scholarly journals Condition dependent strategies of egg size variation in the Common Eider Somateria mollissima

2019 ◽  
Author(s):  
Thomas Kjær Christensen ◽  
Thorsten Johannes Skovbjerg Balsby
Keyword(s):  
Clutch Size ◽  
Body Condition ◽  
Egg Size ◽  
Size Variation ◽  
Common Eider ◽  
Somateria Mollissima ◽  
Individual Level ◽  
Laying Sequence ◽  
The Common ◽  
Using Data

AbstractWe analysed intraclutch egg-size variation in relation to clutch size and to female body condition in the Common Eider Somateria mollissima during an 8-year period. The aim was to assess if eiders adaptively adjusted egg size within the laying sequence in response to different clutch sizes, which potentially could optimise reproductive success through a size advantage in hatchlings. The analyses were performed on both population and individual level using data from recaptured females that changed clutch size between seasons. Based on 1,099 clutches from 812 individual females, population clutch size averaged 4.13 eggs (range: 1-6), with marked annual variation in the dominance of 4- and 5-egg clutches, which constituted c.70% of all clutches. Clutch size was positively related to female pre-laying body condition at both the population and individual level. Egg size varied significantly within and between clutch sizes and changes were significantly related to the laying sequence. First eggs were significantly larger in 4-egg clutches and second eggs smaller (marginally insignificant) than in 5-egg clutches, a pattern also found among individual females changing clutch size between seasons. The relationship between female pre-laying body condition, clutch size and the intraclutch egg-size pattern indicates that both clutch size and egg size is actively adapted to the pre-breeding body condition of the female. We suggest that the observed pattern of intraclutch egg-size variation reflects a finely tuned conditional dependent mechanisms that enable females in a suboptimal condition to optimize reproductive output.

Intraclutch egg-size variation and hatching success in the common eider

1993 ◽  
Vol 71 (3) ◽  
pp. 544-549 ◽  
Author(s):  
Gregory J. Robertson ◽  
Fred Cooke
Keyword(s):  
Egg Size ◽  
Hatching Success ◽  
Size Variation ◽  
Hudson Bay ◽  
Somateria Mollissima ◽  
Physiological Mechanisms ◽  
Common Eiders ◽  
Laying Sequence ◽  
The Common ◽  
Nutrient Reserves

Intraclutch egg-size variation and hatching success were studied in a population of Hudson Bay common eiders (Somateria mollissima sedentaria) at La Pérouse Bay, Manitoba (58°24′N, 94°24′W), to test the hypothesis that females allocate more nutrient reserves to eggs that are more likely to hatch. Egg volumes were calculated for 575 known-sequence eggs in 134 complete clutches of 3–6 eggs. In general, the length of eggs decreased linearly with position in the laying sequence, whereas the breadth of eggs followed a curvilinear pattern, the second or third egg being the widest. For all clutch sizes, the last-laid egg was the smallest and the second- or third-laid egg the largest. Hatching success also varied with position in the laying sequence. Pre-incubation failure declined over the laying sequence, whereas hatching failure (dead, infertile, or rotten eggs) increased. In all cases pre-incubation failure was the major cause of egg loss (84% of total loss). Overall, third and fourth eggs were the most successful and first eggs were the least successful. With one exception, successful and unsuccessful eggs were the same size within a laying sequence. We conclude that there is no clear relationship between egg size and hatching success, and that laying sequence per se has a greater effect on hatching success. Female eiders do not appear to allocate more reserves to eggs that are most likely to hatch, and we consider other proximate, physiological mechanisms to explain the observed pattern of intraclutch egg-size variation.

scholarly journals Condition dependent strategies of egg size variation in the Common Eider Somateria mollissima

PLoS ONE ◽  
2020 ◽  
Vol 15 (7) ◽  
pp. e0226532
Author(s):  
Thomas Kjær Christensen ◽  
Thorsten Johannes Skovbjerg Balsby
Keyword(s):  
Egg Size ◽  
Size Variation ◽  
Common Eider ◽  
Somateria Mollissima ◽  
The Common

