The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Cor Dijkstra - One of the best experts on this subject based on the ideXlab platform.
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Maternal yolk androgens stimulate territorial behaviour in Black-Headed Gull chicks
Biology letters, 2009Co-Authors: Wendt Muller, Cor Dijkstra, Ton G G GroothuisAbstract:Avian eggs contain substantial amounts of maternal androgens. The concentrations of these yolk androgens are affected by the maternal environment, such as the level of social competition, parasite exposure or food conditions. Since yolk androgens have been shown to affect a wide array of offspring traits, they may adjust the chicks to the expected post-hatching environment, but experimental evidence is still scarce. We investigate in colonial breeding Black-Headed Gulls whether high concentrations of yolk androgens, such as those found in environments with high numbers of social interactions, facilitate aggressiveness and territorial behaviour of the chicks. Black-Headed Gulls are highly suitable for this, as the semi-precocial chicks defend the natal territory and food against intruders. We manipulated yolk androgen concentrations and investigated their role in both within-nest and between-nest aggression. We found that chicks hatching from androgen-treated eggs defended the natal territory more often than their nest mates from control eggs, without increasing sibling aggression. This suggests that variation in yolk androgen concentrations in relation to the social environment of the mother may indeed allow adjustment of the offspring's behaviour to the expected frequency of territorial interactions with conspecifics post-hatching.
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multiple pathways of maternal effects in black headed Gull eggs constraint and adaptive compensatory adjustment
Journal of Evolutionary Biology, 2006Co-Authors: Ton G G Groothuis, Corine M Eising, Jonathan D Blount, P F Surai, V Apanius, Cor Dijkstra, Wendt MullerAbstract:We investigated in the Black-Headed Gull whether female deposition of antioxidants and immunoglobulins (enhancing early immune function), and testosterone (suppressing immune function and increasing early competitive skills) correlate suggesting that evolution has favoured the mutual adjustment of different pathways for maternal effects. We also took egg mass, the position of the egg in the laying sequence and offspring sex into account, as these affect offspring survival. Yolk antioxidant and immunoglobulin concentrations decreased across the laying order, while yolk testosterone concentrations increased. This may substantially handicap the immune defence of last-hatched chicks. The decrease in antioxidant levels was greater when mothers had a low body mass and when the increase in testosterone concentrations was relatively large. This suggests that female Black-Headed Gulls are constrained in the deposition of antioxidants in last-laid eggs and compensate for this by enhanced testosterone deposition. The latter may be adaptive since it re-allocates the chick's investment from costly immune function to growth and competitive skills, necessary to overcome the consequences of hatching late from an egg of reduced quality.
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Within clutch co-variation of egg mass and sex in the Black-Headed Gull.
Journal of evolutionary biology, 2005Co-Authors: Wendt Muller, Ton G G Groothuis, Corine M Eising, Serge Daan, Cor DijkstraAbstract:Female birds of several species have control over the production of daughters and sons. However, most studies failed to find a relationship between egg size and sex. This is intriguing as adjustment of egg size would constitute a powerful tool for the female to meet different resource demands of the sexes, particularly in size dimorphic species. Our results show that, within clutches of Black-Headed Gulls (Larus ridibundus) the proportion of males was positively associated with egg mass. This applied for all three laying positions, independently of the absolute egg mass. There was a significant relationship between the distribution of the sexes over the laying sequence and the egg mass change. When egg mass decreased over the sequence, first-laid eggs were male biased and last-laid eggs female biased, and vice versa. The potential adaptive value of this allocation strategy is evaluated with regard to male sensitivity to egg quality and competitive differences between the sexes.
Wendt Muller - One of the best experts on this subject based on the ideXlab platform.
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Maternal yolk androgens stimulate territorial behaviour in Black-Headed Gull chicks
Biology letters, 2009Co-Authors: Wendt Muller, Cor Dijkstra, Ton G G GroothuisAbstract:Avian eggs contain substantial amounts of maternal androgens. The concentrations of these yolk androgens are affected by the maternal environment, such as the level of social competition, parasite exposure or food conditions. Since yolk androgens have been shown to affect a wide array of offspring traits, they may adjust the chicks to the expected post-hatching environment, but experimental evidence is still scarce. We investigate in colonial breeding Black-Headed Gulls whether high concentrations of yolk androgens, such as those found in environments with high numbers of social interactions, facilitate aggressiveness and territorial behaviour of the chicks. Black-Headed Gulls are highly suitable for this, as the semi-precocial chicks defend the natal territory and food against intruders. We manipulated yolk androgen concentrations and investigated their role in both within-nest and between-nest aggression. We found that chicks hatching from androgen-treated eggs defended the natal territory more often than their nest mates from control eggs, without increasing sibling aggression. This suggests that variation in yolk androgen concentrations in relation to the social environment of the mother may indeed allow adjustment of the offspring's behaviour to the expected frequency of territorial interactions with conspecifics post-hatching.
