Great reed warbler Acrocephalus arundinaceus and reed warbler Acrocephalus scirpaceus respond differently to cuckoo dummy at the nest

A cuckoo Cuculus canorus dummy was exposed at 24 nests of great reed warbler Acrocephalus arundinaceus (GRW) and 34 nests of reed warbler Acrocephalus scirpaceus (RW) during the egg-laying stage. The eight GRW pairs attacked the cuckoo directly, striking the dummy, but such a behaviour was not recorded in RWs. Also, other behavioural measures (closest distance from the model, duration of distress calls and number of excitement calls) indicated a lower level of defence by RWs compared to GRWs. In the study area, the parasitism rate was much lower in GRWs (1.7% of nests) than in RWs (11.3%). We suggest that one of the reasons for the lower level of cuckoo parasitism on GRWs is its stronger nest defence and hence higher risk of injury or even death for the cuckoo during egg dumping.     

Temporal patterns of occurrence and transmission of the blood parasite Haemoproteus payevskyi in the great reed warbler Acrocephalus arundinaceus

We studied the prevalence and intensity of the haemosporidian blood parasite Haemoproteus payevskyi in great reed warblers at Lake Kvismaren (6 years) and Lake Segersj? (3 years) in Sweden. Based on microscopic inspection of slides from 282 adult birds, 20.6% showed infection of H. payevskyi in circulating red blood cells in at least 1 year. For parasite prevalence, there was no difference between years, sex, and age classes. However, parasite intensity was higher in females than in males, and this was most pronounced in 1-year-old birds. Individuals scored to carry parasites in year _n were more likely to show parasite infection year _n + 1 than birds scored to be parasite-free in year _n . None of 99 juvenile birds examined at the breeding site in late summer, 4–9 weeks after hatching, showed infection of H. payevskyi. Parasite intensity in infected adult birds decreased in the course of the breeding season and no new or relapse infections were observed during this period. Thus, our data imply that in the great reed warbler, a long-distance migrant to tropical Africa, transmission of H. payevskyi occurs on wintering sites or at stopover sites during migration.     

Philopatry analysis of the great reed warbler (Acrocephalus arundinaceus) based on ringing data in Europe

Ringing databases of the EURING Data Bank and the Hungarian Bird Ringing Centre were analysed in order to investigate the philopatry of the great reed warbler (Acrocephalus arundinaceus) in three European regions. The aim of the study was to find out if there are continent-scale geographic trends in philopatry with respect to the age of the birds. Three clusters were assigned according to their geographic positions: (i) southern part of Europe (Region 1: between 36°–43° latitudes), (ii) middle part of Europe (Region 2: between 43°–49° latitudes) and (iii) northern part of Europe, (Region 3: between 49°–56° latitudes). No significant differences were found between the natal and breeding philopatry in any Regions, except Region 3. The birds ringed as adults in Region 3 were less faithful to their breeding site than those of the other two regions. Natal philopatry of juveniles did not differ between Region 1 and Region 2, but both of them differed in this respect from Region 3. A method for choosing appropriate breeding periods in philopatry studies is also proposed.     

Host nest defense against a color-dimorphic brood parasite: great reed warblers (Acrocephalus arundinaceus) versus common cuckoos (Cuculus canorus)

We tested great reed warbler (Acrocephalus arundinaceus) discrimination against two common cuckoo (Cuculus canorus) female color morphs (gray and rufous) in two areas with different parasitism rates and proportions of the two morphs. Hosts recognized the two cuckoo morphs from a control, the feral pigeon (Columba livia), at Apaj, Hungary (where brood parasitism was heavy), whereas no significant differences among the models were recorded at Lužice, Czech Republic (where the parasitism rate was moderate). At Apaj, the hosts discriminated the rufous morph (which is slightly predominant there) better than the gray morph from the control. Between-site comparison (after controlling for background aggression) revealed that great reed warblers were more aggressive towards the rufous morph at Apaj than at Lužice, whereas their responses to the gray morph did not differ, corresponding with much higher between-site difference in the relative abundance of the rufous morph. Our results suggest that both local parasitism pressure and relative abundance of two female color morphs of a brood parasite may significantly influence host nest defenses.     

