Blue Eggs Research Articles

Maternal transfer of organochlorines and brominated flame retardants in blue tits ( Cyanistes caeruleus)

Although eggs have frequently been used as a biomonitoring tool for contamination with organohalogenated pollutants (OHPs), few studies have investigated the processes of maternal transfer in birds. Here, maternal transfer of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs) was investigated through comparison of the concentrations and profiles between whole homogenised female blue tits ( Cyanistes caeruleus) and their eggs. In addition, we examined if there was an effect of laying order on the concentrations of PCBs, OCPs and PBDEs. PCBs were the most abundant contaminants in female blue tits and their eggs, followed by OCPs and PBDEs. Among the OCPs, p, p′-DDE was the most dominant compound and accounted for more than 80% of the sum OCPs. Egg concentrations decreased significantly in relation to the laying order from 1623 ± 148 ng/g lipid weight (lw) to 1040 ± 47 ng/g lw for the sum PCBs, from 342 ± 24 ng/g lw to 235 ± 17 ng/g lw for the sum OCPs and from 49 ± 5 ng/g lw to 27 ± 5 ng/g lw for the sum PBDEs. When reviewing all studies investigating laying order effects of OHPs in birds, no clear patterns emerged, which may be due to differences in study species and methodology among studies. Despite the fact that there were laying order effects in blue tit clutches, the variance in concentrations of PCBs and PBDEs was larger among clutches than within clutches. Variance in OCP concentrations among clutches was similar to the variance within clutches. These results suggest that one randomly collected blue tit egg from a clutch is useful as biomonitoring tool for PCBs and PBDEs, while for OCPs it is recommended to consistently use the same egg from the laying sequence as a biomonitoring tool. Lipid-normalized concentrations of sum PCBs, sum OCPs and sum PBDEs in female blue tits after clutch completion were comparable to the concentrations in the first-laid eggs. The egg/female lipid concentration ratios for sum PCBs, sum OCPs and sum PBDEs decreased significantly from 1.0 ± 0.09 to 0.7 ± 0.003, 1.1 ± 0.1 to 0.7 ± 0.02 and 1.2 ± 0.14 to 0.8 ± 0.05, respectively, during the course of egg laying. The profiles of the females and eggs differed significantly for the PCBs, OCPs and PBDEs. There was a higher contribution of lower chlorinated PCB congeners (CB 28, CB 52, CB 95, CB 101 and CB 110), BDE 183, p, p′-DDT and other less persistent OCPs in the females compared to their eggs. Maternal transfer in blue tits seemed to be selective for the more bioaccumulative and persistent congeners/compounds.

Pigment allocation to eggs decreases plasma antioxidants in a songbird

Although evidence is accumulating on the adaptive function of female ornamentation, very little is known about maternal allocation decisions involving sexual signaling and other reproductive functions. Blue egg coloration has been suggested as a sexually selected signal of female quality to males, and some recent studies are in accordance with this hypothesis. Blue eggshell coloration results from the deposition of biliverdin pigment by laying females, which is a potent antioxidant. Thus, egg pigmentation should be costly in terms of antioxidants, an assumption of the signaling hypothesis that has not been tested yet. We induced increased reproductive effort in a set of female pied flycatchers Ficedula hypoleuca through nest removal and measured egg pigmentation and plasma antioxidant levels in relation with a control group. Experimental females showed a negative association between egg color and plasma antioxidant levels, while there was no relationship for control birds. This supports that egg pigmentation is costly in terms of general antioxidant defenses and suggests a tradeoff between the allocations to both traits. Furthermore, experimental females with more colorful eggs raised more fledglings, especially when breeding early. Controls did not show a relationship between egg color and reproductive success. Females laying more colorful eggs could have shifted their allocation decisions towards current reproduction, at the expense of their own antioxidant defenses. Our results highlight that blue egg coloration is a life-history trait, subject to tradeoffs with other attributes, and seems to be especially informative under harsh breeding conditions.

