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IRIS colour of humboldt penguins spheniscus humboldti
Abstract
From 1983-1996, the iris colour of 45 to 65 captive Humboldt Penguins Spheniscus humboldti at Emmen Zoo, The Netherlands, was monitored monthly. As chicks and juveniles, Humboldt Penguins at first have dark (grey) indes, which become pale after a while. In most adults the pale indes eventually become red, but some individuals continue having pale irides. Males attain red irides at an earlier age than do females. Two very old males were found to have black irides. In winters on average a slightly redder iris than in the following summer was observed. Iris colour between and within penguin species is darker at higher latitudes. Possible explanations for this are discussed.
... As opposed to the anchoring fibrils and plaques of human corneas [62] (pp. [66][67][68][69][70][71][72], epithelial attachment to Bowman's layer tended to be by way of 'incursions'. Descemet's membrane was also found to thicken with age, while endothelial cell density was greater in the periphery and in younger penguins; some primary cilia extended into the anterior chamber. ...
... Iris colour varies from pale to dark brown between species and may change from juvenile to adult. Scholten noted that, at the genus level, penguins living at higher latitudes have darker irides [69]. Given its common name, surely the most predictable iris colour is the pale yellow of the adult yellow-eyed penguin, while the rockhopper penguin may be differentiated from other crested penguins by its characteristic red irides. ...
Penguins require vision that is adequate for both subaerial and submarine environments under a wide range of illumination. Here we provide a structured overview of what is known about their visual system with an emphasis on how and how well they achieve these goals. Amphibious vision is facilitated by a relatively flat cornea, the power in air varying from 10.2 dioptres (D) to 41.3 D depending on the species, and there is good evidence for emmetropia both above and below water. All penguins are trichromats with loss of rhodopsin 2, a nocturnal feature, but only deeper diving penguins have been noted to have pale oil droplets and a preponderance of rods. Conversely, the diurnal, shallow-diving little penguin has a higher ganglion cell density (28,867 cells/mm2) and f-number (3.5) than those that operate in dimmer light. In most species studied, there is some binocular overlap, but this reduces upon submergence. However, gaps in our knowledge remain, particularly with regard to the mechanism of accommodation, spectral transmission, behavioural measurements of visual function in low light, and neural adaptations to low light. The rarer species also deserve more attention.
... Iris coloration varies across avian species and ranges from the dark colors or black found in many species to the vividly yellow, orange, or red eyes of some passerines and owls (Davidson et al. 2017, Passarotto et al. 2018. Iris color variation is also present among populations of the same species (del Hoyo et al. 2001), or between individuals within the same population (Snyder and Snyder 1974, Picozzi 1981, Scholten 1999. Indeed, in diurnal species, iris color may differ between sexes (Snyder andSnyder 1974, Bortolotti et al. 2003), change with age (Snyder and Snyder 1974, Picozzi 1981, Sweijd and Craig 1991, Wilson and Hartley 2006, and/or correlate with breeding success (Newton and Marquiss 1982). ...
... Although variation in iris color with age is relatively widespread in birds (Snyder and Snyder 1974, Sweijd and Craig 1991, Wilson and Hartley 2006, mechanisms promoting age-induced change in iris pigmentation are still poorly understood (Prum 2006). Previous studies found that iris color correlates with sex, age, and maturity stage, potentially suggesting hormonal control of iris color (Trauger 1974, Picozzi 1981, Newton and Marquiss 1982, Nelson 1983, Scholten 1999, a possibility worth exploring in future work. ...
Birds show huge variation in color displays evolved for communication. However, among colored phenotypic traits, eyes remain largely overlooked, with only a few studies suggesting a potential signaling function or a role in mate recognition and crypsis. Iris color is a remarkably striking feature in the wholly cryptic pattern of many owls, and may potentially play a signaling function, a possibility so far neglected. Here, we studied variation and potential signaling of iris yellowness as an indicator of quality in parent-offspring communication and other social contexts in the Little Owl (Athene noctua) and Eurasian Scops-Owl (Otus scops). Yellowness did not differ between the sexes; however, adults of the two species had more intensely yellow irises than owlets. Most of variation in iris yellowness of owlets occurred between rather than within nests and seemed to be linked to parental qualities of Little Owls, but was unrelated to condition among Eurasian Scops-Owl owlets. In adults, however, we found that iris yellowness of females was positively associated with nest success (an index of female fitness) in Little Owls, but not in Eurasian Scops-Owls. This study suggests that iris color variation is unlikely to play a role in parent-offspring communication for these two owl species, but that iris yellowness of female Little Owls may potentially play a signaling role in social contexts, a possibility that should be studied in the future.