Variation in extra-pair paternity in the polygynous Great Reed Warbler (Acrocephalus arundinaceus)

Summary In five years (1992, 1994–97) we measured the frequency of extra-pair paternity (EPP) in a Bavarian population of polygynous Great Reed Warblers (Fränkische Weiher region: 49°40'N, 10°51'E); these data were compared with corresponding findings in Sweden. Progeny from copulations with a male other than the partner (extra-pair young, EPY) were identified by multi-locus DNA fingerprinting with oligonucleotide probes. In 48 broods with 194 nestlings we found 19 EPY in 5 broods. The extra-pair fertilisation (EPF) rate as a percentage of total juveniles (9.8%) is higher, but that with reference to nests (10.4%) is only insignificantly higher than in Sweden.In contrast to Sweden, neighbour males in our population were never involved in EPF. For two EPF nests the genetic fathers of the EPY were identified; both were unpaired males several years old, with very distant territories (2.4 km away). Both had larger song repertoires than the pair males, and one sang a Great Reed Warbler x Reed Warbler (Acrocephalus scirpaceus) mixed song. In the other cases we were unable to detect the genetic father, either among the neighbouring males or the others tested. Presumably these EPY spring from floater males or rapid mate switching. As in Sweden, EPY were observed in nests of monogamous (2x) as well as polygynous (3x primary females) males. However, in Germany the breeding density was lower and distribution more patchy and the EPF broods were produced earlier (before the median egg-laying date) than those in Sweden. Our comparison supports the hypothesis that the EPF rate is higher in populations with greater genetic variability than in those with less variability. The relatively low EPP rate in this species seems to be due to a close correlation between male and territory characteristics.

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Variation in der Häufigkeit von Fremdvaterschaften beim polygynen Drosselrohrsänger (Acrocephalus arundinaceus)

Zusammenfassung In 5 Jahren (1992, 1994–97) bestimmten wir die Häufigkeit von Fremdvaterschaften beim polygynen Drosselrohrsänger in einer bayerischen Population (Fränkisches Weihergebiet 49°40'N, 10°51'E) und verglichen sie mit entsprechenden Ergebnissen aus Schweden. Nachkommen aus Kopulationen außerhalb des Paarbundes (Fremdjunge, EPY) ermittelten wir mit Multi-locus-DNA-Fingerprinting über Oligonucleotidsonden in 48 Bruten mit 194 Nestlingen. Wir fanden 19 EPY in 5 Bruten. Die Rate an Fremdvaterschaften bezogen auf Jungvögel (9,8%) ist signifikant größer als in Schweden, jedoch nicht diejenige bezogen auf Nester (10,4%).Im Gegensatz zu Schweden waren in unserer Population nie Nachbarmännchen Väter von Fremdjungen. In 2 Nestern konnten die genetischen Väter der EPY gefunden werden. In beiden Fällen handelt es sich um unverpaarte mehrjährige Männchen, die in größerer Entfernung (2,4 km) Reviere hielten. Beide hatten größere Gesangsrepertoires als die Paarmännchen; eines war ein Drosselrohr- x Teichrohrsänger (Acrocephalus scirpaceus)-Mischsänger. In den anderen Fällen konnten wir weder unter den Nachbarmännchen noch unter den anderen überprüften Männchen die genetischen Väter ausfindig machen. Vermutlich sind diese EPY auf Floater-Männchen oder rapid mate switching zurückzuführen.Fremdjunge wurden wie in Schweden sowohl in Nestern von monogam (2x) als auch polygyn verpaarten Männchen (3x Erstweibchen) festgestellt. Im Gegensatz zu den Verhältnissen in Schweden ist die Brutdichte in Deutschland geringer, die Brutverteilung mehr lückenhaft und die EPF-Bruten lagen früher (vor dem Median der Eiablage). Unser Vergleich stützt auch die Hypothese, dass in Populationen mit größerer genetischer Variabilität die Rate von Fremdvaterschaften höher sein sollte als in Populationen mit geringer.Die enge Korrelation zwischen Männchen- und Reviermerkmalen scheint dafür verantwortlich, dass bei dieser Art die Rate von Fremdvaterschaften nicht sehr hoch, d. h. kleiner als das Mittel von polygynen Arten ist.

