Jimena López-Arrabé

Factors Affecting the Presence and Abundance of Generalist Ectoparasites in Nests of Three Sympatric Hole-Nesting Bird Species

Abstract. Nesting cavities constitute micro-environments very likely to be colonized by ectoparasites which feed on blood of the incubating female and the nestlings. Given the negative impact of ectoparasites on nestlings there will be selection on hosts to minimize ectoparasite loads through behavioural defenses. We have addressed the implications of ectoparasitism in three sympatric avian cavity-nesters, namely Pied Flycatchers Ficedula hypoleuca, Blue Tits Cyanistes caeruleus and Nuthatches Sitta europaea, to explore if differences in prevalence and abundance of generalist ectoparasites (blowflies, fleas and mites) can be related to interspecific differences in their nest size, nest composition and cavity microclimate. Furthermore, we have aimed at detecting if interspecific variation in the incidence and intensity of anti-parasite behaviours is a consequence of the abundance of ectoparasites. Differences in nest composition among host species appear not to be the main factor explaining ectoparasite loads, while nest size, breeding phenology, brood size and nest-cavity micro-climate may affect them in different ways for each host-parasite association. Behavioural defenses against parasites are exhibited by all host species but are more intense in the host species with the highest infestation levels (Blue Tits). This study shows different sources of variation in associations between three sympatric avian cavity-nesters and their generalist ectoparasites.

Extent of a white plumage patch covaries with testosterone levels in female Pied Flycatchers Ficedula hypoleuca

AbstractIt is not clear at present if variation in testosterone (T) levels is associated with variation in plumage signal expression in female birds. In Iberian populations of Pied Flycatchers Ficedula hypoleuca, some females exhibit a distinctive white forehead patch similar to that found in males. Both sexes also exhibit conspicuous white patches on wings that vary greatly in size. Males show markedly larger wing patches. These patches are exhibited in social interactions. We have aimed at detecting if naturally occurring variation in T circulation is linked to the expression of forehead patch presence and folded wing white patch area in female Pied Flycatchers. There was marked variation in female plumage patches and in T levels. The area of the wing white patch but not the presence of a forehead patch in females was associated with higher circulating T levels during the incubation phase when controlling for female age and hatching success. Older females, and females suffering a reduced hatching success, also presented lower levels of T. Our study indicates that a female plumage trait that is equivalent to a sexually selected trait in males may signal T levels. Females, like males, may use plumage traits to signal their T-mediated aggressive disposition.ZusammenfassungDas Ausmaß eines weißen Gefiederflecks schwankt bei weiblichen TrauerschnäppernFicedula hypoleucamit dem Testosteronspiegel Derzeit ist unklar, ob Schwankungen im Testosteronspiegel mit Variationen in der Expression von Gefiedersignalen bei weiblichen Vögeln einhergehen. In iberischen Populationen des Trauerschnäppers Ficedula hypoleuca weisen manche Weibchen einen ausgeprägten weißen Stirnfleck auf, der dem der Männchen ähnlich ist. Beide Geschlechter haben außerdem auffällige weiße Flügelflecken, deren Größe sehr variabel ist. Die Flügelflecken der Männchen sind allerdings deutlich größer. Diese Flecken werden bei sozialen Interaktionen präsentiert. Wir haben versucht herauszufinden, ob natürlich auftretende Schwankungen des im Blut zirkulierenden Testosterons bei weiblichen Trauerschnäppern mit der Expression der Stirn- und Flügelflecken zusammenhängen. Flecken und Testosteronspiegel der Weibchen variierten deutlich. Die Fläche des weißen Flügelflecks, jedoch nicht das Vorhandensein des Stirnflecks, hing mit einem höheren Spiegel zirkulierenden Testosterons während der Bebrütungsphase zusammen, wenn Alter der Weibchen und Schlupferfolg im statistischen Modell berücksichtigt wurden. Ältere Weibchen und solche mit reduziertem Schlupferfolg hatten niedrigere Testosteronspiegel. Unsere Studie deutet darauf hin, dass ein weibliches Gefiedermerkmal, das gleichbedeutend mit einem sexuell selektierten Merkmal der Männchen ist, den Testosteronspiegel anzeigen könnte. Weibchen könnten genau wie Männchen Gefiedermerkmale nutzen, um ihre durch Testosteron vermittelte aggressive Neigung zu signalisieren.