... However, the mechanisms involved in generating this variability seem to differ across species 4, 5 . In addition, the intra-specific variation of iris color is often associated with age, sex, social dominance, season and geography 2,8,11,17,18 . Consequently, iris color might provide information about the holder. ...
... Nevertheless, it is unclear whether or not dark female eye is the adaptive trait that was acquired during the coevolutionary arms race against host aggression. Other species that have sexual differences in iris flecking also show that females have more iris flecking than males as shown in the common cuckoo 11 , and more generally, the iris color of males tend to change earlier than females in many species 14,18 . Therefore, it might be useful to compare the sexual and species difference in the amount of iris flecking between the brood and non-brood parasites in the lineage of cuckoos to further elucidate the sexual difference in iris flecking and its adaptive significance with respect to brood parasitism. ...
Bilateral symmetry is assumed to contribute to the evolution of eye color, with the left and right eye being the same color in most vertebrates; yet, few studies tested this assumption. Here, we compared the amount of iris flecking (black spots presented on the iris) between the left and right eye of 76 adult common cuckoos Cuculus canorus. We found considerable variation in the total amount of iris flecking among individuals, with variation being associated with body size and sex. We also found that the amount of iris flecking differed between the left and right eye and that this left-right asymmetry was not random, with the left eye almost always being darker than the right eye. Furthermore, this asymmetry was negatively associated with wing length; however, this effect was limited to individuals with dark eyes. Overall, the asymmetric, but non-random, distribution of iris flecking between the left and right eye may indicate that selection pressures driving asymmetry (such as visual lateralization) act on the development of iris colors, even though this effect might be limited, due to the role of bilateral symmetry.
... Eye color in birds varies by the presence or absence of pigment cells in the iris and the content of pigments in those cells and exhibits striking interspecific variations, ranging from black and dark brown to brilliant colors that cover nearly the full spectrum of the rainbow [7][8][9]. Intraspecific eye color variation is also common and often associated with age and sex in wild birds [8,[10][11][12]. Although the evolutionary drive shaping avian eye color remains largely unknown, recent studies have shed light on the possible coevolution of eye color and behavior or activity rhythm in birds [13][14][15][16]. ...
The eye color of birds, generally referring to the color of the iris, results from both pigmentation and structural coloration. Avian iris colors exhibit striking interspecific and intraspecific variations that correspond to unique evolutionary and ecological histories. Here, we identified the genetic basis of pearl (white) iris color in domestic pigeons ( Columba livia ) to explore the largely unknown genetic mechanism underlying the evolution of avian iris coloration. Using a genome-wide association study (GWAS) in 92 pigeons, we mapped the pearl iris trait to a 9 kb region containing the facilitative glucose transporter gene SLC2A11B . A nonsense mutation (W49X) leading to a premature stop codon in SLC2A11B was identified as the causal variant. Transcriptome analysis suggested that SLC2A11B loss of function may downregulate the xanthophore-differentiation gene CSF1R and the key pteridine biosynthesis gene GCH1 , thus resulting in the pearl iris phenotype. Coalescence and phylogenetic analyses indicated that the mutation originated approximately 5,400 years ago, coinciding with the onset of pigeon domestication, while positive selection was likely associated with artificial breeding. Within Aves, potentially impaired SLC2A11B was found in six species from six distinct lineages, four of which associated with their signature brown or blue eyes. Analysis of vertebrate SLC2A11B orthologs revealed relaxed selection in the avian clade, consistent with the scenario that during and after avian divergence from the reptilian ancestor, the SLC2A11B-involved development of dermal chromatophores likely degenerated in the presence of feather coverage. Our findings provide new insight into the mechanism of avian iris color variations and the evolution of pigmentation in vertebrates.
... For example, in some species, the eye-ring color is known to be carotenoid-based, so their color is largely affected by the food they consume (Bortolotti et al., 2003;Pérez-Rodríguez and Viñuela, 2008) and similarly the eye-ring color of cuckoos reared in captivity become paler, probably due to change in food (Meshcheryagina and Opaev, 2021). In contrast, the iris color may be determined by multiple agents, including various types of pigments, such as melanin and purines (Oliphant, 1987;Waldvogel, 1990;Sweijd and Craig, 1991;Gill and Prum, 2007), patterns including flecking, superficial blood vessels, and eye structures, irrespective of pigmentation, and also vary according to age, sex, and social status (Newton and Marquiss, 1982;Sweijd and Craig, 1991;Scholten, 1999;Bortolotti et al., 2003;Volpato et al., 2003;Guzzetti et al., 2008). In this study, however, we did not measure UV light which birds including host species are able to see. ...
