Gergely Osváth

The Effect of Coccidians on The Condition and Immune profile of Molting House Sparrows (Passer Domesticus)

ABSTRACT. Feather molt is recognized as an energetically costly activity for birds, and parasite infestation during molt has the potential to reduce host fitness because parasites sequester essential nutrients and stimulate the immune system. We manipulated the coccidian parasite load of captive male House Sparrows (Passer domesticus) by suppressing the natural infection of control birds with an anticoccidial drug and infecting experimental birds with coccidian oocysts. Following infestation, the effect of chronic coccidian infection on individual condition, molt and 12 indices of physiological and immunological function was assessed. We found a significant positive relationship between infestation and heterophil/lymphocyte ratio measured at capture, indicating infectioninduced stress. We also found that coccidians negatively affected feather growth during molt: the increase in wing length of the noninfected birds was significantly higher than that of infected birds. In comparison to control birds, infected birds showed a significantly higher concentration of white blood cells and greater blood bactericidal activity. There was also a positive correlation between infection intensity, agglutination and lysis of blood in the experimentally infested birds, which indicated activation of the constitutive innate immune system during infection. Finally, the total antioxidant capacity of the blood increased significantly, while the carotenoid concentration decreased significantly in infected compared with control birds. Therefore, we showed that coccidians stimulated several measures of the constitutive innate immunity, including the bactericidal activity of the blood, and that coccidians can have significant negative effects on the health and possibly fitness of molting House Sparrows.

Interspecific variation in the structural properties of flight feathers in birds indicates adaptation to flight requirements and habitat

Summary1. The functional significance of intra- and interspecific structural variations in the flight feath-ers of birds is poorly understood. Here, a phylogenetic comparative analysis of four structuralfeatures (rachis width, barb and barbule density and porosity) of proximal and distal primaryfeathers of 137 European bird species was conducted.2. Flight type (flapping and soaring, flapping and gliding, continuous flapping or passerinetype), habitat (terrestrial, riparian or aquatic), wing characteristics (wing area, S and aspectratio, AR) and moult strategy were all found to affect feather structure to some extent. Speciescharacterized by low wing-beat frequency flight (soaring and gliding) have broader featherrachises (shafts) and feather vanes with lower barb density than birds associated with moreactive flapping modes of flight. However, the effect of flying mode on rachis width disappearedafter controlling for S and AR, suggesting that rachis width is primarily determined by wingmorphology.3. Rachis width and feather vane density are likely related to differences in force distributionacross the wingspan during different flight modes. An increase in shaft diameter, barb densityand porosity from the proximal to distal wing feathers was found and was highest in specieswith flapping flight indicating that aerodynamic forces are more biased towards the distalfeathers in flapping flyers than in soarers and gliders.4. Habitat affected barb and barbule density, which was greatest in aquatic species, and withinthis group, barb density was greater in divers than non-divers, suggesting that the need for waterrepellency and resistance to water penetration may influence feather structure. However, wefound little support for the importance of porosity in water repellency and water penetration,because porosity was similar in aquatic, riparian and terrestrial species and among the aquaticbirds (divers and non-divers). We also found that barb density was affected by moult pattern.5. Our results have broad implications for the understanding of the selection pressures drivingflight feather functional morphology. Specifically, the large sample size relative to any previousstudies has emphasized that the morphology of flight feathers is the result of a suite of selec-tion pressures. As well as routine flight needs, constraints during moulting, habitat (particu-larly aquatic) and migratory requirements also affect flight feather morphology. Identifying theexact nature of these trade-offs will perhaps inform the reconstruction of the flying modes ofextinct birds.Key-words: barb density, barbule density, flight, flight feathers, functional morphology,moult, rachis width, vane porosity, water repellence, wing morphology

Morphological Adaptations to Migration in Birds

Migratory flight performance has direct or carry-over effects on fitness. Therefore, selection is expected to act on minimizing the costs of migratory flight, which increases with the distance covered. Aerodynamic theory predicts how morphological adaptations improve flight performance. These predictions have rarely been tested in comparative analyses that account for scaling and phylogenetic effects. We amassed a unique dataset of 149 European bird species and 10 morphological traits. Mass-adjusted aspect ratio increased, while mass-adjusted heart weight and wing loading decreased with increasing migration distance. These results were robust to whether the analyses were based on the entire species pool or limited to passerines or migrants. Our findings indicate that selection due to migration acts on wing traits that reduce the energetic cost of transportation to increase the flight range. Consequently, the demands for high ‘exercise organ’ performance might be low, and hence such energetically expensive tissues are not associated (pectoral muscle) or are inversely associated (heart) with migration distance.

