Feathers as a nondestructive biomonitor for persistent organic pollutants.

Keratinous tissues of mammals and humans, such as hair, have been used to determine the exposure to polychlorinated biphenyls (PCBs) and organochlorine pesticides. In the present study, we investigated the accumulation of persistent organic pollutants (POPs; PCBs, p,p'-DDT, p,p'-dichlorodiphenyldichloroethane [DDD], p,p'-dichlorodiphenyldichloroethylene [DDE], hexachlorobenzene [HCB], oxychlordane, trans-nonachlor, polybrominated diphenyl ethers, and polybrominated biphenyls [PBBs]) in feathers of the great tit (Parus major). The accumulation of POPs in feathers and fat samples of 27 adult great tits collected in April 2000 and December 2002 was compared with regard to possible temporal and spatial differences.

Certain aspects of bonobo female sexual repertoire are related to urinary testosterone metabolite levels.

We examined the unknown relationship between testosterone and sexual behaviour in female bonobos (Pan paniscus) on a daily and long-term level. In most animal species, sexual behaviours mainly focus on reproduction. Bonobos, however, also use sexual interactions to a large extent to maintain and restore social relationships.

Sperm competition and sexually size dimorphic brains in birds.

Natural selection may favour sexually similar brain size owing to similar selection pressures in males and females, while sexual selection may lead to sexually dimorphic brains. For example, sperm competition involves clear-cut sex differences in behaviour, as males display, mate guard and copulate with females, while females choose among males, and solicit or reject copulations. These behaviours may require fundamentally different neural government in the two sexes leading to sex-dependent brain evolution.

The combined effect of lead exposure and high or low dietary calcium on health and immunocompetence in the zebra finch (Taeniopygia guttata).

The widespread contamination by lead and the acidification of the environment ask for a better understanding of the effects of the interaction between lead and calcium on various aspects of health, including disease defense, in wildlife. Here, we investigated the effects of chronic exposure to sublethal levels of lead, combined with high or low dietary calcium, on health and several components of immunity in male and female zebra finches (Taeniopygia guttata). Thirty individuals of each sex were randomly assigned to three groups: a control group, a group exposed to lead with an additional calcium source (i.

Relationships between metal concentrations in great tit nestlings and their environment and food.

Metal concentrations (Ag, As, Cd, Cu, Hg, Ni, Pb, Zn) were determined in the feathers and excreta of nestling great tits (Parus major), in their main invertebrate prey (Lepidoptera larvae) and in vegetation samples, all collected from four sites along a pollution gradient. Metal contamination in vegetation samples increased significantly towards the pollution source. The Ag, As, Hg, Ni and Pb concentrations in food samples were significantly higher at the site closest to the pollution source compared to the other three sites.

A strong association between immune responsiveness and natal dispersal in a songbird.

Because parasite faunas typically show considerable spatio-temporal variation, and because parasites can have important fitness consequences, host defence mechanisms, including the immune system, can be expected to coevolve with natal dispersal, i.e. the movement of a newborn individual from its site of birth to its first site of reproduction.

Heavy metal exposure affects the humoral immune response in a free-living small songbird, the great tit (Parus major).

Although many studies have investigated possible effects of heavy metal contamination on components of the immune system in captive birds, studies on the effects of chronic exposure to heavy metals on the immune system of free-living birds are rare. Therefore we studied the effect of heavy metal exposure on the humoral immune responsiveness in free-living great tit (Parus major) populations from four study sites along a pollution gradient near a metallurgic smelter. Although there were no differences in body condition or hematocrit values among great tits from the four study sites, the heavy metal exposure appeared to affect an individual's humoral immune responsiveness, as measured by antibody titers to sheep red blood cells.

The importance of exogenous contamination on heavy metal levels in bird feathers. A field experiment with free-living great tits, Parus major.

