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1.
José M. Aparicio 《Behavioral ecology and sociobiology》1997,41(2):129-137
Lesser kestrels (Falco naumanni) lay clutches which appear excessive as only 3% of them yield as many young as eggs laid. Four hypotheses may explain the
adaptive value of producing surplus eggs: (1) the bet-hedging hypothesis assumes that the environment varies unpredictably
and surplus eggs serve to track uncertain resources; (2) the ice-box hypothesis suggests that surplus offspring serve as a
reserve food during a period of shortage; (3) the progeny choice hypothesis says that parents produce surplus offspring in
order to choose these with higher fitness; and (4) the insurance-egg hypothesis proposes that extra eggs are an insurance
against the failure of any egg. To test the significance of this strategy in the lesser kestrel, an experiment manipu-lating
brood size at hatching was carried out over 2 years, with good and bad feeding conditions. The experiment consisted of adding
a chick to experimental broods where one egg failed to hatch or removing a randomly selected chick from experimental broods
where all eggs had hatched. Independently of annual food availability, pairs with brood sizes reduced by one chick fledged
more nestlings than pairs with brood size equalling their clutch sizes. Body condition of young was also better in the former
group, but only in 1993 (a high-food year). Independently of year, mean local survival of parents with complete broods at
hatching was lower than for parents raising reduced broods. These results supported only the insurance-egg hypothesis which
says that surplus eggs may be an insurance against the failure of any egg, but parents may suffer reproductive costs when
all eggs hatch.
Received: 17 January 1997 / Accepted after revision: 27 April 1997 相似文献
2.
Willow B. English Douglas Schamel Diane M. Tracy David F. Westneat David B. Lank 《Behavioral ecology and sociobiology》2014,68(12):1939-1949
Fisher’s sex ratio theory predicts that on average parents should allocate resources equally to the production of males and females. However, when the cost/benefit ratio for producing males versus females differs, the theory predicts that parents may bias production, typically through underproduction of the sex with greater variation in fitness. We tested theoretical predictions in the red-necked phalarope, a polyandrous shorebird with sex-role reversal. Since females are larger and therefore potentially more expensive to produce and may have greater variation in reproductive success, we predicted from Fisher’s hypothesis a male bias in population embryonic sex ratio, and from sex allocation theory, female biases in the clutches of females allocating more resources to reproduction. We measured eggs and chicks and sexed 535 offspring from 163 clutches laid over 6 years at two sites in Alaska. The embryonic sex ratio of 51.1 M:48.9 F did not vary from parity. Clutch sex ratio (% male) was positively correlated with clutch mean egg size, opposite to our prediction. Within clutches, however, egg size did not differ by sex. Male phalarope fitness may be more variable than previously thought, and/or differential investment in eggs may affect the within-sex fitness of males more than females. Eggs producing males were less dense than those producing females, possibly indicating they contained more yolk relative to albumen. Albumen contributes to chick structural size, while yolk supports survivorship after hatch. Sex-specific chick growth strategies may affect egg size and allocation patterns by female phalaropes and other birds. 相似文献
3.
Vedder O Magrath MJ Niehoff DL van der Velde M Komdeur J 《Behavioral ecology and sociobiology》2012,66(4):603-612
Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little
is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction. However, recent studies
indicate that the occurrence of extra-pair offspring may generally decline with laying order, possibly because stimulation
by eggs induces incubation, which may suppress female motivation to acquire extra-pair paternity. Here we tested whether experimental
inhibition of incubation during the laying phase, induced by the temporary removal of eggs, resulted in increased extra-pair
paternity, in concert with a later cessation of laying, in blue tits (Cyanistes caeruleus). As expected, experimental females showed a more gradual increase in nocturnal incubation duration over the laying phase
and produced larger clutches than controls. Moreover, incubation duration on the night after the first egg was laid predicted
how extra-pair paternity declined with laying order, with less incubation being associated with more extra-pair offspring
among the earliest eggs in the clutch. However, incubation duration on this first night was unrelated to our experimental
treatment and independent of final clutch size. Consequently, the observed decline in extra-pair paternity with laying order
was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring. We suggest that
female physiological state prior to laying, associated with incubation at the onset of laying, determines motivation to acquire
extra-pair paternity independent of final clutch size. This decline in proportion of extra-pair offspring with clutch size
may be a general pattern within bird species. 相似文献
4.