Brain regions associated with visual cues are important for bird migration.

Long-distance migratory birds have relatively smaller brains than short-distance migrants or residents. Here, we test whether reduction in brain size with migration distance can be generalized across the different brain regions suggested to play key roles in orientation during migration. Based on 152 bird species, belonging to 61 avian families from six continents, we show that the sizes of both the telencephalon and the whole brain decrease, and the relative size of the optic lobe increases, while cerebellum size does not change with increasing migration distance. Body mass, whole brain size, optic lobe size and wing aspect ratio together account for a remarkable 46% of interspecific variation in average migration distance across bird species. These results indicate that visual acuity might be a primary neural adaptation to the ecological challenge of migration.

Seasonal Patterns and Relationships among Coccidian Infestations, Measures of Oxidative Physiology, and Immune Function in Free-Living House Sparrows over an Annual Cycle

Temporal variation in oxidative physiology and its associated immune function may occur as a result of changes in parasite infection over the year. Evidence from field and laboratory studies suggests links between infection risk, oxidative stress, and the ability of animals to mount an immune response; however, the importance of parasites in mediating seasonal change in physiological makeup is still debated. Also, little is known about the temporal consistency of relationships among parasite infestation, markers of oxidative status and immune function in wild animals, and whether variation in oxidative measures can be viewed as a single integrated system. To address these questions, we sampled free-living house sparrows (Passer domesticus) every 2 mo over a complete year and measured infestation with coccidian parasites as well as nine traits that reflect condition, oxidative physiology, and immune function. We found significant seasonal variation in coccidian infestation and in seven out of nine condition and physiological variables over the year. However, we found little support for parasite-mediated change in condition, oxidative physiology, and immune functions in house sparrows. In accordance with this, we found no temporal consistency in relationships between the intensity of infestation and physiology. Among measures of oxidative physiology, antioxidants (measured as the total antioxidant capacity and the concentration of uric acid in the plasma) and oxidative damage (measured through the level of malondialdehyde in plasma) positively and consistently covaried over the year, while no such associations were found for the rest of traits (body mass, total glutathione, and leukocyte numbers). Our results show that natural levels of chronic coccidian infection have a limited effect on the seasonal change of physiological traits, suggesting that the variation of the latter is probably more affected by short-term disturbances, such as acute infection and/or season-specific stress stimuli.

A phylogenetic comparative analysis reveals correlations between body feather structure and habitat

correlations between body feather structure and habitat P eter L. Pap*, Orsolya Vincze, Beatrix Wekerle, Timea Daubner, Csongor I. V ag asi, Robert L. Nudds, Gareth J. Dyke and Gergely Osv ath Evolutionary Ecology Group, Hungarian Department of Biology and Ecology, Babes -Bolyai University, Clinicilor Street 5–7, RO-400006 Cluj Napoca, Romania; MTA-DE “Lend€ ulet” Behavioural Ecology Research Group, Department of Evolutionary Zoology and Human Biology, University of Debrecen, Egyetem t er 1, H-4032 Debrecen, Hungary; Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK; and Museum of Zoology, Babes -Bolyai University, Clinicilor Street 5–7, RO-400006 Cluj Napoca, Romania

Large-brained birds suffer less oxidative damage

Large brains (relative to body size) might confer fitness benefits to animals. Although the putative costs of well‐developed brains can constrain the majority of species to modest brain sizes, these costs are still poorly understood. Given that the neural tissue is energetically expensive and demands antioxidants, one potential cost of developing and maintaining large brains is increased oxidative stress (‘oxidation exposure’ hypothesis). Alternatively, because large‐brained species exhibit slow‐paced life histories, they are expected to invest more into self‐maintenance such as an efficacious antioxidative defence machinery (‘oxidation avoidance’ hypothesis). We predict decreased antioxidant levels and/or increased oxidative damage in large‐brained species in case of oxidation exposure, and the contrary in case of oxidation avoidance. We address these contrasting hypotheses for the first time by means of a phylogenetic comparative approach based on an unprecedented data set of four redox state markers from 85 European bird species. Large‐brained birds suffered less oxidative damage to lipids (measured as malondialdehyde levels) and exhibited higher total nonenzymatic antioxidant capacity than small‐brained birds, whereas uric acid and glutathione levels were independent of brain size. These results were not altered by potentially confounding variables and did not depend on how relative brain size was quantified. Our findings partially support the ‘oxidation avoidance’ hypothesis and provide a physiological explanation for the linkage of large brains with slow‐paced life histories: reduced oxidative stress of large‐brained birds can secure brain functionality and healthy life span, which are integral to their lifetime fitness and slow‐paced life history.