Feathers have been used extensively as non-destructive biomonitors for heavy metal pollution. Birds excrete heavy metals into growing feathers during moult. After feather formation, the feathers become isolated from the rest of the body, suggesting that the feathers contain information of circulating heavy metal concentrations in the blood at the time of their development.

Differential effects of testosterone on neuronal populations and their connections in a sensorimotor brain nucleus controlling song production in songbirds: a manganese enhanced-magnetic resonance imaging study.

Nucleus HVC (formerly called high vocal center) of songbirds contains two types of projecting neurons connecting HVC respectively to the nucleus robustus archistriatalis, RA, or to area X. These two neuron classes exhibit multiple neurochemical differences and are differentially replaced by new neurons during adult life: high rates of neuronal replacement are observed in RA-projecting neurons only. The activity of these two types of neurons may also be modulated differentially by steroids.

Brain space for a learned task: strong intraspecific evidence for neural correlates of singing behavior in songbirds.

There is a controversial issue in neuroscience whether the expansion of neural network space permits the development of more complex behavior. One of the best-known model systems for studying the relationship between brain space and behavior is song production and the associated song control system in songbirds. Although the neuroanatomical background of song production is well established, the direct link between song nuclei volumes and song traits remains puzzling.

The effect of heavy metal exposure on egg size, eggshell thickness and the number of spermatozoa in blue tit Parus caeruleus eggs.

In this study we compared the egg size, the eggshell thickness and the number of spermatozoa trapped on the perivitelline layer of the eggs in three blue tit (Parus caeruleus) populations across a heavy metal pollution gradient. No significant differences were observed in egg characteristics among study sites. Eggs from the two most polluted sites however, had significantly less spermatozoa on the perivitelline layer than eggs from the least polluted site.

Urinary testosterone-metabolite levels and dominance rank in male and female bonobos (Pan paniscus).

The correlation between testosterone (T) and dominance rank may vary among species, and is expected to become stronger as the importance of aggressive competition for rank increases. However, it may also vary among social situations within a species, showing a stronger correlation during socially unstable periods. Knowledge on this topic in great apes, especially in females, is scant.

Seasonal fluctuations in plasma testosterone levels and diurnal song activity in free-living male great tits.

The annual course of plasma testosterone (T) and song activity during the day was examined in free-living male great tits (Parus major) in a single year and in a single population. We provide the first study in this species investigating plasma T during the breeding season among and within breeding stages. As expected for a temperate-zone monogamous species, plasma T levels showed a pronounced peak in March at the start of the breeding season and fast decreasing levels thereafter to moderate levels in the parental phase.

Female presence affects male behavior and testosterone levels in the European starling (Sturnus vulgaris).

In this study, we confronted individually housed male European starlings (Sturnus vulgaris) with a female conspecific for 60 min to study the consequences on behavior and plasma testosterone (T) concentrations. Control males experienced a similar procedure, the only difference being that they were tested in the absence of a female. Female presence significantly affected both behavior and plasma T levels of male starlings.

Effects of heavy metal exposure on aggressive behavior in a small territorial songbird.

Several studies have shown that elevated levels of certain heavy metals may affect the behavior of birds and mammals. However, most of these studies were carried out under controlled laboratory conditions; results from free-living populations are scarce. In this study we examined the possible effects of exposure to high heavy metal concentrations on the aggressive behavior of resident great tit (Parus major) males by means of simulated territorial intrusion experiments during the egg-laying and incubation period at a highly polluted and a reference site.

Effects of heavy metal exposure on the condition and health of nestlings of the great tit (Parus major), a small songbird species.

In this study we examined the possible effects of heavy metal exposure on the condition and health of great tit nestlings (Parus major) at four study sites along a pollution gradient near a large non-ferrous smelter in Belgium during three consecutive breeding seasons. Our results showed that nestlings were indeed exposed to large amounts of heavy metals. Excrements contained significantly higher concentrations of several heavy metals (silver, arsenic, cadmium, mercury, lead) near the pollution source than at study sites farther away.

