Changes In Clutch Size Research Articles

The effect of climate change on laying dates, clutch size and productivity of Eurasian Coots Fulica atra

Climate change is affecting many living organisms; however, the responses of many of them remain unknown. In this paper, we present the results regarding the response of a bird species from the rallid family to the increased temperatures during the breeding season. We analysed the breeding data of Eurasian Coots nesting during 30 seasons between 1972 and 2019. During the study period, mean temperatures in April, the month when Coots start nesting, increased by 3.5 °C, and in months corresponding with the species breeding season by 2.6 °C. Breeding Coots advanced their earliest and median laying dates across the study period; however, the duration of their breeding season remained unchanged. We did not detect any significant temporal changes in clutch size, but clutches have become much more variable in size throughout the study period. Nest failures and production of offspring per nest did not change over the study period; however, the production of young per successful nest significantly declined. It is likely that this decline is the effect of mismatch between the period of food abundance (dipterans collected from water), and hatchling emergence, which is advanced due to change in climate. Future studies investigating the occurrence of dipteran resources at water bodies are needed to test this hypothesis.

Consequences of Renesting in Common Terns (Sterna hirundo): Changes in Clutch Size, Egg Mass, and Productivity

Some previous studies of seabirds have suggested that birds renesting after earlier failures may lay smaller clutches and smaller eggs than the same birds in their first nestings. Common Terns (Sterna hirundo) were studied at a site where most first clutches and broods were destroyed by high seas from a hurricane on 22 June 1972. Most or all pairs renested 8-17 d (mean 11.2 d ± 2.1SD) after failure. Renesting pairs had lower clutch size than first-nesting pairs (means 2.11 vs 2.85), lighter eggs (20.08 vs 21.89 g for first eggs in the clutch) and lower productivity (≤ 1.24 vs 2.07 chicks raised to fledging). Two of 34 fledglings from renestings were subsequently encountered as breeders, versus 2 of 30 from surviving first nestings in 1972 and 5 of 73 from the same site in 1971. Hence, renesting contributed offspring to the next generation, although it must have entailed physiological, energetic and temporal costs to the parents.

Nesting behaviour and ecology of the White-browed Fantail Flycatcher (Rhipidura aureola) in Sri Lanka

The White-browed Fantail Flycatcher (Rhipidura aureola) is a widely distributed species in tropical regions of the Indian subcontinent and in Southeast Asia. We determined the breeding biology and nest site characteristics of R. aureola in Sri Lanka during 2012 to 2017. All the nests observed were small cup-shaped and without a ‘tail’ extending below the nest base. Both male and female R. aureola built their nests within 9–13 days with an average mean external diameter, mean internal diameter, and mean depth of, respectively, 6.4 ± 0.32, 5.6 ± 0.22, and 2.9 ± 0.21 cm. The R. aureola we found used various habitats such as home gardens, forest boundaries, sanctuaries, man-made tanks/water bodies, stream banks, tea plantations and road edges to build their nests. We did not find any change in clutch size (2–3 eggs) with different elevation gradients. The eggs were oval-shaped with the ground colour of pale warm yellow-brown to pink and lots of spots or blotches in dark gray-brown. More than 60% of nests were built in a high to medium range of visibility to predators, without a specific location or tree preference, which resulted in nest failure due to predation by domestic cats or birds of prey. Also, we found nest failure due to washing away by abundant rains. Detailed studies on ecological and environmental parameters with respect to nesting or breeding success will help to better understand the species.

Mechanisms of heterochronic change and stasis for clutch size in swifts (Apodiformes)

Since the mid-1800s, explanations in evolution have focused on adaptivity and natural selection, largely at the expense of factors internal to the organism. Today, the importance of internal factors is no longer in dispute. Progress continues to lag, however, on the design of a framework that would allow the integration of their action in evolution. Herein, as part of a wider effort aimed at testing the functionality of the general principle based upon the embryological concepts of induction, competence, and determination (dubbed developmental determination), I present a model for the evolution of clutch size in swifts. It is structured around the physiological mechanism controlling the trait. In indeterminate laying species, it involves an exogenous signal to the female, or induction, and the acquired ability to respond to this signal, or competence. The model explains, with the action of natural selection, how a 2-day shift in the onset of competence induces change in clutch size among species. Through the origin of induction, it predicts the evolutionary transition from indeterminate to determinate laying. Finally, in some species that are indifferent to the general increase in clutch size with latitude, it reveals how both types of developmental transformation may operate to create stasis. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 1067–1079.

