Discovery of ten new specimens of large‐billed reed warbler Acrocephalus orinus,and new insights into its distributional range

We here report the finding of ten new specimens of the poorly known large‐billed reed warbler Acrocephalus orinus. Preliminary identifications were made on the basis of bill, tarsus and claw measurements, and their specific identity was then confirmed by comparison of partial sequences of the cytochrome b gene with a large data set containing nearly all other species in the genus Acrocephalus, including the type specimen of A. orinus. Five of the new specimens were collected in summer in Afghanistan and Kazakhstan, indicating that the species probably breeds in Central Asia, and the data and moult of the others suggest that the species migrates along the Himalayas to winter in N India and SE Asia. The population structure suggests a stable or shrinking population.     

Song in two cryptic species: comparative analysis of Large-billed Reed Warblers Acrocephalus orinus and Blyth’s Reed Warblers Acrocephalus dumetorum

Capsule: Songs of Large-billed Reed Warblers Acrocephalus orinus and Blyth’s Reed Warblers Acrocephalus dumetorum differed in quantitative parameters. Blyth’s Reed Warbler used different modes of singing on breeding grounds and migration stopovers.

Aims: To compare the songs of two cryptic species of reed warblers. To compare Blyth’s Reed Warbler songs in different parts of the breeding range and on migration stopovers in central Asia. To investigate the status of Blyth’s Reed Warblers in central Asia.

Methods: We analysed song recordings of individual singing males and conducted field observations of singing behaviour at migration stopover and breeding sites. The status of Blyth’s Reed Warblers in central Asia was reviewed from the historical Russian literature and other sources.

Results: We found differences between six out of eight variables in songs of Large-billed and Blyth’s Reed Warblers on breeding sites. Blyth’s Reed Warbler songs recorded on migration stopovers showed differences in five variables from Large-billed Reed Warblers and in six variables from breeding Blyth’s Reed Warblers. On migration stopovers, Blyth’s Reed Warblers sang actively but did not stay more than 1–2 days. The evidence suggests that Blyth’s Reed Warbler does not breed in central Asia.

Conclusion: Songs of Large-billed and Blyth’s Reed Warblers could be distinguished by quantitative analysis. Blyth’s Reed Warblers used different modes of singing on breeding sites and migration stopovers. We believe vocalizations of Blyth’s Reed Warblers on migration to be plastic song.     

Breeding phenology,reproductive traits and apparent survival of sympatric Marsh Warbler Acrocephalus palustris and Blyth’s Reed Warbler Acrocephalus dumetorum

Capsule: Sympatric Marsh Warblers Acrocephalus palustris and Blyth’s Reed Warblers Acrocephalus dumetorum differ significantly in their life history traits.

Aims: To provide a direct comparison of demographic parameters among two sympatric populations of the closely related Marsh Warbler and Blyth’s Reed Warbler.

Methods: We examined breeding phenology and reproductive traits at a 25?ha study plot. We use program MARK to estimate daily nest survival and adult apparent survival rates.

Results: On average, Marsh Warblers laid the first eggs 3 days later than Blyth’s Reed Warblers. Mean clutch size in the Marsh Warbler was significantly lower than in the Blyth’s Reed Warbler. There are no significant differences between the two species for nest daily survival, duration of incubation and nestling periods. Apparent survival of adults was slightly higher in Marsh Warblers than in Blyth’s Reed Warblers.

Conclusion: Our findings suggest that two ecologically similar sympatric species differ significantly in terms of life history traits. We assume that observed differences could be the result of adaptations to environmental factors in the central parts of the species’ ranges or due to differences in mortality on migratory pathways or wintering grounds.     

Breeding ecology of the Basra Reed Warbler,Acrocephalus griseldis,in Iraq (Aves: Passeriformes: Acrocephalidae)

The population of the Basra Reed Warbler, Acrocephalus griseldis, which has a limited range confined to the marshlands of central and southern Iraq, has declined substantially due to massive degradation of its main breeding habitat in the Iraqi marshes during the 1980s and 1990s. The breeding habitat and breeding biology is described here. We discovered a remarkable extension of the breeding range in the extreme west of Iraq.     