     

Repertoire size, sexual selection, and offspring viability in the great reed warbler: changing patterns in space and time

Only a few studies have focussed on the consistency of sexualselection patterns in space and time. One such case is the greatreed warbler (Acrocephalus arundinaceus), for which studiesin Germany in 1981–1982 and Sweden in 1987–1991strongly suggested that the size of a male's song repertoirewas the target of mate choice and sexual selection. Studyingthe same German population once again in 1994–2000, weinvestigated the consistency of these patterns over time aswell as between populations. Our reanalysis of the data from1981–1982 shows that male repertoire size was positivelycorrelated with male pairing success (harem size) and with clutchsize (adjusted for seasonal effects), whereas no such correlationswere found during 1994–2000 in the same population. Wesuggest that the earlier correlations were probably caused indirectlyby covariation with territory quality, and that a decline inpopulation size has changed the role of territory quality. Inthe Swedish population, an earlier study found a striking correlationbetween the size of a male's repertoire and the viability ofits offspring, suggesting good-gene effects. In contrast, wefound no such correlation in the German population, neitherin 1981–1982 nor in 1994–2000. We conclude thatrepertoire size does not seem to be a very reliable indicatorof variation in male quality. Interestingly, the analysis ofdata from 1994–2000 showed that male pairing success wasstrongly correlated with measures of strophe length and immediateversatility, traits that have been found to reflect male longevity.Future studies will have to show whether these performance-relatedtraits are more powerful indicators of male quality than isrepertoire size.     

Sex-specific fledgling success and brood sex ratio in the Great Reed Warbler (Acrocephalus arundinaceus)

We examine sex ratio variation and sex-specific probability of successful fledgling in relation to hatching date across 376 broods of Great Reed Warblers (Acrocephalus arundinaceus). The sex ratio of complete broods as well as broods with partial mortality did not deviate significantly from parity (0.5 and 0.53, respectively). Variation in sex ratio between broods was not larger than expected from binomial distribution, thus females seem not to manipulate the sex ratio of their broods in the studied population. As a consequence, sex ratio did not vary in relation to hatching date, years and fishponds. Female offspring showed lower fledgling success than their brothers, but the relationship between probability of successful fledgling and hatching date differed between sexes. Fledgling success of female offspring declined with hatching date more strongly than the success of male offspring. Thus, our study shows that Great Reed Warblers do not adjust offspring sex to match observed seasonal sex-specific variation in survival.     

Factors affecting facultative polygyny and breeding results in the Great Reed Warbler (Acrocephalus arundinaceus)

Summary In a population of Great Reed Warbler (42–53 stationary males) the sex ratio was balanced and occurence of polygynous males (on average 15 % of the males) was more or less compensated by respective number of unmated males. Prospective polygynists arrived earlier in spring on average than monogamists, and got the first female quicker. Their territories were larger (statistically insignificant) and more often situated close to good foraging grounds. The reeds around primary female nests were on average thicker (and taller) and not so dense as in the case of monogamous, secondary and tertiary females. The intensity of nestling feeding (no. of visits per nestling per hour) was higher in the nests of monogamous females, than in primary females, and lowest in secondary and tertiary females nests. Nestlings in secondary and tertiary female broods were on average lighter than in monogamous and primary female broods. The male helped feed nestlings in secondary female nest only exceptionally. In monogamous situation their share in feeding was ca. 50%, and less so in primary female nests. Production of fledglings per female was highest in primary females and lowest in secondary and tertiary females, mainly due to the high starvation rate in the nests of secondary and tertiary females. Generally, collected data strongly suggest that female choice is determined by territory quality, and polygyny threshold hypothesis cannot be rejected. The deception hypothesis cannot be rejected as well in some observed special situations (disruptive territories or polyterritoriality; four cases).

