Yolk androstenedione, but not testosterone, predicts offspring fate and reflects parental quality

Yolk androgen deposition is a widely investigated maternal effect in birds, but its adaptive value is at present unclear. The offspring fitness correlates of natural yolk androgen levels are virtually unknown, whereas manipulations largely focused on testosterone and neglected other androgens. We determined yolk concentrations of the 2 dominant androgens, androstenedione and testosterone, from all eggs in collared flycatcher clutches and followed the fate of individual offspring from these eggs in a crossfostering experiment. Yolk concentration of androstenedione was much higher than that of testosterone. Offspring from eggs with relatively higher androstenedione concentrations within a clutch were relatively large after hatching, grew slower thereafter, and had a higher recruitment rate in subsequent years. The increase of androstenedione with laying order and its within-clutch variance were negatively correlated with a condition-dependent female ornament, perhaps indicating compensatory hormone deposition into later hatching eggs by females in low condition. Yolk testosterone variation within or among clutches was not related to any measured aspect of offspring or parental quality. Our results suggest that in some species, especially those with much more androstenedione than testosterone in the yolk, androstenedione and not testosterone may be the yolk androgen with a long-term function and adaptive deposition pattern.</p

Variation in clutch size in relation to nest size in birds

Peer reviewe

Environmental Studies

With the political turmoil of the late 1960s the concern of human kind was shifted from passiv observer and sufferer of environmental problems to taking an active role in policy making.JRC.E.5-Nuclear chemistr

Males are sensitive - sex-dependent effect of rearing conditions on nestling growth

The sex-dependent effect of environmental conditions on nestlings has been extensively studied in size dimorphic birds. Whether males or females are more sensitive to poor conditions is not yet clear; however, the degree of sexual size-dimorphism, brood size and their interactions seem to influence the pattern. Much less is known about sex-dependent environmental sensitivity in size-monomorphic species, even though it may result in biased sex allocation. We altered the rearing conditions by brood size manipulation in the size-monomorphic collared flycatcher and then examined the sex-specific development of the nestlings. In all analyses, we controlled for the effect of paternity, because one may expect extra-pair young to be of better genetic quality and perform better at least under poor conditions. However, this was not the case, because we did not find any difference in growth rate or fledging size between extra-and within-pair young. We found that male nestlings had the potential for faster growth under favourable conditions, but suffered more under poor conditions. We found no sex x environment interaction for fledging size probably because the growth curves level off before fledging, and the disadvantaged nestlings can catch up with their siblings. The larger sensitivity of males does not explain the previously found seasonal shift in brood sex ratios and contradicts previous findings in another size-monomorphic species where females were more sensitive. This suggests that even in size-monomorphic species, no general rule exists, which determines the more sensitive sex

The effect of parental quality and malaria infection on nestling performance in the Collared Flycatcher (Ficedula albicollis)

Plumage ornamentation often signals the quality of males and, therefore, female birds may choose elaborately ornamented mates to increase their fitness. Such mate choice may confer both direct and indirect benefits to the offspring. Males with elaborate ornaments may provide good genes, which can result in better nestling growth, survival or resistance against parasitic infections. However, these males may also provision their offspring with more food or food of better quality, resulting in nestlings growing at a higher rate or fledging in better condition. In this study, we examined if there was an association between male ornamentation and malaria infection in Collared Flycatchers (Ficedula albicollis). We also investigated offspring performance in relation to malaria infection in the parents and the quality of the genetic and rearing fathers (assessed by the size of two secondary sexual characters) under simulated good and bad conditions (using brood size manipulation). We found that secondary sexual characters did not signal the ability of males to avoid parasitic infections, and malaria infection in the genetic and the rearing parents had no effect on nestling growth and fledging size. Our results do show, however, that it may be beneficial for the females to mate with males with a large forehead patch because wing feathers of nestlings reared by large-patched males grew at a higher rate. Fast feather growth can result in earlier fledging which, in turn, could improve nestling survival in highly variable environments or under strong nest predation

Effects of breeding habitat (woodland versus urban) and metal pollution on the egg characteristics of great tits (Parus major)

