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ABSTRACT: Carry-over effects take place when events occurring in one season influence individual performance in a subsequent season. Blood parasites (e.g. Plasmodium and Haemoproteus) have strong negative effects on the body condition of their hosts and could slow the rate of feather growth on the wintering grounds. In turn, these winter moult costs could reduce reproductive success in the following breeding season. In house martins Delichon urbica captured and studied at a breeding site in Europe, we used ptilochronology to measure growth rate of tail feathers moulted on the winter range in Africa, and assessed infection status of blood parasites transmitted on the wintering grounds. We found a negative association between haemosporidian parasite infection status and inferred growth rate of tail feathers. A low feather growth rate and blood parasite infections were related to a delay in laying date in their European breeding quarters. In addition, clutch size and the number of fledglings were negatively related to a delayed laying date and blood parasite infection. These results stress the importance of blood parasites and feather growth rate as potentially mechanisms driving carry-over effects to explain fitness differences in wild populations of migratory birds.
Oecologia 09/2012; · 3.41 Impact Factor
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ABSTRACT: Dispersal is an important factor that determines the degree of gene flow and, hence, the degree of differentiation among populations.
Using two long-term datasets on natal philopatry and short-distance dispersal in barn swallows Hirundo rustica from Denmark and Spain, we evaluated the fitness costs and benefits and test a number of predictions about the functional
significance of dispersal. The proportion of philopatric individuals was more than six times larger in Spain than in Denmark,
with a higher rate of philopatry in males than in females. Dispersal propensity decreased in both populations during the course
of the study. Males from the more philopatric Spanish population lived longer when philopatric rather than dispersing while
that was not the case for either sex of the less philopatric Danish population. There were large differences in dispersal
propensity among cohorts and breeding sites, suggesting that sites differed in their suitability as sites for immigrants.
We found no evidence consistent with the mate competition hypothesis suggesting that males in better condition or with larger
condition-dependent secondary sexual characters were more likely to be philopatric. These findings suggest that there is a
high degree of intraspecific variation in dispersal propensity between populations, probably relating to local differences
in costs and benefits of philopatry and dispersal.
Behavioral Ecology and Sociobiology 04/2012; 63(8):1197-1205. · 3.18 Impact Factor
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ABSTRACT: Immune responses constitute a major way for hosts to defend themselves against parasites. Because hosts do not habitually
produce strong responses all the time, immune responses might be costly to produce or maintain. We tested experimentally if
the production of a response to a challenge with a novel antigen resulted in a cost in terms of fitness using the highly colonial
house martin Delichon urbica as a model system. We injected adult breeding birds during laying of the first clutch with either Newcastle disease virus
(NDV) or a control injection, and the clutch was subsequently removed to induce relaying. NDV stimulates the non-specific
immune system, causing production of antibodies during a period of more than 2weeks. Accordingly, we found an increase in
leukocyte counts in experimental birds compared to controls. Experimental treatment reduced the frequency of re-laying, caused
a delay in timing of relaying and a reduction in brood size. Quality of nestlings in terms of body size, body mass and T-cell-mediated
immune response did not differ significantly between treatments. Overall, seasonal reproductive success differed significantly
between treatments, showing that the production of an immune response by adult birds is costly in terms of future fecundity.
