Small birds and bats face strong selection pressure to digest food rapidly in order to reduce digesta mass carried during flight. One mechanism is rapid absorption of a high proportion of glucose via the paracellular pathway (transfer between epithelial cells, not mediated by transporter proteins). Intestinal paracellular permeability to glucose was assessed for two nectarivorous passerines, the Australian New Holland honeyeater (Phylidonyris novaehollandiae) and African white-bellied sunbird (Cinnyris talatala) by measuring the bioavailability of radiolabelled, passively absorbed L-glucose. Bioavailability was high in both species and increased with diet sugar concentration (honeyeaters, 37 and 81% and sunbirds, 53 and 71% for 250 and 1000 mmol l L1 sucrose diets, respectively). We conclude that the relative contribution of paracellular to total glucose absorption increases with greater digesta retention time in the intestine, and paracellular absorption may also be modulated by factors such as intestinal lumen osmolality and interaction with mediated glucose uptake. The dynamic state of paracellular absorption should be taken into account in future studies.

The Spix's macaw (Cyanopsitta spixii) is the rarest parrot on earth. The remaining captive population consists of 79 individuals. Captive propagation is ongoing to increase the number of individuals for future reintroduction back into the wild. Unfortunately, from 2004 to 2012, only 33 chicks hatched from 331 eggs. Semen evaluation and assisted reproduction might help to overcome this problem. Therefore, a recently developed electro-stimulated semen collection technique was used in Spix's macaws. Semen collection was successful in 39 of 78 attempts in 10 out of 17 males. Examination of the semen included evaluation of volume, color, consistency, contaminations and pH, as well as determination of motility, viability, morphology, concentration, and total count of spermatozoa. The median volume of semen samples was 5.6 µl. On average, 34.7 ± 21.9% (median 30%) of the sperm were motile and 23.1 ± 22.1% (median 16.5%) were progressively motile. In addition to spermatozoa, round cells were detected in the samples. Median sperm concentration was 15,500/µl (range 500-97,500/µl) and median viability was 50% (range 5-87%). Morphological examination revealed in 26.5% normal spermatozoa, high numbers of malformations of the head (50.2%) and tail region (20.5%), with 29% of all sperm showing multiple abnormalities. Artificial insemination was performed in three females; two eggs laid after artificial insemination had spermatozoa present on the perivitelline layer, suggesting the possible success of the insemination technique. Although no fertilization could be demonstrated, these preliminary results are promising, as they indicate that assisted reproduction might be a tool for species conservation in the Spix's macaw.

SUMMARYNectarivores face a constant challenge in terms of water balance, experiencing water loading or dehydration when switching between food plants or between feeding and fasting. To understand how whitebellied sunbirds and New Holland honeyeaters meet the challenges of varying preformed water load, we used the elimination of intramuscular-injected [ 14 C]-L-glucose and 3 H 2 O to quantify intestinal and renal water handling on diets varying in sugar concentration. Both sunbirds and honeyeaters showed significant modulation of intestinal water absorption, allowing excess water to be shunted through the intestine when on dilute diets. Despite reducing their fractional water absorption, both species showed linear increases in water flux and fractional body water turnover as water intake increased (both afternoon and morning), suggesting that the modulation of fractional water absorption was not sufficient to completely offset dietary water loads. In both species, glomerular filtration rate was independent of water gain (but was higher for the afternoon), as was renal fractional water reabsorption (measured in the afternoon). During the natural overnight fast, both sunbirds and honeyeaters arrested whole kidney function. Evaporative water loss in sunbirds was variable but correlated with water gain. Both sunbirds and honeyeaters appear to modulate intestinal water absorption as an important component of water regulation to help deal with massive preformed water loads. Shutting down glomerular filtration rate during the overnight fast is another way of saving energy for osmoregulatory function. Birds maintain osmotic balance on diets varying markedly in preformed water load by varying both intestinal water absorption and excretion through the intestine and kidneys.Supplementary material available online at

