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Full-Text Articles in Life Sciences
Hummingbirds Fuel Hovering Flight With Newly Ingested Sugar, K. C. Welch, B. H. Bakken, Carlos Martinez Del Rio, R. K. Suarez
Hummingbirds Fuel Hovering Flight With Newly Ingested Sugar, K. C. Welch, B. H. Bakken, Carlos Martinez Del Rio, R. K. Suarez
Carlos Martinez del Rio
We sought to characterize the ability of hummingbirds to fuel their energetically expensive hovering flight using dietary sugar by a combination of respirometry and stable carbon isotope techniques. Broadtailed hummingbirds (Selasphorus platycercus) were maintained on a diet containing beet sugar with an isotopic composition characteristic of C3 plants. Hummingbirds were fasted and then offered a solution containing cane sugar with an isotopic composition characteristic of C4 plants. By monitoring the rates of CO2 production and O-2 consumption, as well as the stable carbon isotope composition of expired CO2, we were able to estimate the relative contributions of carbohydrate and fat, …
The Cyanogenic Glycoside Amygdalin Does Not Deter Consumption Of Ripe Fruit By Cedar Waxwings, H. M. Struempf, J. E. Schondube, Carlos Martinez Del Rio
The Cyanogenic Glycoside Amygdalin Does Not Deter Consumption Of Ripe Fruit By Cedar Waxwings, H. M. Struempf, J. E. Schondube, Carlos Martinez Del Rio
Carlos Martinez del Rio
Cyanogenic glycosides are common secondary compounds in ripe fruits that are dispersed by birds. These substances are toxic to some mammals. We examined the repellent effect of amygdalin, a cyanogenic glycoside, on Cedar Waxwings (Bombycilla cedrorum). Amygdalin did not reduce food ingestion in Cedar Waxwings, even at relatively high concentrations. In addition, these birds did not exhibit preference for amygdalin-free over amygdalin-containing fruit. Cedar Waxwings given artificial food that contained four times the amount of amygdalin found in some wild fruits ingested the equivalent of 5.5 times the oral lethal dose for rats in 4 h without exhibiting any external …
The Fate Of Carbon In Growing Fish: An Experimental Study Of Isotopic Routing, L. J. Kelly, Carlos Martinez Del Rio
The Fate Of Carbon In Growing Fish: An Experimental Study Of Isotopic Routing, L. J. Kelly, Carlos Martinez Del Rio
Carlos Martinez del Rio
The application of stable isotope analysis to ecology requires estimating the contribution of different isotopic sources to the isotopic signatures of an animal's tissues using mixing models. These models make the physiologically unrealistic assumption that assimilated nutrients are disassembled into their elemental components and that these atoms are then reassembled into biomolecules. We quantified the extent to which mixing models yield erroneous results with an experiment using Nile tilapia (Oreochromis niloticus). The tilapia were fed synthetic diets that varied in protein content and in which the carbon isotopic composition of protein differed widely from that of carbohydrates and lipids. We …
Dietary Flexibility And Intestinal Plasticity In Birds: A Field And Laboratory Study, P. Sabat, F. Novoa, F. Bozinovic, Carlos Martinez Del Rio
Dietary Flexibility And Intestinal Plasticity In Birds: A Field And Laboratory Study, P. Sabat, F. Novoa, F. Bozinovic, Carlos Martinez Del Rio
Carlos Martinez del Rio
The adaptive modulation hypothesis posits that the expression of digestive proteins should be modulated in response to intake of their respective substrates. A corollary of this hypothesis suggests that dietary flexibility and digestive plasticity should be correlated. We examined these two hypotheses in two granivorous Chilean birds (Zonotrichia capensis and Diuca diuca) that differ in dietary breadth. D. diuca is a strict granivore, whereas Z. capensis also eats insects. In field-caught birds, the activity of the intestinal dipeptidase aminopeptidase-N was positively correlated with intake of insects in Z. capensis but not in D. diuca. This is the first field documentation …
It Takes Guts (And More) To Eat Fruit: Lessons From Avian Nutritional Ecology, D. J. Levey, Carlos Martinez Del Rio
It Takes Guts (And More) To Eat Fruit: Lessons From Avian Nutritional Ecology, D. J. Levey, Carlos Martinez Del Rio
Carlos Martinez del Rio
No abstract provided.
