A wavelength discrimination function for the hummingbirdArchilochus alexandri

Summary Free-flying black-chinned hummingbirds (Archilochus alexandri) at a site in southeastern Arizona were attracted to artificial feeders displaying narrow spectral bands of light (7 nm half band width). The birds were taught to discriminate between pairs of wavelengths of approximately equal brightness but with a spectral separation of 10 nm. After training, performance of the birds was not significantly changed by alterations in the relative intensities of the two lights. Moreover, when the spectral composition of the test and training lights was made identical, the birds did not learn to make a discrimination on the basis of intensity differences of 0.5 or 1 log unit. In the learned foraging behavior of these hummingbirds, the salience of brightness is therefore inconsequential relative to hue.Discrimination scores for a constant 10 nm separation of test and training wavelengths were determined between 410 and 650 nm. This measure of the spectral dependence of wavelength discrimination shows a deterioration of performance at the red end of the spectrum but not in the blue and violet. Moreover, the minima at 585 and 555 nm indicate more structure than is present in this region of the spectrum in the human hue discrimination curve, and are similar but not identical to data on pigeon. These results are consistent with a growing body of evidence suggesting that the color space of birds may be more than three dimensional.This work was supported by NIH grants EY03266 and EY00222. We are indebted to Sally and Walter Spofford, who generously allowed us to work at their home, Aguila-Rancho, during May and June of 1980, and without whose kind help these experiments could not have been performed.     

Cue use affects resource subdivision among three coexisting hummingbird species

Competition for food can influence the coexistence of speciesvia habitat selection, and learned behavior can influence foragingdecisions. I investigated whether learned behavior and competitionact together to influence species interactions between threecoexisting hummingbird species: black-chinned (Archilochusalexandri), blue-throated (Lampornis clemenciae), and magnificent(Eugenes fulgens) hummingbirds. I found that color cue useby individuals affects not only their foraging choices butalso population-level responses to competition. I presented hummingbirds two types of habitats (rich and poor feeders).All birds shared a preference for the rich feeders, but shiftedpreference toward poor feeders in response to competition.I used color cues to manipulate the amount of information availableto birds and examined the effects of two information states(complete or incomplete) on their foraging choices. I examined hummingbirds' preferences for the rich feeders when both competitordensities and information varied. To relate foraging choicesto energetic intake, I also analyzed energy gained during asingle foraging bout. Males of all species exhibited strongpreferences for rich feeders when they foraged with complete information and low competitor densities. Without complete information,the two subordinate species (black-chinned and magnificent)shifted preference away from rich feeders in response to highdensities of the dominant species (blue-throated). Each subordinatespecies shifted in a unique way: black-chinned hummingbirdsreduced foraging efficiency, while magnificent hummingbirdsreduced foraging time. Birds foraging with complete information remained selective on rich feeders even at high competitor densities.Thus, learned information affected competitive interactions(for rich feeders) among these species.     

Foraging information affects the nature of competitive interactions

If animals can learn environmental cues, how might their use of information affect competitive interactions between species? I used shared‐preference isoleg theory to generate four different predictions regarding possible ways information could affect density‐dependent habitat selection. To test these predictions, I conducted field experiments on the foraging behavior of three coexisting species of hummingbirds. I studied black‐chinned (Archilochus alexandri), blue‐throated (Lampornis clemenciae), and magnificent (Eugenes fulgens) hummingbirds at the Southwestern Research Station in the Chiricahua Mts. of Southeastern Arizona, USA. Blue‐throated hummingbirds behaviorally dominate the other two species. I found that birds foraging with complete information (via learned color cues) avoid some of the negative effects from competition. Birds that foraged with complete information remained highly selective on rich feeders even with high competitor densities. When birds suffered an information deficit, however, the two subordinate species shifted their foraging preferences. The dominant species did not shift preference. Each subordinate's shift reflects its unique place in this competitively structured guild. With high competitor densities, black‐chinneds shifted from selective to opportunistic foraging when they also suffered from an information deficit. Thus, an information deficit caused black‐chinneds to cross over their first isoleg. Rather than reduce foraging efficiency, the magnificents shortened their foraging time. I use the magnificents’ response to competition and an information deficit to explore the possibility that this guild of hummingbirds is centrifugally organized. My results require us to consider the information‐gathering (e.g., learning) abilities of individual decision‐makers when we evaluate density‐dependent habitat selection. Differences in the level of usable information can alter the way coexisting species respond to competitive interactions that potentially structure communities.     