Sexual Dimorphism and Population Differences in Structural Properties of Barn Swallow (Hirundo rustica) Wing and Tail Feathers.

Sexual selection and aerodynamic forces affecting structural properties of the flight feathers of birds are poorly understood. Here, we compared the structural features of the innermost primary wing feather (P1) and the sexually dimorphic outermost (Ta6) and monomorphic second outermost (Ta5) tail feathers of barn swallows (Hirundo rustica) from a Romanian population to investigate how sexual selection and resistance to aerodynamic forces affect structural differences among these feathers. Furthermore, we compared structural properties of Ta6 of barn swallows from six European populations. Finally, we determined the relationship between feather growth bars width (GBW) and the structural properties of tail feathers. The structure of P1 indicates strong resistance against aerodynamic forces, while the narrow rachis, low vane density and low bending stiffness of tail feathers suggest reduced resistance against airflow. The highly elongated Ta6 is characterized by structural modifications such as large rachis width and increased barbule density in relation to the less elongated Ta5, which can be explained by increased length and/or high aerodynamic forces acting at the leading tail edge. However, these changes in Ta6 structure do not allow for full compensation of elongation, as reflected by the reduced bending stiffness of Ta6. Ta6 elongation in males resulted in feathers with reduced resistance, as shown by the low barb density and reduced bending stiffness compared to females. The inconsistency in sexual dimorphism and in change in quality traits of Ta6 among six European populations shows that multiple factors may contribute to shaping population differences. In general, the difference in quality traits between tail feathers cannot be explained by the GBW of feathers. Our results show that the material and structural properties of wing and tail feathers of barn swallows change as a result of aerodynamic forces and sexual selection, although the result of these changes can be contrasting.

Longevity and life history coevolve with oxidative stress in birds

Gerontology is concerned with the evolution of ageing or senes‐ cence, that is, the progressive loss of physiological functions with advanced age, which demographically manifests as decreased re‐ productive and survival rates (Ricklefs, 2008). Life‐history the‐ ory is concerned with the evolution of reproductive and survival rates observed at both the individual and species level (Stearns, 1989). In general, species that feature a slower life‐history strat‐ egy are hypothesized to invest more into self‐maintenance at the expense of reproduction and hence show delayed ageing. On the other hand, reproduction is suggested to take precedence over self‐maintenance in those species that exhibit a faster pace‐ of‐life (Promislow & Harvey, 1990). Consequently, life‐history theory is intertwined with ageing theories. Indeed, life‐history pace and ageing rate appear to have coevolved among free‐liv‐ ing species (Lemaître et al., 2015). However, what physiological mechanisms govern variation in lifespan (gerontology perspec‐ tive) and underpin the inverse relationship between reproduction and survival rates (life‐history theory perspective) remain central questions both on cross‐individual and cross‐species levels (Flatt & Schmidt, 2009). Received: 21 September 2017 | Revised: 25 September 2018 | Accepted: 30 September 2018 DOI: 10.1111/1365-2435.13228

How feathered are birds? Environment predicts both the mass and density of body feathers

1.Studies modelling heat transfer of bird plumage design suggest that insulative properties can be attributed to the density and structure of the downy layer, whereas waterproofing is the result of the outer layer, comprised of contour feathers. In this study, we test how habitat and thermal condition affect feather mass and density of body feathers (contour, semiplume and downy feathers) measured on the ventral and dorsal sides of the body, using a phylogenetic comparative analysis of 152 bird species.2.Our results demonstrate that feather mass and the density of downy feathers are higher in species that inhabit colder environments, whereas total feather density is higher of species breeding under intermediate temperatures compared to the ones breeding under more extreme conditions. The density of contour feathers, depending on the body region, is either quadratically related or negatively correlated with minimum winter temperature.3.The density of contour and downy feathers, measured on both sides of the body, is higher in aquatic than in terrestrial birds. However, among the former, diving behaviour does not select for further increases in body feather mass or density.4.The results of this study provides key insights into how the plumage of birds is adapted to different environments and lifestyles and provides a basis for understanding the diverse range and the evolution of variation in these characteristics. (Less)