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Susan W Nicolson - One of the best experts on this subject based on the ideXlab platform.
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drinking problems on a simple diet physiological convergence in nectar feeding birds
The Journal of Experimental Biology, 2014Co-Authors: Susan W Nicolson, Patricia A FlemingAbstract:Regulation of energy and water are by necessity closely linked in avian Nectarivores, because the easily available sugars in nectar are accompanied by an excess of water but few electrolytes. In general, there is convergence in morphology and physiology between three main lineages of avian Nectarivores that have evolved on different continents – the hummingbirds, sunbirds and honeyeaters. These birds show similar dependence of sugar preferences on nectar concentration, high intestinal sucrase activity and rapid absorption of hexoses via mediated and paracellular routes. There are differences, however, in how these lineages deal with energy challenges, as well as processing the large volumes of preformed water ingested in nectar. While hummingbirds rely on varying renal water reabsorption, the passerine Nectarivores modulate intestinal water absorption during water loading, thus reducing the impact on the kidneys. Hummingbirds do not generally cope with salt loading, and have renal morphology consistent with their ability to produce copious dilute urine; by contrast, as well as being able to deal with dilute diets, honeyeaters and sunbirds are more than capable of dealing with moderately high levels of added electrolytes. And finally, in response to energy challenge, hummingbirds readily resort to torpor, while the passerines show renal and digestive responses that allow them to deal with short-term fasts and rapidly restore energy balance without using torpor. In conclusion, sunbirds and honeyeaters demonstrate a degree of physiological plasticity in dealing with digestive and renal challenges of their nectar diet, while hummingbirds appear to be more constrained by this diet.
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nectar sugar preferences and absorption in a generalist african frugivore the cape white eye zosterops pallidus
Ibis, 2008Co-Authors: Elke Franke, Susan Jackson, Susan W NicolsonAbstract:Sugar preferences and absorption efficiencies were investigated in the Cape White-eye Zosterops pallidus, a generalist frugivore. Unlike the mainly American frugivorous passerines previously studied, Cape White-eyes preferred 20% (weight: weight) solutions of sucrose to glucose or fructose, and apparently possess high sucrase activity because absorption efficiencies for all three sugars were close to 100%. Cape White-eyes rejected 20% solutions containing a fourth nectar sugar, xylose, recently found in the nectar of Protea and Faurea (Proteaceae). Absorption efficiencies for xylose averaged 61%, but we do not know whether this sugar is utilized by the birds. Cape White-eyes thus resemble specialized southern African Nectarivores (Nectariniidae, Promeropidae) in their responses to nectar sugars.
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evolutionary associations between nectar properties and specificity in bird pollination systems
Biology Letters, 2008Co-Authors: Steven D. Johnson, Susan W NicolsonAbstract:A long-standing paradigm in biology has been that hummingbirds and passerine birds select for different nectar properties in the plants they pollinate. Here we show that this dichotomy is false and a more useful distinction is that between specialized and generalized bird pollination systems. Flowers adapted for sunbirds, which are specialized passerine Nectarivores, have nectar similar to that of hummingbird flowers in terms of volume (approx. 10–30 μl), concentration (approx. 15–25% w/w) and sucrose content (approx. 40–60% of total sugar). In contrast, flowers adapted to generalized bird pollinators are characterized by large volumes (approx. 40–100 μl) of extremely dilute (approx. 8–12%) nectar with minimal sucrose (approx. 0–5%). These differences in nectar traits are highly significant even when statistical analyses are based on phylogenetically separate pairwise comparisons between taxa. We present several hypotheses for the association between nectar properties and specificity in bird pollination systems.