Hummingbird color preference within a natural hybrid population of Mimulus aurantiacus (Phrymaceae)

Hummingbird flowers are typically red in color but the reasons for this are not well understood. Relatively few studies have examined hummingbird flower color preferences under natural conditions in which flower color varies within a species. We recorded hummingbird visitation rates to flowers that vary in color from yellow to red in a natural hybrid population between red‐ and yellow‐flowered Mimulus aurantiacus subspecies. We also examined whether there were any correlations between color and flower size or nectar content. Finally, we reviewed the literature on hummingbird color choice tests using feeders and flowers. There were no correlations in this population between flower color and flower size, nectar volume, or sugar concentration. Nevertheless, hummingbirds undervisited the two most yellow color classes, overvisited orange flowers, and visited the two most red color classes in proportion to their frequency in the population. While Hummingbirds preferred flowers expressing red pigments to those that did not, the flowers with the most red hue were not the most attractive, as has been observed in similar studies with other species of Mimulus. While feeder studies generally fail to show hummingbird preference for red, all studies using flowers, including those that control all floral traits other than color, find consistent preference for red. Experiments are suggested that might help disentangle hypotheses for why hummingbirds exhibit this preference.     

Discrimination between learned colors against a new background and in a new place in honeybees, <Emphasis Type="Italic">Apis mellifera</Emphasis> (Hymenoptera,Apidae)

In field experiments, honeybees learned to discriminate between rewarded and unrewarded feeders differing in color. After learning, familiar feeders were presented against a different background or the place of presentation was shifted several meters away. Both innovations decreased the average percentage of correct choices. This decrease is considered to be evidence of “contextual isolation.” This isolation was partial because the discrimination of learned colors was partially retained under the new conditions. This appears to be the first known example of partial contextual isolation. Significant individual differences were revealed. Some bees demonstrated spontaneous color preferences while the others did not. Four out of 34 bees failed to learn the rewarded color even after 30–40 visits.     

Pollinating birds differ in spectral sensitivity

Pollinating animals and their angiosperm hosts often show strong co-adaptation in traits that increase the likelihood of a successful transfer of pollen and nutrient rewards. One such adaptation is the reported colour difference caused by unequal distribution of anthocyanidin pigments amongst plant species visited by hummingbirds and passerines. This phenomenon has been suggested to reflect possible differences in the colour vision of these pollinating birds. The presence of any such difference in colour vision would arguably affect the ecological and evolutionary interactions between flowers and their visitors, accentuating differences in floral displays and attractiveness of plants to the favoured avian pollinators. We have tested for differences in colour vision, as indicated by the amino acid present at certain key positions in the short-wavelength-sensitive type 1 (SWS1) visual pigment opsin, between the major groups of pollinating birds: the non-passerine Trochilidae (hummingbirds), the passerine Meliphagidae (honeyeaters) and Nectariniidae (sunbirds) plus five other Passerida passerine families. The results reveal gross spectral sensitivity differences between hummingbirds and honeyeaters, on the one hand, and the Passerida species, on the other.     

Effect of artificial feeders on pollen loads of the hummingbirds of Cerro de la Muerte, Costa Rica

Although sugar-water feeders are commonly used by enthusiasts to attract hummingbirds, little is known about how they affect hummingbird behavior and flower use. We studied the highland hummingbird assemblage of Cerro de La Muerte, Costa Rica, both at a site with permanent feeders (La Georgina Restaurant) and further from it. We examined how feeder use and monopolization affected seasonal changes in pollen loads during four sampling periods, including dry and wet seasons, from 2003-2005. We expected that species monopolizing the feeders would carry little or no pollen whatsoever, and would have pollen loads characterized by low floral diversity, in contrast with species less dependent on feeders. We obtained pollen samples from 183 individuals of four hummingbird species captured around the feeders using mist nets, which were compared with a pollen reference collection of plants with a pollination syndrome by hummingbirds. The same methods were implemented at a site 3km away from the feeders. Feeder usage was quantified by counting the number of times hummingbirds drank from the feeders in periods of 4min separated by 1min. The effects of hummingbird species and season on pollen load categories were assessed using a nominal logistic regression. The alpha species at the site, the Fiery-throated Hummingbird (Panterpe insignis), dominated the feeders during the dry season. Meanwhile, in the wet season, feeder usage was more evenly distributed across species, with the exception of the Volcano Hummingbird, Selasphorus flammula, which occupies the last place in the dominance hierarchy. Pollen loads of hummingbirds captured near feeders were low in abundance (more than 50% of captured individuals had zero or low pollen loads), and low in species richness (96% of the hummingbirds with pollen from only one plant genus, Centropogon). Overall pollen loads increased during the dry season coinciding with peaks in flower availability, although the majority of captured hummingbirds carried no pollen. Mist nets located 3km from La Georgina returned few captures (one-to-three specimens) per sampling date, contrasting with observations made before feeders were present. These results suggest that sugar-water feeders gather hummingbirds in over considerable distances drawing them away from flowers. The competitive and antagonistic pattern shown between feeders and flowers indicate that natural pollination system could be significantly altered. Supplementing hummingbirds with food seems likely to interfere with pollination networks already stressed by many anthropogenic effects.     