Behavioral Ecology and Sociobiology 04/2012; 61(10):1573-1580. · 3.18 Impact Factor
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Biological Journal of the Linnean Society 01/2012; 105:420-434. · 2.19 Impact Factor
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Alfonso Marzal,
Robert E Ricklefs,
Gediminas Valkiūnas,
Tamer Albayrak,
Elena Arriero,
Camille Bonneaud,
Gábor A Czirják,
John Ewen,
Olof Hellgren,
Dita Hořáková, [......],
Anders P Møller,
Vaidas Palinauskas,
Péter L Pap,
Javier Pérez-Tris,
Ravinder N M Sehgal,
Manuel Soler,
Eszter Szöllosi,
Helena Westerdahl,
Pavel Zetindjiev,
Staffan Bensch
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ABSTRACT: Invasive species can displace natives, and thus identifying the traits that make aliens successful is crucial for predicting and preventing biodiversity loss. Pathogens may play an important role in the invasive process, facilitating colonization of their hosts in new continents and islands. According to the Novel Weapon Hypothesis, colonizers may out-compete local native species by bringing with them novel pathogens to which native species are not adapted. In contrast, the Enemy Release Hypothesis suggests that flourishing colonizers are successful because they have left their pathogens behind. To assess the role of avian malaria and related haemosporidian parasites in the global spread of a common invasive bird, we examined the prevalence and genetic diversity of haemosporidian parasites (order Haemosporida, genera Plasmodium and Haemoproteus) infecting house sparrows (Passer domesticus). We sampled house sparrows (N = 1820) from 58 locations on 6 continents. All the samples were tested using PCR-based methods; blood films from the PCR-positive birds were examined microscopically to identify parasite species. The results show that haemosporidian parasites in the house sparrows' native range are replaced by species from local host-generalist parasite fauna in the alien environments of North and South America. Furthermore, sparrows in colonized regions displayed a lower diversity and prevalence of parasite infections. Because the house sparrow lost its native parasites when colonizing the American continents, the release from these natural enemies may have facilitated its invasion in the last two centuries. Our findings therefore reject the Novel Weapon Hypothesis and are concordant with the Enemy Release Hypothesis.
PLoS ONE 01/2011; 6(7):e21905. · 4.09 Impact Factor
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ABSTRACT: 1. We studied lifetime arrival patterns in the barn swallow (Hirundo rustica L.) in relation to variation in ecological conditions, as reflected by the normalized difference vegetation index (NDVI) in the Sub-Saharan winter quarters and at stopover sites in North Africa. 2. Migratory birds have recently advanced their arrival dates, but the relative role of microevolution and phenotypic plasticity as mechanisms of response to changing environmental conditions remains unknown. To distinguish between these two possibilities, we investigated the change in the arrival date using cross-sectional and longitudinal analyses. 3. We predicted that the effect (i.e. slopes) of environmental conditions in stopover or winter areas on arrival date should be similar using cross-sectional and longitudinal analyses in case phenotypic plasticity is the underlying mechanism, or they should differ in case microevolution is the mechanism. 4. As expected according to a previous cross-sectional study, we found an advance in the arrival date when ecological conditions improve in stopover areas and a delay in the arrival date when ecological conditions improve in the winter quarters. 5. Change in the arrival time at the breeding grounds due to ecological conditions found en route and, in the winter areas, was mainly due to phenotypic plasticity as shown by similarities in the slopes found in these relationships using cross-sectional and longitudinal analyses. 6. We also investigated sex and age of barns swallows as sources of variation in the arrival time with respect to conditions experienced in winter and stopover areas. We found that earlier arrival at the breeding grounds due to prevailing ecological conditions found en route in North Africa was similar for males and females of all age-classes. In contrast, individuals tended to delay departure when ecological conditions improved in the winter quarters, but this delay differed among age classes, with old individuals delaying departure more than middle-aged and yearling birds. 7. The migratory response of individuals to changing climatic conditions experienced during different parts of their life provides evidence for individuals responding differently to prevailing conditions in the winter quarters depending on their age, but not to conditions experienced en route during spring migration.
Journal of Animal Ecology 07/2009; 78(5):981-9. · 4.94 Impact Factor
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ABSTRACT: Some areas have experienced recent dramatic warming due to climate change, while others have shown no change at all, or even recent cooling. We predicted that patterns of selection on life history would differ between southern and northern European populations of a long-distance migratory bird, the barn swallow Hirundo rustica, because global patterns of weather as reflected by large-scale weather phenomena such as the North Atlantic Oscillation (NAO) and the El Niño-Southern Oscillation (ENSO) have different effects on environmental conditions in different parts of the world frequented during the annual cycle. We investigated relationships between mean arrival date, dispersal rate and yearling survival rate among years, using two long-term population studies in Spain and Denmark. We found evidence of a difference in the effects of normalized difference vegetation index in North and West Africa on mean arrival date of male barn swallows, with the effect differing significantly between populations. Second, there was a significant interaction between ENSO and population on dispersal rate, showing that conditions in Africa during winter differentially affected dispersal in the two populations. Finally, the NAO index in winter had an effect on yearling survival that differed between populations. These findings highlight the divergent patterns of response to climate change among populations, and they suggest that climate change can differentially affect important life history traits with potential implications for maintenance of viable populations and gene flow among populations.
