Preen Oil Research Articles

Global Monitoring of Persistent Organic Pollutants (POPs) Using Seabird Preen Gland Oil.

Situated at high positions on marine food webs, seabirds accumulate high concentrations of persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), and hexachlorocyclohexanes (HCHs). Our previous studies proposed the usefulness of seabirds preen gland oil as a nondestructive biomonitoring tool. The present study applied this approach to 154 adult birds of 24 species collected from 11 locations during 2005-2016 to demonstrate the utility of preen gland oil as atool for global monitoring POPs, i.e., PCBs, DDTs, and HCHs. Concentrations of the POPs were higher in the Northern Hemisphere than in the Southern Hemisphere. In particular, ∑20PCBs and∑DDTs were highly concentrated in European shags (Phalacrocorax aristotelis) and Japanese cormorants (Phalacrocorax capillatus), explainable by a diet of benthic fishes. Higher concentrations of γ-HCH were detected in species from the polar regions, possibly reflecting the recent exposure and global distillation of ∑HCHs. We examined the relationship between age and POP concentrations in preen gland oil from 20 male European shags, aged 3-16years old. Concentrations and compositions of POPs were not related to age. We also examined sex differences in the POP concentrations from 24 streaked shearwaters (Calonectris leucomelas) and did not detect a sex bias. These results underline the importance of the geographic concentration patterns and the dietary behavior as determinants species-specific POPs concentrations in preen gland oil.

Malarial infection alters wax ester composition of preen oil in songbirds: Results of an experimental study

ABSTRACT Increased exposure to parasites and other pathogens is one of the principal costs of group living, and animals have evolved diverse behavioral adaptations to detect and avoid parasitized conspecifics. In mammals, it is well established that parasitic infection can affect host body odor and that individuals use this chemical information in mate choice and other social contexts. In birds, despite intense interest in condition-dependent sexually selected displays as indicators of health status, chemical signaling of infection status remains largely unexplored. However, compounds in feather preen oil are increasingly recognized as candidate substances that may mediate chemical signaling in birds. We inoculated Song Sparrows (Melospiza melodia) with hemosporidian parasites (Plasmodium sp.) to determine whether parasitic infection alters the chemical composition of preen oil. We used gas chromatography with flame ionization detection (GC-FID) to separate and quantify the wax esters in preen oil and com...

Preen oil chemical composition encodes individuality, seasonal variation and kinship in black kites Milvus migrans

Evidence that bird odour can encode social information that can be used in chemical communication is growing, but is restricted to a few taxonomic groups. Among birds, diurnal raptors (i.e. birds from the Accipitriformes and Falconiformes order) have always been considered as mainly relying on their visual abilities. Although they seem to have a functional sense of smell, whether their odour can convey social information has yet to be determined. Combining gas‐chromatography‐mass‐spectrometry (GCMS) and microsatellite data, we tested whether chemical compounds from preen gland secretions can encode sex, age, individuality, seasonal differences and genetic relatedness in the gregarious accipitriform black kite Milvus migrans. While no differences in preen oil composition were found between age classes, an individual signature was detected. While a seasonal variation was found in both sexes, compounds differ between sexes in the non‐breeding season. Finally, a significant correlation between chemical proximity and genetic proximity was detected in male–male dyads and male–female dyads but not in female–female dyads. Our study provides the first evidence in raptors that preen secretion can convey information that may potentially be used in individual recognition, reproductive synchronization and inbreeding avoidance, and suggests that raptors may rely upon their olfactory abilities more than previously thought. This study opens promising avenues for further studies in raptor chemical communication.

Contrasting congener profiles for persistent organic pollutants and PAH monitoring in European storm petrels (Hydrobates pelagicus) breeding in Ireland: a preen oil versus feathers approach.

Persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) are anthropogenic contaminants of environmental concern due to their persistence in the environment and capacity to accumulate in biota. Many of these contaminants have been found to have ill effects over wildlife and humans. Birds are known to be particularly affected through endocrine disruption and eggshell thinning. POPs have been banned or restricted through the Stockholm Convention (2001), making monitoring essential for tracking effects of regulation. Seabirds have been used as monitoring tools for being top predators and consuming a diverse array of prey in different trophic levels. Non-destructive sampling has become widely popular using feathers and preen oil, as opposed to carcasses and internal organs. This study aimed to set baseline levels of POP and PAH concentration in a highly pelagic and abundant seabird in Ireland and the Atlantic, the European storm petrel, Hydrobates pelagicus, and to investigate the profiles of contaminant congeners in preen oil and feathers, comparatively. Mean concentrations in preen oil followed: PCB (10.1ng/g ww) > PAH (7.1ng/g ww) > OCP (5.4ng/g ww) > PBDE (3.9ng/g ww), whilst mean concentrations in feathers followed the order: PAH (38.9ng/g ww) > PCB (27.2ng/g ww) > OCP (17.9ng/g ww) > PBDE (4.5ng/g ww). Congener profiles highly differed between preen oil and feathers, and little correlation was found between the matrices. These results demonstrate that the sampling of a single matrix alone (preen oil or feathers) might produce confounding results on contamination in seabirds and that more than one matrix is recommended to obtain a full picture of contamination by persistent organic pollutants.

Valorisation of waste chicken feathers: Optimisation of decontamination and pre-treatment with bleaching agents using response surface methodology

Environmental concerns, rapid oil consumption, the high price of oil, and limited oil reserves are driving research into cheap, biodegradable, sustainable, renewable, and abundantly available green materials. Waste chicken feathers are abundant and cheap by-products from poultry processing plants and their beneficiation offers possible solutions to these issues. Raw chicken feathers are wastes that are mixed with offal fat, debris, blood, preen oil and other wastes from the poultry process. Consequently, feathers are hazardous wastes that are contaminated with bacteria, which makes them odoriferous and unfit for valorisation as is. These contaminants must be removed before possible valorisation otherwise the feathers will not fit for purpose. The effects of oxidative (hydrogen peroxide and sodium hypochlorite) and reductive (Sodium dithionite) compounds as decontamination agents were studied on chicken feathers to assess their decontamination and pre-treatment efficiency and their effects on physicochemical and mechanical properties of the feathers. Statistically designed experiments were used to optimise the decontamination process using response surface methodology with a Box-Behnken experimental design. Regression equations were obtained to analyse microbial count and the optimum process parameters were identified. Under optimised conditions, the treated chicken feathers were characterised and their properties compared with those of unwashed chicken feathers. From the results, it was deduced that the inorganic bleaching treatments were effective removing the microbial impurities from the feathers and their use resulted in enhanced physicochemical properties of the chicken feathers. The untreated chicken feathers had the highest microbial counts (1.48E+ 07 ± 6.72E05 Cfu/g) whereas decontaminated samples showed a reduction in thousand-fold. The impurity removal after washing was about 8–18%.

Songbird chemical signals reflect uropygial gland androgen sensitivity and predict aggression: implications for the role of the periphery in chemosignaling.

Chemical signals can provide useful information to potential mates and rivals. The production mechanisms of these signals are poorly understood in birds, despite emerging evidence that volatile compounds from preen oil may serve as chemosignals. Steroid hormones, including testosterone (T), may influence the production of these signals, yet variation in circulating T only partly accounts for this variation. We hypothesized that odor is a T-mediated signal of an individual's phenotype, regulated in part by androgen sensitivity in the uropygial gland. We quantified natural variation in chemosignals, T, uropygial gland androgen sensitivity, and aggressive behavior in dark-eyed juncos (Junco hyemalis). The interaction between circulating T and androgen receptor transcript abundance significantly correlated with volatile concentrations in male, but not female, preen oil. In both sexes, odorant variables correlated with aggressive response to an intruder. Our results suggest that preen oil volatiles could function as signals of aggressive intent, and, at least in males, may be regulated by local androgen receptor signaling in the uropygial gland. Because these behavioral and chemical traits have been linked with reproductive success, local regulation of androgen sensitivity in the periphery has the potential to be a target of selection in the evolution of avian olfactory signaling.

Presence of persistent organic pollutants in a breeding common tern (Sterna hirundo) population in Ireland.

