Are Hummingbirds Facultatively Ammonotelic? Nitrogen Excretion and Requirements as a Function of Body Size

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. Birdpollinated plants secrete carbohydrate- and water-rich floral nectars that contain exceedingly little protein. Thus, nectarfeeding 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 they ingest large quantities of water their primary nitrogen excretion product may be ammonia. To test these hypotheses, we measured maintenance nitrogen requirements (MNR) and total endogenous nitrogen losses (TENL) in three hummingbird species (Archilochus alexandri, Eugenes fulgens, and Lampornis clemenciae) fed on diets with varying sugar, protein, and water content. We also quantified the form in which the by-products of nitrogen metabolism were excreted. The MNR and TENL of the hummingbirds examined were exceptionally low. However, no birds excreted more than 50% of nitrogen as ammonia or more nitrogen as ammonia than urates. Furthermore, ammonia excretion was not influenced by either water or protein intake. The smallest species (A. alexandri) excreted a significantly greater proportion (125%) of their nitrogenous wastes as ammonia than the larger hummingbirds (≈4%). Our results support the hypothesis that nectar-feeding birds have low protein requirements but cast doubt on the notion that they are facultatively ammonotelic. Our data also hint at a possible size-dependent dichotomy in hummingbirds, with higher ammonia excretion in smaller species. Differences in proportionate water loads and/or postrenal modification of urine may explain this dichotomy

Avian thermoregulation in the heat : evaporative cooling capacity of arid-zone Caprimulgiformes from two continents

Birds in the order Caprimulgiformes (nightjars and allies) have a remarkable capacity for thermoregulation over a wide range of environmental temperatures, exhibiting pronounced heterothermy in cool conditions and extreme heat tolerance at high environmental temperatures. We measured thermoregulatory responses to acute heat stress in three species of Caprimulgiformes that nest in areas of extreme heat and aridity, the common poorwill (Phalaenoptilus nuttallii: Caprimulgidae) and lesser nighthawk (Chordeiles acutipennis: Caprimulgidae) in the Sonoran Desert of Arizona, and the Australian owlet-nightjar (Aegotheles cristatus: Aegothelidae) in the mallee woodlands of South Australia. We exposed wild-caught birds to progressively increasing air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), body temperature (Tb) and heat tolerance limit (HTL; the maximum Ta reached). Comparatively low RMR values were observed in all species (0.35, 0.36 and 0.40 Wfor the poorwill, nighthawk and owletnightjar, respectively), with Tb approximating Ta at 40°C and mild hyperthermia occurring as Ta reached the HTL. Nighthawks and poorwills reached HTLs of 60 and 62°C, respectively, whereas the owlet-nightjar had a HTL of 52°C. RMR increased gradually above minima at Ta of 42, 42 and 35°C, and reached 1.7, 1.9 and 2.0 times minimum resting values at HTLs in the poorwill, nighthawk and owletnightjar, respectively. EWL increased rapidly and linearly as Ta exceeded Tb and resulted in maximum rates of evaporative heat dissipation equivalent to 237–424% of metabolic heat production. Bouts of gular flutter resulted in large transient increases in evaporative heat loss (50–123%) accompanied by only small increments in RMR (<5%). The cavity-nesting/roosting owletnightjar had a lower HTL and less efficient evaporative cooling compared with the species that nest and/or roost on open desert surfaces. The high efficiency of gular flutter for evaporative cooling, combined with mild hyperthermia, provides the physiological basis for defending Tb well below Ta in extreme heat and is comparable to the efficient cooling observed in arid-zone columbids in which cutaneous EWL is the predominant cooling pathway.The National Science Foundation under IOS-1122228 to B.O.W.http://jeb.biologists.org2018-10-01am2018Zoology and Entomolog

Population density estimate of leopards (Panthera pardus) in north-western Mpumalanga, South Africa, determined using spatially explicit capture-recapture methods

AVAILABILITY OF DATA AND MATERIAL : Raw data and material are either published in the manuscript or available in data repository DANS (https://doi.org/10.17026/dans-zvs-betq).Please read abstract in the article.PhD student operating funds available from the School of Animal and Veterinary Sciences at The University of Adelaide.https://link.springer.com/journal/42991hj2023Production Animal Studie

Avian thermoregulation in the heat : evaporative cooling in five Australian passerines reveals within-order biogeographic variation in heat tolerance