Assessing the Effects of Climate on Host-Parasite Interactions: A Comparative Study of European Birds and Their Parasites

BackgroundClimate change potentially has important effects on distribution, abundance, transmission and virulence of parasites in wild populations of animals.Methodology/Principal FindingHere we analyzed paired information on 89 parasite populations for 24 species of bird hosts some years ago and again in 2010 with an average interval of 10 years. The parasite taxa included protozoa, feather parasites, diptera, ticks, mites and fleas. We investigated whether change in abundance and prevalence of parasites was related to change in body condition, reproduction and population size of hosts. We conducted analyses based on the entire dataset, but also on a restricted dataset with intervals between study years being 5–15 years. Parasite abundance increased over time when restricting the analyses to datasets with an interval of 5–15 years, with no significant effect of changes in temperature at the time of breeding among study sites. Changes in host body condition and clutch size were related to change in temperature between first and second study year. In addition, changes in clutch size, brood size and body condition of hosts were correlated with change in abundance of parasites. Finally, changes in population size of hosts were not significantly related to changes in abundance of parasites or their prevalence.Conclusions/SignificanceClimate change is associated with a general increase in parasite abundance. Variation in laying date depended on locality and was associated with latitude while body condition of hosts was associated with a change in temperature. Because clutch size, brood size and body condition were associated with change in parasitism, these results suggest that parasites, perhaps mediated through the indirect effects of temperature, may affect fecundity and condition of their hosts. The conclusions were particularly in accordance with predictions when the restricted dataset with intervals of 5–15 years was used, suggesting that short intervals may bias findings.

Density effect on great tit (Parus major) clutch size intensifies in a polluted environment

Long-term data on a great tit (Parus major) population breeding in a metal-polluted zone around a copper-nickel smelter indicate that, against expectations, the clutch size of this species is decreasing even though metal emissions in the area have decreased considerably over the past two decades. Here, we document long-term population-level changes in the clutch size of P. major and explore if changes in population density, population numbers of competing species, timing of breeding, breeding habitat, or female age distribution can explain decreasing clutch sizes. Clutch size of P. major decreased by one egg in the polluted zone during the past 21 years, while there was no significant change in clutch size in the unpolluted reference zone over this time period. Density of P. major nests was similar in both environments but increased threefold during the study period in both areas (from 0.8 to 2.4 nest/ha). In the polluted zone, clutch size has decreased as a response to a considerable increase in population density, while a corresponding density change in the unpolluted zone did not have such an effect. The other factors studied did not explain the clutch size trend. Fledgling numbers in the polluted environment have been relatively low since the beginning of the study period, and they do not show a corresponding decrease to that noted for the clutch size over the same time period. Our study shows that responses of commonly measured life-history parameters to anthropogenic pollution depend on the structure of the breeding population. Interactions between pollution and intrinsic population characters should therefore be taken into account in environmental studies.

The Predicted Influence of Climate Change on Lesser Prairie-Chicken Reproductive Parameters