Responses of Black-headed Gulls Larus ridibundus to conspecific brood parasitism

Conspecific brood parasitism in birds occurs when a female inserts her egg into the clutch of her own species. If successful, i.e. the parasitic egg is accepted by the host, then the host female or pair rears the offspring of the parasite. In the present study, we studied natural conspecific brood parasitism in Black-headed Gulls (Larus ridibundus), and conducted series of the experiments with mimetic (conspecific) and non-mimetic (conspecific painted light blue) eggs to explore responses of the tested pairs towards these alien eggs. The natural parasitism rate was 10% and the probability of being parasitized significantly increased with nest density. Experimentally parasitized pairs rejected both types of experimental eggs at a similar rate: 14.3 % for mimetic and 25.5% for non-mimetic within 2 days. Non-mimetic eggs were more selectively rejected than mimetic eggs. The relationships between the probability of egg rejection (dependent variable) and predictor (independent) variables were examined by fitting generalized linear models. Contrast and intraclutch variation in ground color and spotting pattern and the volume of the egg had no significant effect on rejection behavior in either non-mimetic or mimetic eggs. However, nest density significantly positively affected rejection behavior of the Black-headed Gulls in both non-mimetic and mimetic treatments.

Ultraviolet and green parts of the colour spectrum affect egg rejection in the song thrush (Turdus philomelos)

Much attention has been devoted to understanding the evolution of egg mimicry in avian brood parasites. The majority of studies have been based on human perception when scoring the mimicry of the parasitic egg. Surprisingly, there has been no detailed study on the recognition and sensitivity towards differently coloured parasitic eggs. We investigated effect of different colours of the experimental eggs measured by ultraviolet (UV)-visible reflectance spectrophotometry on rejection behaviour in the song thrush (Turdus philomelos). We carried out a set of experiments with four blue model eggs representing mimetic eggs, whereas six other colours represented nonmimetic eggs. Our results revealed that two colours originally designed as a mimetic were rejected at a high rate, whereas one group of the nonmimetic was accepted. A multiple regression model of absolute differences between song thrush and experimental eggs on rejection rate showed that the level of mimicry in the UV and green parts of the colour spectrum significantly influenced egg rejection in the song thrush. To our knowledge, this is the first detailed study showing that different colour perception by the birds can affect their responses towards the parasitic egg. These findings suggest that the combination of UV and visible ranges of the spectra plays a major role in the evolution of discrimination processes, as well as in the evolution of the mimicry of the parasitic egg.

The Harriman Expedition, 1899

The Harriman Expedition, 1899 Jennifer Atkinson (bio) On Harriman's dollar, on Harriman's ship, as members of the Harriman expedition, Burroughs and Muir lingered on deck one evening over their tea, debating the nature of Nature. The crew had gone ashore to trade tin plates for sex; the other guests were up on the bow waiting their turns at the telescope. Nature, Muir said, is virginal and remote, like the sheer wall of a glacier. Preferably, Burroughs set down his spoon, a glacier named Muir? No, he said, Nature is a robin's nest, perfectly made for its secret clutch of blue eggs and their brooding mother. This nest of yours, Muir asked, I don't suppose it's the one in view from the Burroughs parlor window? So debate devolved to ad hominem caviling. The great men took to their respective cabins, each in his own respective huff. Mrs. Harriman, sick of adventure, bleeding, miserable with menstrual cramps, pled a headache and left the bow to the astronomers. In circumnavigating the upper deck she came upon the writers' uncleared tea things: two crumpled napkins, two cups, two saucers, sugar tongs, a plate of biscuit crumbs. On shore, the sounds of revelry, from the bow the murmurs of scientific inquiry. Alone, with no one watching, she picked up a sugar lump and set it on her tongue. When it was gone she took another, thinking, to take her mind off her body, of the man who cut the tropic cane, the mangle that pressed the juice, the huge cauldrons that boiled the syrup until the crystals came. She had no idea how the loose sugar was pressed into loaves or these lumps for tea. By now she had eaten five, leaving just two, which she tossed into the sea. Two lumps of sweet in all that salt and dark. And Mrs. Harriman let herself picture the dark beneath the boat: kelp like the kelp that gets washed up on shore, fish like the fish on their dinner plates, an octopus creeping over the rocks, down where the bottom slides off west into a vast dark beyond her willing imaginings. Jennifer Atkinson Jennifer Atkinson is the author of two books of poems, The Dogwood Tree and The Drowned City. She teaches creative writing at George Mason University. Copyright © 2007 The Curators of the University of Missouri