Evaporative heat loss pathways vary among avian orders, but the extent to which evaporative cooling capacity and heat tolerance vary within orders remains unclear. We quantified the upper limits to thermoregulation under extremely hot conditions in five Australian passerines: yellow-plumed honeyeater (Lichenostomus ornatus; ∼17 g), spiny-cheeked honeyeater (Acanthagenys rufogularis; ∼42 g), chestnut-crowned babbler (Pomatostomus ruficeps; ∼52 g), grey butcherbird (Cracticus torquatus; ∼86 g) and apostlebird (Struthidea cinerea; ∼118 g). At air temperatures (Ta) exceeding body temperature (Tb), all five species showed increases in Tb to maximum values around 44–45°C, accompanied by rapid increases in resting metabolic rate above clearly defined upper critical limits of thermoneutrality and increases in evaporative water loss (EWL) to levels equivalent to 670–860% of baseline rates at thermoneutral Ta. Maximum cooling capacity, quantified as the fraction of metabolic heat production dissipated evaporatively, ranged from 1.20 to 2.17, consistent with the known range for passerines, and well below the corresponding ranges for columbids and caprimulgids. Heat tolerance limit (HTL, the maximum Ta tolerated) scaled positively with body mass, varying from 46°C in yellow-plumed honeyeaters to 52°C in a single apostlebird, but was lower than that of three southern African ploceid passerines investigated previously. We argue this difference is functionally linked to a smaller scope for increases in EWL above baseline levels. Our data reiterate the reliance of passerines in general on respiratory evaporative heat loss via panting, but also reveal substantial within-order variation in heat tolerance and evaporative cooling capacity.The National Science Foundation [IOS- 1122228 to B.O.W.].http://jeb.biologists.org2018-07-30am2017Zoology and Entomolog

Paracellular absorption is relatively low in the herbivorous Egyptian spiny-tailed lizard, Uromastyx aegyptia

Extent: 9 p.Absorption of small water-soluble nutrients in vertebrate intestines occurs both by specific, mediated transport and by nonspecific, passive, paracellular transport. Although it is apparent that paracellular absorption represents a significant route for nutrient absorption in many birds and mammals, especially small, flying species, its importance in ectothermic vertebrates has not previously been explored. Therefore, we measured fractional absorption (e) and absorption rate of three paracellular probes (arabinose, L-rhamnose, cellobiose) and of 3-O-methyl D-glucose (absorbed by both mediated and paracellular pathways) by the large herbivorous lizard, Uromastyx aegyptia, to explore the relative importance of paracellular and mediated transport in an ectothermic, terrestrial vertebrate. Fractional absorption of 3-O-methyl D-glucose was high (e = 0.7360.04) and similar to other vertebrates; e of the paracellular probes was relatively low (arabinose e = 0.3160.03, Lrhamnose e = 0.1960.02, and cellobiose e = 0.1460.02), and decreased with molecular mass, a pattern consistent with other vertebrates. Paracellular absorption accounted for approximately 24% of total 3-O-methyl D-glucose uptake, indicating low reliance on this pathway for these herbivorous lizards, a pattern similar to that found in other terrestrial vertebrates, and different from small flying endotherms (both birds and bats).Todd J. McWhorter, Berry Pinshow, William H. Karasov and Christopher R. Trac

Comparative Treatment Outcomes for Patients With Idiopathic Subglottic Stenosis.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked DownloadImportance: Surgical treatment comparisons in rare diseases are difficult secondary to the geographic distribution of patients. Fortunately, emerging technologies offer promise to reduce these barriers for research. Objective: To prospectively compare the outcomes of the 3 most common surgical approaches for idiopathic subglottic stenosis (iSGS), a rare airway disease. Design, setting, and participants: In this international, prospective, 3-year multicenter cohort study, 810 patients with untreated, newly diagnosed, or previously treated iSGS were enrolled after undergoing a surgical procedure (endoscopic dilation [ED], endoscopic resection with adjuvant medical therapy [ERMT], or cricotracheal resection [CTR]). Patients were recruited from clinician practices in the North American Airway Collaborative and an online iSGS community on Facebook. Main outcomes and measures: The primary end point was days from initial surgical procedure to recurrent surgical procedure. Secondary end points included quality of life using the Clinical COPD (chronic obstructive pulmonary disease) Questionnaire (CCQ), Voice Handicap Index-10 (VHI-10), Eating Assessment Test-10 (EAT-10), the 12-Item Short-Form Version 2 (SF-12v2), and postoperative complications. Results: Of 810 patients in this cohort, 798 (98.5%) were female and 787 (97.2%) were white, with a median age of 50 years (interquartile range, 43-58 years). Index surgical procedures were ED (n = 603; 74.4%), ERMT (n = 121; 14.9%), and CTR (n = 86; 10.6%). Overall, 185 patients (22.8%) had a recurrent surgical procedure during the 3-year study, but recurrence differed by modality (CTR, 1 patient [1.2%]; ERMT, 15 [12.4%]; and ED, 169 [28.0%]). Weighted, propensity score-matched, Cox proportional hazards regression models showed ED was inferior to ERMT (hazard ratio [HR], 3.16; 95% CI, 1.8-5.5). Among successfully treated patients without recurrence, those treated with CTR had the best CCQ (0.75 points) and SF-12v2 (54 points) scores and worst VHI-10 score (13 points) 360 days after enrollment as well as the greatest perioperative risk. Conclusions and relevance: In this cohort study of 810 patients with iSGS, endoscopic dilation, the most popular surgical approach for iSGS, was associated with a higher recurrence rate compared with other procedures. Cricotracheal resection offered the most durable results but showed the greatest perioperative risk and the worst long-term voice outcomes. Endoscopic resection with medical therapy was associated with better disease control compared with ED and had minimal association with vocal function. These results may be used to inform individual patient treatment decision-making.Patient-Centered Outcomes Research Institute - PCOR