The Southern High Plains is anticipated to experience significant changes in temperature and precipitation due to climate change. These changes may influence the lesser prairie-chicken (Tympanuchus pallidicinctus) in positive or negative ways. We assessed the potential changes in clutch size, incubation start date, and nest survival for lesser prairie-chickens for the years 2050 and 2080 based on modeled predictions of climate change and reproductive data for lesser prairie-chickens from 2001–2011 on the Southern High Plains of Texas and New Mexico. We developed 9 a priori models to assess the relationship between reproductive parameters and biologically relevant weather conditions. We selected weather variable(s) with the most model support and then obtained future predicted values from climatewizard.org. We conducted 1,000 simulations using each reproductive parameter’s linear equation obtained from regression calculations, and the future predicted value for each weather variable to predict future reproductive parameter values for lesser prairie-chickens. There was a high degree of model uncertainty for each reproductive value. Winter temperature had the greatest effect size for all three parameters, suggesting a negative relationship between above-average winter temperature and reproductive output. The above-average winter temperatures are correlated to La Niña events, which negatively affect lesser prairie-chickens through resulting drought conditions. By 2050 and 2080, nest survival was predicted to be below levels considered viable for population persistence; however, our assessment did not consider annual survival of adults, chick survival, or the positive benefit of habitat management and conservation, which may ultimately offset the potentially negative effect of drought on nest survival.

Trajectories of Reproductive Effort inColeomegilla maculataandHippodamia convergens(Coleoptera: Coccinellidae) Respond to Variation in Both Income and Capital

Lady beetles such as Coleomegilla maculata DeGeer and Hippodamia convergens Guerin-Meneville have been categorized as income breeders because egg maturation depends on resources available during reproduction. However, capital resources acquired during larval feeding influence reproductive success via effects on adult body size and other traits. We produced three sizes of beetles by varying larval access to food and subjected mated females to alternating periods of food surplus and deficit. Both species exhibited temporal variation in clutch size that reflected changes in income, the amplitude of fluctuations being greater in H. convergens. Egg mass in C. maculata appeared to increase as a fixed function of oviposition sequence but also was affected by maternal body size, whereas H. convergens egg mass fluctuated more in response to food supply. Fertility was largely unaffected by income fluctuation but appeared constrained by capital, especially in H. convergens. Dynamic changes in reproductive effort (daily mass of eggs/female mass at emergence) mirrored changes in clutch size, the amplitude of fluctuations being greater in H. convergens, the species with higher reproductive effort. Generally, large females compensated for income fluctuations better than small females, likely because of their greater capital and possibly an ability to consume larger meals when food was available. The greater sensitivity to income observed in H. convergens likely reflects a higher degree of aphid-specificity compared with the more generalist C. maculata because effective exploitation of ephemeral aphid outbreaks would favor rapid reproductive responses to changes in food supply.

Origin of evolutionary change in avian clutch size

Why different bird species lay different numbers of eggs is a question that has long been associated with factors external to the organism, that is, factors which operate on inherited variation in clutch size through the action of natural selection. Yet, while external factors are important, the extent of what is evolutionarily possible rests with the mechanisms developed by birds for clutch-size control. Hitherto neglected, these mechanisms generate factors internal to the organism that are central to the origin of evolutionary change. They are related to the fact that a species-specific range of clutch size arises from the differential survival of pre-ovulatory follicles undergoing growth when the signal causing egg laying to end reaches the ovary. Herein, I examine three internal factors that, together with external factors, could impact the evolution of avian clutch size. Each factor acts by changing either the number of pre-ovulatory follicles present in the ovary at the time of follicular disruption or the timing of this event. These changes to clutch size can be explained by the concept of heterochrony. In light of this, the role of phenotypic plasticity and genes determining clutch size is discussed. Finally, to account for the origin of evolutionary change in clutch size, I detail an hypothesis involving a process similar to Waddington's theory of genetic assimilation.

Declining Reproductive Parameters Highlight Conservation Needs of Loggerhead Turtles (Caretta caretta) in the Northern Gulf of Mexico

Marine turtles in the Gulf of Mexico are at risk due to many anthropogenic threats including habitat degradation, commercial fishing, and petroleum activities. The severity of this risk was made apparent in 2010 with the occurrence of the Deepwater Horizon oil spill. The objectives of this study were to assess long-term trends in abundance and reproductive parameters for this genetically distinct nesting group. From 1994 to 2010, morning surveys were conducted along 3 beaches on the St Joseph Peninsula, Florida, including within our primary study site on Cape San Blas. Nest abundance on all 3 beaches declined by at least 47% (p < 0.01). Mean nesting success on Cape San Blas was 40% and also declined (p = 0.002). Mean clutch size was 108 and mean emergence success was 58%. Throughout the study there were no changes in clutch size and emergence success. We found that nesting characteristics for the northern Gulf of Mexico subpopulation appear similar to those from other loggerhead turtle nesting groups in the southeastern United States in some ways, such as emergence success, timing of peak nesting, and incubation duration and different in other ways such as nesting success. Variation in some of the parameters may indicate turtles among the different nesting groups experience different environmental conditions. The severity of declines in nest abundance and the low nesting success reported for this small subpopulation suggest potentially serious consequences for this nesting group.

