Seasonal and diurnal variations in the energetics and foraging activities of the brown honey eater,Lichmera indistincta

In general, the brown honeyeater, Lichmera indistincta, flies more and expends more energy when visiting flowers in the early morning than at other times. Floral nectar is most abundant early in the day, and nectar energy intake by L. indistincta is greatest at that time. It appears as if birds can only store excess energy during the early part of the day, incurring energy deficits at other times. Unit perching and flight costs are greatest for L. indistincta in winter and spring. As a result, peak total energy expenditures and requirements occur at these times, birds apparently being unable to reduce energy demands by employing nocturnal torpor. Estimates of probable energy uptake by L. indistincta from the plant species studied exceed predicted requirements in all seasons except winter, when it is apparent that birds would need to be especially selective in the plants that they used as major energy sources.     

Short-term regulation of food intake by the brown honeyeater,Lichmera indistincta

• 1.1. Regardless of nectar concentration, there are strong positive correlations between the durations of feeding bouts by Lichmera indistincta and subsequent inter-bout intervals, and energy intake during feeding bouts and energy expenditure during subsequent inter-bout intervals.
• 2.2. Energy utilization by L. indistincta conforms to an accumulation-depletion model, with a portion of the energy acquired during each feeding bout contributing to the gradual diurnal storage of energy that is subsequently used for maintenance during non-foraging periods.
• 3.3. L. indistincta compensates for a decrease in nectar concentration by increasing the frequency of feeding bouts and decreasing the duration of inter-bout intervals.
• 4.4. Changes in the duration of inter-bout intervals caused by alterations to the calorific value of nectar drunk can be explained in terms of the rate at which the stomach empties.

     

Seasonal morphological variations in bird schistosomes

The present work is a contribution to the systematics of Bilhorziello and Dendritobilharzio. Wildfowl was killed in hunting seasons or found dead in Champagne-Ardenne region, France, and autopsied with focus on schistosomes. Seven Anas plotyrhynchos (mallards), one Ardeo cinerea (grey heron) and two Cygnus olor (mute swans) were parasitized by Bilharziella. One C. olor was parasitized by Dendritobilharzia. Depending on season and hosts, various morphological forms of Bilharziello suggesting several species were observed. The differences in male and female worms concerned the morphology of genital apparatus, the spination on suckers, the body size and proportions. However, the comparison of DNA sequences led to a conclusion that these forms belonged to one species, Bilharziella polonica (Kowalewski, 1895). The morphological features and the body sizes of our samples of Dendritobilharzia seemed to differ from the type species of D. pulverulenta (Braun, 1901). Nevertheless, molecular analysis confirmed identity. We hypothesize that the differences in Bilharziella and Dendritobilharzia might be linked to internal host factors (e.g. hormonal levels), and influenced by season, host, and worm age. The definition of the genera Bilharziello and Dendritobilharzio was amended.     

Seasonal variation in thermal energetics of the Australian owlet-nightjar (Aegotheles cristatus)

Many birds living in regions with seasonal fluctuations in ambient temperatures (T_a) typically respond to cold by increasing insulation and adjusting metabolic rate. Seasonal variation in thermal physiology has not been studied for the Caprimulgiformes, an order of birds that generally have basal metabolic rates (BMR) lower than predicted for their body mass. We measured the metabolic rate and thermal conductance of Australian owlet-nightjars (Aegotheles cristatus) during summer and winter using open-flow respirometry. Within the thermoneutral zone (TNZ; 31.3 to 34.8 °C), there was no seasonal difference in BMR or thermal conductance (C), but body temperature was higher in summer- (38.2 ± 0.3 °C) than winter-acclimatized (37.1 ± 0.5 °C) birds. Below the TNZ, resting metabolic rate (RMR) increased linearly with decreasing T_a, and RMR and C were higher for summer- than winter-acclimatized birds. The mean mass-specific BMR of owlet-nightjars (1.27 mL O₂ g^− 1 h^− 1) was close to the allometrically predicted value for a 45 g Caprimulgiformes, but well below that predicted for birds overall. These results suggest that owlet-nightjars increase plumage insulation to cope with low winter T_a, which is reflected in the seasonal difference in RMR and C below the TNZ, rather than adjusting BMR.     