A well-known visual signal, hawk-like features such as yellow eyes and feet, and barred underparts have been recognized as coevolutionary traits obtained against host defense in Cuculus cuckoos. However, the variation of these traits within and among species remains poorly understood because empirical studies quantifying these traits are limited in terms of the number of studies and the number of species concerned, and mostly depend on museum collections. In this study, we quantified and compared these traits as well as other new features (e.g., inner wing spot and underpart background color) in the four sympatric Cuculus cuckoos (Cuculus poliocephalus, Cuculus micropterus, Cuculus optatus, and Cuculus canorus) that were wild-captured in South Korea. We found that the yellow color of the eye ring and feet was fairly consistent across the four species. However, the iris color appeared to vary within a species (e.g., between sexes) and varied more substantially among species from nearly black in C. micropterus to bright yellow in C. canorus. In addition, there were significant differences among species with respect to the thickness of the underpart bars, from the thinnest in C. canorus to the thickest in C. micropterus. We also found that the underpart color (pure white versus yellowish brown) and the number of inner wing spots varied within and among species. These results indicate that although hawk-like traits are widely present in Cuculus cuckoos, detailed quantitative features of these traits vary across species. We discuss the potential reasons that generate such variations and suggest future directions to increase our understanding of visual signals in avian brood parasitism.
... Immature birds usually have dark irises, which turn paler or brighter as they mature. This phenomenon has been described and used for age determination in several families, including penguins, waterfowl, raptors, gulls and some passerines (Trauger, 1974;Snyder & Snyder, 1974;Newton & Marquiss, 1982;Rosenfield & Bielefeldt, 1997;Scholten, 1999;Bortolotti, Smits & Bird, 2003). However, the source of this variety and its potential use for ageing more extensively, as well as the general role of avian eye colour, remain poorly understood (Sweijd & Craig, 1991;Bortolotti, Smits & Bird, 2003;Craig & Hulley, 2004;Negro, Blazquez & Galvan, 2017). ...
Avian eye colour changes with age, but many aspects of this transition are still insufficiently understood. We examined if an individual's sex, age, species and body condition are related to the iris colour in common migratory passerines during their autumn passage through Central Europe. A total of 1,399 individuals from nine numerous species were ringed and examined in late autumn in northern Poland. Each individual was sexed by plumage (if possible) and assigned to one of three classes of the iris colour-typical for immatures, typical for adults and intermediate. We found that the iris was typical in 97.7% cases of immatures and in 75.8% cases of adults and this difference was significant. Species, sex and body mass index (BMI) had no significant influence on the iris colour. We show that iris colour in passerines in late autumn is strongly age-dependent and thus can serve as a reliable feature for ageing in field studies, especially in species difficult to age by plumage. Subjects Ecology, Zoology
... Los pollitos presentan una coloración gris por encima de la cabeza y el dorso ascendente, adelante una zona blanca referida al pecho (Harrison 1996). Los pollitos y juveniles poseen ojos de color oscuro, mientras van desarrollándose estos se aclaran a un color pálido, y cuando ya adulto presenta ojos rojos, aunque al llegar la vejez pierden este color presentando ojos negros (Scholten 1999). Su visión es tan buena en mar como en tierra, es decir es emétrope en ambas condiciones, ya que la córnea es plana en relación a todo el ojo, y presenta una adaptación para acomodarse a la refracción (Sivak et al. 1987 ...
Se ha estudiado los aspectos reproductivos de Spheniscus humboldti en la Isla Pachacamac, Lima (12°18’04.39” S76°54’11.60”O) durante el año 2010. El estudio se basó en la caracterización de la colonia mediante la descripción de las características de los nidos y localización del grupo en la colonia principal de la Isla Pachacamac, denominada el “Embudo”, además se realizaron observaciones del comportamiento reproductivo, así se empleó el método de registros de nidos y presupuestos de tiempo. Los mayores picos reproductivos (puesta) se presentaron en el mes de Abril y Agosto; siendo la segunda temporada reproductiva, de Agosto a Noviembre, la más exitosa respecto a la obtención de volantones. El éxito de incubación fue de 0.45 huevos eclosionados por huevo puesto; el éxito de crianza, 0.58 volantones por huevo eclosionado; y el éxito de anidación 0.47 volantones por nido. El éxito reproductivo de la colonia está influenciado por la cantidad de plumas presente en el nido y la localización del grupo dentro de la colonia, no siendo afectado éste por el tipo de nido (superficial, escarpado y madriguera). Se registraron 46 comportamientos, 27 fueron reproductivos. Se encontró diferencias significativas entre los siete meses de estudio en todos los comportamientos. Los comportamientos sexuales-sociales, agresivos, de construcción del nido y locomoción presentaron diferencias significativas con respecto al sitio de asentamiento. Se concluyó que el comportamiento reproductivo es afectado por el lugar donde se desarrolla la colonia.
