| neural song control system of hummingbirds: comparison to swifts, vocal learning (songbirds) and nonlearning (suboscines) passerines, and vocal learning (budgerigars) and nonlearning (dove, owl, gull, quail, chicken) nonpasserines. | males of certain hummingbird species such as anna's hummingbirds (calypte anna) learn their song during postnatal development. here we report that male anna's hummingbirds and male amazilia hummingbirds (amazilia amazilia), two singing hummingbird species, possess forebrain areas that are similar in morphological appearance, location, and connectivity to the song control areas ra (nucleus robustus archistriatalis), hvc (nucleus hyperstriatalis ventrale, pars caudale, or higher vocal center), and ... | 2000 | 10982462 |
| morphological and molecular characterization of encephalitozoon hellem in hummingbirds. | microsporidiosis was identified as a cause of enteritis in wild, migratory hummingbirds (calypte anna). electron microscopic examinations of parasites showed microsporidian spores with a double spore coat and a polar filament containing four to six coils, compatible with the genus encephalitozoon. molecular analysis of ribosomal rna genes further identified the parasites from droppings and small intestinal segments as encephalitozoon hellem, genotype i. microsporidial spores were identified in 1 ... | 2001 | 19184907 |
| The distribution of zebrin immunoreactive purkinje cell terminals in the cerebellar and vestibular nuclei of birds. | Zebrin II (aldolase C) is expressed in a subset Purkinje cells in the mammalian and avian cerebella such that there is a characteristic parasagittal organization of zebrin immunopositive stripes alternating with zebrin immunonegative stripes. Zebrin is not only expressed in the soma and dendrites of Purkinje cells, but also in their axonal terminals. Here, we describe the distribution of zebrin immunoreactivity in both the vestibular and cerebellar nuclei of pigeons (Columbia livia) and hummingb ... | 2011 | 22105608 |
| eye morphology and retinal topography in hummingbirds (trochilidae: aves). | hummingbirds are a group of small, highly specialized birds that display a range of adaptations to their nectarivorous lifestyle. vision plays a key role in hummingbird feeding and hovering behaviours, yet very little is known about the visual systems of these birds. in this study, we measured eye morphology in 5 hummingbird species. for 2 of these species, we used stereology and retinal whole mounts to study the topographic distribution of neurons in the ganglion cell layer. eye morphology (exp ... | 2015 | 26587582 |
| muscle activation patterns and motor anatomy of anna's hummingbirds calypte anna and zebra finches taeniopygia guttata. | flying animals exhibit profound transformations in anatomy, physiology, and neural architecture. although much is known about adaptations in the avian skeleton and musculature, less is known about neuroanatomy and motor unit integration for bird flight. hummingbirds are among the most maneuverable and specialized of vertebrate fliers, and two unusual neuromuscular features have been previously reported: (1) the pectoralis major has a unique distribution pattern of motor end plates (meps) compare ... | 2013 | 23303319 |
| hummingbird incubation: female attentiveness and egg temperature. | incubating hummingbirds adjust nest attentiveness patterns in different habitats to permit both regulation of egg temperatures for embryonic development and foraging of the adult for positive energy balance. anna's (calype anna) and black-chinned (archilochus alexandri) hummingbirds nesting in california chaparral left the nest six to nine times during each daylight hour. eggs usually cooled only 3-6°c during absences but sometimes cooled up to 20°c during long absences. one anna's hummingbird b ... | 1981 | 28310082 |
| cost of territory establishment in hummingbirds. | time spent in territorial defense was measured during territory establishment for non-breeding black-chinned (archilochus alexandri) and anna's (calypte anna) hummingbirds. newly established territory holders spent more time chasing intruders than neighboring established owners, which served as controls. this higher investment in defense by the new owners was due to 1) a longer time spent per each chase and 2) in some cases, a higher frequency of chases at the onset of territory ownership. | 1980 | 28309667 |
| hyperglycemia in hummingbirds and its consequences for hemoglobin glycation. | we measured levels of glucose and glycated hemoglobin in the blood of three of the world's smallest nectarivorous birds, the anna's (calypte anna), costa's (calypte costae), and ruby-throated hummingbirds (archilochus colubris). plasma glucose levels of hummingbirds that were fasted overnight (17 mm) were higher than those in any mammal and are among the highest ever measured in a fasting vertebrate. glucose levels in hummingbirds just after feeding were extreme, rising as high as 42 mm. the sur ... | 1998 | 9787825 |
| winter range expansion of a hummingbird is associated with urbanization and supplementary feeding. | anthropogenic changes to the landscape and climate cause novel ecological and evolutionary pressures, leading to potentially dramatic changes in the distribution of biodiversity. warm winter temperatures can shift species' distributions to regions that were previously uninhabitable. further, urbanization and supplementary feeding may facilitate range expansions and potentially reduce migration tendency. here we explore how these factors interact to cause non-uniform effects across a species's ra ... | 2017 | 28381617 |
