共查询到20条相似文献,搜索用时 31 毫秒
1.
Rebecca J. Safran Kevin M. Pilz Kevin J. McGraw Stephanie M. Correa Hubert Schwabl 《Behavioral ecology and sociobiology》2008,62(3):427-438
Recently, evidence is mounting that females can adaptively engineer the quality of their offspring via the deposition of yolk
compounds, including carotenoids and androgens. In this study, we simultaneously consider how both carotenoids and androgens
in egg yolk relate to parental quality in barn swallows (Hirundo rustica erythrogaster). First, we found no relationship between concentrations or amounts of yolk androgens and carotenoids. Yolk carotenoids decreased
with laying order, whereas we found no relationship between yolk androgens and laying order. Second, we tested the Investment
Hypothesis, which predicts that high-quality females or females paired to high quality mates, allocate differentially more
of these yolk compounds to their offspring. For carotenoids, we mostly found evidence to counter predictions of the Investment
hypothesis: (1) Carotenoid concentrations varied among females, (2) heavier eggs contained lower carotenoid concentrations,
although heavier yolks contained greater amounts of carotenoids, (3) eggs of earlier-laying females had lower concentrations
in their eggs, and (4) yolk carotenoids were not correlated with clutch size or male plumage ornamentation. For androgens,
we found weak support for the Investment Hypothesis: (1) Yolk androgens varied among females, (2) heavier eggs and yolks contained
greater amounts, although not concentrations of androgens, (3) females paired to more colorful males laid eggs with greater
concentrations of androgens, and (4) no effects of laying date or morphological correlates of female quality on androgen concentrations
in egg yolks. Overall, these findings suggest that each yolk compound may have different functions and therefore may be regulated
by different mechanisms. 相似文献
2.
Diego Rubolini Maria Romano Roberta Martinelli Nicola Saino 《Behavioral ecology and sociobiology》2006,59(3):344-352
Androgen hormones of maternal origin contained in the eggs of avian species are considered to have positive effects on offspring
characteristics and performance. However, negative consequences have also been reported, suggesting that mothers may experience
a trade-off between beneficial and detrimental effects of egg androgens to offspring fitness. We studied the effects of elevated
yolk testosterone (T) concentration on survival, development and phenotype of male and female yellow-legged gull (Larus michahellis) chicks by injecting egg yolks with physiological doses of the hormone. Elevated yolk T resulted in a male-biased post-hatching
sex ratio, T-treated clutches producing a greater proportion of males compared to control ones at day 4 post-hatching, likely
resulting from a reduction of female embryonic survival, whereas no effect of hormone treatment on hatching success or short-term
chick survival was observed. In addition, T depressed post-hatching body mass in both sexes but had no effects on the intensity
of the cell-mediated immune response or skeletal growth. No sex differences in egg characteristics or chick phenotype were
detected. Time to hatching was not affected by T, but females originating from first laid eggs hatched earlier than males
of the same laying order, independently of hormone treatment. However, the implications of sex differences in hatching times
are unclear in the study species. Taken together, our results suggest that female yellow-legged gulls may be constrained in
transferring androgens to their eggs by negative consequences on the viability of female offspring and growth of chicks of
the two sexes. 相似文献
3.
Joanna Rutkowska Tomasz Wilk Mariusz Cichoń 《Behavioral ecology and sociobiology》2007,61(8):1211-1217
There is accumulating evidence that maternal hormones may play a role in offspring sex adjustment, but little is known about
the costs of such hormone-mediated mechanisms. Recent studies have reported sex-specific effects of hormones on offspring
viability. Specifically, we previously found that elevating the plasma androgen level in mothers results in a male-biased
offspring primary sex ratio, but it affects the viability of sons negatively and daughters positively in zebra finches (Taeniopygia guttata; Rutkowska and Cichoń, Anim Behav, 71:1283–1288, 2006). In this study, we studied further fitness consequences of exposure
to elevated yolk androgen levels in zebra finches. We measured growth rate and cellular immune response of nestlings that
hatched from eggs laid by females injected with testosterone during egg laying and nestlings of unaffected control females.
We found that sons of testosterone-treated females grew slower in comparison to sons of control females. The significant interaction
between experimental group and offspring sex indicates that sons of testosterone-treated mothers suffered impaired immune
responsiveness while daughters seemed to benefit from elevated androgen level in terms of enhanced immune responsiveness.