... Avian eyes are often conspicuously coloured and hence difficult to conceal to visually based receivers (Cott 1940). Studies at the intra-specific level have shown that iris colouration can change with age and sex and relates to individual quality in diurnal raptors (Picozzi 1981, Newton and Marquiss 1982, Bortolotti et al. 2003, penguins (Scholten 1999) and brood parasitic cuckoos (Yoo et al. 2017). Also, the greyish eye colour of Jackdaws (Corvus monedula) may serve as a warning signal to indicate that a nest is occupied and deter intrusions by conspecifics (Davidson et al. 2014), globally suggesting that iris colouration may play a role in social contexts (but see however Negro et al. 2017). ...
Birds, due to their multiple colourful displays, constitute a classic paradigm for the study of colour evolution. Although avian eyes are remarkably coloured, the functional basis behind inter‐specific variability in iris colouration remains poorly understood. Owls are an ideal system to shed light on the role of ecology in promoting iris colour evolution as they show inter‐specific variation in iris colour and in niche specialization with some species being strictly nocturnal and others active during the day. Owls perching for hunting at night might be unnoticed by both predators and their prey if they had dark irises, which would predict that dark irises were more likely to evolve in strictly nocturnal species than in diurnal ones. Using phylogenetic comparative models, we tested the camouflage hypothesis for eye colour. Ancestral state reconstruction revealed that the owl ancestor of the family Strigidae was more likely bright‐irided whereas the ancestor of the family Tytonidae was more likely dark‐irided. We found that iris colour and activity rhythm have more likely evolved in concert than independently, and a non‐significant trend of dark eyes to evolve more easily in owl species presenting strictly nocturnal habits than in diurnal species. The transition from diurnality to nocturnality was a previous requisite for the evolution of dark irises in owls. Taken together our results are only partly consistent with the camouflage hypothesis suggesting that dark irises in owls have primarily evolved to enhance concealment in nocturnal conditions. This article is protected by copyright. All rights reserved.
... There are a number of strategies for gender determination in penguins, including behavioural observation during breeding season (Warham 1972a, Kerry et al. 1993, post mortem examination of gonads (Scolaro et al. 1983, Scolaro 1987, laparoscopy or laparotomy (Richner 1989, Boersma & Davis 1987, ultrasonography (Hildebrandt et al. 1996), post-laying cloacal morphometrics (Boersma & Davis 1987), cloacal endoscopy (Samour et al. 1983), chromosome analysis (Seddon & Seddon 1991), radioimmunoassay for blood testosterone and estradiol (Pennington 1996), polymerase chain reaction of genderspecific sequences , Constantini et al. 2008 and discriminant analyses of morphometrics (Ainley & Emison 1972, Warham 1972a). There are also indications that vocalizations and iris colour may be useful for gender determination purposes (Scholten 1999, Miyazaki & Waas 2003. ...
Magellanic Penguins Spheniscus magellanicus are sexually dimorphic while breeding, but in winter the difference is not always sufficiently evident for visual determination of gender. We examined published discriminant functions and produced additional discriminant functions using morphometric data from 408 beachcast Magellanic Penguins from the Centro de Recuperação de Animais Marinhos on the most southerly point of the Brazilian coast (31°15'38"S to 33°45'03"S), for which gender was determined by post mortem examination or polymerase chain reaction. The discriminant functions correctly determined the gender of 70–90% of these penguins. However, an important gender-associated bias was detected, as previously published discriminant functions developed for animals in breeding colonies were systematically misclassifying males as females. A method is proposed to adjust the functions and correct this gender bias. While other methods may be more accurate, gender determination from morphometric data still offers reasonably reliable results and is an accessible, rapid, inexpensive and non-invasive method for determining the gender of Magellanic Penguins.