Automated tracking of wild hummingbird mass and energetics over multiple time scales using radio frequency identification (RFID) technology

We examined the feasibility of automating the collection of hummingbird mass data facilitated by low‐cost, low‐power radio frequency identification (RFID) technology. In a field study in southern Ontario, wild hummingbirds were captured, subcutaneously implanted with passive integrated transponder (PIT) tags, and released over a three‐year period. Tagged hummingbirds were detected at specially designed feeder stations outfitted with low‐cost, low‐power RFID readers coupled with a perch secured to a digital balance. When tagged birds visited the feeder, transponder detection initiated the recording of the perched hummingbird's mass at regular intervals continuing as long as the bird remained. This permitted a nearly continuous record of mass during each visit. Mass data collected from tagged hummingbirds showed consistent trends at multiple temporal scales: the individual feeder visit, single days, and even whole seasons. These results further confirm that RFID technology is safe for use in the smallest birds. The effective detection range is a function of RFID reader power, antenna, and tag size. Yet, we find that careful arrangement of feeders and detectors allows for reliable detection even when detection range is low. When coupled with additional technologies, such as a precision electronic balance, this approach can yield robust serial measures of physiological parameters such as mass, an indicator of energy balance over time.     

Color vision of the budgerigar (<Emphasis Type="Italic">Melopsittacus undulatus</Emphasis>): hue matches,tetrachromacy, and intensity discrimination

Budgerigars, Melopsittacus undulatus, were trained to discriminate monochromatic lights from mixtures of two comparison lights. The addition of small amounts of UV (365 nm) to blue or yellow lights dramatically changed the color for the birds. Hue matches showed the birds to be dichromatic both at long wavelengths (only P565 and P508 active) and at short wavelengths (only P370 and P445 active because of screening of P508 and P565 by cone oil droplets). In mid-spectrum (only P445 and P508 active), a hue match was achieved, but the results were more complicated because two opponent neural processes were activated. All observed hue matches were in quantitative agreement with calculations of relative quantum catch in the pairs of participating single cones and point to the presence of a minimum of three opponent neural processes. For the hue matches at mid- and short wavelengths, the calculations also predict peak values of absorbance of the cone oil droplets associated with P508 and P445. Relative intensity of the training light affected difficult matches at long but not short wavelengths, likely due to achromatic signals from the double cones. With suitable training, birds could make intensity discriminations at short wavelengths, where the double cones have diminished sensitivity.     

Observational Learning in the White-Eared Hummingbird (Hylocharis leucotis): Experimental Evidence

The adoption of new food resources can be facilitated by the ability to learn through observation of other individuals who use them. This behavior, termed observational learning, applies to any problem solving in which a naive individual who has observed an experienced individual learns a behavior faster than another who has not. Hummingbirds consume nectar from flowers of a large number of plant species, which are very diverse in morphology and color. During their local or migratory movements, they can observe the use of floral resources by conspecifics and heterospecifics which may change their foraging preferences. Although there is evidence that hummingbirds can use observational learning to exploit new floral resources, it is necessary to generate additional information by studying different hummingbird species. In this work, the learning performance of White‐eared hummingbirds (Hylocharis leucotis) was studied in the presence or absence of a knowledgeable tutor. In a first experiment, naïve hummingbirds learned to feed on arrays of artificial flower of two colors: red (previously known resource) and yellow (novel resource), where only one color had nectar. Naive hummingbirds visited red flowers faster and more often than rewarded yellow flowers. Individuals with the best performance on each color were further trained to ensure that they only visited flowers of a specific color, and were then used as tutors in the next experiment, in which new naive hummingbirds, caged individually, were allowed to observe them foraging on the artificial arrays. These naïve individual were then exposed alone to the same array used by their tutor. Tutored hummingbirds learned to feed faster and more frequently from nectar‐containing flowers of the array than naive individuals. Likewise, all tutored individuals only visited flowers of the color that had been previously visited by their tutors. This study provides experimental evidence that hummingbirds taken directly from the field can use observational learning as an efficient strategy to access new floral resources.     