Ola Svensson Maria Lissåker Kenyon B. Mobley 《Behavioral ecology and sociobiology》2010,64(8):1325-1331
When parental care is costly, parents should avoid caring for unrelated young. Therefore, it is an advantage to discriminate
between related and unrelated offspring so that parents can make informed decisions about parental care. In the present study,
we test the hypothesis that male sand gobies (Pomatoschistus minutus) recognize and differentially care for their own offspring when given a choice between a nest with sired eggs and a second
nest with eggs sired by an unrelated male. The sand goby is a species with exclusive and costly paternal care. Male parasitic
spawnings (e.g., sneaking) as well as nest takeovers by other males are common. Our results show that nests containing sired
eggs were preferred and received significantly more care, as measured by nest building and nest occupancy, than nests with
foreign eggs even when males cared for both nests. These findings suggest that males respond to paternity cues and recognize
their own clutches. Relative clutch size also had a significant effect on male parental care. When sired clutches were larger
than foreign clutches, males preferred to care for their own nest. In the few cases where males chose to take care of foreign
nests, the foreign clutch was larger than their own clutch. Taken together, our results provide evidence that both paternity
cues and clutch size influence parenting decisions among male sand gobies. 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.
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
7.
JOSÉ A. DÍAZ§ JAVIER PÉREZ-TRIS† JOSÉ L. TELLERÍA ROBERTO CARBONELL‡ TOMÁS SANTOS 《Conservation biology》2005,19(5):1578-1585
Abstract: We studied the effect of habitat fragmentation on female reproductive investment in a widespread lacertid lizard ( Psammodromus algirus ) in a mixed-forest archipelago of deciduous and evergreen oak woods in northern Spain. We captured gravid females in fragments (≤10 ha) and forests (≥ 200 ha) and brought them to the laboratory, where they laid their eggs. We incubated the eggs and released the first cohort of juveniles into the wild to monitor their survival. Females from fragments produced a smaller clutch mass and laid fewer eggs (relative to mean egg mass) than females of similar body size from forests. Lizards did not trade larger clutches for larger offspring, however, because females from fragments did not lay larger eggs (relative to their number) than females from forests. Among the first cohort of juveniles, larger egg mass and body size increased the probability of recapture the next year. Thus, fragmentation decreased the relative fecundity of lizards without increasing the quality of their offspring. Reduced energy availability, increased predation risk, and demographic stochasticity could decrease the fitness of lizards in fragmented habitats, which could contribute to the regional scarcity of this species in agricultural areas sprinkled with small patches of otherwise suitable forest. Our results show that predictable reduction of reproductive output with decreasing size of habitat patches can be added to the already known processes that cause inverse density dependence at low population numbers. 相似文献
8.