Identifying the winter grounds of the recently described Barbary Reed Warbler (Acrocephalus baeticatus ambiguus)

The Iberian and North African populations of reed warblers have been described recently as a separate taxon, ambiguus, forming a sister clade to the Sahelian subspecies minor of African Reed Warbler Acrocephalus baeticatus. Although the breeding range of ambiguus has been identified, the migration strategy of its populations remained unknown. We deployed geolocators and sampled the innermost primary from breeding adults in Spain for stable hydrogen (δ²H) analyses and also analysed stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in feathers collected in two reed warbler taxa (Acrocephalus scirpaceus and Acrocephalus baeticatus ambiguus) in Morocco, to identify the moulting and wintering sites of these populations. Ring recoveries, geolocator tracks and probabilistic assignments to origin from δ²H values indicate that Spanish ambiguus are likely to moult south of the Sahara and winter in West Africa, probably from Mauretania to southern Mali and Ivory Coast. Moroccan ambiguus, however, undergo post-breeding moult north of the Sahara, and possibly then migrate to West Africa. With other populations of ambiguus breeding from Algeria to Libya and probably wintering further east in the Sahelian belt, the Barbary Reed Warbler can therefore be considered a trans-Saharan migrant, with a post-breeding moult strategy that varies between populations, and probably structured according to breeding latitude.     

The use and function of snake skins in the nests of Great Reed Warblers Acrocephalus arundinaceus

We documented and experimentally tested the use of snake skins in construction of nests in a Great Reed Warbler Acrocephalus arundinaceus population in southwestern Slovakia. There was no difference in predation rates of artificial nests that did or did not contain sloughs. We suggest that snake skins in Great Reed Warbler nests may serve as a post‐pairing signal revealing female parental quality.     

Stable isotope ratios in winter‐grown feathers of Great Reed Warblers Acrocephalus arundinaceus,Clamorous Reed Warblers A. stentoreus and their hybrids in a sympatric breeding population in Kazakhstan

Analyses of the stable isotope composition of feathers can provide significant insight into the spatial structure of bird migration. We collected feathers from Great Reed Warblers Acrocephalus arundinaceus, Clamorous Reed Warblers A. stentoreus and a small sample of their hybrids in a sympatric breeding population in Kazakhstan to assess natural variation in stable isotope signatures and delineate wintering sites. The Great Reed Warbler is a long‐distance migrant that overwinters in sub‐Saharan Africa, whereas the Clamorous Reed Warbler performs a short‐distance migration to the Indian sub‐continent. Carbon (δ¹³C), nitrogen (δ¹⁵N) and deuterium (δD) isotope signatures were obtained from winter‐grown feathers of adult birds. There were highly significant differences in δD and less significant differences in δ¹³C between Great and Clamorous Reed Warblers. Thus, our results show that the stable isotope technique, and in particular the deuterium (δD) signal, resolves continental variation in winter distribution between these closely related Acrocephalus species with sympatric natal origin. The isotope signatures of hybrid Great × Clamorous Reed Warblers clustered with those of the Great Reed Warblers. Hence, a parsimonious suggestion is that the hybrids undergo moult in Afrotropical wintering grounds, as do the Great Reed Warblers. The observed δD values fell within the range of expected values based on available precipitation data collected at precipitation stations across the wintering continents of each species. However, the power to predict the winter origin of birds in our study system using these data was weak as the expected values ranged widely at this broad continental scale.     

A wild Marsh Warbler?×?Sedge Warbler hybrid (Acrocephalus palustris?×?A. schoenobaenus) in Norway documented with molecular markers

We present photographic and molecular evidence of a wild Marsh Warbler × Sedge Warbler (Acrocephalus palustris × A. schoenobaenus) hybrid that occurred over three breeding seasons (2007–2009) near Trondheim, Central Norway. The bird had the appearance of a Marsh Warbler but with some typical Sedge Warbler plumage traits. DNA analyses of a few plucked body feathers, using the COI barcode region (mtDNA) and conserved microsatellite loci, confirmed that the bird was a hybrid, with a Marsh Warbler mother and a Sedge Warbler father.     