Oecologia 02/2009; 159(4):859-72. · 3.41 Impact Factor
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ABSTRACT: 1. Recent studies suggest that long tail streamers (narrow outermost tail feathers) of the barn swallow Hirundo rustica , Linnaeus have initially evolved purely via natural selection for enhanced manoeuvrability. According to an alternative view, streamers have evolved initially solely via sexual selection for costly signalling, and their slender profile is merely an adaptation reducing the aerodynamic cost of a long tail ornament. 2. In order to distinguish between these alternative hypotheses we performed a standardized flight-maze experiment, in which we imitated the initial elongation of outermost tail feathers in a streamer-less hirundine, the house martin Delichon urbica , Linnaeus, contrasting the effects on flight manoeuvrability from adding either a broad or a narrow piece of feather. 3. 'Narrow-feathered' house martins (which had initial tail streamers modelled on a natural streamer of the barn swallow) manoeuvred better than 'broad-feathered' house martins (which had the natural shape of tips of experimentally elongated outermost tail feathers left unchanged), independent of elongation of the feather. 4. A small elongation of outermost tail feathers did not significantly improve manoeuvrability either in the case of 'narrow-feathered' or 'broad-feathered' birds. 5. These results suggest that it is the slender shape, but not elongation of streamers that is impor-tant for manoeuvrability, and thus streamer elongation is better explained by the sexual-selection than the improved-manoeuvrability hypothesis. We discuss hypothetical scenarios for evolution of hirundine tail streamers.
Functional Ecology 01/2009; 23:389-396. · 4.57 Impact Factor
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Functional Ecology 10/2008; 23(2):389 - 396. · 4.57 Impact Factor
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ABSTRACT: The second and fourth digit length ratio (2D:4D) is sexually dimorphic in many vertebrates. This ratio has been suggested to provide an estimate of steroid levels encountered during prenatal development, which may have organizational consequences for physiology and behavior of adults. However, recent studies showed that the relation between digit ratio and steroids seems inconsistent and may vary among species and populations. We tested the hypothesis that digit ratios would be correlated with the expression of secondary sexual characters, using the barn swallow (Hirundo rustica) as a model system. This was done by testing whether variation in 2D:4D ratio was correlated with tail length and features of song, which are important secondary sexual characters positively correlated with circulating steroid concentration in adult birds. Furthermore, we examined the prediction that male and female digit ratios would correlate with body mass in an antagonistic way. There was no significant sexual dimorphism in digit ratio, which may be due to low levels of sexual selection in this population. Adult right 2D:4D ratio was negatively linked to tail length but not to male song output. Moreover, right 2D:4D ratio was negatively correlated with body mass in male and positively in females. These results are consistent with high digit ratios reflecting low levels of testosterone in this bird species. Copyright 2008, Oxford University Press.
Behavioral Ecology. 01/2008; 19(1):16-21.
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ABSTRACT: 1. We investigated age-related changes in two reproductive traits (laying date and annual fecundity) in barn swallows Hirundo rustica L. using a mixed model approach to di-stinguish among between- and within-individual changes in breeding performance with age. 2. We tested predictions of age-related improvements of competence (i.e. constraint hypothesis) and age-related progressive disappearance of poor-quality breeders (i.e. selection hypothesis) to explain age-related increase in breeding performance in early life. 3. Reproductive success increased in early life, reaching a plateau at middle age (e.g. at 3 years of age) and decreasing at older age (> 4 years). Age-related changes in breeding success were due mainly to an effect of female age. 4. Age of both female and male affected timing of reproduction. Final linear mixed effect models (LME) for laying date included main and quadratic terms for female and male age, suggesting a deterioration in reproductive performance at older age for both males and females. 5. We found evidence supporting the constraints hypothesis that increases in competence within individuals, with ageing being the most probable cause of the observed increase in breeding performance with age in early life. Two mechanisms were implicated: (1) advance in male arrival date with age provided middle-aged males with better access to mates. Yearling males arrived later to the breeding grounds and therefore had limited access to high-quality mates. (2) Breeding pairs maintaining bonds for 2 consecutive years (experienced pairs) had higher fecundity than newly formed inexperienced breeding pairs. 6. There was no support for the selection hypothesis because breeding performance was not correlated with life span. 7. We found a within-individual deterioration in breeding and migratory performance (arrival date) in the oldest age-classes consistent with senescence in these reproductive and migratory traits.
