Yolk androgens affect offspring hatching, begging, growth and survival in many bird species. If these effects are sex-specific, yolk androgen deposition may constitute a mechanism for differential investment male female offspring. We tested this hypothesis zebra finches. In species, females increase yolk-testosterone levels produce male-biased sex ratios when paired to more attractive males. therefore predicted that especially sons benefit from elevated androgens. Eggs were injected with...

Summary 1. Females of egg‐laying vertebrates may adjust the development their offspring to prevailing environmental conditions by regulating deposition hormones into eggs. Within‐ and amng‐clutch variation in levels steroid were studied egg yolks Black‐Headed Gull ( Larus ridibundus , Linnaeus) relation at nest site. This species breeds colonies different densities habitats, chicks hatch asynchronously. 2. Egg contained very high androstenedione, substantial testosterone moderate...

An increasing number of studies in a variety taxa demonstrate the role maternal sex steroids on offspring development. In avian species, mothers deposit substantial amounts androgens their eggs, and experimental evidence indicates that these influence chick's early Despite well-known organizing brain behaviour, egg hormones almost exclusively focus chick phase. Here, we show experimentally Black-headed gulls enhance development nuptial plumage frequency aggressive sexual displays 1 year...

Avian eggs contain considerable amounts of maternal yolk androgens, which have been shown to beneficially influence the physiology and behaviour chick. As androgens may suppress immune functions, they also entail costs for This is particularly relevant colonial species, such as black-headed gull (Larus ridibundus), in aggregation large numbers birds during breeding season enhances risk infectious diseases hatching To test effect on chick's function, we experimentally manipulated, a field...

Severe feather pecking (SFP) in commercial laying hens is a maladaptive behavior which associated with anxiety traits. Many experimental studies have shown that stress the parents can affect offspring, but until now these effects been neglected addressing problem of SFP commercially kept hens. We therefore studied whether parental stock (PS) affected development and their offspring. used flocks from brown white genetic hybrid because background anxiety. As also be influenced by housing...

Little is known about the relationship between welfare traits and production in laying hen parent stock (PS). In commercial hens pure lines, it that aspects associated with reduced such as high fear, stress, feather pecking can have negative effects on production. Because PS are housed under different conditions than hens, may differ. We therefore studied fear response to a stationary person (SP) novel object (NO), basal plasma corticosterone (CORT) whole-blood serotonin levels (5-HT),...

Handedness is the most noticeable functional expression of cerebral lateralization in humans. However, its developmental process and plasticity remain elusive. It has been postulated that prenatal testosterone (pT) an effect on human development. In present study we examined relationship between pT handedness compared outcome to previously published data language same children.pT was assessed from amniotic fluid healthy pregnant women using radioimmunoassay. Strength direction children (n =...

Maternal hormones are known to be present in avian eggs and can have beneficial effects on chick development. Recently, differences yolk steroid concentrations between the sexes been demonstrated, this context steroids proposed part of sex-determining mechanism. In our study, we show that it is very unlikely androgen alone decisive We found sex-specific strongly depend social rank mother. First, dominant females, but not subdominant allocated significantly more testosterone male than female...

Avian eggs contain substantial amounts of maternal androgens, and several studies have indicated that these are beneficial for the chick. Nevertheless, there is a large systematic variation in hormone concentrations both within between clutches. If androgens also involve costs, this might explain why not all mothers put high levels their However, simultaneous occurrence benefits costs has yet been convincingly demonstrated. We show experimentally yolk suppress immune function simultaneously...

In many species, embryos are exposed to maternal hormones in utero, the egg, or seed. birds, mothers deposit substantial testosterone into their eggs, which enhances competitive ability of offspring. These concentrations vary systematically within clutches different patterns and may enable adaptively fine-tune hierarchies broods. We performed a comparative analysis investigate this hypothesis using broad set avian species. expected species with small size differences among siblings (arising...

The effect of climate warming on the reproductive success ectothermic animals is currently a subject major conservation concern. However, for many threatened species, we still know surprisingly little about extent naturally occurring adaptive variation in heat-tolerance. Here, show that thermal tolerances green turtle ( Chelonia mydas ) embryos single, island-breeding population have diverged response to contrasting incubation temperatures nesting beaches just few kilometres apart. In...

In many animal species, embryos are exposed to maternal hormones that affect their development. Maternal hormone transfer varies with environmental conditions of the mother and is often interpreted as being shaped by natural selection adjust offspring prevailing conditions. Such requires genetic variability, which has not yet been experimentally demonstrated. Our study reports direct evidence for additive variance androgens through a bidirectional on yolk testosterone (T) levels in Japanese...