Bills and tongues of nectar-feeding birds: A review of morphology,function and performance,with intercontinental comparisons

The bills and tongues of nectar-feeding birds differ from continent to continent. The major differences are that: (i) the tongues of A Australian honeyeaters are broader any more fimbricated at the tip than the bifurcated tongues of sunbirds and hummingbirds; (ii) the bills of hummingbirds are more uniformly narrow and taper less markedly towards their tips than those of sun-birds and honeyeaters; and (iii) bill curvatures are generally greater for sunbirds and honey-creepers than for hummingbirds. A variety of hummingbirds has straight or even slightly upturned bills, while bills for all sunbirds, honeycreepers and honeyeaters are decurved to some extent. Despite differences in tongue morphology, hummingbirds, sunbirds and honeyeaters extract nectar at a similar range of rates, averaging approximately 40 γL s^?1 from ad libitum feeders, and 1–15 γL^?1 from flowers. All tongues collect nectar by capillarity, with licking rates of 6–17 s^?1. Licking behaviour has been little studied, although speeds of licking respond to changes in sugar concentration and corolla length. The tongues of honeyeaters are broad, and may need to be brush-tipped in order to allow capillary collection of nectar. Brush-tipped tongues can cover large surface areas on each lick, and may allow honeyeaters to exploit nectar and honeydew that is thinly spread over large surface areas. Bill lengths of nectarivorous birds are similar in all regions, though species of hummingbird have the shortest and longest bills. Bill lengths largely determine the range of floral lengths that can be legitimately probed. Maximum floral lengths exceed bill lengths, since hummingbirds, sunbirds and honeyeaters protrude their tongues beyond the tips of their bills. Rates of nectar extraction, however, decline rapidly once the floral length exceeds bill length. Decurved bills may have evolved in honeyeaters and sunbirds to enable perching birds to reach flowers at the ends of branches more easily. Consistent differences in bill length between the sexes suggest that males and females may exploit different floral resources or different proportions of the same resources. For honeyeaters and sunbirds, males have longer bills than females, but the reverse is true for many hummingbirds.     

The effect of yellow and blue light on magnetic compass orientation in European robins, Erithacus rubecula

To analyze the wavelength dependency of magnetic compass orientation, European robins were tested during spring migration under light of various wavelengths. Under 565-nm green light (control) the birds showed excellent orientation in their migratory direction; a 120° deflection of magnetic North resulted in a corresponding shift in the birds' directional tendencies, indicating the use of the magnetic compass. Under 443-nm blue light, the robins were likewise well oriented. Under 590-nm yellow, however, oriented behavior was no longer observed, although the activity was at the same level as under blue and green light. The spectral range where magnetic orientation is possible thus differs from the range of vision, the former showing parallels to that of rhodopsin absorption. The interpretation of the abrupt change in behavior observed between 565 green to 590 yellow is unclear. There is no simple relationship between magnetoreception and the known color receptors of birds. Accepted: 17 December 1998     

Use of spatial and colour cues by foraging pine siskins (Carduelis pinus): A field study

Pine siskins (Carduelis pinus) frequently forage at known high quality food supplies such as backyard feeders. In this field study, pine siskins visited backyard feeders of differing colour and spatial position. The three feeders contained varying amounts of food in a ratio of 3:2:1. The birds quickly distributed their visits in this ratio to the three feeders. During unbaited tests, two feeders on a given day had their positions swapped. The siskins appeared to primarily use both large-scale spatial or distal cues when foraging as well as local colour cues.     

What do foraging hummingbirds maximize?