We found no effects of androgens on offspring performance at adulthood—neither fecundity of females nor attractiveness of
males was affected. We conclude that the benefits of biasing sex ratio towards males by increasing androgen level in the yolk
may be limited due to negative effects on male offspring performance early in life. 相似文献
4.
E. C. Pariser L. Gilbert N. Hazon K. E. Arnold J. A. Graves 《Behavioral ecology and sociobiology》2012,66(4):519-527
Females are expected to partition resources between offspring in a context-dependent way to maximise total fitness returns
from a reproductive attempt. Female zebra finches (Taeniopygia guttata) vary the allocation of yolk androgens and antioxidants among offspring. Importantly, the balance between androgens and antioxidants
in yolks may be more important than their independent absolute amounts in terms of fitness consequences for developing young.
Therefore, we tested whether the relative allocation of these two resources in yolks varies according to either the Trivers–Willard,
positive or compensatory maternal investment hypothesis. We manipulated male attractiveness using coloured leg bands (red-banded
males appear attractive; green-banded males, unattractive) and measured yolk androgens and antioxidants in each egg, egg sex,
clutch sex ratio and female condition. While female zebra finches manipulated the balance of androgens and antioxidants within
and between clutches in response to mate attractiveness, offspring sex and their own condition, they did not do so in a way
that consistently followed any of the hypotheses. Mothers paired with unattractive males allocated a larger antioxidant/androgen
ratio to daughters than sons. This pattern was reversed when paired to an attractive male; sons received a larger antioxidant/androgen
ratio than daughters. We also found offspring sex ratio decreased with increasing female condition for unattractive males,
but not for attractive males. However, without knowing the fitness consequences of the balance of different egg constituents,
it is difficult to interpret the patterns consistently in terms of the Trivers–Willard, compensatory and positive investment
hypotheses. 相似文献
5.
Amanda J. Gilby Enrico Sorato Simon C. Griffith 《Behavioral ecology and sociobiology》2012,66(11):1519-1529
Differential resource allocation by females across the laying sequence has been hypothesised as a mechanism through which females could either compensate nestlings that hatch last in asynchronous broods or promote brood reduction. In this study we artificially incubated eggs and cross-fostered offspring to manipulate nestlings’ position in the hatching order, to identify whether the competitive ability of nestlings is dependent on position in the laying sequence. In both control and experimentally reversed broods, first hatched chicks had a higher survival than last hatched siblings. Yet, nestlings that hatched from eggs laid in the second half of a clutch begged with a greater intensity than nestlings hatched from eggs laid in the first half of a clutch. In natural broods, the greater begging competitiveness of nestlings from later-laid eggs led to a moderation of sibling competition and these nestlings achieved the same body size and weight as nestlings from eggs laid in the first half of the clutch. The lack of a substantial difference in the size and condition of surviving nestlings in respect to laying order suggests that differential resource allocation across the egg-laying sequence partially compensates for hatching last in asynchronous broods and reduces the negative effects of the nestling size hierarchy. The effect of laying order, brood size and experimental treatment also differed for male and female nestlings. Our study highlights the need to be aware of the complex and subtle effects of nestling sex and laying sequence when investigating genetic and environmental influences on individual fitness. 相似文献
6.
Kristen J. Navara Geoffrey E. Hill Mary T. Mendonça 《Behavioral ecology and sociobiology》2006,60(3):392-398
The deposition of androgens into the yolks of eggs can have long-lasting effects on the growth and development of young birds. It has been proposed that female birds and reptiles deposit yolk androgens according to the differential allocation hypothesis (DAH), which posits the allocation of more resources to offspring sired by more attractive, higher-quality males. We examined deposition patterns of yolk androgens in relation to mate attractiveness in the house finch Carpodacus mexicanus. Contrary to the predictions of the DAH, female house finches deposited significantly more androgens into eggs sired by less attractive males. We propose that, rather than serving as resources, androgens are used as mediators in a compensatory distribution strategy, enabling females to improve the quality of young produced with less attractive males. 相似文献
7.