In an urban environment, birds are exposed to metals, which may accumulate in their tissues and cause oxidative stress. Female birds may eliminate these pollutantsthroughdepositing them intoeggs, thuseggs becomesuitable bioindicators of pollution. In this study, we aimed to analyse whether eggshell spotting pattern, egg volume, egg- shell thickness and egg yolk antioxidant (lutein, tocopherol, retinol and selenium) levels were related to the breeding area (woodland versus urban) and the metal levels in the eggshell of a small passerine species, the great tit ( Parus major ). In the urban habitat, soil and eggshells contained higher concentrations of metals, and soil calcium level was also higher than that in the woodland. Eggshell spotting intensity and egg volume did not differ between eggs laid in the woodland and the urban park, and these traits were not related to the metal levels of the eggshell, suggesting that these egg characteristics are not sensitive indicators of metal pollu- tion. A more aggregated eggshell spotting distribution indicated a higher Cu concentration of the eggshell. We found that eggshells were thinner in the less polluted woodland habitat, which is likely due to the limited Ca availability of the woodland area. Great tit eggs laid in the urban environment had lower yolk lutein, retinol and selenium concentrations, however, as a possible compensation for these lower antioxidant levels, urban fe- males deposited more tocopherol into the egg yolk. It appears that females from different breeding habitats may provide similar antioxidant protection for their offspring against oxidative damage by depositing different speci fi c dietary antioxidants. Egg yolk lutein and retinol levels showed a negative relationship with lead concen- tration of the eggshell, which may suggest that lead had a negative impact on the amount of antioxidants avail- able for embryos during development in great tits

Source Term Identification of Environmental Radioactive Pu/U Particles by their Characterisation with Non-Destructive Analytical Techniques

Six radioactive particles stemming from Thule area (NW-Greenland) were investigated by gamma-ray and L X-ray spectrometry based on radioactive disintegration, scanning electron microscopy coupled with energy-dispersive and wavelength-dispersive X-ray spectrometer, synchrotron radiation based techniques as microscopic X-ray fluorescence, microscopic X-ray absorption near-edge structure (A-XANES) as well as combined X-ray absorption and fluorescence microtomography. Additionally, one particle from Mururoa atoll was examined by microtomography. From the results obtained, it was found out that the U and Pu were mixed in the particles. The U:Pu intensity ratios in the Thule particles varied between 0.05 and 0.36. The results from the microtomography showed that U:Pu ratio was not homogeneously distributed. The 241Am:238 239 240Pu activity ratios varied between 0.13 and 0.17, indicating that the particles originate from different source terms. The oxidation states of U and Pu as determined by A-XANES showed that U(IV) is the preponderant species and for Pu, two types of particles could be evidenced. One set had about 90 Pu(IV) while in the other the ratio Pu(IV):Pu(VI) was about one third.JRC.E.5-Nuclear chemistr

Linked selection and recombination rate variation drive the evolution of the genomic landscape of differentiation across the speciation continuum of Ficedula flycatchers

Speciation is a continuous process during which genetic changes gradually accumulate in the genomes of diverging species. Recent studies have documented highly heterogeneous differentiation landscapes, with distinct regions of elevated differentiation ("differentiation islands") widespread across genomes. However, it remains unclear which processes drive the evolution of differentiation islands; how the differentiation landscape evolves as speciation advances; and ultimately, how differentiation islands are related to speciation. Here, we addressed these questions based on population genetic analyses of 200 resequenced genomes from 10 populations of four Ficedula flycatcher sister species. We show that a heterogeneous differentiation landscape starts emerging among populations within species, and differentiation islands evolve recurrently in the very same genomic regions among independent lineages. Contrary to expectations from models that interpret differentiation islands as genomic regions involved in reproductive isolation that are shielded from gene flow, patterns of sequence divergence (d(XY) relative node depth) do not support a major role of gene flow in the evolution of the differentiation landscape in these species. Instead, as predicted by models of linked selection, genome-wide variation in diversity and differentiation can be explained by variation in recombination rate and the density of targets for selection. We thus conclude that the heterogeneous landscape of differentiation in Ficedula flycatchers evolves mainly as the result of background selection and selective sweeps in genomic regions of low recombination. Our results emphasize the necessity of incorporating linked selection as a null model to identify genome regions involved in adaptation and speciation

The effect of climate change on avian offspring production: A global meta-analysis

Climate change affects timing of reproduction in many bird species, but few stud-ies have investigated its influence on annual reproductive output. Here, we assess changes in the annual production of young by female breeders in 201 populations of 104 bird species (N = 745,962 clutches) covering all continents between 1970 and 2019. Overall, average offspring production has declined in recent decades, but considerable differences were found among species and populations. A total of 56.7% of populations showed a declining trend in offspring production (significant in 17.4%), whereas 43.3% exhibited an increase (significant in 10.4%). The results show that climatic changes affect offspring production through compounded effects on ecological and life history traits of species. Migratory and larger-bodied species experienced reduced offspring production with increasing temperatures during the chick-rearing period, whereas smaller-bodied, sedentary species tended to produce more offspring. Likewise, multi-brooded species showed increased breeding success with increasing temperatures, whereas rising temperatures were unrelated to repro-ductive success in single-brooded species. Our study suggests that rapid declines in size of bird populations reported by many studies from different parts of the world are driven only to a small degree by changes in the production of young