum temperature-related variables were analysed on a seasonal basis for the period of 1958,59 to 2000,01. The results show continually fewer days with extreme low minimum temperature since the mid-1980s. However, no significant change in the 1 day temperature difference was observed during the same period, indicating little change in the frequency of cold surges. Also, during the period analysed, there is a significant positive trend in the seasonal mean temperature, a negative trend in the frequency of the extreme cold days, and no significant trend in the seasonal occurrence of cold surges. Northern Hemisphere geopotential height fields before and after 1986,87, i.e. the start of successive positive anomalies in the winter surface air temperature over South Korea, showed a substantial decrease throughout the troposphere over the polar region. In the upper levels the overall pattern becomes more wavelike, with eddies embedded between meanders. The differences in the lower troposphere are remarkably similar to the Arctic oscillation, although the centre in the North Atlantic is shifted toward western Europe and differences in the North Pacific are relatively weaker than those in the polar region. The recent positive phase of the Arctic oscillation may contribute to these abrupt changes in wintertime daily minimum temperatures over South Korea. El Niño,southern oscillation phenomena appear to contribute to the interannual variation of cold surge days in South Korea. Years with no cold surges were experienced during La Niña episodes. On the other hand, all years with more than four cases of cold surges were during El Niño episodes. Copyright © 2004 Royal Meteorological Society [source] Spatial and temporal variation of fire regimes in a mixed conifer forest landscape, Southern Cascades, California, USAJOURNAL OF BIOGEOGRAPHY, Issue 8 2001R. Matthew Beaty Aim In this study, we evaluated the fire-forest mosaic of a mixed conifer forest landscape by testing the hypothesis that pre-fire suppression fire regime parameters vary with species composition (tree species), and environment (i.e. slope aspect, slope position, elevation). Location Our study was conducted in the 1587 ha Cub Creek Research Natural Area (CCRNA), Lassen National Forest, CA, USA. Methods We quantified the return interval, seasonal occurrence, size, rotation period, and severity of fires using dendroecology. Results Slope aspect, potential soil moisture, forest composition, and fire regime parameters in our study area co-vary. Median composite and point fire return intervals (FRI) were longest on higher, cooler, more mesic, north-facing (NF) slopes covered with white fir (Abies concolor), Douglas fir (Pseudotsuga menziesii),white fir, and red fir (A. magnifica),white fir forests, shortest on the dry, south-facing (SF) slopes covered with ponderosa pine (Pinus ponderosa),white fir forests and intermediate on west-facing slopes dominated by white fir,sugar pine (P. lambertiana),incense cedar (Libocedrus decurrens) forests. The spatial pattern for length of fire rotation (FR) was the same as that for FRI. Fires in CCRNA mixed conifer forests occurred mainly (90%) in the dormant season. Size of burns in CCRNA mixed conifer forests were generally small (mean=106 ha), however, during certain drought years widespread fires burned across fuel breaks and spread throughout the watershed. Fire severity was mainly high on upper slopes, low on lower slopes and moderate and low severity on middle slopes. Patterns of fire severity also varied with slope aspect. Fire frequency decreased dramatically in CCRNA after 1905. Conclusions In CCRNA, fire regime parameters [e.g. FRI, fire extent, FR, fire severity] varied widely with species composition, slope aspect and slope position. There was also temporal variation in fire extent with the most widespread fires occurring during drought years. The important contributions of topography and climate to variation in the fire regime indicates that exogenous factors play a key role in shaping the fire-forest structure mosaic and that the fire-forest structure mosaic is more variable, less predictable and less stable than previously thought. Finally, some characteristics of the fire regime (i.e. fire severity, season of burn) in CCRNA are different than those described for other mixed conifer forests and this suggests that there are geographical differences in mixed conifer fire regimes along the Pacific slope. [source] Stiff Limb Syndrome: End of Spectrum or A Separate Entity?PAIN MEDICINE, Issue 3 2009Usha K. Misra DM ABSTRACT Background., Stiff-person syndrome is a rare disorder characterized by rigidity of axial or limb muscles with episodes of co-contraction of agonist and antagonist muscles during the spasms. In some patients axial or limb involvement may predominate and may have unusual manifestations. Design., Case report. Setting., Tertiary care teaching hospital. Patient., A 42-year-old farmer presented with seasonal occurrence of hiccup and vomiting during summer months for the last 3 years. He had painful lower limb spasms lasting for 2,3 minutes every 10,15 minutes for the past 20 days. His neurological examination was normal, erythrocyte sedimentation rate (ESR) was 50 mm at 1st hour, and cerebrospinal fluid protein 78 mg/dL without pleocytosis. Radiograph of chest, abdominal ultrasound, and craniospinal magnetic resonance imaging were normal. The patient improved on diazepam. Conclusion., Our patient is a forme fruste of stiff person syndrome with hiccups and vomiting due to diaphragmatic spasm. [source] | |||||||||||||