Summary Hainsworth and Wolf (1976) reported that under certain conditions hummingbirds made food choices which did not maximize their net rate of energy intake while foraging. They concluded that the birds were not foraging optimally. We show here that their birds probably maximized a different utility function, the net energy per unit volume consumed (NEVC), which appears to be an optimal choice on a time scale longer than that of a foraging bout. Our own experiments with Archilochus colubris support the conclusion that hummingbirds make foraging decisions that maximize NEVC. A simulation model shows that, in nature, NEVC maximization would require fewer foraging trips and visits to fewer flowers per day to balance daily energy budgets. For territorial birds this can lead to smaller territory sizes and reduced costs of territorial defense. Plants that evolutionarily increase corolla length to enhance pollinator specificity need only increase nectar concentration slightly to maintain the same net energy per unit volume consumed (NEVC) by a given hummingbird pollinator.     

Risk‐averse inflorescence departure in hummingbirds and bumble bees: could plants benefit from variable nectar volumes?

Most hermaphroditic, many-flowered plants should suffer reduced fitness from within-plant selfing (geitonogamy). Large inflorescences are most attractive to pollinators, but also promote many flower visits during a single plant visit, which may increase selfing and decrease pollen export. A plant might avoid the negative consequences of attractiveness through modification of the floral display to promote fewer flower visits, while retaining attractiveness. This report shows that increasing only the variance in nectar volume per flower results in fewer flower visits per inflorescence by wild hummingbirds ( Selasphorus rufus ) and captive bumble bees ( Bombus flavifrons ) foraging on artificial inflorescences. Inflorescences were either constant (all flowers contained the same nectar volume) or variable (half the flowers were empty, the other half contained twice as much nectar as in the constant flowers). Both types of inflorescence were simultaneously available to foragers. Risk-averse foraging behaviour was expressed as a patch departure preference: birds and bees visited fewer flowers on variable inflorescences, and this preference was expressed when resource variability could be determined only by concurrent sampling. When variance treatments were clearly labelled with colour and offered to hummingbirds, the departure effect was maintained; however, when preference was measured by inflorescence choice, birds did not consistently prefer to visit constant inflorescences. The reduced visitation lengths on variable inflorescences by both birds and bees documented in this study imply that variance in nectar production rates within inflorescences may represent an adaptive trait to avoid the costs of geitonogamy.     

The power of feeder-mask respirometry as a method for examining hummingbird energetics

Many birds spend important portions of their time and energy flying. For this reason, quantification of metabolic rates during flight is of crucial importance to understanding avian energy balance. Measurement of organismal gas exchange rates using a mask enclosing the whole head or respiratory orifices has served as an important tool for studying animal energetics because it can free the rest of the body, permitting movement. Application of so-called “mask respirometry” to the study of avian forward flight energetics presents unique challenges because birds must be tethered to gas analysis equipment thus typically necessitating use of a wind tunnel. Resulting potential alterations to a study organism's behaviour, physiology, and aerodynamics have made interpretation of such studies contentious. In contrast, the study of hovering flight energetics in hummingbirds using a specialized form of mask respirometry is comparatively easy and can be done without a wind tunnel. Small size, hovering flight, and a nectarivorous diet are characteristics shared by all hummingbird species that make these birds ideally suited for this approach. Specifically, nectar feeders are modified to function as respirometry masks hummingbirds voluntarily respire into when hover-feeding. Feeder-mask based respirometry has revealed some of the highest vertebrate metabolic rates in hovering hummingbirds. In this review I discuss techniques for the successful measurement of metabolic rate using feeder-mask respirometry. I also emphasize how this technique has been used to address fundamental questions regarding avian flight energetics such as capacities for fuel use and mechanisms by which ecology, behaviour and energy balance are linked.     

Rhodamine immunohistofluorescence applied to plant tissue.

Tissue slices from the roots and seeds of sanifoin (Onobrychis viciifolia, Scop.) exhibit bright autofluorescence when illuminated with blue (495 nm) light. This autofluorescence is indistinguishable from the fluorescence emission of fluorescein, the commonly used fluorochrome in immunohistochemical staining procedures. Rhodamine isothiocyanate, when coupled to immunoglobulin, and excited with green light at 546 nm, exhibits a reddish-orange fluorescence with an emission maximum at 590 nm. Plant tissue has little or no autofluorescence when illuminated at this wavelength and viewed with a 580 nm barrier filter. Therefore, use of rhodamine for immunohistochemical localization in plant tissue avoids interpretative complications due to inherent autofluorescence.     