Effect of age and testosterone on autumnal neurogenesis in male European starlings (Sturnus vulgaris).

The male European starling (Sturnus vulgaris) is an open-ended learner that increases its repertoire throughout life. In parallel, the volume of high vocal center (HVC) is larger in older birds than in yearlings. We labeled with the thymidine analog 5'-bromodeoxyuridine (BrdU) the cells that are generated during the fall in the brain of adult males that were 2 or more years old and in yearling males that were treated with exogenous testosterone (T) or kept intact before BrdU administration.

Are corticosterone levels a good indicator of food availability and reproductive performance in a kittiwake colony?

We evaluated the use of corticosterone to gauge forage availability and predict reproductive performance in black-legged kittiwakes (Rissa tridactyla) breeding in Alaska during 1999 and 2000. We modeled the relationship between baseline levels of corticosterone and a suite of individual and temporal characteristics of the sampled birds. We also provided supplemental food to a sample of pairs and compared their corticosterone levels with that of pairs that were not fed.

Variation of heavy metals within and among feathers of birds of prey: effects of molt and external contamination.

In this study we examined the effect of external contamination on the heavy metal (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn) concentration in feathers. We compared the heavy metal content among the 10 primary wing feathers of sparrowhawks (Accipiter nisus), little owls (Athene nocta) and barn owls (Tyto alba) and the variation within the outermost tail feather of sparrowhawks and tawny owls (Strix aluco). The concentration of Hg was significantly higher in feathers molted first, suggesting that levels in feathers reflect levels in the blood during formation.

Breeding performance of great tits (Parus major) along a gradient of heavy metal pollution.

The possible effects of heavy metal pollution on various breeding parameters of the great tit (Parus major) were studied at four study sites in a pollution gradient near a large nonferrous smelter in Belgium during three consecutive breeding seasons. Significantly more females interrupted their laying period near the pollution source than did females farther away. At the two most polluted sites, hatching success was significantly reduced compared to two lesser-polluted study sites.

Effects of testosterone on Reelin expression in the brain of male European starlings.

Reelin, a large glycoprotein defective in reeler mice, is assumed to determine the final location of migrating neurons in the developing brain. We studied the expression of Reelin in the brain of adult male European starlings that had been treated or not with exogenous testosterone. Reelin-immunoreactive cells and fibers were widely distributed in the forebrain including areas in and around the song control nucleus, HVC.

Castration does not decrease nonreproductive aggression in yearling male European starlings (Sturnus vulgaris).

In the nonbreeding season, some bird species express high levels of aggression despite basal plasma testosterone (T) concentrations. Consequently, nonreproductive aggression is believed to be independent of plasma T. In the present study, we investigated the effect of castration on nonreproductive aggressive behavior in yearling male European starlings (Sturnus vulgaris).

Context-dependent effects of castration and testosterone treatment on song in male European starlings.

Most seasonally breeding songbirds display dramatic seasonal fluctuations in plasma testosterone (T) levels and mate attraction behaviors, including song. However, males of some songbird species, such as the European starling (Sturnus vulgaris), continue to sing at high levels after the breeding season, when T levels are basal. In male starlings song during the breeding season functions mainly to attract mates, whereas song during the nonbreeding season appears unrelated to reproduction.

Great tit (Parus major) nestlings as biomonitors of organochlorine pollution.

In this study we investigated the accumulation of organochlorine compounds (HCB, 3 HCH-isomers, p,p'-DDT and its metabolites and 18 PCB congeners) in the muscle and fat tissue of nestling great tits (Parus major) from four study sites located in an area with extensive environmental contamination. The concentration of p,p'-DDT, p,p'-DDD, alpha-, beta-, gamma-HCH, and PCB congeners 128 and 149 were below the limit of detection in all muscle and fat samples. In muscle tissue the concentrations of HCB and congeners 28, 52, 101, 110, and 194 were in more than 50% of the cases below detection limit and these data were excluded from statistical analysis.