Nest-dwelling ectoparasites reduce antioxidant defences in females and nestlings of a passerine: a field experiment.

Ectoparasites may imply a cost in terms of oxidative stress provoked by inflammatory responses in hosts. Ectoparasites may also result in costs for nestlings and brooding females because of the direct loss of nutrients and reduced metabolic capacity resulting from parasite feeding activities. These responses may involve the production of reactive oxygen and nitrogen species that may induce oxidative damage in host tissues. Our goal was to examine the effect of ectoparasites in terms of oxidative stress for nestlings and adult females in a population of pied flycatchers Ficedula hypoleuca. We manipulated the entire nest ectoparasite community by reducing ectoparasite loads in some nests through a heating treatment and compared them with a control group of nests with natural loads. A marker of total antioxidant capacity (TAS) in plasma and total levels of glutathione (tGSH) in red blood cells as well as a marker of oxidative damage in plasma lipids (malondialdehyde; MDA) were assessed simultaneously. Levels of tGSH were higher in heat-treated nests than in controls for both females and nestlings. Higher TAS values were observed in females from heat-treated nests. In nestlings there was a negative correlation between TAS and MDA. Our study supports the hypothesis that ectoparasites expose cavity-nesting birds to an oxidative challenge. This could be paid for in the long term, ultimately compromising individual fitness.

Only Some Ectoparasite Populations are Affected by Nest Re-Use: an Experimental Study on Pied Flycatchers

Summary. Nest re-use in birds is rare but since appropriate cavities may be scarce, cavity-nesting birds may often re-use those that were occupied in previous seasons. Old nest material may contain and/or attract more ectoparasites than fresh material. Therefore it is important to understand the effects of nest re-use on the abundance of different ectoparasite species of different virulence and their impli cation for breeding parameters and nestling condition. We studied the consequences of nest re-use in a population of pied flycatchers Ficedula hypoleuca breeding in central Spain by offering them both nest-boxes with old nest material and cleaned nest-boxes. We monitored breeding activity from the early stages of nest construction until fledging, and then finally removed nests to estimate ectoparasite abun dances. Occupation rates were similar for both treatments. We found that blowfly and flea abundances were significantly higher in old nests than in new nests, but the abundance of mites, the most virulent ectoparasites on our host study population, was not affected by the presence of old nest material. Nestling growth with respect to tarsus length and mass was not affected by nest re-use although wing length was marginally and significantly reduced by nest re-use. There was no association between ectoparasite abundance and nestling growth and condition. These results question the generality of assumed higher infestations in re-used nests, on which a certain critique of nest-box studies has been based.

Males feed their mates more and take more risks for nestlings with larger female-built nests: an experimental study in the Nuthatch Sitta europaea

Nest size has been suggested to be a sexually selected signal, allowing individuals to obtain reliable information about partner quality and thereby optimize paternal investment in reproduction. Studies concerning the potential role of nests as signals are scarce for avian species in which the female is the only builder. We have aimed at understanding whether males’ reproductive investment (e.g., provisioning rates and risk taking) change in relation to experimental manipulation of nest size in the Nuthatch, Sitta europaea, as would be predicted if nest size is a sexually selected signal reflecting female’s quality. To that end, we have experimentally manipulated nest size by approximately doubling its size and leaving other nests as controls. Experimental manipulation led males to increase their incubation feeding rates, and females from the experimental group showed higher levels of glutathione (tGSH), an important endogenous antioxidant whose synthesis may be enhanced indirectly through nutrition. Although male provisioning rates during the nestling stage did not differ between experimental groups, males responded to nest size manipulation by visiting nests sooner after human disturbance (an index of risk taking) as compared to control nests. Our study suggests that nest size constitutes a signal of female quality which elicits differential allocation of male resources both to females themselves and to their broods. Higher risk taking in favor of offspring by mates of strongly signaling females may denote an improvement in offspring survival chances in the field.Significance statementAnimals transfer information to other individuals through different traits. Given that nest building involve a large expenditure of time and energy for the builder, nest size may allow individuals to obtain reliable information about partner quality and thereby optimize paternal investment in reproduction. Despite the importance of females as nest-builders in a majority of avian species, studies concerning the potential role of nests as signals are scarce for avian species in which the female is the only builder. Our experimental study suggests that nest size constitutes a signal of female quality which elicits differential allocation of male resources both to females themselves and to their broods. Males from enlarged nests intensified their provisioning rates to females during the incubation stage and assumed higher risks for their broods after human disturbance.