Scott Forbes 《Behavioral ecology and sociobiology》2010,64(3):475-483
In avian families, some offspring are rendered unequal by parental fiat. By imposing phenotypic handicaps (e.g., via asynchronous
hatching) upon certain of their offspring and not others, parents structure the sibship into castes of advantaged “core” offspring
and disadvantaged “marginal” offspring that results in an asymmetric sibling rivalry. Here, I show how this family structure
scales up to population level reproductive consequences. In a 17-year study of red-winged blackbirds (Agelaius phoeniceus), I show that year-to-year variation in the number of surviving offspring is driven primarily by variation in the number
of marginal offspring at hatching and their posthatching survival. Clutch size, core brood at hatching, and fledging varied
little from year to year and had little direct effect on year-to-year variation in total brood size at fledging; conversely,
variation in the size of the marginal brood at hatching and at fledging was much greater. Marginal but not core brood size
at hatching rose with mean clutch size; in years where parents laid larger average clutches they did so by adding marginal
progeny. The mean posthatching survival of marginal offspring was always lower than that of core offspring in a given year,
and there was no overlap in the distributions. The highest mean survival of marginal offspring across years fell below the
lowest mean survival of core offspring; broods were deeply structured. There was an overall female bias among fledglings,
and the sex ratio varied across years, with a higher proportion of the smaller female nestlings in years of below average
reproductive success. Such variation was especially pronounced in the marginal brood where a higher incidence of brood reduction
allowed greater potential for sex-biased nestling mortality. In years of the highest average reproductive success, the sex
ratio in the marginal brood approached equality, whereas in years of the lowest average reproductive success, more than two
thirds of 8-day-old nestlings were female. Structuring the brood into core and marginal elements allowed parents to modulate
both offspring number and sex under ecological uncertainty with direct consequences for population-level reproductive success.
They produced fewer and less expensive fledglings in below average years and more and more expensive fledglings in above average
years. 相似文献
9.
Past investment in offspring may be important in determining a parent's ability to reproduce in the future and, hence, should affect the relative value of current offspring. However, there have been surprisingly few clear tests of whether animals actually adjust parental care in response to diminished opportunities for future reproduction. We modified the experimental protocol of Sargent and Gross [Behav Ecol Sociobiol (1985) 17:43–45] to examine offspring desertion by mallards ( Anas platyrhynchos), and decoupled the influence of past investment from expected current benefits by controlling for the effect of offspring age on clutch value. Using 9 years of nest mortality data, we accounted for the increasing prospects of egg survival with clutch age by calculating clutch sizes throughout incubation with equivalent expected benefits. Applying this approach, we experimentally reduced 203 clutches at two different incubation stages such that they had equivalent expected benefits but differed in the amount of past investment. Nest desertion rates did not differ between early- and late-incubated clutches that had equivalent expected benefits. Rather, the probability of desertion increased with the severity of the clutch reduction treatment. These results suggest that female mallards adjust parental care according to the expected benefits of current offspring, rather than to diminished prospects for future reproduction due to past investment. We further examined whether females assessed expected benefits on the basis of clutch size alone or clutch size adjusted for the age of the clutch. Using Akaike's Information Criterion, the most parsimonious model to explain the probability of deserting an experimentally reduced clutch included both the proportion of the clutch remaining and clutch age. Thus, female mallards appear to fine-tune their level of parental care not only according to the relative number of offspring in the clutch, but also to the increased prospects for offspring survival as they age. 相似文献
10.
Nick J. Royle Margaret E. Hall Jonathan D. Blount Scott Forbes 《Behavioral ecology and sociobiology》2011,65(2):313-323
Despite their importance to offspring fitness outcomes, there has been little previous work on egg-mediated maternal effects
in avian brood parasites which lay their eggs in the nests of other species. Here, we examine patterns of egg yolk antioxidant
deposition in an avian host (red-winged blackbird, Agelaius phoeniceus) and their brood parasite (brown-headed cowbird, Molothrus ater). Cowbird nestlings compete directly for food with host blackbird chicks and succeed, despite hatching from a smaller egg,
by begging more intensely and growing as or more rapidly than their hosts. Dietary-derived antioxidants, such as carotenoids
and vitamins E and A, deposited in egg yolk, may enhance growth rate and reduce oxidative stress, and therefore provide a
potential mechanism by which female cowbirds could enhance the competitiveness of their young in host nests. However, provision
of antioxidants to eggs is costly so we predicted that female cowbirds should adjust the amount of antioxidants in response
to variation in host quality. We found that whilst red-winged blackbird clutches parasitised by cowbirds did not differ in
the pattern of antioxidant deposition compared to non-parasitised clutches, levels of vitamin E deposited in cowbird eggs
were closely matched to that of the individual host clutch in which cowbirds laid their egg. This supports the prediction
that female cowbirds adjust the antioxidant concentration of their eggs to increase the likely competitiveness of their offspring
in the host nest into which they are laid and may help explain the success of cowbirds in competing with larger host young. 相似文献
11.