Diego Gil Alfonso Marzal Florentino de Lope Marisa Puerta Anders P. Møller 《Behavioral ecology and sociobiology》2006,60(1):96-100
Female birds deposit in the yolks of eggs substantial amounts of androgens, such as testosterone and androstenedione. These
androgens have been shown to speed up nestling development, induce a fast development of ornaments and increase dominance
in adults. Experiments in several species have reported that females invest greater amounts of androgens in the eggs fathered
by attractive males, suggesting that yolk androgen is a costly investment for either the offspring or the mother. There is
some evidence that nestling immunocompetence may be partially suppressed by high levels of yolk androgens, but it is not known
whether this is also the case for females. We tested this hypothesis in the house martin by inducing an immune challenge through
an injection of sheep red blood cells, a standard challenge of the humoral immune system. Experimental birds laid eggs with
lower amounts of yolk androstenedione than controls, and there was a similar non-significant trend for testosterone. Furthermore,
the probability of laying a replacement clutch was higher for birds that had laid a first clutch with relatively high levels
of yolk testosterone. These results suggest that yolk androgen deposition is limited by immune costs in the female, and that
only females in good condition may afford to invest high levels of androgen in eggs in this species. 相似文献
8.
Maternal yolk androgens in bird eggs represent an important pathway along which offspring phenotype is shaped. Most of the
hormone-mediated maternal effects are highly important in the context of sibling competition. However, there is also increasing
evidence for long-lasting effects far beyond the nestling period, and these effects may have important consequences on the
reproductive success of the offspring. Here, we investigated the effects of experimentally elevated yolk testosterone concentrations
on growth and reproduction in female canaries. Elevated yolk testosterone concentrations enhanced the post-natal growth rate,
but not the asymptotic mass, and reduced the survival probability. The latter may be a consequence of the higher growth rate,
which may have rendered females hatching from testosterone-treated eggs (T-females) more vulnerable to harsh environmental
conditions. Adult T-females made a larger investment in their clutch by laying more but not heavier eggs than females hatching
from control-treated eggs. Our results suggest that the observed long-lasting effect on clutch size relates to changes in
the growth trajectory rather than being a direct consequence of testosterone, since studies manipulating early growth conditions
obtained similar results. Clearly, further studies are now required in order to investigate the intriguing relationship between
yolk testosterone, elevated growth rates, and clutch size. 相似文献
9.
János Török Rita Hargitai Gergely Hegyi Zoltán Matus Gábor Michl Péter Péczely Balázs Rosivall Gyula Tóth 《Behavioral ecology and sociobiology》2007,61(4):541-550
Birds may influence the fitness of their offspring by transmission of different amounts of carotenoids to their eggs. Carotenoids
play crucial roles in antioxidant protection and immune defence mechanisms, but they may be available to females in limiting
amounts. Therefore, their allocation to the eggs may be influenced by the female’s condition, age and environmental circumstances.
Furthermore, the quality of the male parent, which affects the reproductive value of the offspring, may also influence this
investment. In this correlational study, we investigated proximate and ultimate factors that may lead to variation in yolk
lutein, zeaxanthin and β-carotene concentrations among and within clutches of a wild passerine, the collared flycatcher (Ficedula albicollis). We found that carotenoid concentration was positively associated with caterpillar supply at the time of egg formation,
which suggests a proximate constraint of carotenoid availability on yolk composition. Neither female condition, body size,
age, nor male plumage ornamentation, age and body size correlated with carotenoid deposition. Yolk β-carotene concentration
was found to be positively linked to yolk testosterone concentration. We suggest that females allocated more β-carotene to
their eggs to mitigate the potentially detrimental effects of elevated steroid concentration. We found that concentration
of β-carotene increased with laying order. The possible function of this pattern may be to enhance the resistance to oxidative
stress and pathogens of the disadvantaged last-hatching nestling, suggesting that collared flycatchers pursue a compensatory,
“brood survival” strategy. 相似文献
10.