Journal of Animal Ecology 10/2007; 76(5):915-25. · 4.94 Impact Factor
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ABSTRACT: Homeobox genes regulate development of digits, and it has been suggested that the ratio of length of second to length of fourth
digit reflects such genetic effects in a sex-specific manner. We show that digit ratios in the sexually dichromatic house
sparrow Passer domesticus differ between sexes, with males having higher ratios than females, and that individuals produce consistent ratios on the
two feet. If Homeobox or other genes had pleiotropic effects on development of digits, behavior, and physiology of males and
females, we would expect secondary sexual characters and immunity to be related to digit ratio in a sex-specific manner. The
size of the visible part of the black badge in February (a secondary sexual character), but not total badge size, was positively
correlated with digit ratios, suggesting that males with more male-like digit ratios had larger visible badges. Because of
sex-specific effects of development on secondary sexual characters and immunity, we predicted sex-specific differences in
immune response to be related to digit ratio. House sparrows with large digit ratios had weaker T cell-mediated immune response
than individuals with small digit ratios, particularly in females, implying that females with more male-like digit ratios
had weak immune responses. These findings are consistent with the hypothesis that early development, as reflected by digit
ratios, and genetics affect the expression of adult characters that are supposedly strongly contributing to fitness.
Behavioral Ecology and Sociobiology 05/2007; 61(8):1161-1168. · 3.18 Impact Factor
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ABSTRACT: Currently, there is no agreement about the suitability of haematocrit (the proportion of blood volume occupied by packed red blood cells) as a predictor of condition in birds. In order to clarify this point, genetic and environmental components of phenotypic variation for a number of traits were estimated in nestling Barn Swallows Hirundo rustica by means of a partial cross-fostering experiment. The studied traits were haematocrit, two morphological traits used as estimates of condition in birds (body mass and body mass relative to body size) and a morphological trait that presumably is not associated with condition (tarsus length). First, we found that body mass relative to body size was related to haematocrit, supporting the suggestion that haematocrit reflects condition in this species. Secondly, we found that the coefficient of residual (i.e. environmental) variation of haematocrit was larger than that of tarsus length, but smaller than those of body mass or body mass relative to body size. Under the hypothesis that traits closely related to condition (and, ultimately, to fitness) are characterized by large residual variance, these results also suggest that haematocrit is related to condition, but that this relationship must be weak. Therefore, the use of haematocrit as an estimate of condition is not recommended. Finally, heritabilities of the studied traits were calculated, differing significantly from zero only for tarsus length, the trait with the smallest residual variation. However, a consistent pattern in the relationship between heritability and genetic variation was not found.
Ibis 12/2006; 149(1):128 - 134. · 2.43 Impact Factor
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ABSTRACT: Female birds deposit in the yolks of eggs substantial amounts of androgens, such as testosterone and androstenedione. These
androgens have been shown to speed up nestling development, induce a fast development of ornaments and increase dominance
in adults. Experiments in several species have reported that females invest greater amounts of androgens in the eggs fathered
by attractive males, suggesting that yolk androgen is a costly investment for either the offspring or the mother. There is
some evidence that nestling immunocompetence may be partially suppressed by high levels of yolk androgens, but it is not known
whether this is also the case for females. We tested this hypothesis in the house martin by inducing an immune challenge through
an injection of sheep red blood cells, a standard challenge of the humoral immune system. Experimental birds laid eggs with
lower amounts of yolk androstenedione than controls, and there was a similar non-significant trend for testosterone. Furthermore,
the probability of laying a replacement clutch was higher for birds that had laid a first clutch with relatively high levels
of yolk testosterone. These results suggest that yolk androgen deposition is limited by immune costs in the female, and that
only females in good condition may afford to invest high levels of androgen in eggs in this species.