| mechanical constraints on flight at high elevation decrease maneuvering performance of hummingbirds. | high-elevation habitats offer ecological advantages including reduced competition, predation, and parasitism [1]. however, flying organisms at high elevation also face physiological challenges due to lower air density and oxygen availability [2]. these constraints are expected to affect the flight maneuvers that are required to compete with rivals, capture prey, and evade threats [3-5]. to test how individual maneuvering performance is affected by elevation, we measured the free-flight maneuvers ... | 2016 | 27939316 |
| hummingbirds control turning velocity using body orientation and turning radius using asymmetrical wingbeat kinematics. | turning in flight requires reorientation of force, which birds, bats and insects accomplish either by shifting body position and total force in concert or by using left-right asymmetries in wingbeat kinematics. although both mechanisms have been observed in multiple species, it is currently unknown how each is used to control changes in trajectory. we addressed this problem by measuring body and wingbeat kinematics as hummingbirds tracked a revolving feeder, and estimating aerodynamic forces usi ... | 2016 | 27030042 |
| electrostatic charge on flying hummingbirds and its potential role in pollination. | electrostatic phenomena are known to enhance both wind- and insect-mediated pollination, but have not yet been described for nectar-feeding vertebrates. here we demonstrate that wild anna's hummingbirds (calypte anna) can carry positive charges up to 800 pc while in flight (mean ± s.d.: 66 ± 129 pc). triboelectric charging obtained by rubbing an isolated hummingbird wing against various plant structures generated charges up to 700 pc. a metal hummingbird model charged to 400 pc induced bending o ... | 2015 | 26421845 |
| hovering performance of anna's hummingbirds (calypte anna) in ground effect. | aerodynamic performance and energetic savings for flight in ground effect are theoretically maximized during hovering, but have never been directly measured for flying animals. we evaluated flight kinematics, metabolic rates and induced flow velocities for anna's hummingbirds hovering at heights (relative to wing length r = 5.5 cm) of 0.7r, 0.9r, 1.1r, 1.7r, 2.2r and 8r above a solid surface. flight at heights less than or equal to 1.1r resulted in significant reductions in the body angle, tail ... | 2014 | 24990291 |
| into turbulent air: size-dependent effects of von kármán vortex streets on hummingbird flight kinematics and energetics. | animal fliers frequently move through a variety of perturbed flows during their daily aerial routines. however, the extent to which these perturbations influence flight control and energetic expenditure is essentially unknown. here, we evaluate the kinematic and metabolic consequences of flight within variably sized vortex shedding flows using five anna's hummingbirds feeding from an artificial flower in steady control flow and within vortex wakes produced behind vertical cylinders. tests were c ... | 2014 | 24671978 |
| characterization of avian poxvirus in anna's hummingbird (calypte anna) in california, usa. | avian poxvirus (genus avipoxvirus, family poxviridae) is an enveloped double-stranded dna virus that may be transmitted to birds by arthropod vectors or mucosal membrane contact with infectious particles. we characterized the infection in anna's hummingbird (calypte anna; n = 5 birds, n = 9 lesions) by conducting diagnostic tests on skin lesions that were visually similar to avian poxvirus lesions in other bird species. skin lesions were single or multiple, dry and firm, pink to yellow, with sca ... | 2013 | 24502725 |
| structure of the vortex wake in hovering anna's hummingbirds (calypte anna). | hummingbirds are specialized hoverers for which the vortex wake has been described as a series of single vortex rings shed primarily during the downstroke. recent findings in bats and birds, as well as in a recent study on anna's hummingbirds, suggest that each wing may shed a discrete vortex ring, yielding a bilaterally paired wake. here, we describe the presence of two discrete rings in the wake of hovering anna's hummingbirds, and also infer force production through a wingbeat with contributi ... | 2013 | 24174113 |
| very low force-generating ability and unusually high temperature dependency in hummingbird flight muscle fibers. | hummingbird flight muscle is estimated to have among the highest mass-specific power output among vertebrates, based on aerodynamic models. however, little is known about the fundamental contractile properties of their remarkable flight muscles. we hypothesized that hummingbird pectoralis fibers generate relatively low force when activated in a tradeoff for high shortening speeds associated with the characteristic high wingbeat frequencies that are required for sustained hovering. our objective ... | 2013 | 23580719 |