Persistent organic pollutants (POPs) are chemical compounds of environmental concern due to their toxic, persistent nature and their ability to bio-accumulate in biological tissue. Seabirds, for often being at the top of the food web, have been used as monitors of environmental pollutants. Adverse effects caused by POPs have been reported in common terns (Sterna hirundo) since the 1970s. Egg shell thinning, embryo and hatchling deformities have been reported for this species. Environmental legislation, such as the Oslo-Paris Convention (OSPAR), has agreed on the monitoring of concentration of POPs in common terns. This study set out to investigate contemporary concentrations of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and brominated flame retardants (BFRs) in common terns breeding in Ireland, along with congener profiles. Investigation was conducted in live (n=15) and dead birds (n=20) to test for the efficiency of different methodologies using preen oil and feathers versus liver and preen gland. Mean concentrations of POPs followed the order: PCB (36.48ng/g ww feather) > PAH (30.01ng/g ww feather) > OCP (13.36ng/g ww feather) > BFR (1.98ng/g ww feather) in live birds; and PAH (46.65ng/g ww preen gland) > PCB (44.11ng/g ww preen gland) > OCP (15.15ng/g ww liver) > BFR (5.07ng/g ww liver) in dead birds. Comparison of contaminant results with toxicity pre-established levels concluded that this population of common terns in Ireland is not at risk of anomalies caused by POPs. However, some levels are higher in comparison to the ones established by OSPAR's EcoQO and must be monitored periodically.

The Bacterial Community Found on the surface Purple Martin (Progne subis) Eggs

Introduction: The community of microorganisms that lines the surface of avian eggs is the first line of defense against infection by pathogenic bacteria. The protective role of this community is derived from its composition and several studies have focused on identifying the bacterial components. While a diverse group of avian species has been studied, multiple species within the same family have not been independently studied. This depth is necessary to determine the degree of flexibility or plasticity within the community. Method: The goal of this study was to identify the bacterial microorganisms found lining the eggshells of an avian species classified within the Hirundinidae family, the Purple Martin (Progne subis). Culture-dependent techniques revealed a predominance of Pseudomonas before and after clutch completion. Result: Interestingly our results correlate with studies involving Pied Flycatchers, House Wrens, and Eurasian Magpies rather than Tree and Violet-Green Swallows. Conclusion: Given the variances between Pied Flycatchers, House Wrens, Eurasian Magpies and Purple Martins in regard to breeding habitat, diet, nest construction, and incubation behaviors, we hypothesize that a strong selective force may be provided by uropygial gland secretions or preen oil.

Preen oil and bird fitness: a critical review of the evidence.

The uropygial gland is a holocrine complex exclusive to birds that produces an oleaginous secretion (preen oil) whose function is still debated. Herein, I examine critically the evidence for the many hypotheses of potential functions of this gland. The main conclusion is that our understanding of this gland is still in its infancy. Even for functions that are considered valid by most researchers, real evidence is scarce. Although it seems clear that preen oil contributes to plumage maintenance, we do not know whether this is due to a role in reducing mechanical abrasion or in reducing feather degradation by keratinophilic organisms. Evidence for a function against pathogenic bacteria is mixed, as preen oil has been demonstrated to act against bacteria in vitro, but not in vivo. Nor is it clear whether preen oil can combat pathogenic bacteria on eggshells to improve hatching success. Studies on the effect of preen oil against dermatophytes are very scarce and there is no evidence of a function against chewing lice. It seems clear, however, that preen oil improves waterproofing, but it is unclear whether this acts by creating a hydrophobic layer or simply by improving plumage structure. Several hypotheses proposed for the function of preen oil have been poorly studied, such as reduction of drag in flight. Similarly, we do not know whether preen oil functions as repellent against predators or parasites, makes birds unpalatable, or functions to camouflage birds with ambient odours. On the other hand, a growing body of work shows the important implications of volatiles in preen oil with regard to social communication in birds. Moreover, preen oil clearly alters plumage colouration. Finally, studies examining the impact of preen oil on fitness are lacking, and the costs or limitations of preen-oil production also remain poorly known. The uropygial gland appears to have several non-mutually exclusive functions in birds, and thus is likely to be subject to several selective pressures. Therefore, future studies should consider how the inevitable trade-offs among different functions drive the evolution of uropygial gland secretions.