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Voraussetzungen für fakultative Polygynie beim Drosselrohrsänger (Acrocephalus arundinaceus)

Zusammenfassung Das Geschlechterverhältnis in der untersuchten Drosselrohrsänger-Population von 42 bis 53 war ausgeglichen. Das Auftreten polygyner (durchschnittlich 15 % der ) wurde mehr oder weniger durch eine entsprechende Anzahl unverpaarter kompensiert. Prospektiv polygyne kamen durchschnittlich früher an als monogame und waren schneller verpaart. Ihre Reviere waren (statistisch nicht signifikant) größer und lagen näher zu günstigen Nahrungsgebieten. Das Schilf in der Nähe der Nester von Erst- war durchschnittlich dicker (und höher) als und nicht so dicht wie bei Einzel- oder Zweit- und Dritt- . Die Fütterungsfrequenz der Nestlinge (Anzahl der Besuche beider Altvögel mit Futter pro Nestling pro Stunde) war bei Nestern von Einzel- höher als bei Erst- und am niedrigsten bei Nestern von Zweit- und Dritt-. Nestlinge von Zweit- und Dritt- waren durchschnittlich leichter als solche von Einzel-und Erst- . halfen nur ausnahmsweise bei der Fütterung von Nestlingen von Zweit- . Bei monogamen Paaren beteiligten sich die ungefähr zur Hälfte an der Fütterung der Nestlinge, bei Nestern von Erst- in geringerem Umfang. Der Ausfliegeerfolg war am höchsten beim Erst- und am niedrigsten bei Zweit- und Dritt- , hauptsächlich bedingt durch Verhungern der Nestlinge. Allgemein legen die Daten nahe, da\ die die nach der Revierqualität auswählen und daß das Polygynieschwellenmodell vonOrians undVerner nicht abgelehnt werden kann. Einige Beobachtungen stützen die Hypothese, daß in bestimmten Situationen (unübersichtliche Reviere, Polyterritorialität) durch Täuschung polygyn werden.

     

Establishment and maintenance of the breeding territory in the polygynous great reed warbler

Settlement of male great reed warblers in the breeding ground was highly asynchronous at Lake Biwa in Japan. It took over 1 month from the appearance of the first male to a saturation in number of males. In resource-defense-polygyny, males are expected to try to defend as large an area as possible in the optimal habitat. In fact, a small number of the earliest settling males divided up the breeding ground almost completely as territories among themselves and these were later reduced in size with the addition of later settlers. The reduction was not due to a seasonal decline of aggressiveness on the part of the owners but to a higher level of intrusion pressure by later arriving males. The neighbor-neighbor relationship, once established, was rather stable. Home range overlap was small and territorial contacts were few between neighbors. Territorial boundaries seem not to shift despite the addition of new males as long as the neighbors were the same. The stable relationships between neighbors are expected to help the earlier resident to maintain his large and good territories throughout the breeding season and hence polygyny is favored in this species.     

Breeding in the monsoon: semi-annual reproduction in the Seychelles warbler ( Acrocephalus sechellensis )

Despite the absence of pronounced changes in day length, there is considerable climatological seasonality in the tropics. Its expression can be complex like in the monsoon climate of the Indian Ocean Islands. The land mass distribution on both sides of the equator leads to seasonal changes in prevailing wind direction and seasonal patterns in food supply, which are distinct between different coasts. Here we assess that territory quality of the Seychelles warbler, endemic to the small island of Cousin peaks during the South East monsoon (April to September) in most of the island. The Southeastern wind-exposed side is exceptional by being generally poor and having slightly increased food supply in the opposite season (NW monsoon; October to March). In response, the warblers in most territories breed primarily during the SE season, while on the SE shores they tend to breed in both seasons. The result is a semi-annual periodicity in breeding. Individual pairs can breed in 6 months intervals. In the poorer territories on the SE shore most of them indeed do this, while in the richer central habitats most pairs restrict themselves to the best (SE) season. The frequency of breeding thereby increases with territory quality in the SE season, and decreases with quality in the NW season. Withholding from breeding in the NW season despite the high food supply may have long-term advantages for the birds occupying the richer habitat. Such flexible adjustment of seasonality to local circumstances requires not only an immediate response mechanism but also access to accurate information about time of year. The subtle sensitivity of tropical songbirds to photoperiod, demonstrated so convincingly by Eberhard Gwinner (Biological rhythms, Hokkaido University Press, Sapporo, pp19–40, 2005), may well have profound adaptive meaning in taking temporally optimized reproductive decisions in response to both food and time of year.