Behavioral Ecology and Sociobiology 04/2006; 60(1):96-100. · 3.18 Impact Factor
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ABSTRACT: A. P. Moller, F. de Lope and N. Saino: Reproduction and migration in relation to senescence in the barn swallow Hirundo rustica: A study of avian 'centenarians'. Senescence reflects the decrease in age-dependent residual reproductive value, and a previous study of a cohort of migratory barn swallows (Hirundo rustica) that had reached advanced ages for this species (at least five years old) provided evidence consistent with senescence such as reduced reproductive performance and increased abundance of parasites. We studied a population of migratory barn swallows over a number of years. Several questions were asked including 1) how do longer lived birds compare to shorter lived individuals of the same species, 2) is there a difference in individuals of the same species that live in different geographical regions, and 3) how do patterns of reproduction change during aging? We compared the phenotypes of 87 individuals from three populations in Denmark, Italy and Spain that had reached at least five years old with those of control individuals matched for sex, arrival date and breeding site. These controls only became one year old, i.e., they were not found thereafter and both groups of individuals were compared in their first year of life. Results showed that there were no significant differences in any of 11 morphological characters or in the abundance of three ectoparasites between the two groups of birds. Females that eventually became very old had relatively smaller first clutches as one year olds than did one year old controls, while males that eventually became very old had mates that laid clutches that were relatively larger than those of controls. Annual fecundity showed a similar pattern, with an increased sex difference in fecundity between birds from Spain than in Italy and in Denmark. Danish barn swallows that achieved older ages had relatively lower haematocrits than control individuals of the same sex, age and arrival date captured at the same site, while the difference in haematocrits between these two categories of individuals was small for Italian birds. Spring arrival date was relatively earlier in Danish males that eventually became very old compared to control males of the same age and tail length (a correlate of fitness) that arrived at the same site, while the two age categories of females did not differ in arrival date. In the Spanish population there was no difference in arrival date between the birds that aged most successfully and controls for either sex. We will discuss these findings in relation to current senescence theories.
Age 12/2005; 27(4):307-318. · 6.28 Impact Factor
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ABSTRACT: Malarial parasites are supposed to have strong negative fitness consequences for their hosts, but relatively little evidence supports this claim due to the difficulty of experimentally testing this. We experimentally reduced levels of infection with the blood parasite Haemoproteus prognei in its host the house martin Delichon urbica, by randomly treating adults with primaquine or a control treatment. Treated birds had significantly fewer parasites than controls. The primaquine treatment increased clutch size by 18%; hatching was 39% higher and fledging 42% higher. There were no effects of treatment on quality of offspring, measured in terms of tarsus length, body mass, haematocrit or T-cell-mediated immune response. These findings demonstrate that malarial parasites can have dramatic effects on clutch size and other demographic variables, potentially influencing the evolution of clutch size, but also the population dynamics of heavily infected populations of birds.
Oecologia 03/2005; 142(4):541-5. · 3.41 Impact Factor
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ABSTRACT: Bird song has been hypothesized to evolve, partly, to signal health status of males, and song features should therefore correlate with parasite load. Immune function, parasitism, and secondary sexual characters can, however, differ between age classes, and any apparent relationship between song and parasite loads can be the result of systematic age effects. We tested for an age-dependent relationship between sexually selected characters and measures of parasitism in a Spanish population of the barn swallow Hirundo rustica. A comparison across age classes revealed that chewing lice load, song duration, mean peak amplitude frequency of songs, and tail length differed significantly between yearlings and adults. In a longitudinal analysis, we found significant evidence for mean peak amplitude frequency of songs, tail length and chewing louse parasitism, and a nonsignificant tendency for song duration to change with age of an individual. We found a significant association between song duration and chewing louse load and between hematocrit and peak amplitude frequency of the rattle, the typical harsh terminal syllable. In tests for associations between song traits and health status, while controlling for age, age and chewing louse load were independently related to song duration. We found a significant relationship between pairing success and song duration, implying that females may use this song trait in their choice of parasite-free males. Although the song of the barn swallow may provide information about both male age and parasite resistance, signaling of health status appears to be independent of age effects, in accordance with the theory of parasite-mediated sexual selection, suggesting that male signals can be used as reliable indicators of parasitism. Copyright 2005.