Are Hummingbirds Facultatively Ammonotelic? Nitrogen Excretion And Requirements As A Function Of Body Size, T. J. Mcwhorter, D. R. Powers, Carlos Martinez Del Rio
Are Hummingbirds Facultatively Ammonotelic? Nitrogen Excretion And Requirements As A Function Of Body Size, T. J. Mcwhorter, D. R. Powers, Carlos Martinez Del Rio
Carlos Martinez del Rio
Most birds are uricotelic. An exception to this rule may be nectar-feeding birds, which excrete significant amounts of ammonia under certain conditions. Although ammonia is toxic, because it is highly water soluble its excretion may be facilitated in animals that ingest and excrete large amounts of water. Bird-pollinated plants secrete carbohydrate- and water-rich floral nectars that contain exceedingly little protein. Thus, nectar-feeding birds are faced with the dual challenge of meeting nitrogen requirements while disposing of large amounts of water. The peculiar diet of nectar-feeding birds suggests two hypotheses: (1) these birds must have low protein requirements, and (2) when …
Does Gut Function Limit Hummingbird Food Intake?, T. J. Mcwhorter, Carlos Martinez Del Rio
Does Gut Function Limit Hummingbird Food Intake?, T. J. Mcwhorter, Carlos Martinez Del Rio
Carlos Martinez del Rio
Many nectar-feeding bird species decrease food intake when sugar concentration in food is increased. This feeding response can be explained by two alternative hypotheses: compensatory feeding and physiological constraint. The compensatory feeding hypothesis predicts that if birds vary intake to maintain a constant energy intake to match energy expenditures, then they should increase intake when expenditures are increased. Broad-tailed hummingbirds were presented with sucrose solutions at four concentrations (292, 584, 876, and 1,168 mmol L-1) and exposed to two environmental temperatures (10 degrees and 22 degrees C). Birds decreased volumetric food intake in response to sugar concentration. However, when they …
Do Nectar- And Fruit-Eating Birds Have Lower Nitrogen Requirements Than Omnivores? An Allometric Test, E. Tsahar, Z. Ara, I. Izhaki, Carlos Martinez Del Rio
Do Nectar- And Fruit-Eating Birds Have Lower Nitrogen Requirements Than Omnivores? An Allometric Test, E. Tsahar, Z. Ara, I. Izhaki, Carlos Martinez Del Rio
Carlos Martinez del Rio
We used an allometric approach to compare the minimum nitrogen requirements (MNR) and the total endogenous nitrogen loss (TENL) of nectar- and fruit-eating birds with those of omnivorous birds. These two parameters were 4x higher in omnivores than in nectarivores and frugivores. In nectarivorous-frugivorous birds, MNR was 152.8 mg N kg(-0.76) day(-1); in omnivorous birds, it was 575.4 mg N kg(-0.76) day(-1). Similarly, TENL was 54.1 mg N kg(-0.69) day(-1) in nectarivores-frugivores, and 215.3 mg N kg(-0.69) day(-1) in omnivores. The residuals of the allometric relationships between TENL and MNR and body mass were positively correlated, which suggests that a …
Are The Low Protein Requirements Of Nectarivorous Birds The Consequence Of Their Sugary And Watery Diet? A Test With An Omnivore, E. Tsahar, Carlos Martinez Del Rio, Z. Arad, J. P. Joy, I. Izhaki
Are The Low Protein Requirements Of Nectarivorous Birds The Consequence Of Their Sugary And Watery Diet? A Test With An Omnivore, E. Tsahar, Carlos Martinez Del Rio, Z. Arad, J. P. Joy, I. Izhaki
Carlos Martinez del Rio
Nectar-feeding birds have remarkably low nitrogen requirements. These may be due either to adaptation to a low-protein diet or simply to feeding on a fluid diet that minimizes metabolic fecal nitrogen losses. We measured minimal nitrogen requirements (MNR) and total endogenous nitrogen loss (TENL) in the omnivorous European starling Sturnus vulgaris, fed on an artificial nectar-like fluid diet of varying concentrations of sugar and protein. The MNR and TENL of the birds were similar and even slightly higher than allometrically expected values for birds of the starlings' mass (140% and 103%, respectively). This suggests that the low measured nitrogen requirements …