Low frequency of extrapair paternity in the polygynous great reed warbler, Acrocephalus arundinaceus

We carried out DNA fingerprinting on 553 young (130 broods)great reed warblers (Acrocephalus arundnaceus) in 1987–1991.In the study population, where 40% of the males become polygynous,there was a low frequency of extrapair fertilizations (EPF).When data from all five years were pooled, 3.1% of the youngwere sired by extrapair males (EPF-males) and 5.4% of the broodscontained extrapair young. We found no cases of extrapair maternity;young with 6–17 mismatched DNA bands (n= 17) had highband sharing with their putative mothers (range = 0.52–0.72)but low band sharing with their putative fathers (range = 0.24–0.40).In broods exposed to EPF, on average 53% of the young were siredby EPF-males. We found the genetic father to each of the illegitimateyoung. In all cases the same EPF-male sired all extrapair youngin a brood. Broods containing EPF-young tended to be initiatedlate during the breeding season. Breeding attempts were ratherevenly distributed over two months, thus this breeding asynchronywould have facilitated EPFs. There was no difference in EPFfrequency between broods where the pair males had left theirfemales unguarded during parts of their fertile periods andbroods where males guarded throughout the fertile periods. Nestswith extrapair young had significantly shorter mean distanceto the closest male neighbor and more male neighbors within100 m than nests without extrapair young. We found no indicationthat females engaged in EPF to get parental care from the EPF-males,or because they were forced to copulate with extrapair males.The low frequency of EPF suggested that females did not seekgenetic diversity to their brood. We cannot rule out the possibilitythat females engaged in EPF to insure fertility. However, datasupporting this hypothesis were weak. Instead, our data supportthe conclusion that females engaged in EPF to increase the geneticquality of their offspring, and that females may have used malesong repertoire size as a cue when choosing EPF partners.     

First data on complete summer moult in the Great Reed Warbler (Acrocephalus arundinaceus) in northern Italy

Summary Complete summer moult in the Great Reed Warbler (Acrocephalus a. arundinaceus) is a rare phenomenon, and only two cases have so far been reported for Europe. In 5 years of summer ringing in Val Campotto, Northern Italy, 12 different individuals were found in complete moult. Only the two innermost primaries are generally renewed, with more advanced stages of moult involving up to 6 primaries, the tertials and the first secondaries. A single bird controlled in three subsequent years was always found at a similar degree of primary moult.     

Known and predicted African winter distributions and habitat use of the endangered Basra reed warbler ( Acrocephalus griseldis) and the near-threatened cinereous bunting ( Emberiza cineracea)

The Basra reed warbler (Acrocephalus griseldis) and the cinereous bunting (Emberiza cineracea) are the only two Western Palearctic passerine bird species that overwinter in East Africa and are classified by BirdLife International as endangered and near-threatened, respectively. To refine the African wintering ranges of these two species, we made an effort to collect as much distributional data as possible. We then used the available point-locality data to predict the wintering distributions using a Geographic Information Systems (GIS) based inductive modelling technique called BIOCLIM. For this purpose, we developed four environmental GIS layers that are presumed to reflect the environmental preferences of migrant birds. Our data showed that the known winter distribution of the Basra reed warbler was concentrated in Kenya, Tanzania, Malawi and Mozambique, where it was usually found in dense vegetation growing in coastal scrub, woodland thickets, swamps, marshes, flooded pools and grasslands, and along ditches and edges of rivers, ponds, lagoons and lakes. The predicted winter distribution of this species includes most of East Africa but, given the habitat preferences of this species, is probably limited to low-lying areas near the coastline. The known winter distribution of the cinereous bunting is so far limited to Eritrea, where the species has been observed in October, November, February and March, in sparsely vegetated, sandy or rocky habitats on coastal plains and deserts. The predicted winter distribution of this species includes the plains and hills along the Red Sea coasts in southern Egypt, Sudan, Eritrea, Ethiopia and Sudan, as well as a few inland areas in Sudan, Ethiopia and Kenya.Communicated by F. Bairlein     