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Response of avian Nectarivores to the flowering of Aloe marlothii: a nectar oasis during dry South African winters
Journal of Ornithology, 2008Co-Authors: Craig T. Symes, Susan W Nicolson, Andrew E. MckechnieAbstract:In southern Africa, Aloe marlothii flowers during the dry winter season and offers copious dilute nectar to a variety of birds. Avian abundance and community composition were monitored at an A. marlothii forest at Suikerbosrand Nature Reserve, South Africa. Sampling occurred during two summer months (February–March) when no flowers were present, and six months (May–October) that spanned the winter flowering. We hypothesized that an influx of occasional Nectarivores to the A. marlothii forest during flowering would lead to significant changes in the avian community. Overall bird abundance increased 2–3 fold at the peak of nectar availability (August). We recorded 38 bird species, of 83 species detected during transects, feeding on A. marlothii nectar; this diverse assemblage of birds belonged to 19 families, including Lybiidae, Coliidae, Pycnonotidae, Sylviidae, Cisticolidae, Muscicapidae, Sturnidae, Ploceidae and Fringillidae. Surprisingly, only two species of sunbird (Nectariniidae) were observed feeding on A. marlothii nectar, and both occurred in low abundance. We predicted that competition for nectar resources would be high, but few aggressive inter- and intra-specific interactions occurred between birds while feeding on inflorescences. During peak flowering, insect feeders (insectivores, omnivores, Nectarivores) fed on nectar during the cold morning when insect activity was low, whilst non-insect feeders (frugivores and granivores) fed on nectar in the middle of the day. Our study highlights the importance of A. marlothii nectar as a seasonal food and water source for a diverse assemblage of occasional Nectarivores.
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osmoregulatory response to acute diet change in an avian Nectarivore rapid rehydration following water shortage
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2004Co-Authors: Patricia A Fleming, D A Gray, Susan W NicolsonAbstract:Nectarivores may be required to switch between water conservation and water excretion as rapidly as they change food plants in nature. We examined the rehydration response in Whitebellied Sunbirds (Nectarinia talatala) that had been fed a concentrated sucrose diet (2.5 mol/l) for 2 days and then were switched to a diet 10 x less concentrated (0.25 mol/l) on the morning of the third day. We measured water gain as well as cloacal fluid (CF) volume hourly over 12 h, and analysed CF osmolality and calculated osmotic excretion. CF was also assayed for the osmoregulatory hormone aldosterone (ALDO). As in most water-deprived birds, whitebellied sunbirds cope with water shortage when fed a concentrated sugar diet by almost completely ceasing to void CF. Although osmolality of CF is high, volumes are not sufficient to maintain a steady rate of excretion and the birds retain osmolytes. Immediately upon switching to dilute diet, sunbirds produce copious volumes of CF and osmotic excretion is elevated and maintained at high levels over the first 6 h of rehydration. This stabilises by the afternoon at levels expected for hydrated birds. Some 2-3 h after peak osmotic excretion, there is a peak in the discrepancy between water intake and output, mirrored in an increase in ALDO output. These data suggest that excretion of retained osmolytes is undertaken as soon as water is available, with changes in the body fluid composition occurring subsequently. This study vindicates the use of CF to obtain repeated measurements of changes in the osmoregulatory steroid ALDO in small birds.
Patricia A Fleming - One of the best experts on this subject based on the ideXlab platform.