Experimental enlargement of nest size does not increase risk of predation or brood parasitism in the Great Reed Warbler Acrocephalus arundinaceus

We assessed whether nest size affects the probability of nest loss using dyads of large and small (large being twice the size of small) inactive Great Reed Warbler Acrocephalus arundinaceus nests placed at similar sites in Great Reed Warbler territories. Large nests were not predated significantly more frequently than small nests. Experimentally enlarged active Great Reed Warbler nests suffered non‐significantly higher predation compared with non‐manipulated control nests. Our experiments did not support the nest‐size hypothesis and suggested that nest size does not appear to be a factor affecting the risk of nest predation in this species. The probability of brood parasitism by the Common Cuckoo Cuculus canorus was also unaffected by experimental nest enlargement, supporting the commonly accepted hypothesis that the Common Cuckoo searches for suitable host nests by host activity during nest building rather than nest size.     

Artmerkmale am Fu? adulter Teich- und Sumpfrohrs?nger (Acrocephalus scirpaceus, A. palustris) und ihre Funktion

Zusammenfassung 1. Der Sumpfrohrsänger(A. palustris) unterscheidet sich vom Teichrohrsänger(A. scirpaceus) durch einen kleineren Fuß.2. An sicher bestimmten Altvögeln der beiden Arten wurden verschiedene Fußmaße auf ihre Trennschärfe hin geprüft. Alle untersuchten Fußteile sind beim Sumpfrohrsänger etwas kürzer. Bei komplexen (aus mehreren Segmenten zusammengesetzten) Maßen summieren sich die geringfügigen Längenunterschiede der einzelnen Elemente zu brauchbaren Größen.3. Verläßlichstes Unterscheidungsmerkmal ist die Innere Fußspanne einschließlich Krallen (= Länge der Hinter- und Innenzehe mit den zugehörigen Krallen I, II). Sie mißt im Mittel beim Sumpfrohrsänger 25,0 mm, beim Teichrohrsänger 27,8 mm. Als Bestimmungsmerkmal darf sie nur bei Altvögeln angewandt werden.4. Die Bauunterschiede am Fuß werden funktionell gedeutet. Der Sumpfrohrsänger, der weniger Vertikalklettern zeigt, hat die dafür besonders wichtigen Elemente (Hinter- und Innenzehe, Krallen) schwächer ausgebildet.

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Speciesspecific characters in the feet of adult Reed and Marsh Warblers(Acrocephalus scirpaceus, A. palustris) and their function

Summary 1. The Marsh Warbler(A. palustris) may be distinguished from the Reed Warbler(A. scirpaceus) in that the former has a smaller foot, with shorter toes than the latter.2. Various measurements of elements of the feet were taken from adults, which were identified with certainty. These were tested for their selectivity. In all the segments investigated, it was found that the foot of the Marsh Warbler was proportionately shorter. The measurements of single segments showed little difference between the two forms, however if summed up, the compound measurements showed significant differences.3. The best criterion was found to be the measurement of the inner foot span (taken from the tip of the hind claw to the tip of the inner claw). The mean measurement of this for the Marsh Warbler was 25,0 mm, and for the Reed Warbler 27,8 mm.4. The functional significance of these differences in foot morphology were discussed. The Marsh Warbler is not as well adapted for climbing vertical stems as the Reed Warbler. Correspondingly, the foot elements, important for climbing vertically, were weaker.

     

The effect of interspecific aggression on territorial dynamics in Acrocephalus Warblers in a marsh area of north-western Italy

Observations carried out on an Acrocephalus community in north-western Italy during the breeding period have confirmed the occurrence of interspecific territoriality, with Acrocephalus arundinaceus aggressively dominant toward A. scirpaceus and A. palustris. The adaptive character of such an interspecific territoriality is discussed. Data seem to suggest that shifts in territories are also depending on interspecific interactions, even though intraspecific interactions have been confirmed to have the major weight in such a phenomenon. Great Reed Warbler territories resulted to be significantly larger than those of Marsh and Reed Warbler. It may be supposed that the Great Reed Warbler has larger territories as a consequence of its stronger aggressiveness.     