Food conditions affect yolk testosterone deposition but not incubation attendance

In many bird species with hatching asynchrony, yolk androgens increase across the laying sequence. This has been hypothesized to represent a compensatory mechanism for disadvantages of later-hatching chicks – via positive effects of yolk androgens on early competitiveness and growth. However, the costs and benefits of this compensatory strategy probably depend on environmental factors determining the survival chances of the chicks such as the food conditions, which should, therefore, influence maternal yolk androgen deposition.We studied the consequences of manipulated food conditions on the expected level of hatching asynchrony in canaries (Serinus canaria) assigning females to either a low (=LQ) or high quality (=HQ) diet. We measured the incubation behaviour (as incubation attendance) and the yolk androgen deposition in order to investigate whether and how females modulate hatching asynchrony in relation to the food conditions.Females on a HQ diet laid larger and heavier clutches, showed a stronger increase in yolk testosterone content towards the last-laid eggs, but did not alter their incubation attendance. Thus, females on a HQ diet seem to favour the survival of later hatching chicks, as indicated by their yolk testosterone deposition pattern. However, females on a HQ diet laid larger clutches and might need to compensate more in order to achieve a similar degree of hatching asynchrony than females on a LQ diet, given the lack of plasticity in incubation attendance. This suggests that canary females respond to food manipulations mainly via changes in clutch size rather than by altering the degree of hatching asynchrony.

Nutritional implications for sexual cannibalism in a sexually dimorphic orb web spider

AbstractModels predicting mechanisms driving sexual cannibalism in spiders with sexual size dimorphism (SSD) often assume that spiders use post‐copulatory food to channel nutrients into eggs and fecundity is altered through changes in clutch size or egg mass. I tested these assumptions using an orb web spider with extreme SSD,Argiope keyserlingi. I fed mated female spiders prey of either high protein‐low energy or low protein‐high energy composition. I measured egg energy density; a measure of the relative volumes of yolk and albumen. I predicted that ifA. keyserlingiincrease their egg energy density upon feeding on prey of a specific nutrient composition, they could enhance their fecundity by investing in more energy dense eggs. However, if the egg energy densities are dissimilar to their post‐copulatory prey they must be drawing energy from their somatic reserves to invest in eggs. In a further experiment I allowed female spiders to mate with and cannibalize males to determine if cannibalism induces similar effects on egg energy density. Male spider protein energy ratio was measured and found to resemble the high protein‐low energy prey. I found disagreement between the composition of post‐copulatory food and eggs in both experiments. Additionally, spiders fed high protein‐low energy prey lost weight indicating that they draw on their energy reserves to invest in eggs. I thus concluded that spiders that feed on high protein‐low energy prey or on males increase their egg energy density and, possibly, fecundity. However, the nutrient content of the prey or males cannot provide for investment in eggs. The energy invested in eggs is drawn from somatic reserves, probably induced by an as yet undescribed physiological trigger.

A long‐term study of the population dynamics of Common Eiders Somateria mollissima: why do several parameters fluctuate markedly?