The theory of sex allocation suggests that if the reproductive value and the cost of producing/rearing offspring differ between
male and female offspring, parents should invest differently in sexes depending on environmental conditions. Female parents
could allocate more resources to eggs of one sex to compensate potential sex-dependent constraints later during the nestling
period. In this study, we tested the influence of environmental conditions on sexual dimorphism in eggs of Eurasian kestrels
(Falco tinnunculus) by experimentally manipulating food availability before laying. We found that an increase in food abundance before laying
did not increase egg mass but changed sex-dependent resource distribution in eggs. In food-supplemented pairs, but not in
control pairs, egg mass and hatchling mass were similar between males and females. In addition, we found, in the food-supplemented
group, that the latest hatched females showed shorter hatching times than in the control group. In control pairs, female eggs,
hatchlings and nestlings were heavier than males. In addition, male fledglings in the food-supplemented group gained less
mass than those in the control group. As that food abundance was only increased until the onset of laying, female kestrels
were expected to invest in eggs taking food abundance before egg formation as a predictor of future conditions during brood
rearing. Our study shows that environmental conditions before laying promote a subtle adjustment of the resources invested
in both sexes of offspring rather than in other breeding parameters. This adjustment resulted in a shortening of hatching
time of the last hatched females that possibly gives them advantages in their competitive capacity with respect to male nest-mates. 相似文献
11.
Vladimír Remeš 《Behavioral ecology and sociobiology》2011,65(6):1257-1266
Females can adaptively adjust phenotype of their offspring via deposition of various compounds into eggs, including androgens
and other hormones. Here, I investigated how egg yolk androgens (testosterone and androstenedione) related to environmental
conditions and parental traits in the great tit (Parus major) across three breeding seasons. Male and female traits studied included age, condition and multiple feather ornaments, both
carotenoid- and melanin-based (carotenoid and UV chroma of yellow breast feathers, area of black breast band and white cheek
immaculateness). Yolk mass increased with laying temperature, laying date and area of male black breast band. Concentration
of androgens increased with breeding density, territory quality and carotenoid chroma of male yellow breast feathers and was
higher in mates of 1 year old as compared to older males. Yolk androgens were not related to any of the female traits analysed.
These patterns were thus consistent with (1) social and environmental effects on yolk mass and composition and (2) both positive
and negative differential allocation strategies of resource allocation in females. Overall, male traits were the most important
predictors of egg yolk characteristics in this socially monogamous songbird. 相似文献
12.
Thomas W. Pike 《Behavioral ecology and sociobiology》2005,58(4):407-413
A number of recent reports have documented offspring sex ratio biases in birds. However, to date the potential mechanisms that have been put forward to explain the proximate basis for these deviations are entirely speculative. Using a captive population of domestic pigeons (Columba livia domestica), I tested the hypothesis that mothers in relatively poor physical condition should overproduce daughters by manipulating maternal body condition around the time of egg laying by continuous egg removal and differing feeding regimes. During treatment, females were fed a controlled quantity of food. This, combined with the high energetic costs of repeated egg production caused a significant reduction in maternal body weight. In contrast, during control when food was available ad libitum, maternal body weight did not decline, despite repeated egg production. No significant deviation from parity was evident in the sex ratio of either the first or second eggs during control, whereas during treatment a significant female bias was evident in not only the first egg, but also in the second egg. The absence of single-egg clutches, the rarity of infertile eggs and the lack of laying delays between eggs strongly suggests that the mechanism of sex ratio adjustment in pigeons occurs prior to ovulation. The highly skewed sex-distribution within the two-egg clutches and the unexpectedly large amount of variation in the yolk weight of eggs produced during treatment (but not control) are consistent with the expectations of pre-ovulatory selective resorption of wrong sex ovarian follicles. 相似文献
13.
Common murres (Uria aalge) are highly colonial; pairs often breed at the highest possible densities, in bodily contact with neighbors. At Bluff, a colony
in western Alaska, we tested for synchrony in egg laying at various spatial scales and found little evidence for higher synchrony,
either within study plots of 15–195 pairs, or within subplots containing several pairs, than among plots in a 5-year study.
Egg laying of neighbors generally was more synchronous than expected based on overall frequency distributions in laying dates,
however. Breeding success was positively correlated with the number of breeding neighbors and the number of neighbors tending
eggs or nestlings at the time of egg laying. Breeding success of pairs with neighbors was positively related to the breeding
success of neighbors. Pairs that produced eggs synchronously with at least one neighboring pair had higher success than those
that began breeding either before or after their neighbors. Most reproductive failures at Bluff are due to accidental egg
loss and predation on eggs by common ravens, Corvus corax, soon after laying. By occupying space where a raven might otherwise land and defending their own eggs, active breeding neighbors
locally reduce the probability of egg predation. Active breeding neighbors also are less likely to flush and accidentally
dislodge nearby eggs when disturbed than are nonbreeders. Murres breeding synchronously with neighbors have the highest assurance
of the presence of active breeding neighbors both at the time of egg laying and throughout their reproductive attempts. Groups
of neighboring murres can be considered small “selfish herds,” demonstrating by-product mutualism through their continued
presence and defense of their own eggs and nestlings. Despite the advantages of breeding synchronously with neighbors, early
breeding may often be favored, however.