Csaba Moskát Erik C. Rosendaal Myra Boers Anikó Zölei Miklós Bán Jan Komdeur 《Behavioral ecology and sociobiology》2011,65(5):1045-1053
Hosts of the common cuckoo (Cuculus canorus), an avian brood parasite, develop antiparasite defense mechanisms to increase their reproductive success. Ejection of the
parasite egg and desertion of the parasitized nest are the most typical adaptations in response to brood parasitism, but nest
desertion may also occur in response to partial clutch reduction, independently from parasitism. Some great reed warblers
(Acrocephalus arundinaceus) showed both mechanisms in the same incidence of cuckoo parasitism: in 18% of successful ejections of the parasite eggs,
they deserted their nests. We studied if such cases of post-ejection nest-desertion are caused by brood parasitism or reduced
clutch value. We experimentally parasitized clutches consisting of five or three host eggs with two painted conspecific eggs
to mimic parasitic eggs, as multiple parasitism is frequent in the area. Although hosts ejected these parasitic eggs in both
clutch categories (100% and 67% for the larger and smaller inital clutch sizes, respectively), we found that after manipulation,
post-ejection nest-desertion frequently occurred at small (3-egg) clutches (40%), but rarely at large (5-egg) clutches (17%).
The same phenomenon also occurred when unparasitized 3-egg clutches were reduced by two eggs, but not when 5-egg clutches
were reduced in the same way. A logistic regression model revealed that only initial clutch size affected nest desertion of
parasitized nests in our experiments. Therefore, we conclude that post-ejection nest-desertion is not a second antiparasite
mechanism, which might serve as a redundant antiparasite defense, but a reaction to typically small and further decreased
clutch size. 相似文献
12.
Kai Lindström 《Behavioral ecology and sociobiology》1998,42(2):101-106
This study tested experimentally whether clutch size and the cost of care affect filial cannibalism in the sand goby, Pomatoschistus minutus. Evolutionary models of filial cannibalism suggest that egg eating has evolved as a way for the male parent to prolong his
breeding season. These models assume that eggs function as an alternative energy source for the constrained parent. I manipulated
clutch size by allowing males to mate with either one or two females, representing a small and a large clutch, respectively.
The addition of a small male shore crab, a common egg predator, increased the cost of care. I quantified fat reserves as a
measure of the condition of guarding males. Males who did not build nests had lower fat reserves than males who built nests,
suggesting that males with low energy reserves do not start breeding. Males with small clutches lost their nest to the crab
more often than males with large clutches. Neither filial cannibalism nor the amount of eggs eaten were affected by the treatments.
Males who consumed eggs had a higher fat percentage than males who did not eat eggs. The result that males with small clutches
lost their nests to the crabs supports the idea that eggs are defended only if the benefit from continued care will outweigh
the cost and that males therefore are sensitive to the trade-off between present and future reproductive success.
Received: 15 May 1997 / Accepted after revision: 15 November 1997 相似文献
13.
For birds with altricial young, the brood-rearing period is one of the most energetically expensive periods in their lives and may be the bottleneck for fitness. Because parents are expected to be prudent in allocating resources between reproduction and self-maintenance, food supply should be an important factor determining reproductive decisions during brood rearing. Parents with abundant food are expected to have enhanced fitness because they are able to reduce their work rates and increase their own survival chances, because their offspring may be of higher quality, or some combination of these. However, few studies have simultaneously documented all of these variables in a single investigation. We performed a food supplementation experiment to test how food supply influenced provisioning decisions by parent American kestrels (Falco sparverius). Female kestrels showed a strong response to extra food and reduced their provisioning rates. As a result, supplemented females had higher return rates than control females, suggesting significant effects of food on female survival. Because females used extra food to increase their fitness, our results suggest that kestrels raising offspring are limited by food. Male kestrels whose nests were supplemented also responded to extra food by reducing provisioning, but to a much lesser extent than their mates. Male parents did not appear to benefit from supplementation, as their return rates were similar to control males. The total amount of food received on a daily basis by nestlings was similar between supplemented and control nests. Supplemented offspring therefore did not fledge in better condition or have higher survival rates than control nestlings; the only significant factor consistently affecting offspring condition and survival was weather. 相似文献
14.