Coloured nectar is a rare phenomenon best known from islands and insular habitats. Islands are also known for lizard pollination, where coloured nectar potentially acts as a visual cue to attract pollinators, advertising the sweet reward. However, nectar may also contain secondary metabolites with toxic or deterrent effects. The aim of this study was to determine which factors are important as artificial nectar choice determinants to the Madagascar giant day gecko, Phelsuma grandis, an island pollinator: artificial nectar colour, artificial nectar colour saturation, artificial nectar conspicuousness and/or the presence of the alkaloid nicotine. Coloured artificial nectar and the darkest artificial nectar colour saturation were found to be important visual cues for the geckos, while the contrast between artificial nectar and petal colour was not. Geckos were deterred only by high nicotine concentrations (1000 lM in 0.63 M sucrose) and may even prefer low nicotine concentrations to sucrose-only solutions. Given their overall fondness for sugar solutions, Madagascar giant day geckos are likely to be important pollinators of Malagasy plant species that produce enough nectar to attract them, and plants with coloured nectar and/or secondary metabolites may have evolved those traits to attract the geckos in particular.The role of lizards as seed dispersers and pollinators is relatively unknown among animal-plant interactions. Most reports of nectar consumption by lizards are from islands. Lizards may reach relatively high densities on islands as a result of low predation levels, and insect pollinators are often scarce on islands (reviewed in Olesen & Valido 2003). Consequently, it has been suggested that insectivorous lizards have expanded their diets to include fruit and nectar; this niche broadening has led to their playing unusual roles as pollinators and seed dispersers (Eifler 1995;Traveset & Saez 1997;Olesen & Valido 2003;Kaiser-Bunbury et al. 2009).Another feature of plant-animal interactions on islands is the presence of coloured nectar (Hansen et al. 2007a). Although the information is insufficient, this floral trait appears to be more common in circumstances where invertebrate pollination is limited, such as insularity, high altitudes and where vertebrate pollinators are abundant; these correlates are not necessarily mutually exclusive (Hansen et al. 2007a). In addition to being a visual cue to vertebrate pollinators, it has been suggested that coloured nectar acts as an honest signal, where the flower advertises the strength and presence of its reward: the more saturated the colour of the nectar (i.e. the darker it is) the stronger the signal (Olesen et al. 1998;Johnson et al. 2006;Hansen et al. 2007a).A large variety of nectar colours has been found to occur in nature (Hansen et al. 2007a). Plants that are known or suspected to be pollinated by lizards (Trochetia boutoniana, T. blackburniana and Nesocodon mauritianus) have (human-perceived) coloured nectar in the clear to red range and bell-shaped ...

Nectar-feeding birds ingest excess water and risk loss of solutes when they excrete it. Previous work has shown that white-bellied sunbirds (Cinnyris talatala) are unable to maintain energy balance on extremely dilute sucrose diets without salts (e.g. <0.25 mol l(-1)), and that they lose more electrolytes (i.e. Na(+) and K(+)) via cloacal fluid on these diets than on more concentrated diets. Using white-bellied sunbirds and New Holland honeyeaters (Phylidonyris novaehollandiae) we tested the effect of adding electrolytes to a 0.1 mol l(-1) sucrose diet, by including equimolar NaCl and KCl at concentrations from 5 to 40 mmol l(-1) and the individual salts at 20 mmol l(-1). Addition of salts enabled both species to drink significantly more of the 0.1 mol l(-1) sucrose diet than in the absence of salts, and mass loss during the experiment was reduced when salt was included. The larger honeyeaters may be more susceptible to electrolyte depletion than the smaller sunbirds. On 20 mmol l(-1) combined salts, both sunbirds and honeyeaters consumed eight times their body mass in fluid daily. KCl alone had no effect. Birds are thus limited in their consumption of extremely dilute diets by increasing losses of Na(+). This was confirmed by measuring plasma Na(+) levels, which decreased in both species in the absence of dietary Na(+). In addition, sucrose assimilation efficiencies were slightly, but significantly lower when sunbirds were fed salt-free diet, while glucose levels in ureteral urine remained extremely low. It is concluded that Na(+) depletion on very dilute salt-free diets does not affect Na(+)-glucose transport activity in the kidney, but interferes with sugar digestion and/or assimilation in the intestine.