Restricted dispersal in a long-distance migrant bird with patchy distribution,the great reed warbler

In patchily distributed species dispersal connects local populations into metapopulations. Reliable quantifications of dispersal are therefore crucial to understanding the population dynamics and genetic structure of such metapopulation systems. The great reed warbler (Acrocephalus arundinaceus) inhabits eutrophic lakes and has a patchy breeding distribution. In this study we investigated the dispersal pattern of the great reed warbler based on an extensive capture-recapture effort covering a large census area (22,500 km²). At two adjacent breeding sites (10 km apart) in southern Central Sweden, the "main study area", we ringed the majority of adult and nestling great reed warblers between 1992 and 1999. In 1998 and 1999, we opportunistically searched for territorial males at the majority of the Swedish breeding sites, and were able to examine about 56% of all males in the region. Analyses of recaptured males demonstrated that philopatry predominated. Sixty-nine percent of the recruiting nestlings returned to breed in the main study area (their natal area), and 92% of the resighted adults were found at the same breeding locality in both study years. Breeding dispersal was significantly more restricted than natal dispersal. Additional data on natal and breeding dispersal within the main study area in 1992-1999 suggested that females were as philopatric as males. The overall high level of philopatry, with only occasional longer dispersal distances documented, yielded a root-mean-square dispersal distance of 33 km per generation. High philopatry, short dispersal distances and similar dispersal patterns of male and female great reed warblers contrast the findings among birds in general, but conform to data of species having patchy breeding habitat and isolated populations. Restricted dispersal suggests limited gene flow even among several Swedish populations, which is in line with some previous findings of the population ecology of the great reed warbler: (1) structured mtDNA lineages among European populations; (2) small-scale population differences in song patterns; and (3) low genetic variation and occurrence of inbreeding depression in our main study population.     

Polymorphism and transcription of Mhc class I genes in a passerine bird, the great reed warbler

 The class I genes of the major histocompatibility complex (Mhc) are here investigated for the first time in a passerine bird. The great reed warbler is a rare species in Sweden with a few semi-isolated populations. Yet, we found extensive Mhc class I variation in the study population. The variable exon 3, corresponding to the α₂ domain, was amplified from genomic DNA with degenerated primers. Seven different genomic class I sequences were detected in a single individual. One of the sequences had a deletion leading to a shift in the reading frame, indicating that it was not a functional gene. A randomly selected clone was used as a probe for restriction fragment length polymorphism (RFLP) studies in combination with the restriction enzyme Pvu II. The RFLP pattern was complex with 21–25 RFLP fragments per individual and extensive variation. Forty-nine RFLP genotypes were detected in 55 tested individuals. To study the number of transcribed genes, we isolated 14 Mhc class I clones from a cDNA library from a single individual. We found eight different sequences of four different lengths (1.3–2.2 kilobases), suggesting there are at least four transcribed loci. The number of nonsynonymous substitutions (d _N ) in the peptide binding region of exon 3 were higher than the number of synonymous substitutions (d _S ), indicating balancing selection in this region. The number of transcribed genes and the numerous RFLP fragments found so far suggest that the great reed warbler does not have a "minimal essential Mhc" as has been suggested for the chicken. Received: 13 May 1998 / Revised: 18 August 1998     

Cross‐continental migratory connectivity and spatiotemporal migratory patterns in the great reed warbler