Territorial behaviour in an Australian nectar-feeding bird

The red wattlebird, a large Australian honey eater, defends feeding territories from other nectar-feeding birds. One such territory decreased in size and experienced fewer intruders as the density of flowers increased. Daily energy production from the nectar in the territory closely approximated the energy requirements of the territory holder. The bird was probably minimizing energetic costs rather than maximizing energy intake.     

Successional trends in the energetics of forest bird communities

Thirty forest bird communities were studied with regard to the changes in structural indices (number of species, density, biomass, species diversity H') and in energetics (energy flow A, production P, ecological efficiency P/A) in temporal and spatial gradients. All these characteristics increase during temporal succession; in natural deciduous forest there is a two-peak pattern of the increase, with the maximum in 15–20 yr old forest ("time ecotone"; A = 692.9 Megajoules ha⁻¹ season⁻¹, H'= 4.2 bits), In artificially managed pine forest these indices rise monotonically, reaching a maximum in sub-climax (A = 426.2 MJ ha⁻¹ season⁻¹, H'= 4.2 bits). In a deciduous forest a tendency exists to decrease the ecological efficiency (from 8% to 2%), while in a coniferous stand this variable remains low (2%) and almost constant during succession. In a spatial gradient, the highest values of energy flow and species diversity occur in forest stands with moderate soil/water regime and of ecotonal character (A = 851.2 MJ ha⁻¹ season⁻¹, H'= 4.5 bits). All mature forest bird communities show similar values of diversity (4.2–4.5 bits) and ecological efficiency (appr. 2%), though they differ in the rate of energy flow. The relation of these findings to the current concepts of ecological succession are discussed.     

The diet and digestive energetics of an Australian short-necked turtle, Emydura macquarii

We described the diet of Emydura macquarii, an omnivorous turtle from south-eastern Australia, compared its digestive performance on diets of fish or plants at two temperatures, and related how both diet and temperature affect its food selection in nature. Filamentous algae constituted 61% of the stomach content of E. macquarii. The turtles rarely fed on motile prey, but selected carrion from the lagoon bottom and terrestrial insects (Diptera, Hymenoptera and Coleoptera) trapped on the surface of the water. Digestive efficiency of E. macquarii was affected little by body temperature, in contrast to consumption rates and rates of passage which were strongly influenced by both temperature and diet. In combination, these responses resulted in a slower rate of digestion at 20 degrees C than at 30 degrees C. Digestive efficiency of E. macquarii on a herbivorous diet at 30 degrees C (49%) was about half that of turtles on a carnivorous diet (91%), but they had longer transit times (118 h on the plant diet versus 70 h). Lower consumption rates and longer mean retention times in turtles fed plants compared those fed fish relate to slower digestive processing of the plant. Rapid processing and higher consumption rates of fish by E. macquarii resulted in higher energy gains compared to turtles consuming plants (almost 100 times more energy at 30 degrees C). The laboratory results suggest that fish carrion and aquatic and terrestrial invertebrates are probably essential dietary items of E. macquarii in the wild, because its metabolic requirements cannot be met from aquatic macrophytes alone.     

Seasonal variations in the blood constituents of an air-breathing fish, Channa punctatus Bloch

A year long study based on monthly observations on the haematology of female Channa punctatus with respect to haemoglobin, haematocrit values, total erythrocyte and leucocyte numbers together with a differential enumeration of various leucocytes viz. thrombocytes small and large lymphocytes, monocytes, neutrophils, eosinophils and basophils is recorded. The study showed that the total erythrocytic number, haemoglobin and haematocrit values decrease during the breeding time i.e. July to September. The thrombocyte number significantly increased while the neutrophilic number showed a decrease. The physiological significance of these changes is discussed with reference to the available literature.     