Received: 22 January 1996/Accepted after revision: 16 June 1996 相似文献
14.
Balázs Rosivall 《Behavioral ecology and sociobiology》2008,62(6):1037-1042
In avian sex ratio studies, results often differ between species and between populations within species. Some researchers
argued that positive results were simply statistical artefacts and that sex ratio adjustment did not exist. However, many
of the proposed mechanisms of sex ratio adjustment result in costly laying gaps. In these cases, females laying large clutches
may restrict the sex manipulation to the first egg of the clutch. Consequently, detectability of sex ratio adjustment on the
level of the clutch can be low. Though obvious, this fact is often neglected in the literature. Using simulations, I show
that the proportion of undetected sex manipulation can be surprisingly high when the manipulation is restricted to the first
egg. If the sample size is 50 broods, there is 47% and 71% chance in 6- and 12-egg clutches, respectively, that sex manipulation
is undetected. Even with large samples (n = 100), the figures are 15% and 46%. These data suggest that nonsignificant results for clutch sex ratios do not necessarily
mean that sex is not manipulated in a portion of the brood, e.g. in first-laid eggs. Hence, whenever possible, data on laying
order-specific sex manipulation should also be collected. Without such data, contradictory results on brood sex ratios should
be interpreted cautiously. 相似文献
15.
Vertebrate eggs contain maternal steroid hormones in their yolks; and in avian species the concentration of these steroids vary within and among clutches. The organizational actions of these variable doses of maternal steroids in the avian egg, analogous to those regulating the development of sexually dimorphic traits, are little explored. In this study, we examined the organizational effects of yolk testosterone in the house sparrow,
Passer domesticus, a sexually dichromatic passerine bird in which males are characterized by the presence of a throat patch or badge of black feathers that varies in size among males. We injected a physiological dose of testosterone or vehicle into eggs in the field, removed nestlings, and hand-raised them in the laboratory. At 5 months of age, we investigated treatment effects on plumage and behavior. Males that hatched from testosterone-injected eggs developed a larger badge than males that hatched from vehicle-injected (control) eggs. However, testosterone did not induce the expression of a badge in females. In staged dyadic encounters, both males and females hatched from testosterone-injected eggs were more successful at obtaining and defending a food source than individuals of the same sex hatched from control eggs. The results suggest that variable concentrations of maternal testosterone in the eggs of the house sparrow organize the expression of a plumage trait in males and behavior in both sexes.Communicated by J. Graves 相似文献
16.
Cor Dijkstra Bernd Riedstra Arjan Dekker Vivian C. Goerlich Serge Daan Ton G. G. Groothuis 《Behavioral ecology and sociobiology》2010,64(9):1393-1402
When the reproductive value of male and female offspring varies differentially, parents are predicted to adjust the sex ratio
of their offspring to maximize their fitness (Trivers and Willard, Science 179:90–92, 1973). Two factors have been repeatedly linked to skews in avian offspring sex ratio. First, laying date can affect offspring
sex ratio when the sexes differ in age of first reproduction, such that the more slowly maturing sex is overproduced early
in the season. Second, position of the egg in the laying sequence of a clutch may affect sex ratio bias since manipulating
the sex of the first eggs may be least costly to the mother. We studied both factors in two non-domesticated pigeon species.
Both the Wood pigeon (Columba palumbus) and the Rock pigeon (Columba livia) have long breeding seasons and lay two-egg clutches. In the field, we determined the sex of Wood pigeon nestlings. In Rock
pigeons, housed in captivity outdoors, we determined embryo sex after 3 days of incubation. On the basis of their sex-specific
age of first reproduction, we predicted that males, maturing at older age than females, should be produced in majority early
and females later in the year. This was confirmed for both species. The bias was restricted to first eggs. Rock pigeons produced
clutches throughout the year and show that the sex of the first egg followed an annual cycle. To our knowledge, this study
presents the first evidence of a full annual rhythm in adaptive sex allocation in birds. We suggest that this reflects an
endogenous seasonal program in primary sex ratio controlled by a preovulatory mechanism. 相似文献
17.