Migratory connectivity describes to which degree different breeding populations have distinct (non‐overlapping) non‐breeding sites. Uncovering the level of migratory connectivity is crucial for effective conservation actions and for understanding of the evolution of local adaptations and migratory routes. Here we investigate migration patterns in a passerine bird, the great reed warbler Acrocephalus arundinaceus, over its wide Western Palearctic breeding range using geolocators from Spain, Sweden, Czech Republic, Bulgaria and Turkey. We found moderate migratory connectivity: a highly significant spatial structure in the connections between breeding and sub‐Saharan non‐breeding grounds, but at the same time a partial overlap between individual populations, particularly along the Gulf of Guinea where the majority of birds from the Spanish, Swedish and Czech populations spent their non‐breeding period. The post‐breeding migration routes were similar in direction and rather parallel for the five populations. Birds from Turkey showed the most distinctive migratory routes and sub‐Saharan non‐breeding range, with a post‐breeding migration to east Africa and, together with birds from Bulgaria, a previously unknown pre‐breeding migration over the Arabian Peninsula indicating counter‐clockwise loop migration. The distances between breeding and sub‐Saharan non‐breeding sites, as well as between first and final sub‐Saharan non‐breeding sites, differed among populations. However, the total speed of migration did not differ significantly between populations; neither during post‐breeding migration in autumn, nor pre‐breeding migration in spring. There was also no significant relationship between the total speed of migration and distance between breeding and non‐breeding sites (neither post‐ nor pre‐breeding) and, surprisingly, the total speed of migration generally did not differ significantly between post‐breeding and pre‐breeding migration. Future challenges include understanding whether non‐breeding environmental conditions may have influenced the differences in migratory patterns that we observed between populations, and to which extent non‐breeding habitat fluctuations and loss may affect population sizes of migrants.     

Age-related changes in song repertoire size and song type sharing in the Whinchat Saxicola rubetra

In many oscine passerines males’ songs, the repertoire size increases with age. At the same time it often remains unknown when and where males learn new songs. To infer the Whinchat Saxicola rubetra song learning strategy, we described and catalogued song-type repertoire, revealed age differences and examined song sharing strategies among neighbouring and distant males. We recorded song vocalizations of 40 males in a limited (104 ha) study plot during four years. Whinchats produce short and discrete songs with clear intersong pauses. In total 45 song types were allocated, the individual repertoire size averaged 23.5 ± 7.6 song types (range 9–34 song types). The males’ age significantly influenced the song-type repertoire size. The second calendar year (first breeding) males had a lower repertoire size than the older males. The majority of song types were shared by less than half of males in our sample. The Jaccard similarity indexes varied from 0.5 to 0.7. We could not find a relationship between males’ song sharing and geographic distances between their nests. We assume that Whinchat males learned new songs in the local population before territory establishment.     

Dynamics of parasitemia of malaria parasites in a naturally and experimentally infected migratory songbird, the great reed warbler Acrocephalus arundinaceus

Little is known about the development of infection of malaria parasites of the genus Plasmodium in wild birds. We used qPCR, targeting specific mitochondrial lineages of Plasmodium ashfordi (GRW2) and Plasmodium relictum (GRW4), to monitor changes in intensities of parasitemia in captive great reed warblers Acrocephalus arundinaceus from summer to spring. The study involved both naturally infected adults and experimentally infected juveniles. The experiment demonstrated that P. ashfordi and P. relictum lineages differ substantially in several life-history traits (e.g. prepatent period and dynamics of parasitemia) and that individual hosts show substantial differences in responses to these infections. The intensity of parasitemia of lineages in mixed infections co-varied positively, suggesting a control mechanism by the host that is general across the parasite lineages. The intensity of parasitemia for individual hosts was highly repeatable suggesting variation between the host individuals in their genetic or acquired control of the infections. In future studies, care must be taken to avoid mixed infections in wild caught donors, and when possible use mosquitoes for the experiments as inoculation of infectious blood ignores important initial stages of the contact between the bird and the parasite.