... Naše analýza ukázala, že celková spolehlivost pro kritérium A se sice pohybuje kolem deklarovaných 90 %, ale pro samce se jeví jako vhodnější použít kritérium B. To nepochybně úzce souvisí s naším poměrně zajímavým zjištěním, že u samců dochází k vymizení juvenilních znaků rychleji než u samic. Náš výsledek není ale zas tolik překvapivý, protože minimálně pro zbarvení duhovky je u řady druhů známo, že ke změnám v jejím zbarvení u samic dochází později než u samců, ať už je to u vrubozobých (Trauger 1974, Nelson 1983, dravců (Picozzi 1981, Newton & Marquiss 1982, Poprach 2009) nebo tučňáků (Scholten 1999). Možným vysvětlením těchto rozdílů mezi pohlavími, které se nabízí, je, že za adultní zbarvení duhovky zodpovídají samčí pohlavní hormony (Trauger 1974). ...
Age is an important indicator of a bird's experience affecting the timing of migration, mortal-ity, social status and reproductive success. Researchers and ringers should be thus able to age the studied birds correctly. However, a common method of ageing based on the contrast be-tween retained juvenile feathers and adult plumage cannot be applied in many species after complete moult. We tested a simple score combining the colouration of iris, tarsus and tongue spots in the Great Reed Warbler (Acrocephalus arundinaceus). This method was developed to discern young, second calendar-year birds (2K) from adult, after second calendar-year (+2K) individuals in spring. We used 272 score values of 164 retrapped birds with age known from ringing data. The two age categories differed significantly in score, the values of which de-creased with age of the birds. Juvenile characters disappeared faster in males than in females. An analysis of reliability of the method showed that the border value originally suggested by Bensch et al. (1998) is the best for females. However, this criterion would misclassify a signifi-cant proportion of 2K males as +2K birds which would significantly decrease the sample size in 2K males. We propose a more reliable criterion allowing for sex differences and leaving a certain proportion of birds with intermediate score values as undetermined (+1K). Similar scores would be desirable for other species where the plumage after the first complete moult does not allow reliable age determination.
Humboldt penguin (Spheniscus humboldti)
Population and Habitat Viability Assessment Workshop
Final Report
We describe overlooked patterns and age-related variation in the iris coloration of the Red-bellied Grackle (Hypopyrrhus pyrohypogaster), a range-restricted threatened species of the Colombian Andes. Whereas adults exhibit a bicolored pale-yellow/scarlet red iris, juveniles show a dark iris, ranging from dark brown to grayish brown. In addition, we report the first case for a Neotropical species of temporary heterochromia iridis, an uncommon phenomenon in birds, from recaptures of a female Red-bellied Grackle in 2010. Our observations suggest that this case of heterochromia may be related to stress and changes in blood flow to the eye. Resumen Describimos patrones y variación relacionada con la edad en la coloración del iris del Cacique Candela (Hypopyrrhus py-rohypogaster), una especie amenazada con distribución restringida en los Andes Colombianos. Mientras los adultos presen-tan un iris bicolor con amarillo pálido y rojo escarlata, los juveniles muestran un iris oscuro que va desde café oscuro a café grisáceo. Adicionalmente, reportamos el primer caso para una especie Neotropical de heterocromía temporal en la colora-ción del iris, un fenómeno poco común en aves, a partir de una hembra de Cacique Candela recapturada en 2010. Sugeri-mos que este caso de heterocromía pudo estar relacionado con el estrés y cambios de flujo sanguíneo al ojo.
Although they can provide valuable information on at-sea ecology, data-loggers may adversely affect energetics, diving performance, and breeding success of equipped birds. With the aim of determining the effects of leg-attached data-loggers on the activity budgets of Humboldt penguins (Spheniscus humboldti) while on land, we equipped birds kept at the Landau Zoo, Landau, Germany, with such devices. We followed them during sample periods and recorded the occurrence and length of behaviors. Birds quickly habituated to the devices within 1 day of deployment, and mean rates of device-pecking were low (0.7–1.7 pecks/hr), with device-induced behaviors accounting for <1% of the mean daily activity budget. The method of device attachment appears behaviorally less stressful than the traditional tape-based system in which devices are normally attached to the penguin's back. By facilitating the testing of newly developed data-loggers on captive birds, or the development of methods for device attachment, zoos and aquaria may strengthen their role in animal conservation by helping research on free-ranging animals. Zoo Biol 21:365–373, 2002. © 2002 Wiley-Liss, Inc.
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