| backward flight in hummingbirds employs unique kinematic adjustments and entails low metabolic cost. | backward flight is a frequently used transient flight behavior among members of the species-rich hummingbird family (trochilidae) when retreating from flowers, and is known from a variety of other avian and hexapod taxa, but the biomechanics of this intriguing locomotor mode have not been described. we measured rates of oxygen uptake (v(o2)) and flight kinematics of anna's hummingbirds, calypte anna (lesson), within a wind tunnel using mask respirometry and high-speed videography, respectively, ... | 2012 | 23014570 |
| analysis of the transitional flow field over a fixed hummingbird wing. | we analyzed the flow fields characterized by chord-based reynolds numbers of 5000 to 15,000 over a stationary model of a hummingbird (calypte anna) wing. utilizing two experimental techniques, constant-temperature anemometry and stereo particle image velocimetry, the high-fidelity results depict a laminar-to-turbulent transition process that develops over the wing. at both zero and non-zero angles of attack the spectrum of the velocity signals is wide. at non-zero angles of attack the flow separ ... | 2013 | 22996450 |
| wingbeat kinematics and motor control of yaw turns in anna's hummingbirds (calypte anna). | the biomechanical and neuromuscular mechanisms used by different animals to generate turns in flight are highly variable. body size and body plan exert some influence, e.g. birds typically roll their body to orient forces generated by the wings whereas insects are capable of turning via left-right wingbeat asymmetries. turns are also relatively brief and have low repeatability, with almost every wingbeat serving a different function throughout the change in heading. here we present an analysis o ... | 2012 | 22933610 |
| dietary protein level affects iridescent coloration in anna's hummingbirds, calypte anna. | many animal displays involve colorful ornamental traits that signal an individual's quality as a mate or rival. brilliant iridescent ornaments are common, but little is currently known about their production cost and signaling value. one potential cost of colorful ornaments is the acquisition of limited dietary resources that may be involved, directly or indirectly, in their production. protein, the primary component of bird feathers and of many nanostructural components of iridescent traits, is ... | 2012 | 22837446 |
| flying in the rain: hovering performance of anna's hummingbirds under varied precipitation. | flight in rain represents a greater challenge for smaller animals because the relative effects of water loading and drop impact are greater at reduced scales given the increased ratios of surface area to mass. nevertheless, it is well known that small volant taxa such as hummingbirds can continue foraging even in extreme precipitation. here, we evaluated the effect of four rain intensities (i.e. zero, light, moderate and heavy) on the hovering performance of anna's hummingbirds (calypte anna) un ... | 2012 | 22810431 |
| neuromuscular control of wingbeat kinematics in anna's hummingbirds (calypte anna). | hummingbirds can maintain the highest wingbeat frequencies of any flying vertebrate - a feat accomplished by the large pectoral muscles that power the wing strokes. an unusual feature of these muscles is that they are activated by one or a few spikes per cycle as revealed by electromyogram recordings (emgs). the relatively simple nature of this activation pattern provides an opportunity to understand how motor units are recruited to modulate limb kinematics. hummingbirds made to fly in low-densi ... | 2010 | 20581280 |
| hovering and forward flight energetics in anna's and allen's hummingbirds. | aerodynamic theory predicts that the mechanical costs of flight are lowest at intermediate flight speeds; metabolic costs of flight should trend similarly if muscle efficiency is constant. we measured metabolic rates for nine anna's hummingbirds (calypte anna) and two male allen's hummingbirds (selasphorus sasin) feeding during flight from a free-standing mask over a range of airspeeds. ten of 11 birds exhibited higher metabolic costs during hovering than during flight at intermediate airspeeds, ... | 2015 | 20455711 |
| hovering energetics and thermal balance in anna's hummingbirds (calypte anna). | we studied the energetics of hover-feeding anna's hummingbirds, using three different simultaneous techniques: heat loss as estimated via thermal imaging, metabolic rate as measured at a feeder mask using flow-through respirometry, and aerodynamic power estimated from wingbeat kinematic data. these three methods yielded comparable estimates of power output at ambient air temperatures ranging from 18 degrees to 26 degrees c, whereas heat imbalance at higher air temperatures (up to 34 degrees c) s ... | 2010 | 20350142 |
| why do calypte hummingbirds "sing" with both their tail and their syrinx? an apparent example of sexual sensory bias. | courtship displays frequently include complex signals that females use to pick a mate. male costa's hummingbirds (calypte costae) generate two acoustic signals during courtship: a vocal song produced close to a female and a dive-sound produced during a courtship dive. the song and dive-sound sound similar, and both were assumed to be produced vocally by the syrinx. here, we show that they are not; whereas the song is produced by the syrinx, the dive-sound is produced by high-frequency fluttering ... | 2010 | 19916787 |