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the plant pathogen phytophthora cinnamomi influences habitat use by the obligate Nectarivore honey possum tarsipes rostratus
Australian Journal of Zoology, 2016Co-Authors: Shannon J Dundas, G Hardy, Patricia A FlemingAbstract:Introduced plant pathogens can devastate susceptible plant communities, and consequently impact on animal communities reliant on plants for food and habitat. Specifically, plant pathogens change the floristic diversity of vegetation communities, thereby reducing availability of food sources for fauna (e.g. pollen and nectar) and result in major changes to habitat structure when canopy and understorey plant species succumb to disease. Phytophthora cinnamomi poses a threat to flowering plant species (e.g. Banksia species) which are important food sources for nectarivorous fauna. The honey possum (Tarsipes rostratus) is the only obligate nectarivorous non-flying mammal living on a restrictive diet of nectar and pollen; consequently, these tiny mammals are likely to be particularly vulnerable to the landscape-wide devastation caused by P. cinnamomi. We investigated habitat selection by honey possums in a vegetation community infested with P. cinnamomi to determine how these mammals respond to habitat affected by this pathogen. Over four seasons, 18 honey possums were fitted with radio-transmitters and tracked to identify habitat preferences. Vegetation surveys were compared for locations selected by honey possums (as determined from tracking) and randomly selected sites. Radio-tracking revealed that sites selected by honey possums were significantly taller, denser, and more floristically diverse than their paired random locations. The presence of P. cinnamomi influences habitat use by honey possums, but animals show resilience in terms of using the best of what is available in both P. cinnamomi–affected and unaffected locations. Habitat patches comprising less susceptible species, or plants that have yet to succumb to infection, provide refuge and food resources for honey possums. Management to reduce the spread of existing P. cinnamomi infestations and prevent contamination of new locations will benefit vegetation communities and associated faunal communities, while identifying honey possum food plant species that are resilient to the pathogen may support revegetation attempts.
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drinking problems on a simple diet physiological convergence in nectar feeding birds
The Journal of Experimental Biology, 2014Co-Authors: Susan W Nicolson, Patricia A FlemingAbstract:Regulation of energy and water are by necessity closely linked in avian Nectarivores, because the easily available sugars in nectar are accompanied by an excess of water but few electrolytes. In general, there is convergence in morphology and physiology between three main lineages of avian Nectarivores that have evolved on different continents – the hummingbirds, sunbirds and honeyeaters. These birds show similar dependence of sugar preferences on nectar concentration, high intestinal sucrase activity and rapid absorption of hexoses via mediated and paracellular routes. There are differences, however, in how these lineages deal with energy challenges, as well as processing the large volumes of preformed water ingested in nectar. While hummingbirds rely on varying renal water reabsorption, the passerine Nectarivores modulate intestinal water absorption during water loading, thus reducing the impact on the kidneys. Hummingbirds do not generally cope with salt loading, and have renal morphology consistent with their ability to produce copious dilute urine; by contrast, as well as being able to deal with dilute diets, honeyeaters and sunbirds are more than capable of dealing with moderately high levels of added electrolytes. And finally, in response to energy challenge, hummingbirds readily resort to torpor, while the passerines show renal and digestive responses that allow them to deal with short-term fasts and rapidly restore energy balance without using torpor. In conclusion, sunbirds and honeyeaters demonstrate a degree of physiological plasticity in dealing with digestive and renal challenges of their nectar diet, while hummingbirds appear to be more constrained by this diet.
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osmoregulatory response to acute diet change in an avian Nectarivore rapid rehydration following water shortage
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2004Co-Authors: Patricia A Fleming, D A Gray, Susan W NicolsonAbstract:Nectarivores may be required to switch between water conservation and water excretion as rapidly as they change food plants in nature. We examined the rehydration response in Whitebellied Sunbirds (Nectarinia talatala) that had been fed a concentrated sucrose diet (2.5 mol/l) for 2 days and then were switched to a diet 10 x less concentrated (0.25 mol/l) on the morning of the third day. We measured water gain as well as cloacal fluid (CF) volume hourly over 12 h, and analysed CF osmolality and calculated osmotic excretion. CF was also assayed for the osmoregulatory hormone aldosterone (ALDO). As in most water-deprived birds, whitebellied sunbirds cope with water shortage when fed a concentrated sugar diet by almost completely ceasing to void CF. Although osmolality of CF is high, volumes are not sufficient to maintain a steady rate of excretion and the birds retain osmolytes. Immediately upon switching to dilute diet, sunbirds produce copious volumes of CF and osmotic excretion is elevated and maintained at high levels over the first 6 h of rehydration. This stabilises by the afternoon at levels expected for hydrated birds. Some 2-3 h after peak osmotic excretion, there is a peak in the discrepancy between water intake and output, mirrored in an increase in ALDO output. These data suggest that excretion of retained osmolytes is undertaken as soon as water is available, with changes in the body fluid composition occurring subsequently. This study vindicates the use of CF to obtain repeated measurements of changes in the osmoregulatory steroid ALDO in small birds.