Annual variation in common eider egg size: effects of temperature, clutch size, laying date, and laying sequence

1995 ◽  
Vol 73 (9) ◽  
pp. 1579-1587 ◽  
Author(s):  
Gregory J. Robertson
Keyword(s):  
Clutch Size ◽  
Egg Size ◽  
Annual Variation ◽  
Size Variation ◽  
Egg Laying ◽  
Laying Date ◽  
Somateria Mollissima ◽  
Ambient Temperatures ◽  
Common Eiders ◽  
N 93

Annual variation in volumes of eggs laid by common eiders (Somateria mollissima sedentaria) nesting at La Pérouse Bay, Manitoba (58°43′N, 93°27′W), was studied over 3 years (1991–1993). Temperatures during the egg-laying period were higher in 1991 than in 1992 and 1993. However, the eiders began nesting in 1993 at the same time as in 1991, whereas in 1992 the eiders began laying approximately 2 weeks later. Eiders laid significantly smaller clutches in 1992 than in the other 2 years. Egg size did not correlate with clutch size or laying date in any year. However, eiders laid smaller eggs in 1992 and 1993 than in 1991. In five egg clutches, the pattern of intraclutch egg-size variation was different among years. The last laid eggs of five egg clutches were disproportionately smaller in 1992 and 1993 (cold years) than those laid in 1991. Minimum daily temperatures before the egg-laying period (during rapid yolk development) were positively correlated with egg size. However, this effect was not significant when year and egg sequence were controlled for. Egg-size variation was correlated with the overall ambient temperatures during the laying period, whereas annual clutch-size variation was correlated with laying date, suggesting that the proximate mechanisms affecting clutch and egg size are different.

scholarly journals Estimating Repeatability of Egg Size

The Auk ◽  
2001 ◽  
Vol 118 (2) ◽  
pp. 500-503 ◽  
Author(s):  
Paul L. Flint ◽  
Robert F. Rockwell ◽  
James S. Sedinger
Keyword(s):  
Clutch Size ◽  
Egg Size ◽  
Size Variation ◽  
Egg Laying ◽  
Nested Model ◽  
Sequence Number ◽  
Nested Design ◽  
Black Brant ◽  
Laying Sequence ◽  
Analytical Approaches

Abstract Measures of repeatability have long been used to assess patterns of variation in egg size within and among females. We compared different analytical approaches for estimating repeatability of egg size of Black Brant. Separate estimates of repeatability for eggs of each clutch size and laying sequence number varied from 0.49 to 0.64. We suggest that using the averaging egg size within clutches results in underestimation of variation within females and thereby overestimates repeatability. We recommend a nested design that partitions egg-size variation within clutches, among clutches within females, and among females. We demonstrate little variation in estimates of repeatability resulting from a nested model controlling for egg laying sequence and a nested model in which we assumed laying sequence was unknown.

Egg size and clutch size in three species of Nihonotrypaea (Decapoda: Thalassinidea: Callianassidae) from western Kyushu, Japan

2006 ◽  
Vol 86 (1) ◽  
pp. 103-111 ◽  
Author(s):  
K. Kubo ◽  
K. Shimoda ◽  
A. Tamaki
Keyword(s):  
Clutch Size ◽  
Egg Size ◽  
Relative Size ◽  
Size Variation ◽  
Middle Part ◽  
Reproductive Period ◽  
Late Winter ◽  
Estuarine System ◽  
Ariake Sound ◽  
Interspecific Comparisons