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multiple pathways of maternal effects in black headed Gull eggs constraint and adaptive compensatory adjustment
Journal of Evolutionary Biology, 2006Co-Authors: Ton G G Groothuis, Corine M Eising, Jonathan D Blount, P F Surai, V Apanius, Cor Dijkstra, Wendt MullerAbstract:We investigated in the Black-Headed Gull whether female deposition of antioxidants and immunoglobulins (enhancing early immune function), and testosterone (suppressing immune function and increasing early competitive skills) correlate suggesting that evolution has favoured the mutual adjustment of different pathways for maternal effects. We also took egg mass, the position of the egg in the laying sequence and offspring sex into account, as these affect offspring survival. Yolk antioxidant and immunoglobulin concentrations decreased across the laying order, while yolk testosterone concentrations increased. This may substantially handicap the immune defence of last-hatched chicks. The decrease in antioxidant levels was greater when mothers had a low body mass and when the increase in testosterone concentrations was relatively large. This suggests that female Black-Headed Gulls are constrained in the deposition of antioxidants in last-laid eggs and compensate for this by enhanced testosterone deposition. The latter may be adaptive since it re-allocates the chick's investment from costly immune function to growth and competitive skills, necessary to overcome the consequences of hatching late from an egg of reduced quality.
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Within clutch co-variation of egg mass and sex in the Black-Headed Gull.
Journal of evolutionary biology, 2005Co-Authors: Wendt Muller, Ton G G Groothuis, Corine M Eising, Serge Daan, Cor DijkstraAbstract:Female birds of several species have control over the production of daughters and sons. However, most studies failed to find a relationship between egg size and sex. This is intriguing as adjustment of egg size would constitute a powerful tool for the female to meet different resource demands of the sexes, particularly in size dimorphic species. Our results show that, within clutches of Black-Headed Gulls (Larus ridibundus) the proportion of males was positively associated with egg mass. This applied for all three laying positions, independently of the absolute egg mass. There was a significant relationship between the distribution of the sexes over the laying sequence and the egg mass change. When egg mass decreased over the sequence, first-laid eggs were male biased and last-laid eggs female biased, and vice versa. The potential adaptive value of this allocation strategy is evaluated with regard to male sensitivity to egg quality and competitive differences between the sexes.
Ton G G Groothuis - One of the best experts on this subject based on the ideXlab platform.
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Maternal yolk androgens stimulate territorial behaviour in Black-Headed Gull chicks
Biology letters, 2009Co-Authors: Wendt Muller, Cor Dijkstra, Ton G G GroothuisAbstract:Avian eggs contain substantial amounts of maternal androgens. The concentrations of these yolk androgens are affected by the maternal environment, such as the level of social competition, parasite exposure or food conditions. Since yolk androgens have been shown to affect a wide array of offspring traits, they may adjust the chicks to the expected post-hatching environment, but experimental evidence is still scarce. We investigate in colonial breeding Black-Headed Gulls whether high concentrations of yolk androgens, such as those found in environments with high numbers of social interactions, facilitate aggressiveness and territorial behaviour of the chicks. Black-Headed Gulls are highly suitable for this, as the semi-precocial chicks defend the natal territory and food against intruders. We manipulated yolk androgen concentrations and investigated their role in both within-nest and between-nest aggression. We found that chicks hatching from androgen-treated eggs defended the natal territory more often than their nest mates from control eggs, without increasing sibling aggression. This suggests that variation in yolk androgen concentrations in relation to the social environment of the mother may indeed allow adjustment of the offspring's behaviour to the expected frequency of territorial interactions with conspecifics post-hatching.