| courtship dives of anna's hummingbird offer insights into flight performance limits. | behavioural displays are a common feature of animal courtship. just as female preferences can generate exaggerated male ornaments, female preferences for dynamic behaviours may cause males to perform courtship displays near intrinsic performance limits. i provide an example of an extreme display, the courtship dive of anna's hummingbird (calypte anna). diving male anna's hummingbirds were filmed with a combination of high-speed and conventional video cameras. after powering the initial stage of ... | 2009 | 19515669 |
| flight costs of long, sexually selected tails in hummingbirds. | the elongated tails adorning many male birds have traditionally been thought to degrade flight performance by increasing body drag. however, aerodynamic interactions between the body and tail can be substantial in some contexts, and a short tail may actually reduce rather than increase overall drag. to test how tail length affects flight performance, we manipulated the tails of anna's hummingbirds (calypte anna) by increasing their length with the greatly elongated tail streamers of the red-bill ... | 2009 | 19324747 |
| fiber type homogeneity of the flight musculature in small birds. | studies of medium- and large-bodied avian species have suggested that variation in flight muscle composition is related to differences in flight behavior. for example, slow-twitch or tonic fibers are generally found only in the flight muscles of non-volant or soaring/gliding birds. however, we know comparatively little about fiber composition of the muscles of the smallest birds. here we describe the fiber composition of muscles from the wings, shoulders, and legs of two small avian species, whi ... | 2009 | 19162216 |
| the anna's hummingbird chirps with its tail: a new mechanism of sonation in birds. | a diverse array of birds apparently make mechanical sounds (called sonations) with their feathers. few studies have established that these sounds are non-vocal, and the mechanics of how these sounds are produced remains poorly studied. the loud, high-frequency chirp emitted by a male anna's hummingbird (calypte anna) during his display dive is a debated example. production of the sound was originally attributed to the tail, but a more recent study argued that the sound is vocal. here, we use hig ... | 2008 | 18230592 |
| dietary sugar as a direct fuel for flight in the nectarivorous bat glossophaga soricina. | it is thought that the capacity of mammals to directly supply the energetic needs of exercising muscles using recently ingested fuels is limited. humans, for example, can only fuel about 30%, at most, of exercise metabolism with dietary sugar. using indirect calorimetry, i.e. measurement of rates of o(2) consumption and co(2) production, in combination with carbon stable isotope techniques, we found that nectarivorous bats glossophaga soricina use recently ingested sugars to provide approximatel ... | 2008 | 18203985 |
| oxidation rate and turnover of ingested sugar in hovering anna's (calypte anna) and rufous (selasphorus rufus) hummingbirds. | hummingbirds obtain most of their dietary calories from floral nectar ingested during hovering flight. despite the importance of dietary sugar to hummingbird metabolism, the turnover of newly ingested carbon in the pool of actively metabolized substrates has not been adequately characterized in hovering hummingbirds. by combining respirometry with stable carbon isotope analysis of respired breath, we show that in rufous (selasphorus rufus) and anna's (calypte anna) hummingbirds at high foraging ... | 2007 | 17562889 |
| oxygen consumption rates in hovering hummingbirds reflect substrate-dependent differences in p/o ratios: carbohydrate as a 'premium fuel'. | the stoichiometric relationship of atp production to oxygen consumption, i.e. the p/o ratio, varies depending on the nature of the metabolic substrate used. the latest estimates reveal a p/o ratio approximately 15% higher when glucose is oxidized compared with fatty acid oxidation. because the energy required to produce aerodynamic lift for hovering is independent of the metabolic fuel oxidized, we hypothesized that the rate of oxygen consumption, vo2, should decline as the respiratory quotient, ... | 2007 | 17562888 |
| hummingbirds rely on both paracellular and carrier-mediated intestinal glucose absorption to fuel high metabolism. | twenty years ago, the highest active glucose transport rate and lowest passive glucose permeability in vertebrates were reported in rufous and anna's hummingbirds (selasphorus rufus, calypte anna). these first measurements of intestinal nutrient absorption in nectarivores provided an unprecedented physiological foundation for understanding their foraging ecology. they showed that physiological processes are determinants of feeding behaviour. the conclusion that active, mediated transport account ... | 2006 | 17148346 |
| ammonotely in a passerine nectarivore: the influence of renal and post-renal modification on nitrogenous waste product excretion. | most aquatic vertebrates are ammonotelic, whereas terrestrial vertebrates are typically uricotelic or ureotelic. however, the principal form of nitrogenous waste product in the urine of an animal may vary, depending on environmental conditions. anna's hummingbird (calypte anna) was found to switch from uricotely at high ambient temperature (t(a)) to ammonotely at lower t(a), when energy demands and consequent nectar intake rates were high. in extension of this, we hypothesised that nectarivorous ... | 2002 | 12042332 |