M. Itzkowitz M. J. Draud J. L. Barnes M. Haley 《Behavioral ecology and sociobiology》1998,42(3):149-155
Male beaugregory damselfish (Stegastes leucostictus) spent more time courting larger females in both two-choice and single presentations. Female size was significantly correlated
with gonad weight. We also verified that female fecundity was extremely variable within a natural population. We found that
male reproductive success was highly correlated with both clutch size and clutch number. However, clutch size was not significantly
correlated with clutch number, indicating that males that received larger clutches did not receive more egg clutches. Furthermore,
there was no difference between the number of offspring produced by males that mated with the largest females and by males
that mated with the most females. Thus, although males preferred larger females, males produced similar numbers of offspring
by mating with large females or mating with many females.
Received: 7 March 1997 / Accepted after revision: 1 November 1997 相似文献
15.
Nicola Saino Maria Romano Diego Rubolini Manuela Caprioli Roberto Ambrosini Mauro Fasola 《Behavioral ecology and sociobiology》2010,64(11):1813-1821
Parental decisions can determine offspring experience of environmental conditions. Such ‘maternal’ effects act both before and after hatching via, e.g., egg quality or the social milieu predisposed by parents. Resource availability may constrain the expression of adaptive maternal effects, and the specific pattern of allocation of these effects among offspring depending on their sex or birth order can result in different fitness payoffs to parents. Declining egg mass with laying order observed in several bird species may constitute an adaptive strategy of parental favouritism towards early hatching offspring with larger reproductive value but may also result from nutritional constraints on laying effort. A previous study has shown that the small size of the third, last laid (c-)egg in yellow-legged gull (Larus michahellis) clutches depends on food availability and that food-supplemented mothers increase the size of their female but not male c-eggs. Here, we show that increased mass of c-eggs laid by females supplemented with food after clutch initiation depends on increased albumen mass, which, in turn, enhances the size of daughters at hatching. Because asynchronous hatching results in a competitive disadvantage of c-chicks, present results suggest that mothers relieved from nutritional constraints enhance the size of daughters to compensate for their larger susceptibility to hatching last. The study also confirms the role of egg albumen content in determining hatchling size, previously experimentally detected only in one species in the wild. The effect of increased egg mass on offspring size persisted at least until day 8 after hatching, when, however, it did not vary with sex, suggesting intense negative selection on small female c-chicks in control broods. Hence, maternal effects mediated by egg albumen content had persistent effects on offspring size. 相似文献
16.
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
17.
Summary By measuring daily intake of food, we compared the cost of incubation for small and large clutches in adult Bengalese finches (Lonchura striata var. domestica). Natural clutches of captive finches were experimentally manipulated to produce two egg or six egg clutches. While incubating large clutches, parents ate significantly more food and took longer to hatch their first egg than did the same birds when provided with small clutches. This supports the hypothesis that the cost of incubation increases with clutch size. This cost should influence other energy allocation decisions in birds such as determination of clutch size and parental investment decisions. 相似文献
18.