Relationship between the fatty acid composition of uropygial gland secretion and blood of meat chickens receiving different dietary fats

Manipulation of the fatty acid composition of chicken feed has been shown to be effective for improving the nutritional value of chicken products. Currently, however, evaluation of the effectiveness of this approach requires invasive blood sampling or post mortem tissue sampling of the birds. Preen oil can be collected non-invasively from live birds. So this study aimed to test the hypothesis that the fatty acid composition of preen oil reflects that of the blood. Male and female meat chickens (Cobb 500) were fed a diet supplemented with 4% (w/w) flaxseed oil (high n-3 polyunsaturates) or beef tallow (mostly monounsaturates and saturates) for 6 weeks. Preen oil and whole blood samples (n = 9 birds per sex/diet treatment group) were collected freshly post mortem for fatty acid analysis. Preen oil analysis showed that ~97% of fatty acids were saturates, with a small percentage of n-6 polyunsaturates and traces of other types. There were negligible n-3 polyunsaturates in preen oil. Proportions of some saturated fatty acids were slightly, but significantly, affected by diet (C16:0 (P < 0.05) and C17:0 (P < 0.01)) or by gender (C10:0 and C18:0) (P < 0.05). Some fatty acids with odd numbers of carbon atoms (e.g. C17:0 and C19:0) were found in relatively high concentrations in preen oil, despite not being detectable in either the diet or blood. In conclusion, the fatty acid composition of preen oil does not accurately reflect the fatty acid profile of the blood; it is not, therefore, a suitable alternative for determining fatty acid status of meat chickens.

Social Environment Has a Primary Influence on the Microbial and Odor Profiles of a Chemically Signaling Songbird

Chemical signaling is an underappreciated means of communication among birds, as may be the potential contributions of symbiotic microbes to animal chemical communication in general. The dark-eyed junco (Junco hyemalis) produces and detects volatile compounds that may be important in reproductive behavior. These compounds are found in preen oil secreted by the uropygial gland, and this gland supports diverse bacterial communities including genera known to produce some of these volatile compounds. We investigated the relative contributions of shared environments and genetic relatedness in shaping juncos’ symbiotic bacterial communities, and investigated whether these bacterial communities underlie juncos’ chemical signaling behavior. We sampled parents and nestlings at 9 junco nests during one breeding season at Mountain Lake Biological Station in Virginia, USA. From each individual, we collected swabs of the uropygial gland and the cloaca, preen oil, and a small blood sample for paternity testing. We characterized junco bacterial communities through 16S rRNA gene surveys and preen oil volatile compounds via gas chromatography-mass spectrometry. Nest membership and age class had the strongest influence on the structure of bacterial and volatile profiles. We compared father-offspring similarity based on paternity, and nestling similarity in nests containing full siblings and half siblings, and found that relatedness did not noticeably affect bacterial or volatile profiles. While we cannot rule out an influence of genetic relatedness on these profiles, it is clear that shared environments are more influential in shaping bacterial and volatile profiles among juncos. We did not find significant covariation between individual bacterial and volatile profiles. Possible explanations for this result include: 1) bacteria do not underlie volatile production; 2) ample redundancy in volatile production among bacterial types obscures covariation; or 3) the relationship is confounded by the fact that, unlike glands exclusively dedicated to chemical communication, uropygial glands have multiple functions, and symbiotic bacteria are hypothesized to contribute to each of these. Therefore, different bacteria may contribute to different phenotypes of the avian holobiont. Future work will include cultivation, metabolomic, genomic, and behavioral assay approaches to tease these scenarios apart.

Uropygial gland and bib colouration in the house sparrow.