Female aggressiveness towards female decoys decreases with mate T level in the pied flycatcher

Social selection is expected to favour the evolution of female aggressive defence of nesting resources in cavity-nesting birds, which may be also mediated by testosterone (T) levels. Male T levels could express male dominance and thereby territorial safety for female partners and thereby reduce their need for aggressive defence. Here, we explored the role of T levels in female-female competition in a songbird, the pied flycatcher Ficedula hypoleuca. In an experiment with female decoys placed close to the nestbox at the end of laying, we explored if female aggressiveness is related to their own T level or to mate T level. T levels of males and females were measured in the middle of the nestling period. Mean female aggressiveness towards decoys in three presentations was estimated through proximity to the decoy and number of attacks by females, two variables which were positively associated. Aggressiveness by female nest owners to female decoys was negatively related to male T level but unrelated to own T level. There was no assortative mating with respect to T level. Female aggressiveness is more strongly related to the hormonal status of mates than to their own.

Selection of nest site and nesting material in the Eurasian Nuthatch Sitta europaea

The selection of nest sites and nesting material may have important implications for avian reproductive behaviour and performance. Nest construction may involve costs arising from transporting material that may be reduced considerably if nest materials are located close to the nest site. Eurasian Nuthatch Sitta europaea nests in our nest box study area are mainly composed of pine bark flakes or alternatively of strips of bark of the widespread shrub Cistus laurifolius, with variable amounts of mud being used for plastering the entrance. Several small streams run through the area — an oak Quercus pyrenaica forest with a few scattered pines Pinus sylvestris. Here we show that Nuthatches collected pine bark only when nest sites were situated close to pines, used more mud when breeding close to streams and selected nest sites closer to streams than a sympatric species not using mud, the Pied Flycatcher Ficedula hypoleuca. Nuthatches used pine bark only when there was a pine tree less than 100 m away from the nest box and selected Cistus bark when transport distance was greater. We suggest that the selection of nest sites and nest materials in this species may be constrained by the costs of transporting nest material.

The Significance of Nest Structure and Nesting Material for Hole-Nesting Passerines: an Experimental Study with Nuthatches Sitta europaea

Abstract. Nest structure and nesting material may have important consequences for avian reproductive behaviour and performance. Nuthatches Sitta spp. build nests made of loose bark flakes without any structure or nest cup to contain eggs and nestlings. We have aimed at understanding the implications of unstructured bark flake nests in Nuthatches for microclimatic conditions in the nest, ectoparasite infestation, parental care and nestling begging through a nest exchange experiment. To that end, we have experimentally replaced natural bark nests of Nuthatches Sitta europaea by structured moss nests built at the same time by Great Tits Parus major for some pairs and compared their ectoparasite abundances, nest microclimate variables and the behaviour of nestlings and parents with those in natural Nuthatch nests. The experimental treatment did not affect ectoparasite loads. Nest-boxes containing structured nests made of moss showed higher and more variable temperatures, higher thermal maxima and less variable humidity conditions than unstructured control nests made of bark flakes. However, bark flakes conserve heat better than moss during the night and morning hours, which may be transmitted to buried eggs and nestlings and reduce incubation and brooding costs for females. This may explain why females remained out for longer during incubation recesses at natural nests. Nestlings of 9 days in natural nests rested further apart than nestlings in structured experimental nests although there were no differences with respect to begging intensity between the two treatments. Hatching and fledging success was similar in both groups but experimental nests resulted in nestlings with shorter tarsi and wings before fledging. The poorer nestling growth in experimental nests cannot be explained by effects of ectoparasites, nestling aggregation or nestling begging or parental care. Adaptations for remaining buried in the nest material and the heat-conserving properties of loose bark flakes may reduce energy costs for nestlings during female absences.