Nesting Behavior and Nestling Care of the Pavonine Quetzal (Pharomachrus pavoninus)

I describe the nesting behavior of the Pavonine Quetzal (Pharomachrus pavoninus) at Los Amigos in the southeastern Peruvian Amazon. I found a single nest cavity 4.2 m above ground in a dead snag in terra firme forest. The cavity contained two pale blue eggs each with a few small brown-buff speckles, of which one hatched. I observed incubation between 18 February and 2 March 2004. Based on an average of 0.7 observation hrs/day, the male appeared to incubate during most of the day from at least 0950 hrs until sunset (near 1745 hrs) when the pair would switch before nightfall. The female appeared to incubate at night and during the early morning. Fifty-six percent of 32 food deliveries observed between 6 and 26 March were tree frogs and 44% were fruits. The nestling fledged on 26 March, 20 days after the first observed food provisioning. The nestling period is estimated to be 21–24 days. The plumage development of the nestling, vocalizations, and other observations are discussed and compared with the Resplendent Quetzal (Pharomachrus mocinno).

Dorothy Wordsworth as a Young Woman

Previous articleNext article No AccessDorothy Wordsworth as a Young WomanPamela WoofPamela Woof Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Wordsworth Circle Volume 38, Number 3Summer 2007The Wordsworth-Coleridge Association Meeting, 2006 Article DOIhttps://doi.org/10.1086/TWC24045137 Views: 18Total views on this site © 2007 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.

Are blue eggs a sexually selected signal of female collared flycatchers? A cross-fostering experiment

Impressive variation in egg colouration among birds has puzzled evolutionary biologists for a long time. The most frequently studied selective forces moulding egg colouration—predation and brood parasitism—have either received little empirical support or may play a role in only a minority of species. A novel hypothesis has suggested that egg colour may be significantly influenced by sexual selection. Females may deposit a blue-green pigment biliverdin into eggshells instead of using it for themselves as a powerful antioxidant. By this handicap, females may signal their quality to males, which are then hypothesized to increase their paternal effort. We experimentally tested the hypothesis in the collared flycatcher (Ficedula albicollis), a species laying blue-green eggs. We cross-fostered clutches between nests to disentangle effects of female/territory quality and egg colour on paternal effort and nestling quality. The results supported two assumptions of sexual signalling through egg colour hypothesis: Blue pigment seems to be a limited resource for females, and female quality is positively correlated with the intensity of the blue-green colour. However, we did not find support for the main prediction of the hypothesis, as male parental effort parameters (feeding frequencies to nestlings and intensity of nest defence) were unrelated to egg colour. We discuss possible reasons for the discrepancy between our results and previous correlative analyses that supported the hypothesis that blue egg colour may be a postmating, sexually selected signal in females.