Birds frequently signal different qualities by plumage colouration, mainly during mating. However, plumage colouration is determined during the moult, and therefore it would indicate the quality of individual birds during the moult, not its current quality. Recent studies, however, suggest that birds could modify plumage colouration by using cosmetic preen oil produced by the uropygial gland. In this study, I show that bib colouration is related to uropygial gland size and body condition in male house sparrows (Passer domesticus). Moreover, I conducted an experiment in which a group of sparrows were inoculated with an antigen, mimicking an illness. In control birds, short-term changes in bib colouration were related to both body condition and change in uropygial gland size. Therefore, birds that reduced uropygial gland size showed a greater colouration change. However, bib colouration did not change with the change in uropygial gland size in experimental birds inoculated with the antigen. Given that the experiment did not affect preen oil production or consumption, this finding tentatively suggests that the immune challenge provoked a change in the composition of preen oil, affecting its cosmetic properties. In short, the results of this study suggest that (1) male house sparrows produce cosmetic preen oil that alters the colouration of their bibs; (2) the more change in uropygial gland size, the more change in bib colouration; and (3) in this way, bib colouration has the potential to signal current health status, since less healthy birds showed less capacity to change bib colouration.

Niche Partitioning of Feather Mites within a Seabird Host, Calonectris borealis.

According to classic niche theory, species can coexist in heterogeneous environments by reducing interspecific competition via niche partitioning, e.g. trophic or spatial partitioning. However, support for the role of competition on niche partitioning remains controversial. Here, we tested for spatial and trophic partitioning in feather mites, a diverse and abundant group of arthropods. We focused on the two dominant mite species, Microspalax brevipes and Zachvatkinia ovata, inhabiting flight feathers of the Cory’s shearwater, Calonectris borealis. We performed mite counts across and within primary and tail feathers on free-living shearwaters breeding on an oceanic island (Gran Canaria, Canary Islands). We then investigated trophic relationships between the two mite species and the host using stable isotope analyses of carbon and nitrogen on mite tissues and potential host food sources. The distribution of the two mite species showed clear spatial segregation among feathers; M. brevipes showed high preference for the central wing primary feathers, whereas Z. ovata was restricted to the two outermost primaries. Morphological differences between M. brevipes and Z. ovata support an adaptive basis for the spatial segregation of the two mite species. However, the two mites overlap in some central primaries and statistical modeling showed that Z. ovata tends to outcompete M. brevipes. Isotopic analyses indicated similar isotopic values for the two mite species and a strong correlation in carbon signatures between mites inhabiting the same individual host suggesting that diet is mainly based on shared host-associated resources. Among the four candidate tissues examined (blood, feather remains, skin remains and preen gland oil), we conclude that the diet is most likely dominated by preen gland oil, while the contribution of exogenous material to mite diets is less marked. Our results indicate that ongoing competition for space and resources plays a central role in structuring feather mite communities. They also illustrate that symbiotic infracommunities are excellent model systems to study trophic ecology, and can improve our understanding of mechanisms of niche differentiation and species coexistence.

Polychlorinated Biphenyls in the Plasma and Preen Oil of Black-Footed Albatross (Diomedea nigripes) Chicks and Adults on Midway Atoll, North Pacific Ocean.

Polychlorinated biphenyls (PCBs) are ubiquitous in the environment. Midway Atoll, located in the North Pacific Ocean, was occupied by the military during and after World War II. However, Midway Atoll has become a national wildlife refuge and home to many different seabirds today, including the black-footed albatross (Diomedea nigripes) (BFAL). The profiles and toxic equivalents (TEQ) of PCB congeners in the plasma and preen oil of BFAL chicks and adults were determined in this study. The concentrations of the total PCBs in the plasma samples of chicks and adults collected in Midway Atoll ranged from 2.3 to 223.8 (mean 80.1) and 22.8 to 504.5 (mean 158.6) ng g-1 (wet weight, ww), respectively. The TEQs ranged from 0.2 to 0.6 (mean 0.4) and 0.4 to 1.6 (mean 0.9) pg g-1 ww, respectively, in the plasma samples of chicks and adults from Midway Atoll. The major congeners in the plasma samples of chicks and adults included PCBs 31, 87, 97, 99, 118, 138, 153, and 180, accounting for 70% of the total PCBs. The concentrations of the total PCBs in the adult preen oil samples ranged from 1693 to 39404 (mean 10122) ng g-1 (ww), of which 97% were PCBs 105, 118, 128, 138, 153, 161, 172, and 183.