Islands in a desert: breeding ecology of the African Reed Warbler Acrocephalus baeticatus in Namibia

The continental African Reed Warbler Acrocephalus baeticatus, like its relative the Seychelles Warbler Acrocephalus sechellensis, breeds in isolated patches. We studied the mating system of the African Reed Warbler to see whether this species, like the Seychelles Warbler, shows co-operative breeding. The African Reed Warbler is not polygynous. The majority breed monogamously (88%, n = 65), however in 12% of the territories three adult unrelated birds (mostly males) were observed participating in the brooding and feeding of nestlings, suggesting a polyandrous breeding system. Multilocus DNA fingerprinting revealed that the helping bird was unrelated to the pair birds. The percentage of nests with helpers was low compared to rates found in the Seychelles Warbler or Henderson Reed Warbler Acrocephalus vaughani taiti. This could be due to the scarcity of potential helpers or to the fact that, although limited, birds still had the opportunity to disperse within a meta-population structure in search of vacant territories. The presence of helpers was associated with increased hatching success due to lower predation rates, but not with increased fledging success. Another possible benefit of helping behaviour in this species could be improved predator detection and mobbing. Nest predation was high and warblers tended to build their nests in the highest, most dense reed patches available in their territory. There was no relation between habitat quality, measured as insect food availability, and the occurrence of helpers.     

Grazing in remnant wetland habitats in an arid region: direct and indirect effects on two specialist bird species

Capsule: Grazing by livestock can have complex effects on drivers of population change in the Clamorous Reed Warbler Acrocephalus stentoreus and Dead Sea Sparrow Passer moabiticus.

Aims: To investigate the effect on two specialist bird species on wetland degradation in the Jordan Valley.

Methods: The direct and indirect effects of grazing on the probability of occurrences of two specialist bird species, Clamorous Reed Warbler A. stentoreus and Dead Sea Sparrow P. moabiticus, were analysed during the breeding season at the patch scale, using path analysis.

Results: Tamarix shrub density was a strong predictor for the presence of both species. Grazing had a negative total effect on both; a significant indirect effect on Dead Sea Sparrow via its impact on the mean height of shrubs, and a significant, negative indirect effect on Clamorous Reed Warbler by reducing reed cover. Intensive grazing and browsing by livestock including goats, sheep and camels, apparently had a negative effect on the overall density of native Tamarix shrubs, while promoting encroachment by invasive Prosopis juliflora.

Conclusion: This may be part of a long-term cascade leading to an ecological transition and loss of important wetland habitats in the arid Jordan Valley.     

Geographic variation in parasitism rates of two sympatric cuckoo hosts in China

Rates of brood parasitism vary extensively among host species and populations of a single host species. In this study, we documented and compared parasitism rates of two sympatric hosts, the Oriental Reed Warbler (Acrocephalus orientalis) and the Reed Parrotbill (Paradoxornis heudei), in three populations in China. We found that the Common Cuckoo (Cuculus canorus) is the only parasite using both the Oriental Reed Warbler and Reed Parrotbill as hosts, with a parasitism rate of 22.4%-34.3% and 0%-4.6%, respectively. The multiple parasitism rates were positively correlated with local parasitism rates across three geographic populations of Oriental Reed Warbler, which implies that higher pressure of parasitism lead to higher multiple parasitism rate. Furthermore, only one phenotype of cuckoo eggs was found in the nests of these two host species. Our results lead to two conclusions: (1) The Oriental Reed Warbler should be considered the major host of Common Cuckoo in our study sites; and (2) obligate parasitism on Oriental Reed Warbler by Common Cuckoo is specialized but flexible to some extent, i.e., using Reed Parrotbill as a secondary host. Further studies focusing on egg recognition and rejection behaviour of these two host species should be conducted to test our predictions.     

Estimating fat and protein fuel from fat and muscle scores in passerines

Fat is the prime energy source for birds during prolonged exercise, but protein is also catabolized. Estimates of the amount of catabolizable fat and protein (termed fat and protein fuel) are therefore important for studying energetics of birds. As fat and protein fuel can only be measured by sacrificing individuals or by use of technically complex methods, scoring systems were invented to estimate fat and protein fuel of birds in the field. The visible subcutaneous fat deposits and the thickness of the flight muscles are each scored on an ordinal scale but these scales do not correspond linearly to fat and protein fuel within species, which is needed for analyses such as flight range estimates. We developed an anova ‐type model to estimate fat and protein fuel from fat scores (FS) and muscle scores (MS) along with total mass and a size measurement. Using data from 11 337 individuals of eight passerine species (Common Nightingale Luscinia megarhynchos, Eurasian Reed Warbler Acrocephalus scirpaceus, Melodious Warbler Hippolais polyglotta, Willow Warbler Phylloscopus trochilus, Orphean Warbler Sylvia hortensis, Garden Warbler Sylvia borin, Common Whitethroat Sylvia communis, Subalpine Warbler Sylvia cantillans) mist‐netted in Mauritania, West Africa, we tested for independence of FS and MS and for variation in the relationship between scores and associated mass in response to physiological state. FS, MS and third primary length (size) explained variation in body mass of all eight species analysed (R²: 0.56–0.77). The parameter estimates of the model showed that fat and protein fuel increased monotonically with increasing fat and muscle scores. In two species we found small differences in the estimates between physiological states (seasons). We evaluated our model by comparing the predicted body mass of birds with both FS and MS equal to 0 with the mean body mass of individuals mist‐netted with both scores equal to zero. The values were very close. The amount of fat extracted from dead Garden and Willow Warblers was within the range of predicted fat fuel derived from the model. We conclude that our model is a useful non‐invasive method to estimate simultaneously mean fat and protein fuel of small passerines and we provide recommendations on its use.     