Liliana D’Alba Matthew D. Shawkey Peter Korsten Oscar Vedder Sjouke A. Kingma Jan Komdeur Steven R. Beissinger 《Behavioral ecology and sociobiology》2010,64(6):1037-1045
Female birds can influence offspring fitness by varying the relative quantities of egg components they deposit within and
between clutches. Antimicrobial proteins (lysozyme, ovotransferrin, and avidin) are significant components of the avian albumen
and likely aid in defense of embryos from microbial infection. Within clutches, females may enhance antimicrobial defense
of early-laid eggs to protect them from the high risk of infection incurred before the onset of incubation. Among entire clutches,
females may invest more resources in young sired by more attractive males because they have higher reproductive value. We
tested these hypotheses by quantifying antimicrobial protein distribution within and among clutches in blue tit eggs. Contrary
to our hypothesis, clutches showed no differential deposition of lysozyme or avidin within clutches, but eggs laid in the
middle of the sequence had higher concentrations of ovotransferrin than eggs in the beginning and end. Consistent with our
second hypothesis, we found that females produced eggs with higher concentrations of lysozyme (although not ovotransferrin
or avidin) when mated to more attractive (more UV-reflective) males. Furthermore, females mated to polygynous males deposited
less lysozyme than those mated to monogamous males. These data suggest that allocation of lysozyme at the clutch level may
be a maternal effect mediated by male qualities. 相似文献
19.
K. Martin F. G. Cooch R. F. Rockwell F. Cooke 《Behavioral ecology and sociobiology》1985,17(3):257-263
Summary The roles of male and female lesser snow geese (Anser caerulescens) in offspring care are well documented, but we know little about flexibility in these roles and how essential they are for offspring survival. We asked whether uni-parental care was adequate, which sex was required at various stages of the reproductive cycle, and what the costs and consequences were of variable amounts of parental care. We found that two parents were important in acquiring nest sites and producing clutches. Widows losing mates during the latter part of laying or in early incubation experienced similar rates of success in hatching clutches to paired females, but males losing mates during incubation experienced total nest failure. Partial clutch loss, hatch loss, intraspecific nest parasitism, duration of incubation periods and gosling weights at hatch did not differ for pairs or widows. In 1983 at La Pérouse Bay, Manitoba, Canada, widows and pairs had similar incubation behaviour, but widows were harassed more and spent more time in full alert posture while on their nests. In 1952 and 1953 at Southhampton Island, Northwest Territories, widows were significantly lighter in body weight prior to hatch than paired females. Thus while widows can bring clutches to hatch successfully, the loss of mates may result in additional physiological costs. Although all possibilities have not been tested experimentally, it appears that costs to uni-parental care up to hatch are not significant. Data collected so far on consequences of uni-parental care provided during the post-hatch period are equivocal, as in one year survival of goslings from single parent broods seemed poor and in another it did not appeart to differ from pairs. The minimum amount of parental care required to raise snow goslings from hatch to recruitment has yet to be determined. 相似文献
20.
Jesús M. Avilés Deseada Parejo Juan Rodríguez 《Behavioral ecology and sociobiology》2011,65(8):1549-1557
In altricial birds, resource allocation during early developmental stages is the result of an interaction between parental
feeding decisions and scramble competition between nestmates. Hatching asynchrony in birds leads to a pronounced age hierarchy
among their offspring. Therefore, whenever parents exert control over resource allocation parents feeding asynchronous broods
should simultaneously assess individual offspring internal condition and age. In this study, we first studied whether the
highly ultraviolet (UV) reflective body skin of nestlings in the asynchronous European Roller (Coracias garrulus; roller hereafter) relates to nestling quality. In a second stage, we experimentally studied parental biases in food allocation
towards senior and junior sibling rollers in relation to a manipulation of UV reflectance of the skin of their offspring.
Heavier roller nestlings had less brilliant and less UV saturated skins than weaker nestlings. In our experiment, we found
that parents with large broods preferentially fed nestlings presenting skin coloration revealing small body size (i.e. control
nestlings) over nestlings presenting skin coloration revealing large body size (i.e. UV-blocked nestlings). Within the brood,
we found that parental food allocation strategy depended on nestling age: parents preferentially fed senior nestlings signalling
small body size, but did not show preference between control and UV-blocked junior nestlings. These results emphasise that
parent rollers use UV cues of offspring quality while balancing the age of their offspring to adjust their feeding strategies,
and suggest that parents may adopt finely tuned strategies of control over resource allocation in asynchronous broods. 相似文献