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multiple pathways of maternal effects in black headed Gull eggs constraint and adaptive compensatory adjustment
Journal of Evolutionary Biology, 2006Co-Authors: Ton G G Groothuis, Corine M Eising, Jonathan D Blount, P F Surai, V Apanius, Cor Dijkstra, Wendt MullerAbstract:We investigated in the Black-Headed Gull whether female deposition of antioxidants and immunoglobulins (enhancing early immune function), and testosterone (suppressing immune function and increasing early competitive skills) correlate suggesting that evolution has favoured the mutual adjustment of different pathways for maternal effects. We also took egg mass, the position of the egg in the laying sequence and offspring sex into account, as these affect offspring survival. Yolk antioxidant and immunoglobulin concentrations decreased across the laying order, while yolk testosterone concentrations increased. This may substantially handicap the immune defence of last-hatched chicks. The decrease in antioxidant levels was greater when mothers had a low body mass and when the increase in testosterone concentrations was relatively large. This suggests that female Black-Headed Gulls are constrained in the deposition of antioxidants in last-laid eggs and compensate for this by enhanced testosterone deposition. The latter may be adaptive since it re-allocates the chick's investment from costly immune function to growth and competitive skills, necessary to overcome the consequences of hatching late from an egg of reduced quality.
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Within clutch co-variation of egg mass and sex in the Black-Headed Gull.
Journal of evolutionary biology, 2005Co-Authors: Wendt Muller, Ton G G Groothuis, Corine M Eising, Serge Daan, Cor DijkstraAbstract:Female birds of several species have control over the production of daughters and sons. However, most studies failed to find a relationship between egg size and sex. This is intriguing as adjustment of egg size would constitute a powerful tool for the female to meet different resource demands of the sexes, particularly in size dimorphic species. Our results show that, within clutches of Black-Headed Gulls (Larus ridibundus) the proportion of males was positively associated with egg mass. This applied for all three laying positions, independently of the absolute egg mass. There was a significant relationship between the distribution of the sexes over the laying sequence and the egg mass change. When egg mass decreased over the sequence, first-laid eggs were male biased and last-laid eggs female biased, and vice versa. The potential adaptive value of this allocation strategy is evaluated with regard to male sensitivity to egg quality and competitive differences between the sexes.
Piotr Minias - One of the best experts on this subject based on the ideXlab platform.
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Relaxation of selective constraints shapes variation of toll-like receptors in a colonial waterbird, the Black-Headed Gull.
Immunogenetics, 2020Co-Authors: Patrycja Podlaszczuk, Piotr Indykiewicz, Janusz Markowski, Piotr MiniasAbstract:Nonspecific innate immune response is activated by toll-like receptors (TLRs), which recognize conserved molecular motifs characteristic for a broad spectrum of pathogens. In this study, we examined nucleotide substitution patterns and allelic diversity at five TLR genes in a wild nonpasserine bird, the Black-Headed Gull Chroicocephalus ridibundus. We hypothesized that balancing selection can maintain high allelic diversity of TLR genes in the Black-Headed Gull because of its ecological characteristics, coloniality, and migratoriness, which are associated with increased exposure and transmission of pathogens. Although we found moderately high levels of sequence polymorphism (8–49 haplotypes retrieved per locus within a sample of 60 individuals), most of these haplotypes were recorded at low frequencies within our study population. At the same time, we found no convincing evidence for the role of balancing selection in the maintenance of this variation (Tajima’s D 1) were recorded only at two loci (TLR5 and TLR7). This pattern is consistent with relaxation of selective constraints, where most mutations are slightly deleterious and usually removed by purifying selection. No differences in the diversity and nucleotide substitution rates were found between endosomal loci responsible for viral RNA sensing and loci responsible for the recognition of extracellular pathogens. Our study provides the first information on evolutionary mechanisms shaping polymorphism of TLRs in a species from Lari suborder (Gulls and allies) and suggests that TLR genes may be poorly responsive to ecological and life-history characteristics of hosts.