| changes in the composition of the urine of yellow-vented bulbuls (pycnonotus xanthopygos): the effects of ambient temperature, nitrogen, and water intake. | uricotely (uric acid >50% of urinary nitrogen) in birds was once considered ubiquitous. however, anna's hummingbirds (calypte anna) have been shown to be an exception to this rule; under conditions of low ambient temperature (t(a)) and on a nitrogen-free diet, they increased their water intake and often became ammonotelic (ammonia >50% of urinary nitrogen). our aim was to identify the effects of nitrogen intake, water intake, and t(a) on the ammonia excretion of yellow-vented bulbuls (pycnonotus ... | 2013 | 11731976 |
| oxygen consumption during hover-feeding in free-ranging anna hummingbirds. | rates of oxygen consumption during hover-feeding of wild, unrestrained, adult male anna hummingbirds (calypte anna) were measured with an artificial outdoor feeder converted into a respirometer mask. a computer sampled changes in o2 concentration in air drawn through the mask, automatically detecting the presence of a hummingbird from a drop in the o2 concentration, and photoelectrically timing the duration over which the feeder functioned as a mask. birds coming to the feeder were weighed on a ... | 1986 | 3746193 |
| mechanical determinants of nectar feeding strategy in hummingbirds: energetics, tongue morphology, and licking behavior. | to explore the mechanical determinants of feeding strategies for nectar feeders, we develop a fluid dynamical and behavioral model describing the mechanics and energetics of capillary feeding in hummingbirds. behavioral and morphological data for calypte and archilochus are used to test and illustrate this model. we emphasize the important differences between capillary and suction mechanisms of fluid feeding. model predictions of nectar intake rates and nectar volumes per lick are consistent wit ... | 1983 | 28310488 |
| territorial responses to energy manipulations in the anna hummingbird. | territorial activity in the anna hummingbird (calypte anna) was measured while energy availability on the territory was varied. on days when energy availability was unlimited, residents defended highly exclusive territories primarily by energetically expensive defense behaviors. as energy availability decreased, exclusiveness declined gradually, relative use of energetically inexpensive defense increased, and owners spent less time on the territory.territorial behavior also varied with short ter ... | 1978 | 28309739 |
| time, energy, and territoriality of the anna hummingbird (calypte anna). | the male anna hummingbird accommodates seasonal changes in energy demands by varying its allocation of time and energy among different activities; total energy expenditures change relatively little. augmented terrritorial defense during the breeding season is made possible by increased feeding efficiency due to the availability at this time of very nectar-rich flowers. | 1971 | 17812193 |
| detection and prevalence of haemoproteus archilochus (haemosporida, haemoproteidae) in two species of california hummingbirds. | haemosporidian blood parasites are transmitted to a wide range of avian hosts via blood-sucking dipteran vectors. microscopy has revealed an impressive diversity of avian haemosporidia with more than 250 species described. moreover, pcr and subsequent sequence analyses have suggested a much greater diversity of haemosporidia than morphological analyses alone. given the importance of these parasites, very few studies have focused on the charismatic hummingbirds. to date, three haemoproteus specie ... | 2017 | 28534106 |
| hovering hummingbird wing aerodynamics during the annual cycle. i. complete wing. | the diverse hummingbird family (trochilidae) has unique adaptations for nectarivory, among which is the ability to sustain hover-feeding. as hummingbirds mainly feed while hovering, it is crucial to maintain this ability throughout the annual cycle-especially during flight-feather moult, in which wing area is reduced. to quantify the aerodynamic characteristics and flow mechanisms of a hummingbird wing throughout the annual cycle, time-accurate aerodynamic loads and flow field measurements were ... | 2017 | 28878971 |
| on the autorotation of animal wings. | botanical samaras spin about their centre of mass and create vertical aerodynamic forces which slow their rate of descent. descending autorotation of animal wings, however, has never been documented. we report here that isolated wings from anna's hummingbirds, and also from 10 species of insects, can stably autorotate and achieve descent speeds and aerodynamic performance comparable to those of samaras. a hummingbird wing loaded at its base with the equivalent of 50% of the bird's body mass desc ... | 2017 | 28077761 |
| neurons responsive to global visual motion have unique tuning properties in hummingbirds. | neurons in animal visual systems that respond to global optic flow exhibit selectivity for motion direction and/or velocity. the avian lentiformis mesencephali (lm), known in mammals as the nucleus of the optic tract (not), is a key nucleus for global motion processing [1-4]. in all animals tested, it has been found that the majority of lm and not neurons are tuned to temporo-nasal (back-to-front) motion [4-11]. moreover, the monocular gain of the optokinetic response is higher in this direction ... | 2017 | 28065606 |