Three species of the callianassid genus Nihonotrypaea occur in the Ariake Sound estuarine system, southern Japan; they consist of two tidal-flat species (N. harmandi; N. japonica) and one boulder-beach species (N. petalura), with maximum population densities of 1440, 343, and 12 ind m−2, respectively. Nihonotrypaea harmandi and N. petalura are distributed along the coastline from the outermost part of the sound to the open sea, while N. japonica occurs in the middle part of the sound. Nihonotrypaea japonica has an extended reproductive period from late winter to autumn, while those of the other species are from late spring or summer to autumn. Interspecific comparisons were made for recently laid egg size (as volume) and clutch size (as number of eggs per female). Only in N. japonica was a seasonal egg size variation observed, being significantly larger in winter to spring (mean=0.106 mm3) than in summer (0.080 mm3). By contrast, clutch size was significantly smaller in winter to spring, resulting in nearly the same clutch volume per female (product of the mean egg volume and clutch size) between the seasons. Among the three species, the egg size was ordered as N. japonica (overall mean volume through the seasons=0.092 mm3)>>N. petalura (0.057 mm3)>N. harmandi (0.054 mm3). The clutch size was ordered as N. harmandi>N. petalura≈N. japonica. The clutch volume was ordered as N. japonica≈N. harmandi>N. petalura. The smallest clutch volume value for N. petalura female showed an opposite trend to the relative size of the major cheliped found in a previous study.

Female sociality in the common eider duck during brood rearing

1982 ◽  
Vol 60 (12) ◽  
pp. 3326-3331 ◽  
Author(s):  
J. K. Schmutz ◽  
R. J. Robertson ◽  
F. Cooke
Keyword(s):  
Maternal Care ◽  
Adaptive Significance ◽  
Common Eider ◽  
Somateria Mollissima ◽  
Brood Rearing ◽  
The Common ◽  
Nutrient Reserves ◽  
Prolactin Hormone

This study investigates the potential adaptive significance of the behavior of female common eider ducks (Somateria mollissima) which have no young of their own ("aunts") but accompany other females and young. "Aunts" exhibited ambivalent aggression and protection toward ducklings. There was no evidence that the presence of "aunts" enhanced the survival of the ducklings they accompanied. Both females which had their clutch removed and females which had not laid eggs behaved as "aunts." The level of circulating prolactin hormone in "aunts" was lower than in incubating females and similar to the basal level of males. We therefore rejected the hypothesis that maternal care was misdirected during hormonal adjustment from breeding to nonbreeding. We suggest that "aunts" which have lost a clutch or brood, spend some time feeding away from the colony, and then return to the nesting grounds after replenishing their nutrient reserves. Upon returning, "aunts" may select sites for nesting in future years. During this time, they are temporarily attracted to broods. We propose that "aunts" flock and fend off predators during an attack in an attempt to seek safety in a flock rather than to protect ducklings of other females.

Within-clutch egg-size variation in a subsocial bug: the positional effect hypothesis

2006 ◽  
Vol 84 (11) ◽  
pp. 1540-1544 ◽  
Author(s):  
Shin-ichi Kudo
Keyword(s):  
Predation Risk ◽  
Clutch Size ◽  
Egg Size ◽  
Size Variation ◽  
Instar Nymph ◽  
Offspring Size ◽  
Egg Mass ◽  
Female Body Size ◽  
Positional Effect ◽  
Effect Hypothesis

If there are differences in predation risk among the offspring within a clutch, parents should allocate less resources to the offspring facing higher risk. Predation risk, and thus offspring size, may depend on the spatial position of individual offspring within a clutch. To test this positional effect hypothesis, I examined egg-size (egg-mass) variation in the subsocial bug Elasmucha signoreti Scott, 1874 (Hemiptera: Acanthosomatidae). In subsocial insects, including Elasmucha , in which females guard their clutches against predators by covering the clutch with their bodies, there are large differences in survival between offspring at the centre and at the periphery of the clutch. There was considerable variation in reproductive output among females; female body size was positively correlated with egg mass but not with clutch size. Females laid significantly lighter eggs in the peripheral, and thus more vulnerable, part of the clutch. No phenotypic trade-off between egg mass and clutch size was detected. Egg mass was positively correlated with hatched first-instar nymph mass. Thus, E. signoreti females seem to allocate their resources according to the different predation risks faced by the offspring within a clutch. I suggest that the positional effect hypothesis can generally be applicable to species whose females lay eggs in clutches and that the eggs suffer different mortality rates which depend on their spatial positions within the clutch.

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