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osmoregulation in an avian Nectarivore the whitebellied sunbird nectarinia talatala response to extremes of diet concentration
The Journal of Experimental Biology, 2003Co-Authors: Patricia A Fleming, Susan W NicolsonAbstract:Water intake of Nectarivores is intrinsically linked to nectar concentration. Osmoregulation in whitebellied sunbirds Nectarinia talatala (body mass 9.3±0.1 g, mean ± S.D., N =7), was examined by feeding them sucrose solutions, equivalent to extreme diet concentrations (0.07–2.5 mol l–1 sucrose; 2–65% w/w), with and without supplementary drinking water. Total water gain was 33–515% of body mass daily. Cloacal fluid (CF) volume increased with diet dilution from 0.4% to 309% of body mass while increases in evaporative water loss (obtained by difference) were also recorded. Osmolality of CF demonstrated the largest scope yet recorded for a bird and was significantly correlated with water flux: mean values were 6–460 mosm kg–1 H2O (minimum 3, maximum 1900 mosm kg–1). When supplementary water was provided, its consumption by birds fed concentrated diets (2.5 mol l–1 sucrose) led to a dramatic reduction in CF osmolality, from 461±253 to 80±119 mosm kg–1 fluid. Sunbirds maintained energy balance on sucrose diets varying tenfold in concentration, from 0.25 to 2.5 mol l–1; however, on extremely dilute diets (0.07 and 0.1 mol l–1 sucrose, lower than natural nectar concentrations) their inability to maintain energy balance was probably due to excess preformed water. Total osmotic excretion and concentrations of Na+ and K+ increased with high water fluxes, and are a possible physiological constraint for nectarivorous birds on artificial dilute diets devoid of electrolytes. Even low electrolyte levels in nectars may be adequate to replace these losses, but other physiological limitations to the intake of dilute nectars are increased energetic costs of solute recovery, increased heat loss and interference with digestive processes. Sunbirds therefore deal with sugar solutions spanning the range of nectar concentrations by shutting down water excretion on concentrated diets, or, on dilute diets, by producing extremely dilute CF with some of the lowest solute concentrations recorded.
Karen D. Holl - One of the best experts on this subject based on the ideXlab platform.
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Landscape context mediates avian habitat choice in tropical forest restoration. PLoS One 2014
2016Co-Authors: Leighton J. Reid, Chase D. Mendenhall, Abel J. Rosales, Rakan A. Zahawi, Karen D. HollAbstract:Birds both promote and prosper from forest restoration. The ecosystem functions birds perform can increase the pace of forest regeneration and, correspondingly, increase the available habitat for birds and other forest-dependent species. The aim of this study was to learn how tropical forest restoration treatments interact with landscape tree cover to affect the structure and composition of a diverse bird assemblage. We sampled bird communities over two years in 13 restoration sites and two old-growth forests in southern Costa Rica. Restoration sites were established on degraded farmlands in a variety of landscape contexts, and each included a 0.25-ha plantation, island treatment (trees planted in patches), and unplanted control. We analyzed four attributes of bird communities including frugivore abundance, Nectarivore abundance, migrant insectivore richness, and compositional similarity of bird communities in restoration plots to bird communities in old-growth forests. All four bird community variables were greater in plantations and/or islands than in control treatments. Frugivore and Nectarivore abundance decreased with increasing tree cover in the landscape surrounding restoration plots, whereas compositional similarity to old-growth forests was greatest in plantations embedded in landscapes with high tree cover. Migrant insectivore richness was unaffected by landscape tree cover. Our results agree with previous studies showing that increasing levels of investment in active restoration are positively related to bird richness and abundance, but differences in the effects of landscape tree cover on foraging guilds and community composition suggest that trade-off
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landscape context mediates avian habitat choice in tropical forest restoration