Hatching asynchrony in avian species leads to age and size differences between nestlings within a brood, handicapping last-hatched chicks in the sibling rivalry. Starvation due to this competitive disadvantage has been regarded as the primary cause of an increase in mortality with hatching order. However, for gulls it has also been suggested that disease is the cause of mortality for last-hatched chicks, possibly through reduced immunocompetence and thereby an enhanced susceptibility to infection. In addition, the male-biased mortality reported for several gull species may be related to a higher vulnerability to diseases in males compared to females. To determine the potential influence of the immune system on these mortality patterns, we investigated the T-cell-mediated immunity (CMI) of black-headed gull chicks in relation to hatching order and sex. We found a significant decrease in the CMI with hatching order. This result may be causally related to systematic changes in maternal yolk steroids and carotenoids within the laying sequence. For second-laid eggs, male CMI was significantly lower than female CMI. This is possibly linked to higher plasma levels of testosterone in male embryos which might have an immunosuppressive effect. If so, this effect is masked in eggs of either high (first egg) or low (last egg) quality. Chicks with low CMI showed enhanced mortality rates. Thus the differences in immune response are likely to contribute to the observed mortality patterns. However, hatching order significantly affected mortality independently of CMI, suggesting that competitive disadvantage due to hatching asynchrony is also important.Communicated by M. Webster 相似文献
18.
A recent hypothesis suggests that birds’ blue-green egg colors may be a sexually selected signal of female (and potentially
nestling) quality that males use to make parental investment decisions. While there is some empirical support for this idea,
both theory and observations question its validity. To test this hypothesis experimentally, we examined the influence of egg
color on male American robin Turdus migratorius behavior by replacing natural clutches with four artificial eggs that were all either pale or vividly colored, close to the
extremes in natural egg coloration. At the end of the incubation period, three unrelated nestlings were fostered into each
experimental nest, and parental provisioning behavior was monitored when nestlings were 3, 6, and 9 days old. Male provisioning
rate for 3-day-old nestlings was significantly higher in the vivid egg treatment compared to both the pale egg treatment and
untreated controls, but there was no effect of egg color on paternal behavior at the older nestling stages. Male feeding rate
at unmanipulated nests was only weakly positively related to natural egg color (chroma) when nestlings were 3 days old. These
results suggest that blue-green egg color may act as a post-mating signal of female quality or investment in this species,
but our findings do not exclude the possibility that egg color pigmentation also serves other adaptive functions. 相似文献
19.
Rita Hargitai Kathryn E. Arnold Márton Herényi József Prechl János Török 《Behavioral ecology and sociobiology》2009,63(6):869-882
Offspring survival can be influenced by resources allocated to eggs, which in turn may be affected by the environmental factors
the mother experiences during egg formation. In this study, we investigated whether experimentally elevated social interactions
and number of neighbouring pairs influence yolk composition of collared flycatchers (Ficedula albicollis). Social challenge was simulated by presentation of a conspecific female. Experimental females spent more time near the cage
and produced eggs with higher androgen concentration, but local breeding density did not affect yolk androgen level. Moreover,
we found that females exposed to more intra-specific interactions and those that bred at higher density produced eggs with
smaller yolk. These females may be more constrained in foraging time due to more frequent social encounters, and there might
be increased competition for food at areas of higher density. In contrast, the present study did not reveal any evidence for
the effect of social environment on yolk antioxidant and immunoglobulin levels. However, we found that yolk lutein and immunoglobulin
concentrations were related to the female’s H/L ratio. Also, yolk lutein and α-tocopherol levels showed a seasonal increase
and were positively related to the female’s plasma carotenoid level. Mothers may incur significant costs by transferring these
compounds into the eggs, thus only females in good physiological condition and those that lay eggs later, when food is probably
more abundant, could allocate higher amounts to the eggs without compromising their defence mechanisms. Our results suggest
that environmental circumstances during egg formation can influence conditions for embryonic development. 相似文献
20.
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. 相似文献