Who reviews what you do at the zoo? Considerations for research ethics with captive exotic animals

Research in zoos is an important scientific endeavor that requires several complex considerations in order to occur. Among those many considerations are the ethics involved in conducting zoo research. However, it is not always clear how zoo researchers should go about resolving any research ethics matters, even determining when some type of research ethics committee should be involved in those deliberations. Our paper attempts to provide some resolutions for these issues, namely in three sections: (1) a brief history of human and animal research ethics, (2) general guidelines for zoo research ethics applications, and (3) theoretical, ethical dilemmas at the zoo. In each section, we consider pragmatic attempts to resolve any issues, as well as provide examples to illustrate our points. The primary focus of the paper is to facilitate consideration of the wide array of ethical factors any zoo researcher might encounter, as well as provide a basic set of ethical guidelines for zoo research. We also emphasize the importance of the welfare of the animals for all zoo research projects

The integration of diet, physiology, and ecology of nectar-feeding birds La integración de la dieta, fisiología, y ecología en aves nectarívoras

Balance between energy acquisition and expense is critical for the survival and reproductive success of organisms. Energy budgets may be limited by environmental factors as well as by animal design. These restrictions may be especially important for small endotherms such as hummingbirds, which have exceedingly high energy demands. 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 (Selasphorus platycercus) and Green-backed fire crown hummingbirds (Sephanoides sephaniodes) were presented with diets varying in energy density and exposed to various environmental temperatures. Birds decreased volumetric food intake in response to sugar concentration. However, when they were exposed to lower environmental temperatures, and hence increased thermoregulatory demands, they did not increase their rate of energy consumption and lost mass. These results support the existence of a physiological constraint to the energy budgets of hummingbirds. Digestive and peripheral organ function limitations may impose severe challenges to the energy budgets of these small endotherms, and therefore play a significant role in determining their distribution, ecology, and natural history.El balance entre la adquisición y el uso de energía es crítico para la reproducción y sobrevivencia. Los presupuestos energéticos de los organismos pueden estar limitados tanto por factores ambientales como por su fisiología. Estas restricciones pueden ser especialmente importantes para pequeños endotérmos como los colibríes (picaflores) que tienen costos energéticos altos por unidad de masa. Muchas especies de aves nectarívoras reducen el consumo de alimento cuando la concentración de azúcar aumenta. Esta respuesta puede ser explicada por dos hipótesis alternativas: compensación alimenticia y restricciones fisiológicas. La primera hipótesis predice que las aves varían el consumo para mantener la ingesta de alimento ajustada a sus gastos energéticos. Por ende, cuando los gastos energéticos aumentan, el consumo debe aumentar. Colibríes vibradores (Selasphorus platycercus) y picaflores (Sephanoides sephaniodes) fueron alimentados con dietas de contenido energético variable y expuestos a varias temperaturas ambientales. Las aves redujeron el volumen consumido en respuesta a un incremento en la concentración de azúcar. Sin embargo, cuando fueron expuestos a bajas temperaturas, y por lo tanto a mayores demandas de termoregulación, no aumentaron su consumo de energía y perdieron masa corporal. Estos resultados indican la existencia de una limitante fisiología que restringe a los presupuestos energéticos de los colibríes. Limitaciones funcionales (digestivas o periféricas) pueden imponer seríos dilemas para los presupuestos de energía de estos pequeños endotérmos y por lo tanto jugar un papel significativo en su distribución, ecología, e historia natural