The evolution of egg colour and patterning in birds

Avian eggs differ so much in their colour and patterning from species to species that any attempt to account for this diversity might initially seem doomed to failure. Here I present a critical review of the literature which, when combined with the results of some comparative analyses, suggests that just a few selective agents can explain much of the variation in egg appearance. Ancestrally, bird eggs were probably white and immaculate. Ancient diversification in nest location, and hence in the clutch's vulnerability to attack by predators, can explain basic differences between bird families in egg appearance. The ancestral white egg has been retained by species whose nests are safe from attack by predators, while those that have moved to a more vulnerable nest site are now more likely to lay brown eggs, covered in speckles, just as Wallace hypothesized more than a century ago. Even blue eggs might be cryptic in a subset of nests built in vegetation. It is possible that some species have subsequently turned these ancient adaptations to new functions, for example to signal female quality, to protect eggs from damaging solar radiation, or to add structural strength to shells when calcium is in short supply. The threat of predation, together with the use of varying nest sites, appears to have increased the diversity of egg colouring seen among species within families, and among clutches within species. Brood parasites and their hosts have probably secondarily influenced the diversity of egg appearance. Each drives the evolution of the other's egg colour and patterning, as hosts attempt to avoid exploitation by rejecting odd-looking eggs from their nests, and parasites attempt to outwit their hosts by laying eggs that will escape detection. This co-evolutionary arms race has increased variation in egg appearance both within and between species, in parasites and in hosts, sometimes resulting in the evolution of egg colour polymorphisms. It has also reduced variation in egg appearance within host clutches, although the benefit thus gained by hosts is not clear.

First Observation of Cavity Nesting by a Female Blue Grosbeak

On 21 May 2003, we discovered a completed Blue Grosbeak (Passerina caerulea) nest in an Eastern Bluebird (Sialia sialis) nest box. On 28 May, the nest contained four whitish-tan eggs with light-brown, streaky and spotty markings, an unusual color pattern for Blue Grosbeak eggs. Species' identification was confirmed by capturing the breeding female in the nest box, and confirmed again later with identification of the chicks as Blue Grosbeaks. To our knowledge, this is the first published account of cavity nesting, artificial or otherwise, for this species.

Evidence for the signaling function of egg color in the pied flycatcher Ficedula hypoleuca

A recent hypothesis proposes that the bright colors, especially blue and green, of many avian eggs may function as signals of female or offspring phenotypic quality or condition to males in species with biparental care, inducing them to allocate more effort to their offspring. The pigment determining blue and green egg colors is an antioxidant whose availability for eggshell coloring may be limited. To test the signaling function on a species with blue eggs, the pied flycatcher Ficedula hypoleuca, we measured egg color with a spectrophotometer on the day of laying and obtained two principal components from their reflectance spectra that together explained 99% of variation and represented shell lightness, and hue and saturation, respectively. We also measured female immunocompetence during the nestling period through the response to phytohemagglutinin as a measure of cell-mediated immunity and the response to a tetanus vaccination as a measure of humoral immunity. The total amount of immunoglobulins in blood of females and of nestlings before fledging was also estimated. Mean within-clutch egg darkness was positively associated with both measures of female immunocompetence, while better female condition was associated with colors tending away from intermediate and toward short wavelengths. Ageing female laid lighter eggs. The mean within-brood level of nestling IgY was also associated with mean within-clutch egg colors tending away from intermediate and toward short wavelengths. Mean egg darkness decreased linearly during the laying sequence, suggesting pigment limitation. Males were observed frequently visiting nests during the laying period, allowing them to observe eggs before the start of incubation. These results support the signaling hypothesis for explaining bright colors of avian eggs.

BLUE AND GREEN EGG-COLOR INTENSITY IS ASSOCIATED WITH PARENTAL EFFORT AND MATING SYSTEM IN PASSERINES: SUPPORT FOR THE SEXUAL SELECTION HYPOTHESIS