Capsule The population dynamics of an Eider population has been studied from1958 to 2006 to evaluate the causes of changes in abundance and breeding potential. Aims To evaluate the changes in clutch size, survival rate of adult ducks, the extent of non‐breeding, and recruitment to the breeding population of Common Eiders nesting on Coquet Island, Northumberland. Methods Survival rates, recruitment and size of the population have been determined by an annual mark-recapture study, while the numbers of nests and clutch size have been directly recorded each year. Results There was marked annual variation in the number of ducks alive, their mortality rates, extent of non‐breeding, clutch size and recruitment of adult ducks. Overall, the annual survival rate and clutch size decreased, and numbers of adult ducks, and presumably the population, peaked on two occasions. Conclusions No density‐dependent effects were identified and the size of the population was mainly determined by changes in the adult survival rates. Because of non‐breeding, nest counts were an unreliable measure of the population size. It is suggested that food shortage is the main factor that has produced the long‐term changes in the population and there is an indication that adverse conditions for Eiders have extended over much of northern Europe in recent years. Identification of why the duckling survival rates were so low and whether these can be increased offers the most likely means of active conservation of this species and would involve management of feeding sites rather than breeding areas.

Do the Height and Location of Black-Crowned Night Heron (Nycticorax nycticorax) Nests Affect Egg Production and Breeding Success?

Changes in clutch size and fledging success associated with the height and distance from shore of nests were investigated in a colony of Black-crowned Night Heron at Poyrazlar Lake, Turkey. A total of 100 nests in five plots were surveyed in 2007. Nest height varied between 45–300 cm, with a tendency to be lower further from shore. Clutch size appeared independent of nest location and variable, with 37% of nests with two eggs, 32% with three eggs, 22% with four eggs and 9% with five eggs. Fledging success was approximately 67% for plot 1, nearest to shore, but increased up to 94% for plot 5, furthest from shore.

Replacement Nesting and Double-Brooding in Malaysian PloversCharadrius peronii: Effects of Season and Food Availability

In shorebirds, the prevalence of successive clutching and types of associated breeding strategies differ among species, environments and individuals. Although several studies have examined successive clutching behaviour in holarctic species, little research has been conducted in the tropics. To assess the full range of reproductive strategies and better understand breeding constraints in tropical environments, we characterised successive clutching behaviour in 54 and 79 colour-banded Malaysian Plovers Charadrius peronii over two years in the Gulf of Thailand. We also examined monthly changes in clutch size, clutch volume, prey availability and breeding success because temporal variability in breeding conditions can affect the prevalence, timing of, and parental role-division between successive clutches. Short intervals between clutches, successive monogamy, high within-season site fidelity, double-brooding, and complete biparental care were general characteristic of successive clutching behaviour. We did not detect any declines in clutch size, clutch volume, prey availability and reproductive success during the course of the breeding season. For Malaysian Plovers, the stable and progressively favourable prey supply and weather conditions, lack of migration, and intense competition for breeding habitats may have contributed to a breeding system constrained more by habitat availability than by time. In these environments, pairs may retain mates and breed multiple times during the long breeding season.

Edge Effects in the Great Tit: Analyses of Long‐term Data with GIS Techniques

In contemporary fragmented landscapes, edges are commonplace, and understanding the effects of edge environments is thus essential for the conservation of forest communities. The reproductive output of forest passerines is often reduced close to forest edges. Possible explanations include overcrowding by conspecifics, elevated rates of predation, and the occurrence of lower-quality habitat and/or individuals at forest edges. We attempted to separate these processes by examining edge effects in the absence of nest predation and by effectively controlling for differences in breeding density and the quality of habitats and individuals. We used an edge distance index (EDI), which accounts for the number and distribution of edges in close proximity to a breeding location, to help explain variation in breeding density, nesting success, and reproductive traits of 8308 pairs of Great Tits (Parus major) breeding between 1965 and 2005, in Wytham, near Oxford, United Kingdom. Results from linear mixed modeling confirmed higher breeding density and a higher proportion of immigrant individuals at forest edges. Nevertheless, independently of these effects, we also found that birds laying later, with smaller clutches but larger eggs, were typical of edge environments. The number of offspring recruited to the breeding offspring per breeding attempt was also reduced at edges, both directly and mediated through changes in clutch size and laying date. Edge effects on life histories were detectable within individual females and up to 500 m from the woodland edge. Woodland edges are increasingly common in contemporary fragmented landscapes. Therefore these results, which suggest a pervasive effect of edges on reproduction, are of considerable importance to the management and conservation of forest communities.