Oxidative status in nestlings shows different associations with parental carotenoid-based plumage ornaments depending on parental sex and year: a study of rock sparrows Petronia petronia

Carotenoid-based colouration in birds has been suggested to be a sexually selected signal, allowing individuals to obtain reliable information about the quality of antioxidant resources. Moreover, oxidative stress levels during early development may have medium- and long-term fitness consequences. Rock sparrows (Petronia petronia) display a carotenoid-based breast patch in both sexes which has been shown to function as a signal of phenotypic quality in sexual and social interactions. We studied a rock sparrow population in central Spain aiming to test whether the extent of the carotenoid-based breast patch is associated with offspring growth and oxidative status. We have used plasma malondialdehyde (MDA) level in plasma as a measure of oxidative damage, and total antioxidant status of plasma (TAS) and total glutathione (tGSH) levels in red blood cells as measures of antioxidant defences. The study included the extremely late breeding season of 2013 and the phenologically more normal season of 2014. Unfavourable conditions for breeding resulted in smaller nestlings in 2013. Male breast patch size showed a negative association with nestling tarsus length and, strikingly, a positive association with nestling MDA. It also showed a positive relationship with nestling wing length in interaction with year. Nestlings in late and larger broods showed higher tGSH levels. Female breast patch size showed positive associations with nestling tGSH levels, indicating positive links of maternal ornamentation with offspring condition. Moreover, TAS values were only positively associated with female patch size under favourable conditions, as shown by the interaction with year. Associations of carotenoid-based parental plumage ornaments with offspring growth and oxidative status depends on parental sex and environmental conditions. Carotenoid-based plumage traits signal parental quality in female rock sparrows, while paternal ornaments seemingly do not reflect parental quality. To our knowledge, this is the first study to investigate the association between female plumage ornaments and offspring antioxidant capacity. The same signal may reflect different parental attributes in the two sexes in sexually monomorphic species.

Oxidative Stress in Early Life: Associations with Sex, Rearing Conditions, and Parental Physiological Traits in Nestling Pied Flycatchers.

Conditions experienced during juvenile development can affect the fitness of an organism. During early life, oxidative stress levels can be particularly high as a result of the increased metabolism and the relatively immature antioxidant system of the individual, and this may have medium- and long-term fitness consequences. Here we explore variation in levels of oxidative stress measured during early life in relation to sex, rearing conditions (hatching date and brood size), and parental condition and levels of oxidative markers in a wild population of the pied flycatcher (Ficedula hypoleuca) followed for 2 yr. A marker of total antioxidant status (TAS) in plasma and total levels of glutathione (GSH) in red blood cells, as well as a marker of oxidative damage in plasma lipids (malondialdehyde [MDA]), were assessed simultaneously. Our results show that nestling total GSH levels were associated with parental oxidative status, correlating negatively with maternal MDA and positively with total GSH levels of both parents, with a high estimated heritability. This suggests that parental physiology and genes could be determinants for endogenous components of the antioxidant system of the offspring. Moreover, we found that total GSH levels were higher in female than in male nestlings and that hatching date was positively associated with antioxidant defenses (higher TAS and total GSH levels). These results suggest that different components of oxidative balance are related to a variety of environmental and intrinsic—including parental—influencing factors. Future experimental studies must disentangle the relative contribution of each of these on nestling oxidative status and how the resulting oxidative stress at early phases shape adult phenotype and fitness.