PLOS ONE, 2014Co-Authors: Leighton J. Reid, Chase D. Mendenhall, Abel J. Rosales, Rakan A. Zahawi, Karen D. HollAbstract:Birds both promote and prosper from forest restoration. The ecosystem functions birds perform can increase the pace of forest regeneration and, correspondingly, increase the available habitat for birds and other forest-dependent species. The aim of this study was to learn how tropical forest restoration treatments interact with landscape tree cover to affect the structure and composition of a diverse bird assemblage. We sampled bird communities over two years in 13 restoration sites and two old-growth forests in southern Costa Rica. Restoration sites were established on degraded farmlands in a variety of landscape contexts, and each included a 0.25-ha plantation, island treatment (trees planted in patches), and unplanted control. We analyzed four attributes of bird communities including frugivore abundance, Nectarivore abundance, migrant insectivore richness, and compositional similarity of bird communities in restoration plots to bird communities in old-growth forests. All four bird community variables were greater in plantations and/or islands than in control treatments. Frugivore and Nectarivore abundance decreased with increasing tree cover in the landscape surrounding restoration plots, whereas compositional similarity to old-growth forests was greatest in plantations embedded in landscapes with high tree cover. Migrant insectivore richness was unaffected by landscape tree cover. Our results agree with previous studies showing that increasing levels of investment in active restoration are positively related to bird richness and abundance, but differences in the effects of landscape tree cover on foraging guilds and community composition suggest that trade-offs between biodiversity conservation and bird-mediated ecosystem functioning may be important for prioritizing restoration sites.
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Compositional and functional attributes of bird communities predicted by restoration treatments and landscape tree cover.
2014Co-Authors: Leighton J. Reid, Chase D. Mendenhall, Abel J. Rosales, Rakan A. Zahawi, Karen D. HollAbstract:Error bars represent ±1 s.e.m. (A–C) Controls are represented by squares; islands by triangles, and plantations by circles. (A) Sørensen similarity of bird communities in restoration sites to bird communities in reference forest (550 m tree cover buffer); (B) frugivore abundance per observation (7 observations per point; 350 m buffer); (C) Nectarivore abundance per observation (450 m buffer); (D) migrant insectivore richness (equal sampling intensity). Significance calculated using pairwise Wilcoxon rank sum tests with Bonferroni corrections (all P
Mercado Jorge - One of the best experts on this subject based on the ideXlab platform.
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Una nueva metodología para el análisis palinológico de muestras coprológicas en vertebrados polinizadores
Universidad de Sucre: Facultad de Ciencias Agropecuarias, 2013Co-Authors: Mercado Jorge, Pérez C. AlexanderAbstract:We described a method to analyze pollen samples from Nectarivore bats` hez. With this protocol is possible to extract the grain of pollen without strong chemicals and in a less time. We present the advantages this protocol has in front of conventional techniques used to carry out palynologycal analysis.Describimos un método para analizar muestras de polen en heces de murciélagos nectarívoros, optimizando el análisis palinológico sin el uso de químicos fuertes y en menor tiempo, demostrando las ventajas de nuestro protocolo frente a las técnicas convencionales de análisis de dietas de animales nectarívoros
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Una Nueva Metodología Para El Análisis Palinológico De Muestras Coprológicas En Vertebrados Polinizadores A New Methodology For The Palynological Analysis Of Feces
'Universidad de Sucre', 2013Co-Authors: Mercado Jorge, Perez AlexanderAbstract:We described a method to analyze pollen samples from Nectarivore bats’ hez. With this protocol is possible to extract the grain of pollen without strong chemicals and in a less time. We present the advantages this protocol has in front of conventional techniques used to carry out palynologycal analysis.Describimos un método para analizar muestras de polen en heces de murciélagos nectarívoros, optimizando el análisis palinológico sin el uso de químicos fuertes y en menor tiempo, demostrando las ventajas de nuestro protocolo frente a las técnicas convencionales de análisis de dietas de animales nectarívoros
Leighton J. Reid - One of the best experts on this subject based on the ideXlab platform.