Among several adaptive explanations proposed to account for variation in avian egg color, that related to sexual selection is of particular interest because of its possible generality. Briefly, it proposes that because biliverdin (the pigment responsible for blue-green eggshell coloration) is an antioxidant, deposition in the eggshell by laying females may signal the capacity of females to control free radicals, despite the handicap of removing this antioxidant from their body. If males adjust parental effort in response to the intensity of the blue coloration of eggs, thereby investing more in the offspring of high-quality mates, blue eggs may represent a postmating sexually selected signal in females. Here, by image and spectrophotometric analyses of the eggs of European passerines, we tested two different predictions of the hypothesis. First, variables related to intraspecific variation in parental effort (i.e., the duration of the nestling period controlled for body mass) should be positively related to the intensity of blue-green color of the eggshell across species. Second, there should be a positive relationship between intensity of blue-green color of eggs and degree of polygyny. These predictions were supported: intensity of blue-green coloration (i.e., chroma) was significantly related to the duration of the nestling period and to degree of polygyny after controlling for possible confounding variables (i.e., body mass, incubation period, and nest type) and similarity due to common descent. Nest type (hole or nonhole) also explained a significant proportion of variation in egg chroma, perhaps reflecting different selection pressures (i.e., light conditions, risk of parasitism) affecting species with the two types of nests.

Egg colouration and male parental effort in the pied flycatcher Ficedula hypoleuca

A recent hypothesis posits that the bright colours of many avian eggs may act like signals of female genetic quality or condition to males in species with biparental care, inducing them to work harder for their offspring. We measured the colour of blue eggs of pied flycatchers Ficedula hypoleuca in Central Spain with a spectrophotometer on the day of laying, and also quantified the provisioning effort by males and females during the last days of the nestling period. Both chromaticity coordinates in the CIELAB colour space (blue to yellow, green to red) showed significant associations with male provisioning rates, explaining more than 20% of variation in male parental effort. Male provisioning rates were positively correlated with nestling condition, thereby potentially contributing to female fitness. This evidence is only tentative until experimental confirmation, but suggests that males are affected by the colour of their mates’ eggs, a possibility not considered hitherto in the study of sexual selection.

Effect of host egg color dimorphism on interactions between the vinous‐throated parrotbill (Paradoxornis webbianus) and common cuckoo (Cuculus canorus)

To investigate the effect of host egg color dimorphism on the vinous‐throated parrotbill (Paradoxornis webbianus) – common cuckoo (Cuculus canorus) interactions, we monitored breeding nests of vinous‐throated parrotbills, and conducted model egg experiments, using two colors: white and blue. Of the 190 nests examined in this study, cuckoo parasitism occurred at 10 nests (8 blue and 2 white egg clutches, respectively), and only blue cuckoo eggs were found. This frequency was similar to the egg‐color ratio of all host nests found (151 blue and 39 white egg clutches). Vinous‐throated parrotbills showed high rejection rate towards both cuckoo eggs and model ones. There was a significant difference in rejection rates towards mimetic (blue) and non‐mimetic (white) eggs in blue egg clutches. Mimetic eggs put in nests took significantly longer to be rejected than non‐mimetic ones. The most common rejection method used by the hosts was egg ejection (puncture‐ejection). The costs of ejecting non‐mimetic eggs tended...

The effect of heavy metal exposure on egg size, eggshell thickness and the number of spermatozoa in blue tit Parus caeruleus eggs

In this study we compared the egg size, the eggshell thickness and the number of spermatozoa trapped on the perivitelline layer of the eggs in three blue tit (Parus caeruleus) populations across a heavy metal pollution gradient. No significant differences were observed in egg characteristics among study sites. Eggs from the two most polluted sites however, had significantly less spermatozoa on the perivitelline layer than eggs from the least polluted site. Our results suggest a significant effect of pollution on blue tit sperm concentrations in the infundibulum. Determining the number of spermatozoa on the egg membranes is relatively cheap and straightforward, which renders this technique a new and useful tool in biomonitoring.

Did Blue Eggs of Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) Cuckoos Evolve to Counter Host Discrimination?