Urban nectarivorous bird communities in Cape Town,South Africa,are structured by ecological generalisation and resource distribution

Biological communities are increasingly faced with novel urban habitats and their response may depend on a combination of biological and habitat traits. The response of pollinator species to urban habitats are of particular importance because all species involved in the pollination mutualism may be affected. Nectarivorous bird communities worldwide show varying tolerances to urban areas, but studies from Africa are lacking. We investigated nectarivorous bird communities in a medium‐sized South African city and asked which biological and garden traits best predict the community assembly of specialist and opportunistic nectarivorous birds. Information was collected on garden traits and the frequency of nine nectarivorous bird species for 193 gardens by means of a questionnaire. Information on biological traits of birds was obtained from published literature. Habitat generalism and tree nesting were identified as the most important biological traits influencing bird occurrence in gardens. A greater diversity of indigenous bird‐pollinated plants and the presence of sugar water feeders increased the numbers of nectar specialist birds and species richness of nectarivorous birds. While bird baths increased the species richness of nectar specialist birds, opportunistic birds’ urban adjustment was further facilitated by large vegetated areas in gardens and limited by the distance to the nearest natural habitat. In conclusion, though some biological traits and dispersal barriers seem to limit urban adjustment, a combination of natural and artificial nectar resource provisioning could facilitate this adjustment.     

Seasonal energetics of northern phocid seals

The metabolic rate of harp (Pagophilus groenlandicus), harbor (Phoca vitulina), and ringed seals (Pusa hispida) was measured at various temperatures in air and water to estimate basal metabolic rates (BMRs) in these species. The basal rate and body composition of three harp seals were also measured throughout the year to examine the extent to which they vary seasonally. Marine mammalian carnivores generally have BMRs that are over three times the rates expected from body mass in mammals generally, both as a response to a cold-water distribution and to carnivorous food habits with the basal rates of terrestrial carnivores averaging about 1.8 times the mean of mammals. Phocid seals, however, have basal rates of metabolism that are 30% lower than other marine carnivores. Captive seals undergo profound changes in body mass and food consumption throughout the year, and after accounting for changes in body mass, the lowest rate of food intake occurs in summer. Contrary to earlier observations, harp seals also have lower basal rates during summer than during winter, but the variation in BMR, relative to mass expectations, was not associated with changes in the size of fat deposits. The summer reduction in energy expenditure and food consumption correlated with a reduction in BMR. That is, changes in BMR account for a significant portion of the seasonal variation in energy expenditure in the harp seal. Changes in body mass of harp seals throughout the year were due not only to changes in the size of body fat deposits, but also to changes in lean body mass. These results suggest that bioenergetics models used to predict prey consumption by seals should include time-variant energy requirements.     

Seasonal variations in nematode assemblages on an Australian temperate ocean beach; the effect of heavy seas and unusually high tides

Free-living nematodes inhabiting a sandy beach exposed to strong ocean waves were sampled at bimonthly intervals for two years. Six 1.3-litre core samples were taken on each occasion down to a depth of 60 cm. The numbers of each species and their status as juveniles, males and females (with or without eggs) was recorded. In the common species all these stages occur throughout the year, but the population increases in the warmer months of the year and falls to a much lower level in winter. Most species are dispersed throughout the sand to a depth of at least 60 cm, but several species where almost always found below the water table at about 60 cm. The faunal composition of the nematode assemblages changed significantly from month to month. Additional samples were taken to monitor the effects of very strong waves coupled with a very high tide which remodelled the beach. The nematode fauna was partially reconstituted by this event. It is concluded that the intertidal beach fauna is a dynamic extension of the near shore sub-littoral nematode fauna.     