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Shortcomings of Discriminant Functions: A Case Study of Sex Identification in the Black-Headed Gull
Ardeola, 2019Co-Authors: Piotr Indykiewicz, Piotr Minias, Jarosław Kowalski, Patrycja PodlaszczukAbstract:The Black-Headed Gull Larus ridibundus, like many other Gulls, has monomorphic plumage, which impedes sex identification in the field. We analysed the size of the hood, eye ring and wing tip and found that putative ornaments did not differ between sexes in this species. We formulated a novel discriminant function for Black-Headed Gulls using morphometric measurements of live individuals (i.e. total head length, bill depth, and the sixth rectrix length), intentionally excluding data from dead birds, which were on average significantly smaller than their living conspecifics. We also tested cross-application of discriminant functions previously developed for Black-Headed Gulls, proving that sexing individuals from different populations, even geographic neighbours, based on a single discriminant function risks errors and showing that discriminant functions cannot be treated as a universal tool for sex identification across space and time. —Indykiewicz, P., Minias, P., Kowalski, J. & Podlaszczuk, P. (2019). Shortcomings of discriminant functions: a case study of sex identification in the Black-Headed Gull. Ardeola, 66: 361-372.
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Central–periphery gradient of individual quality within a colony of Black‐headed Gulls
Ibis, 2018Co-Authors: Piotr Indykiewicz, Patrycja Podlaszczuk, Maciej Kamiński, Radosław Włodarczyk, Piotr MiniasAbstract:Central nesting sites within avian colonies are often more profitable in terms of fitness, as they can offer better protection against predators compared with colony edges. Thus, central sites are expected to attract high‐quality individuals, which should produce a clear central–periphery gradient in the phenotypic quality of nesting individuals and reproductive output within colonies. The aim of this study was to assess spatial patterns of individual quality within a colony of a common larid, the Black‐headed Gull Chroicocephalus ridibundus. We found that laying was advanced in the central zone of the colony when compared with the periphery, and central pairs tended to lay larger eggs and had higher hatching success than peripheral pairs. Centrally nesting individuals had higher blood haemoglobin concentrations, size‐corrected body mass and heterozygosity (males only), indicating their better condition and higher genetic quality. In contrast, central females had lower plasma albumin concentration, which could possibly be attributed to their greater investment in egg production. Finally, pairs breeding in the central zone of the colony had an elevated heterophil/lymphocyte ratio, suggesting that social stress can be recognized as an important cost of nesting in dense aggregations. The results provide empirical support for central–periphery gradients in the individual quality of colonially nesting Black‐headed Gulls, indicating that spatial gradients in pair quality should be carefully taken into account when conducting research on colonial birds.
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Extra-pair paternity in the Black-Headed Gull: is it exceptional among colonial waterbirds?
Behaviour, 2017Co-Authors: Piotr Indykiewicz, Patrycja Podlaszczuk, Piotr MiniasAbstract:Although nesting at high densities promotes frequent interactions with individuals other than social mates, the rate of extra-pair paternity (EPP) in colonial waterbirds is generally low. So far, the highest EPP rate within this group has been reported in the Black-Headed Gull Chroicocephalus ridibundus breeding in a colony in Czech Republic (33% broods with extra-pair offspring). In this study, we used a set of microsatellite loci to analyse parentage in 34 Gull families (102 nestlings) from northern Poland. We recorded intra-specific brood parasitism in 10.8% of broods, but no evidence for EPP was found. The striking discrepancy between our results and previous estimates of EPP rate in the Black-Headed Gull strongly indicate that promiscuity is a context-dependent strategy in this species and that its prevalence may greatly vary between populations. We recommend that a special care should be taken while using single-population data on EPP in the inter-specific comparative analyses.
Gregory P Mudge - One of the best experts on this subject based on the ideXlab platform.
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abundance diet and salmonella contamination of Gulls feeding at sewage outfalls
Water Research, 2000Co-Authors: Peter N Ferns, Gregory P MudgeAbstract:Abstract The abundance and activity of Gulls at sewage outfalls in South Wales and southern England was studied between 1972 and 1999. In winter, the Black-Headed Gull was the most abundant species, followed by herring, common and lesser black-backed Gulls. The abundance of Black-Headed Gulls and herring Gulls was significantly correlated with the volume of sewage discharged. Sewers supported only a small portion of the Gull populations present in both areas, and a higher proportion of juvenile birds were present than at other feeding sites. Sewage comminution increased the numbers of Black-Headed Gulls feeding, but infrequent intermittent discharge reduced them by over a half. Gulls selectively consumed waste foodstuffs from sewage and thus helped recycle some of its organic constituents. However, some individuals carried bacterial pathogens, and could thus have contaminated nearby bodies of freshwater, or grassland, by washing and roosting there. Full sewage treatment, as planned for most of the discharges in both study areas is likely to provide the most effective means of Gull control.