AbstractHughes (1997) hypothesized that the blue coloration of Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) cuckoo eggs evolved in response to egg discrimination by their hosts. From that hypothesis, we predicted that cuckoo hosts would eject ancestral nonmimetic (white) eggs, but be more likely to accept mimetic (blue) eggs. American Robins (Turdus migratorius) and Gray Catbirds (Dumetella carolinensis) were used to test that hypothesis because they are ejecter species that lay blue eggs and have been parasitized by Coccyzus cuckoos. Hughes' egg-mimicry hypothesis was not supported because robins and catbirds did not significantly eject white cuckoo eggs more frequently than blue cuckoo eggs. Indeed, most robins accepted both egg types. Furthermore, the observational evidence for egg mimicry is not convincing because only 5 of the 15 host species that Hughes (1997) described as having eggs that “fully or nearly match” the egg color of Black-billed and Yellow-billed cuckoos actually do so.

Eggs, Jurisdiction, and the Internet

A long time ago hens did not lay white or brown eggs but eggs in primary colours: red, yellow and blue. Since, depending on the colour of the eggs, their taste and quality varied, the farming industry split into red, yellow and blue industries catering for different markets. Those industries that dealt with the respective eggs became over the years highly competitive. And what was initially no more than a common understanding, namely, that hens laying red eggs belonged to the red industry, while hens laying blue and yellow eggs belonged to the blue and yellow industries, turned over the years into customary egg law, with each industry having its clearly demarcated area of competence. As it happened, due to interbreeding, some hens normally laying, for example, red eggs would very occasionally lay purple eggs or orange eggs. Also on occasion, some hens would stop altogether from laying eggs of a primary colour, but would lay orange, purple, brown or green eggs. These eggs and hens presented a problem, albeit not a severe one, as they remained very much the exception. Hens laying blue eggs were kept apart from hens laying red eggs and from those laying yellow eggs. Nevertheless, solutions to these problematic eggs and hens had to be found.

Did Blue Eggs of Black-Billed (Coccyzus erythropthalmus) and Yellow-Billed (C. americanus) Cuckoos Evolve to Counter Host Discrimination?

Did Blue Eggs of Black-Billed (Coccyzus erythropthalmus) and Yellow-Billed (C. americanus) Cuckoos Evolve to Counter Host Discrimination?

Does Egg Rejection Account for the Low Incidence of Cowbird Parasitism in Chestnut-Collared Longspurs (Calcarius Ornatus)?

AbstractWe experimentally parasitized Chestnut-collared Longspur (Calcarius ornatus) nests with mimetic and nonmimetic Brown-headed Cowbird (Molothrus ater) eggs to determine whether the low frequency of parasitism reported for that grassland host is due to egg rejection behavior. Longspurs accepted all 23 mimetic eggs (real and wooden) and rejected 9 of 22 blue nonmimetic eggs. Our results suggest longspurs accept cowbird eggs even though they are physically capable of ejecting them from their nest. Thus, the low parasitism frequency reported for that species is not a result of egg rejection behavior, but may be due to antiparasite strategies that reduce their chances of being parasitized (e.g. nest defense behavior).

Did Blue Eggs of Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) Cuckoos Evolve to Counter Host Discrimination?

Abstract Hughes (1997) hypothesized that the blue coloration of Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) cuckoo eggs evolved in response to egg discrimination by their hosts. From that hypothesis, we predicted that cuckoo hosts would eject ancestral nonmimetic (white) eggs, but be more likely to accept mimetic (blue) eggs. American Robins (Turdus migratorius) and Gray Catbirds (Dumetella carolinensis) were used to test that hypothesis because they are ejecter species that lay blue eggs and have been parasitized by Coccyzus cuckoos. Hughes' egg-mimicry hypothesis was not supported because robins and catbirds did not significantly eject white cuckoo eggs more frequently than blue cuckoo eggs. Indeed, most robins accepted both egg types. Furthermore, the observational evidence for egg mimicry is not convincing because only 5 of the 15 host species that Hughes (1997) described as having eggs that “fully or nearly match” the egg color of Black-billed and Yellow-billed cuckoos a...