The diet and digestive energetics of an Australian short-necked turtle, Emydura macquarii

We described the diet of Emydura macquarii, an omnivorous turtle from south-eastern Australia, compared its digestive performance on diets of fish or plants at two temperatures, and related how both diet and temperature affect its food selection in nature. Filamentous algae constituted 61% of the stomach content of E. macquarii. The turtles rarely fed on motile prey, but selected carrion from the lagoon bottom and terrestrial insects (Diptera, Hymenoptera and Coleoptera) trapped on the surface of the water. Digestive efficiency of E. macquarii was affected little by body temperature, in contrast to consumption rates and rates of passage which were strongly influenced by both temperature and diet. In combination, these responses resulted in a slower rate of digestion at 20°C than at 30°C. Digestive efficiency of E. macquarii on a herbivorous diet at 30°C (49%) was about half that of turtles on a carnivorous diet (91%), but they had longer transit times (118 h on the plant diet versus 70 h). Lower consumption rates and longer mean retention times in turtles fed plants compared those fed fish relate to slower digestive processing of the plant. Rapid processing and higher consumption rates of fish by E. macquarii resulted in higher energy gains compared to turtles consuming plants (almost 100 times more energy at 30°C). The laboratory results suggest that fish carrion and aquatic and terrestrial invertebrates are probably essential dietary items of E. macquarii in the wild, because its metabolic requirements cannot be met from aquatic macrophytes alone.     

Seasonal phytoplankton variations in the shallow Pahlavi Mordab,Iran

Pelagic phytoplankton variations in the shallow, western basin of the Pahlavi Mordab, Iran were monitored by the chlorophyll a, gross oxygen productivity and cell enumeration techniques. Annual maxima were 29.4 mg/m³, 0.98 mg O₂/l/hr and 32, 639, 467 cells/liter respectively and were recorded from late summer until early autumn. During the spring and summer, dense growths of Ceratophyllum, Hydrilla and Myriophyllum flourished. Competition between the phytoplankton and submerged aquatic macrophytes was minimal following late summer, when water depths increased following heavy seasonal precipitation and the die-back of submerged aquatic macrophytes occurred.     

Seasonal variation in hippocampal volume in a food-storing bird,the black-capped chickadee

Black-capped chickadees (Parus atricapillus) in upstate New York show a peak in food-hoarding intensity in October. We caught chickadees at six different times of the year and measured the volume of several brain structures. We found that the hippocampal formation, which is involved in spatial memory for cached food items, has a larger volume, relative to the rest of the brain, in October than at any other time of the year. We conclude that there is an association between the intensity of food hoarding and the volume of the hippocampal formation and suggest that the enhanced anatomy might be caused by the increased use of spatial memory. © 1995 John Wiley & Sons, Inc.     

Seasonal ultrastructural variations in pinealocytes of the woodchuck,Marmota monax

The ultrastructure of the pinealocyte in the woodchuck, Marmota monax, was studied during the four seasons of the year. Fall cells have a fairly uniform cytoplasmic density, organelles consistent with synthetic and/or secretory activity and rather extensive pericapillary and intercellular spaces. Many winter pinealocytes are nearly devoid of ribosomes and granular endoplasmic reticulum but contain lipid droplets associated with mitochondria. Pericapillary and intercellular spaces are minimal. Spring glands have the greatest variation in cytoplasmic density with intercellular and pericapillary spaces similar to that seen in fall glands. Cells containing electron dense cytoplasm have Golgi zone associated, secretory granules, free ribosomes, short sections of granular endoplasmic reticulum and dense bodies. Cells with a more electron lucent cytoplasm are similar to the most frequently observed summer pinealocytes which have numerous Golgi zones but few associated secretory granules. Microtubules are prominent in the cytoplasm of these cells, the plasma membranes are smooth and intercellular and pericapillary spaces are minimal. A yearly rhythm or cyclic activity of the pinealocyte is suggested.