Avian olfactory displays: a hypothesis for the function of bill-wiping in a social context

Bill-wiping, or the scraping by a bird of its bill along a substrate, has been observed in social contexts and cited as an irrelevant displacement activity. However, several behaviors once categorized as displacement behaviors have since been shown to serve adaptive functions. Here, we hypothesize that bill-wiping may function in social interactions by releasing odors from the waxy residue of preen oil on the bill. We assessed behavioral context associated with bill-wiping by comparing the frequency of bill-wiping by free-living male songbirds when presented with a caged male or female conspecific paired with playback; males bill-wiped significantly more often in response in a courtship context and in a mate-guarding context than in a territorial context. Bill-wiping frequency correlated with courtship behaviors, such as tail spreading and singing short-range songs, but not with aggressive behaviors. We also noted attributes of individuals that engaged in bill-wiping during courtship and found that younger, smaller males performed this behavior more frequently than older, larger males. Finally, we conducted a captive Y-maze experiment to test whether dried preen oil residue would be more detectable if it were manipulated (scratched to potentially release odor) or unmanipulated. Preliminary evidence suggests that males could be more responsive to manipulated preen oil, though stronger tests are needed. Taken together, our results suggest a functional hypothesis: bill-wiping during courtship may be an olfactory display that releases odor that may be detected by potential mates and rivals. We conclude by suggesting ways in which future work can test the olfactory display hypothesis.

A biochemical approach for identifying plastics exposure in live wildlife

Summary Plastic pollution is a long‐standing ubiquitous issue. Global use of plastics is continuing to rise, and there is increasing interest in understanding the prevalence and risk associated with exposure of wildlife to plastics, particularly in the marine environment. In order To facilitate an assessment of ingestion of plastics in seabird populations, we developed a minimally invasive tool that allows for detection of exposure to plastics. Using a simple swabbing technique in which the waxy preen oil is expressed from the uropygial gland of birds, we successfully tested for the presence of three common plasticizers: dimethyl, dibutyl and diethylhexyl phthalate [dimethyl phthalate, dibutyl phthalate and bis(2‐ethylhexyl)‐phthalate, respectively]. These plasticizers are prevalent in the manufacturing of plastic end‐user items which often end up in the marine environment. Using gas chromatography–mass spectrometry and protocols to reduce background contamination, we were confidently able to detect targeted plasticizers at low levels. The method described has broad applicability for detecting plastics exposure in wildlife at individual, population and species levels. Furthermore, the approach can be readily modified as needed to survey for plastics exposure in taxa other than seabirds. Applying the simple, minimally invasive approach we describe here is particularly appealing for detecting plastics exposure at population and species levels, it shows promise for quantification and it has no observed detrimental impacts to wildlife.

Variation in preen oil composition pertaining to season, sex, and genotype in the polymorphic white-throated sparrow.

Evidence for the the ability of birds to detect olfactory signals is now well documented, yet it remains unclear whether birds secrete chemicals that can be used as social cues. A potential source of chemical cues in birds is the secretion from the uropygial gland, or preen gland, which is thought to waterproof, maintain, and protect feathers from ectoparasites. However, it is possible that preen oil also may be used for individual recognition, mate choice, and signalling social/sexual status. If preen oil secretions can be used as socio-olfactory signals, we should be able to identify the volatile components that could make the secretions more detectable, determine the seasonality of these secretions, and determine whether olfactory signals differ among relevant social groups. We examined the seasonal differences in volatile compounds of the preen oil of captive white-throated sparrows, Zonotrichia albicollis. This species is polymorphic and has genetically determined morphs that occur in both sexes. Mating is almost exclusively disassortative with respect to morph, suggesting strong mate choice. By sampling the preen oil from captive birds in breeding and non-breeding conditions, we identified candidate chemical signals that varied according to season, sex, morph, and species. Linear alcohols with a 10-18 carbon chains, as well as methyl ketones and carboxylic acids, were the most abundant volatile compounds. Both the variety and abundances of some of these compounds were different between the sexes and morphs, with one morph secreting more volatile compounds in the non-breeding season than the other. In addition, 12 compounds were seasonally elevated in amount, and were secreted in high amounts in males. Finally, we found that preen oil signatures tended to be species-specific, with white-throated sparrows differing from the closely related Junco in the abundances and/or prevalence of at least three compounds. Our data suggest roles for preen oil secretions and avian olfaction in both non-social as well as social interactions.