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Landscape context mediates avian habitat choice in tropical forest restoration. PLoS One 2014
2016Co-Authors: Leighton J. Reid, Chase D. Mendenhall, Abel J. Rosales, Rakan A. Zahawi, Karen D. HollAbstract:Birds both promote and prosper from forest restoration. The ecosystem functions birds perform can increase the pace of forest regeneration and, correspondingly, increase the available habitat for birds and other forest-dependent species. The aim of this study was to learn how tropical forest restoration treatments interact with landscape tree cover to affect the structure and composition of a diverse bird assemblage. We sampled bird communities over two years in 13 restoration sites and two old-growth forests in southern Costa Rica. Restoration sites were established on degraded farmlands in a variety of landscape contexts, and each included a 0.25-ha plantation, island treatment (trees planted in patches), and unplanted control. We analyzed four attributes of bird communities including frugivore abundance, Nectarivore abundance, migrant insectivore richness, and compositional similarity of bird communities in restoration plots to bird communities in old-growth forests. All four bird community variables were greater in plantations and/or islands than in control treatments. Frugivore and Nectarivore abundance decreased with increasing tree cover in the landscape surrounding restoration plots, whereas compositional similarity to old-growth forests was greatest in plantations embedded in landscapes with high tree cover. Migrant insectivore richness was unaffected by landscape tree cover. Our results agree with previous studies showing that increasing levels of investment in active restoration are positively related to bird richness and abundance, but differences in the effects of landscape tree cover on foraging guilds and community composition suggest that trade-off
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landscape context mediates avian habitat choice in tropical forest restoration
PLOS ONE, 2014Co-Authors: Leighton J. Reid, Chase D. Mendenhall, Abel J. Rosales, Rakan A. Zahawi, Karen D. HollAbstract:Birds both promote and prosper from forest restoration. The ecosystem functions birds perform can increase the pace of forest regeneration and, correspondingly, increase the available habitat for birds and other forest-dependent species. The aim of this study was to learn how tropical forest restoration treatments interact with landscape tree cover to affect the structure and composition of a diverse bird assemblage. We sampled bird communities over two years in 13 restoration sites and two old-growth forests in southern Costa Rica. Restoration sites were established on degraded farmlands in a variety of landscape contexts, and each included a 0.25-ha plantation, island treatment (trees planted in patches), and unplanted control. We analyzed four attributes of bird communities including frugivore abundance, Nectarivore abundance, migrant insectivore richness, and compositional similarity of bird communities in restoration plots to bird communities in old-growth forests. All four bird community variables were greater in plantations and/or islands than in control treatments. Frugivore and Nectarivore abundance decreased with increasing tree cover in the landscape surrounding restoration plots, whereas compositional similarity to old-growth forests was greatest in plantations embedded in landscapes with high tree cover. Migrant insectivore richness was unaffected by landscape tree cover. Our results agree with previous studies showing that increasing levels of investment in active restoration are positively related to bird richness and abundance, but differences in the effects of landscape tree cover on foraging guilds and community composition suggest that trade-offs between biodiversity conservation and bird-mediated ecosystem functioning may be important for prioritizing restoration sites.
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Compositional and functional attributes of bird communities predicted by restoration treatments and landscape tree cover.
2014Co-Authors: Leighton J. Reid, Chase D. Mendenhall, Abel J. Rosales, Rakan A. Zahawi, Karen D. HollAbstract:Error bars represent ±1 s.e.m. (A–C) Controls are represented by squares; islands by triangles, and plantations by circles. (A) Sørensen similarity of bird communities in restoration sites to bird communities in reference forest (550 m tree cover buffer); (B) frugivore abundance per observation (7 observations per point; 350 m buffer); (C) Nectarivore abundance per observation (450 m buffer); (D) migrant insectivore richness (equal sampling intensity). Significance calculated using pairwise Wilcoxon rank sum tests with Bonferroni corrections (all P