| visual guidance of forward flight in hummingbirds reveals control based on image features instead of pattern velocity. | information about self-motion and obstacles in the environment is encoded by optic flow, the movement of images on the eye. decades of research have revealed that flying insects control speed, altitude, and trajectory by a simple strategy of maintaining or balancing the translational velocity of images on the eyes, known as pattern velocity. it has been proposed that birds may use a similar algorithm but this hypothesis has not been tested directly. we examined the influence of pattern velocity ... | 2016 | 27432982 |
| burst muscle performance predicts the speed, acceleration, and turning performance of anna's hummingbirds. | despite recent advances in the study of animal flight, the biomechanical determinants of maneuverability are poorly understood. it is thought that maneuverability may be influenced by intrinsic body mass and wing morphology, and by physiological muscle capacity, but this hypothesis has not yet been evaluated because it requires tracking a large number of free flight maneuvers from known individuals. we used an automated tracking system to record flight sequences from 20 anna's hummingbirds flyin ... | 2015 | 26583753 |
| aerial shaking performance of wet anna's hummingbirds. | external wetting poses problems of immediate heat loss and long-term pathogen growth for vertebrates. beyond these risks, the locomotor ability of smaller animals, and particularly of fliers, may be impaired by water adhering to the body. here, we report on the remarkable ability of hummingbirds to perform rapid shakes in order to expel water from their plumage even while in flight. kinematic performance of aerial versus non-aerial shakes (i.e. those performed while perching) was compared. oscil ... | 2012 | 22072447 |
| the retinal projection to the nucleus lentiformis mesencephali in zebra finch (taeniopygia guttata) and anna's hummingbird (calypte anna). | in birds, the nucleus of the basal optic root (nbor) and the nucleus lentiformis mesencephali (lm) are retinal recipient nuclei involved in the analysis of optic flow and the generation of the optokinetic response. in both pigeons and chickens, retinal inputs to the nbor arise from displaced ganglion cells (dgcs), which are found at the margin of the inner nuclear and inner plexiform layers. the lm receives afferents from retinal ganglion cells, but whether dgcs also project to lm is a matter of ... | 2018 | 29340763 |
| functional divergence of bitter taste receptors in a nectar-feeding bird. | nectar may contain many secondary metabolites that are commonly toxic and bitter-tasting. it has been hypothesized that such bitter-tasting secondary metabolites might keep the nectar exclusive to only a few pollinators. to test this hypothesis, we examined functional changes of bitter taste receptor genes (tas2rs) in a species of nectar-feeding bird (anna's hummingbird) by comparing these genes with those from two closely related insect-feeding species (chimney swift and chuck-will's widow). we ... | 2019 | 31551065 |
| pretectal projections to the oculomotor cerebellum in hummingbirds (calypte anna), zebra finches (taeniopygia guttata), and pigeons (columba livia). | in birds, optic flow is processed by a retinal-recipient nucleus in the pretectum, the nucleus lentiformis mesencephali (lm), which then projects to the cerebellum, a key site for sensorimotor integration. previous studies have shown that the lm is hypertrophied in hummingbirds, and that lm cell response properties differ between hummingbirds and other birds. given these differences in anatomy and physiology, we ask here if there are also species differences in the connectivity of the lm. the lm ... | 2019 | 30950058 |
| concentrations of retinol and α-tocopherol in tissue samples from anna's hummingbirds (calypte anna). | retinol (vitamin a) and α-tocopherol (vitamin e) concentrations were measured in tissue samples (liver, heart, pectoral muscle, and brain) from anna's hummingbirds (calypte anna). hummingbirds were after-hatch year birds that were sourced from various rehabilitation centers throughout california. tissues samples were analyzed using high-performance liquid chromatography (hplc). minimum, maximum, mean, standard deviation (sd), and median ppm concentrations were calculated for each vitamin and tis ... | 2020 | 33134339 |
| characterizing the nectar microbiome of the non-native tropical milkweed, asclepias curassavica, in an urban environment. | in increasingly urban landscapes, the loss of native pollen and nectar floral resources is impacting ecologically important pollinators. increased urbanization has also brought about the rise of urban gardens which introduce new floral resources that may help replace those the pollinators have lost. recently, studies have shown that the microbial communities of nectar may play an important role in plant-pollinator interactions, but these microbial communities and the floral visitors in urban env ... | 2020 | 32877468 |