Body‐mass‐dependent trade‐off between immune response and uropygial gland size in house sparrowsPasser domesticus

Parasites greatly impact host fitness. The immune system is fundamental to combat endoparasites, and survival increases with greater investment in immunity. Some ectoparasites, by contrast, are reportedly combated by the use of the uropygial gland, an organ exclusive to birds, which secretes an oily substance (preen oil) that is spread on plumage. However, both mounting an immune response against a parasite and producing uropygial gland secretion depend on the same resources, a situation which may induce trade‐offs between the two antiparasitic functions. In this study, I experimentally test whether immune response is traded off against uropygial gland size in the house sparrowPasser domesticus. In the experiment, a group of sparrows were injected with an antigen (lipopolysaccharide, LPS), which stimulates the immune system, while the other group received a sham injection. The uropygial gland of LPS‐treated birds decreased significantly more than that of the control birds after treatment. Nevertheless, the effect of the treatment was limited to house sparrows with low body mass, suggesting that heavy house sparrows were able to produce an immune response while maintaining a relatively large uropygial gland. Given that uropygial gland size is strongly related to production of preen oil, these results suggest that preen oil production declines in birds in poor body condition when resources are preferentially diverted to other demanding functions, such as the immune system. Considering that the uropygial gland is involved in several fitness‐related processes in birds, the trade‐off between immune response and uropygial gland size may have important consequences for bird life histories.

An experimental test in Mallards (Anas platyrhynchos) of the effect of incubation and maternal preen oil on eggshell microbial load

Microbial infection is one of the main factors reducing survival in the first stages of life in oviparous species, and recent studies have shown that the avian eggshell harbors an important variety of microorganisms that can rapidly multiply and penetrate the shell, leading to a decrease in hatchability. Here, we report the results of an experiment in which we examined how incubation and maternal preen oil affect the growth of avian eggshell microbes, using the Mallard (Anas platyrhynchos) as a model species. We compared the bacterial and fungal loads on the shell of non-incubated eggs and eggs incubated by females having free or blocked access to their preen gland. An increase of eggshell bacterial loads was observed in all conditions, but bacterial growth was higher on the shell of incubated eggs than on non-incubated eggs. We did not find any significant difference in eggshell bacterial growth for eggs incubated by females with free or blocked access to their preen gland. In addition, fungal growth during our experiment was not affected by incubation or the mother’s preen oil. Our findings are in contrast with those of previous studies which showed that incubation limited or had no effect on eggshell bacterial growth. Differences in environmental conditions and/or species ecology may explain the difference between the results of our experiment and those of previous studies. Our study provides the first data on the effect of maternal preen oil on eggshell microorganisms, showing that preen oil does not limit eggshell microbial growth.

Environmental and biological monitoring of persistent organic pollutants in waterbirds by non-invasive versus invasive sampling

Three main groups of persistent organic pollutants (POPs); namely organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenylethers (PBDEs) were quantified in water and sediment samples, as well as in various invasive and non-invasive samples from waterbirds in the Büyük Menderes River (BMR). Liver and muscle tissues, blood, and preen gland oil samples of yellow-legged gull (Larus michahellis) and Euroasian coot (Fulica atra) were collected both from the origin (Işıklı Lake) and the estuary (Söke) of the river, blood and preen gland oil samples of grey heron (Ardea cinerea) and pelican (Pelecanus crispus) were collected from the estuary only. In addition, non-hatched eggs from several above species and Mediterranean gull (Larus melanocephalus), in either station were collected. In all samples, POP contamination was measured and the potential usefulness of those invasive and non-invasive sampling for biomonitoring was evaluated. Activities of antioxidant enzymes were measured as potential indicators of POP exposure and of changes in the cellular defence. Venous blood proved to be a promising biomonitor for the concentrations in liver and muscle, especially for PCBs. Activities of antioxidant enzymes were correlated with the liver concentrations of several OCP congeners. The measured egg DDE concentrations were below the established threshold concentrations for the risk of hatch and reproductive success.