Ornamental bill color rapidly signals changing condition

Ornamental bill color is postulated to function as a condition‐dependent signal of individual quality in a variety of taxonomically distant bird families. Most red, orange, and yellow bill colors are derived from carotenoid pigments, and carotenoid deposition in ornamentation may trade off with their use as immunostimulants and antioxidants or with other physiological functions. Several studies have found that bill color changes in response to physiological perturbations, but how quickly such changes can occur remains unclear. We tested the hypothesis that carotenoid‐based orange bill color of American goldfinches Spinus tristis responds dynamically to rapid changes in physiological stress and reflects short‐term changes in condition. We captured male and female goldfinches and measured bill color in the field and again under captive conditions several hours later. The following day, the captive birds were injected with either immunostimulatory lipopolysaccharide (LPS) or a control saline and changes in bill color were measured over a five day period. Yellow saturation of the bill decreased within 6.5 h between the field and captivity measures on the first day, presumably in response to capture stress. Over the longer experimental period, bill hue and luminance decreased significantly, whereas saturation significantly increased in both LPS and control groups. Bill hue and luminance decreased significantly more in birds treated with LPS than in control birds. Among LPS treated birds, individuals expressing high bill color at the beginning of the experiment lost more color than ‘low‐color’ birds, but still retained higher color at the end of the experiment, suggesting that birds that invest heavily in bill coloration are able to sustain high costs in the face of a challenge. Bill color change may have resulted from rapid reallocation of carotenoids from ornamentation to immune function. However, the complex shifts in bill color over time suggest that bill color may be influenced by multiple carotenoid compounds and/or changes in blood flow or chemistry in vessels just beneath the translucent keratinized outer layer of the bill. We conclude that bill color is a dynamic, condition‐dependent trait that strategically and reliably signals short‐term fluctuations in physiological condition.     

Resource defense and monopolization in a marked population of ruby‐throated hummingbirds (Archilochus colubris)

Resource defense behavior is often explained by the spatial and temporal distribution of resources. However, factors such as competition, habitat complexity, and individual space use may also affect the capacity of individuals to defend and monopolize resources. Yet, studies frequently focus on one or two factors, overlooking the complexity found in natural settings. Here, we addressed defense and monopolization of nectar feeders in a population of free‐ranging ruby‐throated hummingbirds marked with passive integrated transponder (PIT tags). Our study system consisted of a 44 ha systematic grid of 45 feeders equipped with PIT tag detectors recording every visit made at feeders. We modeled the number of visits by competitors (NVC) at feeders in response to space use by a focal individual potentially defending a feeder, number of competitors, nectar sucrose concentration, and habitat visibility. Individuals who were more concentrated at certain feeders on a given day and who were more stable in their use of the grid throughout the season gained higher exclusivity in the use of those feeders on that day, especially for males competing against males. The level of spatial concentration at feeders and its negative effect on NVC was, however, highly variable among individuals, suggesting a continuum in resource defense strategies. Although the apparent capacity to defend feeders was not affected by competition or nectar sucrose concentration, the level of monopolization decreased with increasing number of competitors and higher nectar quality. Defense was enhanced by visibility near feeders, but only in forested habitats. The reverse effect of visibility in open habitats was more difficult to interpret as it was probably confounded by perch availability, from which a bird can defend its feeder. Our study is among the first to quantify the joint use of food resource by overlapping individuals unconstrained in their use of space. Our results show the importance of accounting for variation in space use among individuals as it translated into varying levels of defense and monopolization of feeders regardless of food resource distribution.     

Behaviour and pleiotropy: Generalization of gene effects in the colour preferences of Japanese quail chicks (C. coturnix japonica)

Two lines of Japanese quail (Coturnix coturnix japonica) were artificially selected for colour preferences in 16 generations; one line for preference of blue over red, another for preference of red over blue. A genetic control line was maintained without selection, in parallel generations. Subjects of the blue-selected line exhibited general preferences for the shorter over the longer wavelengths, when tested with stimulus pairs of large hue differences. In similar situations red-line subjects preferred the shorter wavelength, within pairs above 542 nm. The relative strength of colour preferences in the three lines remained significantly different under conditions of both large and small hue differences. Genetic influences in preferences and preference, generalizations were detectable equally well with stimuli administered through wide-band gelatin filters and stimuli administered through narrow-band interference filters. In addition to demonstrating behavioural pleiotropy, the data counterindicated genetic variation in colour vision as a factor in the mediation of gene effects in the quail's colour preferences.