Strong artificial selection in the wild results in predicted small evolutionary change

Estimates of genetic variation and selection allow for quantitative predictions of evolutionary change, at least in controlled laboratory experiments. Natural populations are, however, different in many ways, and natural selection on heritable traits does not always result in phenotypic change. To test whether we were able to predict the evolutionary dynamics of a complex trait measured in a natural, heterogeneous environment, we performed, over an 8-year period, a two-way selection experiment on clutch size in a subdivided island population of great tits (Parus major). Despite strong artificial selection, there was no clear evidence for evolutionary change at the phenotypic level. Environmentally induced differences in clutch size among years are, however, large and can mask evolutionary changes. Indeed, genetic changes in clutch size, inferred from a statistical model, did not deviate systematically from those predicted. Although this shows that estimates of genetic variation and selection can indeed provide quantitative predictions of evolutionary change, also in the wild, it also emphasizes that demonstrating evolution in wild populations is difficult, and that the interpretation of phenotypic trends requires great care.

CHANGES IN EGG SIZE AND CLUTCH SIZE WITH ELEVATION IN A WYOMING POPULATION OF MOUNTAIN BLUEBIRDS

Abstract Few studies have examined how avian life-history traits vary within populations as elevation increases and climate becomes more severe. We compared egg and clutch sizes of Mountain Bluebirds (Sialia currucoides) nesting at two elevations (1500 m and 2500 m above sea level) in the Bighorn Mountains of Wyoming over two years. Eggs laid by females at the high-elevation site were, on average, significantly (6%) smaller in volume than eggs laid by their lower-elevation counterparts. Across elevations, egg size showed a significant positive correlation with female body condition (weight relative to size), and high-elevation females had significantly lower indices of condition than low-elevation females. Temperatures during clutch formation were colder at the high-elevation site, and egg size was negatively related to temperature after controlling for the effects of female condition. Clutches of females at high elevations were, on average, marginally smaller (by 5%, 0.3 eggs) than clutches of low-elevat...

Intra‐individual variation in clutch and offspring size in an oviparous snake

AbstractIntra‐individual variation can be extremely informative in understanding the evolution of life‐history traits. In this study, we examined intra‐individual variation in clutch and offspring size for brown house snakes Lamprophis fuliginosus, a species that can lay up to six clutches in the laboratory within a 12‐month interval without a refractory period. The number of clutches produced per female during this interval ranged from two to six, and there was no significant relationship between the total number of clutches laid and maternal body size. Unlike results from lizards and turtles, house snakes showed no significant changes in clutch size or offspring size among successive clutches, and individual repeatability of both traits was moderate to high. House snakes in this study also showed a strong negative relationship between clutch size and offspring size for all clutches produced, as expected by life‐history theory. Our data indicate that house snakes show much less intra‐individual variation than most other reptile species examined. However, this high level of consistency may be due to regulation of food availability under laboratory conditions. This will be varied in future experiments to test the degree of plasticity exhibited by individual females for these traits.

Brood rearing costs affect future reproduction in the precocial common goldeneye Bucephala clangula

Life‐history theory assumes a trade‐off between current reproductive effort and future reproductive success. There are a large number of studies demonstrating reproductive trade‐offs in different animal taxa, particularly in birds. Most bird studies have focused on the costs of chick rearing in altricial species. These costs have been assumed to be low in precocial species, but this aspect has been little studied. We used long‐term individual reproductive data from the common goldeneye Bucephala clangula, an iteroparous precocial duck with uniparental female care, to examine whether brood rearing carries costs that affect future reproductive performance. All females were experienced breeders, and possible differences in female quality were ruled out. We compared within‐individual (between‐year) changes in clutch size, hatching date and body mass between females that had reared a brood in the previous year and females that had not. It turned out that brood rearing involved a cost in terms of clutch size and hatching date the next year, but not in terms of body mass: females that had reared a brood in the previous year laid relatively smaller clutches and laid relatively later than females that had not reared a brood. Our results show that normal brood rearing in a precocial species involves costs that affect future reproduction.