| determination of neonicotinoids and butenolide residues in avian and insect pollinators and their ambient environment in western canada (2017, 2018). | to examine the spatial, and temporal variation and potential sources of pesticide concentrations, primarily neonicotinoid insecticides, in hummingbirds in western canada, we sampled their cloacal fluid from sites in british columbia and saskatchewan, canada in 2017-2018. at a sub-sample of those sites, we also measured pesticides in honey bee (apis mellifera) nectar, water, and sediment. we collected cloacal fluid from 5 species of hummingbirds (n = 26 sites) in british columbia (bc) and saskatc ... | 2020 | 32563110 |
| anti-microbial activity of whole blood and plasma collected from anna's hummingbirds (calypte anna) against three different microbes. | hummingbirds are essential pollinators in many ecosystems, making their conservation critical. as is the case with many species, hummingbirds are now facing a variety of challenges resulting from anthropogenic changes. as populations shift and species interactions change, disease is likely to pose a significant threat. there is a basic understanding of which pathogens currently affect a variety of hummingbird species, however there is a paucity of information about their immune systems capacity ... | 2020 | 32525884 |
| ecological release of the anna's hummingbird during a northern range expansion. | during range expansions, species can experience rapid population growth if changes in climate or interspecific interactions remove limits on growth rates in novel habitats. here i document a century of range expansion in the anna's hummingbird (calypte anna) and investigate the causes of its recent abundance through a combination of demographic, climatic, and phenological analyses. christmas bird count records indicate that populations have been growing in california since the early twentieth ce ... | 2019 | 31553208 |
| spatial and temporal resolution of the visual system of the anna's hummingbird (calypte anna) relative to other birds. | hummingbirds are an emerging model for studies of the visual guidance of flight. however, basic properties of their visual systems, such as spatial and temporal visual resolution, have not been characterized. we measured both the spatial and temporal visual resolution of anna's hummingbirds using behavioral experiments and anatomical estimates. spatial visual resolution was determined behaviorally using the optocollic reflex and anatomically using peak retinal ganglion cell densities from retina ... | 2020 | 31393209 |
| analysis of insecticide exposure in california hummingbirds using liquid chromatography-mass spectrometry. | external feather rinses and homogenized whole-carcass tissue matrix from two hummingbird species found in california (calypte anna and archilochus alexandri) were analyzed for the presence of nine insecticides commonly used in urban settings. using a liquid chromatography-high-resolution mass spectrometry (lc-hrms) analytical method, samples were quantitatively tested for the following neonicotinoids: dinotefuran, nitenpyram, thiamethoxam, acetamiprid, thiacloprid, clothianidin, imidacloprid, an ... | 2019 | 30941712 |
| microbial communities in hummingbird feeders are distinct from floral nectar and influenced by bird visitation. | human provisioning can shape resource availability for wildlife, but consequences for microbiota availability and exchange remain relatively unexplored. here, we characterized microbial communities on bills and faecal material of hummingbirds and their food resources, including feeders and floral nectar. we experimentally manipulated bird visitation to feeders and examined effects on sucrose solution microbial communities. birds, feeders and flowers hosted distinct bacterial and fungal communiti ... | 2019 | 30836877 |
| avoiding topsy-turvy: how anna's hummingbirds (calypte anna) fly through upward gusts. | flying organisms frequently confront the challenge of maintaining stability when moving within highly dynamic airflows near the earth's surface. either aerodynamic or inertial forces generated by appendages and other structures, such as the tail, may be used to offset aerial perturbations, but these responses have not been well characterized. to better understand how hummingbirds modify wing and tail motions in response to individual gusts, we filmed anna's hummingbirds as they negotiated an upw ... | 2019 | 30718291 |
| ascending flight and decelerating vertical glides in anna's hummingbirds. | hummingbirds are observationally well known for their capacity to vertically ascend whilst hovering, but the underlying mechanics and possible energetic limits to ascent rates are unclear. decelerations during vertical ascent to a fixed target may also be associated with specific visual responses to regulate the body's trajectory. here, we studied climbing flight and subsequent deceleration in male anna's hummingbirds (calypte anna) over an approximately 2 m vertical distance. birds reached vert ... | 2018 | 30355613 |
| how the hummingbird wingbeat is tuned for efficient hovering. | both hummingbirds and insects flap their wings to hover. some insects, like fruit flies, improve efficiency by lifting their body weight equally over the upstroke and downstroke, while utilizing elastic recoil during stroke reversal. it is unclear whether hummingbirds converged on a similar elastic storage solution, because of asymmetries in their lift generation and specialized flight muscle apparatus. the muscles are activated a quarter of a stroke earlier than in larger birds, and contract su ... | 2018 | 30323114 |
