Alejandro Cantarero

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.

Plasma Antioxidant Capacity and Oxidative Damage in Relation to Male Plumage Ornamental Traits in a Montane Iberian Pied Flycatcher Ficedula hypoleuca Population

Abstract. Melanin-based plumage ornaments may express individual quality in the context of social and sexual selection. Oxidative stress and antioxidant defences may be expressed through melanin-based plumage traits. Male Pied Flycatchers Ficedula hypoleuca exhibit eumelanic dorsal plumage and white feather patches on forehead and wing feathers. Although these traits have been related to sexual selection in some populations, no physiological correlate of variation in these characters has been previously shown. Here we test if these plumage traits are related to plasma oxidative stress and antioxidant capacity. We captured males while feeding nestlings in a population breeding at high altitude (1200–1400 m) in central Spain and collected blood samples from brachial veins. Percentage black on dorsal plumage and extension of white on folded wing and forehead were obtained from digital photographs. Plasma samples were analysed in the laboratory to obtain lipid peroxidation as a measure of oxidative damage by quantifying malondialdehydes (MDA), and antioxidant capacity. When controlling for male mass, breeding date and brood size, only forehead patch size was negatively associated with plasma lipid peroxidation levels and positively related to antioxidant capacity. There was no association among different plumage traits. Thus forehead patch size in montane Iberian populations may signal male phenotypic quality through plasma oxidative stress and antioxidant capacity possibly due to altitudinal effects on oxidative stress.

Is nestling growth affected by nest reuse and skin bacteria in Pied Flycatchers Ficedula hypoleuca

Abstract. Bacteria may colonize avian nests with unknown repercussions on nestling growth and health, although bacteria on nest materials may easily colonize nestling skin and growing feathers. Cavity nesters may have to build their nests on top of used nest materials, given restrictions on cavity availability. Nest reuse may favour bacterial colonization of nest materials and nestling skin and thereby affect nestling feather growth. To test these possibilities, we conducted a study of Pied Flycatchers Ficedula hypoleuca breeding in nest-boxes in central Spain. We left a sample of nest-boxes without removing old nest materials in 2010 and compared bacterial loads of nest materials, control inert objects and nestling belly skin in reused nests with those in new nests in 2011. Nestlings raised in reused nests had higher bacterial loads on their belly skin than those in new nests, while no difference between nest types for nest materials and control inert objects were found. There was a marginally significant tendency for wing length before fledging to be lower in reused nests, but no trend for mass or tarsus length. The bacterial loads of nests showed a negative association with feather growth of nestlings as expressed through wing length but not with tarsus length or mass growth. These results indicate an association between nest reuse and bacterial growth on nestling skin not hitherto detected. They also suggest a possible impairment of flight capacity at fledging mediated by nest bacterial communities which are in direct contact with nestling skin and growing feathers.

Oxidative damage in relation to a female plumage badge: evidence for signalling costs

Badges of status may be controlled by costs derived from increased aggression from dominant individuals. This cost could be translated into elevated metabolic levels and a concomitant disruption of oxidative balance. Some females in Iberian pied flycatcher Ficedula hypoleuca populations exhibit a white forehead patch similar to that exhibited by all males in this species, functioning in aggressive interactions between females when competing for breeding sites. To test if social stress imposes costs on signalling, we painted white patches on females without natural patches (NP) and compared them with females with natural control (NU). We also over-painted the natural patch in other females (FP) and compared to females with control natural patches (FU). We obtained for the whole sample of females data on reproductive investment, morphology and oxidative damage measured by blood malondialdehydes (MDA), and in a subsample of females variables related to parental care during incubation and the early nestling stage. FP and FU did not differ significantly in any variable which negates an effect of paint itself. However, NP females showed significant higher levels of MDA than NU females when controlling for breeding success for the whole sample, and for female incubation attendance for the parental care subsample. When including the four treatments, there was a significant interaction between the paint treatment and the presence/absence of badges before the experiment when controlling for the significant negative effect of incubation attendance on MDA. Addition of a badge to females without one leads to increased oxidative damage possibly mediated by social control. Badges of status in female pied flycatchers may operate as badges of oxidative status.

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.

Extra-pair matings, context-dependence and offspring quality: a brood manipulation experiment in pied flycatchers

Extra-pair paternity (EPP) in socially monogamous species has been associated with the genetic benefits incurred by females through extra-pair mate choice. There is conflicting evidence in the literature concerning the importance of such benefits possibly due to their context-dependence. To ascertain if there are such context-dependent genetic benefits, we conducted a brood manipulation experiment in pied flycatchers (Ficedula hypoleuca) breeding in central Spain. We found that extra-pair mates (EPM) are frequently not nearest neighbours. Cuckolded males and EPM did not differ from other males in any measured trait, and were not different either when cuckolds and cuckolders were compared within broods. Within-pair offspring (WPO) and extra-pair offspring (EPO) did not differ with respect to heterozygosity and no association of heterozygosity of either offspring or males and females with EPP could be detected. Moreover, the competitive context in the nest induced by brood manipulations affected the growth of nestlings and showed an interaction with paternity differences in nestling mass but in the opposite direction to the prediction of context-dependence, i.e., EPO were lighter than WPO in enlarged broods but not in control broods. Furthermore, EPO had shorter tarsi than WPO in all treatments. Mortality in the nest showed an association with brood manipulation treatment, but not with paternity or its interaction with treatment. Thus, we have not found any evidence of genetic benefits, context-dependent or otherwise, of EPP in our study population. The evidence of poor quality EPO does not support a mixed reproductive strategy of females in our population.

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.

Bacteria on nestling skin in relation to growth in pied flycatchers

AbstractThe association between skin bacterial communities and nestling growth is poorly understood. We estimated the abundance of heterotrophic bacteria on skin of nestlings and their association with growth in the pied flycatcher Ficedula hypoleuca. At two different nestling ages, we swabbed a delimited area of the naked belly skin of nestlings and measured them. Skin bacterial loads on day 13, but not on day 7, were positively associated with brood size and with nestling wing length. Larger broods develop in less hygienic conditions, which may stimulate bacterial growth. Skin bacteria may favor wing feather growth through competition with harmful bacteria, or faster feather growth may facilitate bacterial growth through the accumulation of remains on the skin surrounding growing feathers.ZusammenfassungDas verhältnis zwischen hautbakterien und wachstum bei nestlingen des trauerschnäppers Die Zusammenhänge zwischen Hautbakteriengemeinschaften und dem Wachstum von Nestlingen sind bisher kaum bekannt. Wir bestimmten die Häufigkeit heterotropher Bakterien auf der Haut von Nestlingen und deren Verbindung mit dem Wachstum bei Trauerschnäppern Ficedula hypoleuca. Dazu wurden die Nestlinge in zwei verschiedenen Altersstadien gemessen und gleichzeitig ein Abstrich von einer definierten Stelle der nackten Bauchhaut genommen. Die Besiedlung der Haut mit Bakterien am 13., nicht jedoch am 7. Lebenstag, zeigte einen positiven Zusammenhang mit der Brutgröße sowie mit der Flügellänge der Nestlinge. Größere Bruten entwickeln sich unter weniger hygienischen Bedingungen, was das Bakterienwachstum begünstigen könnte. Hautbakterien könnten durch Konkurrenz mit schädlichen Bakterien das Wachstum der Schwungfedern begünstigen; alternativ könnte ein schnelleres Federwachstum durch die Ansammlung von Hautresten rund um wachsende Federn die Bakterienvermehrung fördern.

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.