Using individual-condition measures to predict the long-term importance of habitat extent for population persistence

Habitat loss and fragmentation are causing widespread population declines, but identifying how and when to intervene remains challenging. Predicting where extirpations are likely to occur and implementing management actions before losses result may be more cost-effective than trying to reestablish lost populations. Early indicators of pressure on populations could be used to make such predictions. Previous work conducted in 2009 and 2010 identified that the presence of Eastern Yellow Robins (Eopsaltria australis) in 42 sites in a fragmented region of eastern Australia was unrelated to woodland extent within 500 m of a site, but the robins’ heterophil:lymphocyte (H:L) ratios (an indicator of chronic stress) were elevated at sites with low levels of surrounding woodland. We resurveyed these 42 sites in 2013 and 2014 for robin presence to determine whether the H:L ratios obtained in 2009 and 2010 predicted the locations of extirpations and whether the previous pattern in H:L ratios was an early sign that woodland extent would become an important predictor of occupancy. We also surveyed for robins at 43 additional sites to determine whether current occupancy could be better predicted by landscape context at a larger scale, relevant to dispersal movements. At the original 42 sites, H:L ratios and extirpations were not related, although only 4 extirpations were observed. Woodland extent within 500 m had become a strong predictor of occupancy. Taken together, these results provide mixed evidence as to whether patterns of individual condition can reveal habitat relationships that become evident as local shifts in occupancy occur but that are not revealed by a single snapshot of species distribution. Across all 85 sites, woodland extent at scales relevant to dispersal (5 km) was not related to occurrence. We recommend that conservation actions focus on regenerating areas of habitat large enough to support robin territories rather than increasing connectivity within the landscape

The integration of diet, physiology, and ecology of nectar-feeding birds

ABSTRACT Balance between energy acquisition and expense is critical for the survival and reproductive success of organisms. Energy budgets may be limited by environmental factors as well as by animal design. These restrictions may be especially important for small endotherms such as hummingbirds, which have exceedingly high energy demands. 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 (Selasphorus platycercus) and Green-backed fire crown hummingbirds (Sephanoides sephaniodes) were presented with diets varying in energy density and exposed to various environmental temperatures. Birds decreased volumetric food intake in response to sugar concentration. However, when they were exposed to lower environmental temperatures, and hence increased thermoregulatory demands, they did not increase their rate of energy consumption and lost mass. These results support the existence of a physiological constraint to the energy budgets of hummingbirds. Digestive and peripheral organ function limitations may impose severe challenges to the energy budgets of these small endotherms, and therefore play a significant role in determining their distribution, ecology, and natural history. Key words: energetics, digestion, feeding behavior, hummingbirds, nectarivory. RESUMEN El balance entre la adquisici6n y el uso de energfa es crftico para la reproducci6n y sobrevivencia. Los presupuestos energeticos de Ios organismos pueden estar limitados tanto por factores ambientales como por su fisiologfa. Estas restricciones pueden ser especialmente importantes para pequefios endotermos como Ios colibrfes (picaflores) que tienen costos energeticos altos por unidad de masa. Muchas especies de aves nectarfvoras reducen el consumo de alimento cuando la concentraci6n de azucar aumenta. Esta respuesta puede ser explicada por dos hip6tesis alternativas: compensaci6n alimenticia y restricciones fisiol6gicas. La primera hip6tesis predice que !as aves varfan el consumo para mantener la ingesta de alimento ajustada a sus gastos energeticos. Por ende, cuando Ios gastos energeticos aumentan, el consumo debe aumentar. Colibrfes vibradores (Selasphorus platycercus) y picaflores (Sephanoides sephaniodes) fueron alimentados con dietas de contenido energetico variable y expuestos a varias temperaturas ambientales. Las aves redujeron el volumen consumido en respuesta a un incremento en la concentraci6n de azucar. Sin embargo, cuando fueron expuestos a bajas temperaturas, y por lo tanto a mayores demandas de termoregulaci6n, no aumentaron su consumo de energfa y perdieron masa corporal. Estos resultados indican la existencia de una limitante fisiologfa que restringe a Ios presupuestos energeticos de Ios colibrfes. Limitaciones funcionales (digestivas o perifericas) pueden imponer serf os dilemas para Ios presupuestos de energfa de estos pequefios endotermos y por lo tanto jugar un papel significativo en su distribuci6n, ecologfa, e historia natural