Behavioral Ecology. 01/2005; 16(3):580-591.
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ABSTRACT: Recent studies have suggested that the proximal part of the swallow (Hirundo rustica) tail streamer appears to aid turning flight, as expected if streamers evolved initially purely through natural selection for enhanced manoeuvrability. However, the evolution of slender aerodynamically advantageous streamers is also predicted by an alternative hypothesis, which suggests that such a trait could develop primarily to ameliorate the aerodynamic cost of a long size-dimorphic tail. To distinguish between these hypotheses, we have investigated for the effect on manoeuvrability of trimming the tips of the outer tail feathers into short streamers, without lengthening these feathers, in two streamerless hirundine species--the house martin (Delichon urbica) and the sand martin (Riparia riparia). This allowed us to examine the aerodynamic costs and benefits of streamers at an early evolutionary stage that predates elongation of the outermost tail feathers through female choice. We showed that such initial streamers enhance manoeuvrability in streamerless hirundines, confirming the findings of recent studies. However, in contrast to these studies, we showed that improved manoeuvrability resulting from streamers could arise before the outermost tail feathers have become elongated (e.g. owing to female choice). The occurrence of such an aerodynamic advantage depends on the ancestral shape of a forked tail. This provides support for the hypothesis that streamers, like those in the barn swallow, might evolve initially purely through natural selection for enhanced manoeuvrability.
Proceedings of the Royal Society B: Biological Sciences 10/2004; 271(1550):1831-8. · 5.41 Impact Factor
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ABSTRACT: Previous studies have shown no significant effect of experimental tail length manipulation in female barn swallows (Hirundo rustica) at the beginning of a breeding season on reproductive success or behavior during that breeding season. In the present study, we investigate if tail length manipulation had any effect on reproductive performance the following year, the so-called long-term effect, in contrast to the short-term effects already studied. We found that females with experimentally elongated external tail feathers at the beginning of a breeding season produced less offspring during the breeding season the following year than did females with shortened or unmanipulated tails. These results suggest that tail elongation caused flight deficiencies that deteriorated the condition of females and eventually reduced reproductive success. The finding of long-term effects but no significant short-term effects for female tail elongation suggests that female barn swallows have the ability to adjust immediate parental investment. Detrimental effects of long tails in females in terms of decreased reproductive success might explain why female tails are not as long as those of males. Finally, females mated to long-tailed (sexually attractive) males decreased their reproductive success the following year more than did females mated to short-tailed males, possibly owing to differential parental effort causing a deterioration of their condition. Copyright 2003.
Behavioral Ecology. 01/2003; 14(4):451-456.
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ABSTRACT: Structural coloration has been hypothesized to play a role in sexual selection, and we tested whether this was the case in a field study of the barn swallow Hirundo rustica. The dorsal iridescent plumage of barn swallows has a strong reflectance in the ultraviolet (UV) region, with adult males on average reflecting 8-9% more than adult females, as revealed by a 2-year study in southwestern Spain. The correlation between structural coloration (described by the reflectance in the UV part of the spectrum, UV chroma and blue chroma) and three other secondary sexual characters significantly associated with male mating success (tail length, tail asymmetry, and red facial coloration) was weak and generally nonsignificant. Nor was there a significant relationship between color parameters and body condition. We tested for an association between structural coloration of the dorsal plumage and sexual selection in a number of independent tests. Arrival date of males was not significantly related to color; there was no significant relationship between coloration and probability of survival or age; mated males did not have stronger reflectance than unmated males; and the duration of the premating period was not significantly related to color. Reproductive success was not significantly correlated with plumage coloration in males, nor was the feeding rate of offspring by brightly colored males higher than that of males with less bright plumage. Given that sample sizes were large, and the power of statistical tests high, we conclude that current sexual selection on the coloration of the dorsal plumage in the barn swallow is, at best, weak. Copyright 2002.
Behavioral Ecology. 01/2002; 13(6):728-736.