| iridescent colouration of male anna's hummingbird (calypte anna) caused by multilayered barbules. | the male anna's hummingbird features a brightly reddish-pink reflecting gorget, due to large stacks of melanosomes in the feather barbules, arranged in layers separated by keratin. direct observations together with detailed scatterometry demonstrated that the barbules reflect incident light in an approximately specular manner. the structural colouration is iridescent, i.e. varies with a changing angle of light incidence. spectrophotometrical measurements of the barbule reflectance and absorbance ... | 2018 | 30298342 |
| hummingbirds and bumble bees exposed to neonicotinoid and organophosphate insecticides in the fraser valley, british columbia, canada. | to measure exposure to neonicotinoid and other pesticides in avian pollinators, we made novel use of cloacal fluid and fecal pellets from rufous (selasphorus rufus) and anna's (calypte anna) hummingbirds living near blueberry fields in the fraser river valley and vancouver island, british columbia, canada. to examine on-farm exposure to pesticides in invertebrate pollinators, we also collected bumble bees native to canada (bombus mixtus, bombus flavifrons, and bombus melanopygus), their pollen, ... | 2018 | 29974994 |
| leukocyte reference intervals for free-ranging hummingbirds in northern california, usa. | hummingbirds are specialized nectarivores and important ecological pollinators that are the focus of conservation efforts as well as scientific investigations of metabolism and flight dynamics. despite their importance, basic information is lacking about hummingbird blood cells. we aimed to establish reference intervals for total and differential leukocyte counts from healthy free-ranging hummingbirds in northern california. hummingbirds were captured in four counties in spring and summer of 201 ... | 2018 | 29616883 |
| hovering hummingbird wing aerodynamics during the annual cycle. ii. implications of wing feather moult. | birds usually moult their feathers in a particular sequence which may incur aerodynamic, physiological and behavioural implications. among birds, hummingbirds are unique species in their sustained hovering flight. because hummingbirds frequently hover-feed, they must maintain sufficiently high flight capacities even when moulting their flight feathers. a hummingbird wing consists of 10 primary flight feathers whose absence during moult may strongly affect wing performance. using dynamic similari ... | 2018 | 29515884 |
| clinical findings and normative ocular data for free-living anna's (calypte anna) and black-chinned (archilochus alexandri) hummingbirds. | to estimate the prevalence of ocular disease and obtain normative ocular data for free-living hummingbirds. | 2019 | 29461005 |
| evaluation of proctophyllodes huitzilopochtlii on feathers from anna's (calypte anna) and black-chinned (archilochus alexandri) hummingbirds: prevalence assessment and imaging analysis using light and tabletop scanning electron microscopy. | proctophyllodes huitzilopochtlii atyeo & braasch 1966 (acariformes: astigmata: proctophyllodidae), a feather mite, was found on feathers collected from five hummingbird species in california. this mite has not been previously documented on feathers from anna's (calypte anna [lesson 1829]) or black-chinned (archilochus alexandri [bourcier & mulsant 1846]) hummingbirds. a total of 753 hummingbirds were evaluated for the presence of mites by species (allen's n = 112; anna's n = 500; black-chinned n ... | 2018 | 29444089 |
| visual sensory signals dominate tactile cues during docked feeding in hummingbirds. | animals living in and interacting with natural environments must monitor and respond to changing conditions and unpredictable situations. using information from multiple sensory systems allows them to modify their behavior in response to their dynamic environment but also creates the challenge of integrating different, and potentially contradictory, sources of information for behavior control. understanding how multiple information streams are integrated to produce flexible and reliable behavior ... | 2017 | 29184479 |
| de novo pacbio long-read and phased avian genome assemblies correct and add to reference genes generated with intermediate and short reads. | reference-quality genomes are expected to provide a resource for studying gene structure, function, and evolution. however, often genes of interest are not completely or accurately assembled, leading to unknown errors in analyses or additional cloning efforts for the correct sequences. a promising solution is long-read sequencing. here we tested pacbio-based long-read sequencing and diploid assembly for potential improvements to the sanger-based intermediate-read zebra finch reference and illumi ... | 2017 | 29020750 |
| glomerular and medullary architecture in the kidney of anna's hummingbird. | hummingbirds have rates of water turnover that are among the highest of any bird, consuming up to five times their body mass in nectar each day. to determine if the processing of these extraordinary volumes of water is associated with structural specializations in the kidney, we examined the renal morphology of anna's hummingbird (calypte anna) using scanning electron microscopy of vascular and tubular casts. the glomerular tufts are simple, containing a single, unbranched capillary that is spir ... | 1999 | 29847878 |