CuckooCuclus canorus parasitism onAcrocephalus Warblers in Southern Moravia in The Czech Republic

Summary The Reed Warbler,Acrocephalus scirpaceus, in the Lednice area, Southern Moravia in the Czech Republic, was parasitized by the Cuckoo,Cuculus canorus, at a rate of at least 18.0 %. The Cuckoo eggs showed poor mimesis with the Reed Warbler eggs, but showed a greater resemblance to the eggs of other species breeding in the area, including the Great Reed Warbler,A. arundinaceus. This latter species was also parasitized, but we did not find enough nests to obtain a reliable estimate for the rate of parasitism. The parasitized Reed Warblers rejected the Cuckoo eggs at a high rate (42.1 %) and therefore both the hatching success and the breeding success of the Cuckoo was considerably lower than shown by comparable results from Britain. On the background of these results (poor mimesis of the Cuckoo eggs and a high rejection rate by the hosts) the question of the degree of specialization versus generalism in the Cuckoo's host preference is discussed.

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Zusammenfassung Teichrohrsänger im Gebiet von Lednice (Südmähren, Tschechei) waren mindestens zu 18 % vom Kuckuck parasitiert. Die Kuckuckseier glichen jenen der Teichrohrsänger nur wenig, waren jedoch den Eiern anderer im Gebiet brütender Arten einschließlich des Drosselrohrsängers ähnlicher. Drosselrohrsänger waren auch parasitiert; wir fanden jedoch nicht genug Nester, um eine Parasitierungsrate ermitteln zu können. 42,1 % der Kuckuckseier wurden vom Teichrohrsänger nicht angenommen; daher waren Schlüpf- und Ausfliegerate des Kuckucks merklich geringer als in vergleichbaren Ergebnissen aus Großbritannien. Vor dem Hintergrund unserer Ergebnisse — geringe Angleichung der Kuckuckseier und hohe Ablehnungsrate durch die Wirtsart — wird die Frage von Spezialisierung und Generalismus in der Wirtswahl des Kuckucks diskutiert.

     

Parasitierung und Brutverluste durch den Kuckuck (Cuculus canorus) bei Teich- und Sumpfrohrs?nger (Acrocephalus scirpaceus,A. palustris) in Mittel- und Westeuropa

Zusammenfassung Nach 52 brutbiologischen Untersuchungen und Angaben der Parasitierung durch den KuckuckCuculus canorus bei Teich- und SumpfrohrsängernAcrocephalus scirpaceus,A. palustris wird für Mittel- und Westeuropa eine durchschnittliche Parasitierung von 8,3±7,8 % bei Teich- und von 6,3±6,6 % bei Sumpfrohrsängern berechnet (Tab. 1). Wegen der hohen Streuung beträgt der Median beim Teichrohrsänger 9 % und beim Sumpfrohrsänger nur 1,2 %. Selbst unter der Annahme einer gewissen Unausgewohgenheit des Datenmateriales übertreffen diese Werte bei weitem die aller anderen häufigen Kuckuckswirte in Mittel- und Westeuropa. Die Parasitierung des Teichrohrsängers ist fast flächendeckend, beim Sumpfrohrsänger dagegen mehr lückig über die Region verteilt (Abb. 1). Die Parasitierungsfrequenz scheint im Osten und Süden geringer als im Nordwesten. Ihre hohe Brutbestandsdichte macht die beiden Rohrsänger zu idealen Kuckuckswirten. Es gibt Hinweise, daß die Parasitierung bei beiden Arten zunimmt (Abb. 2). Darüberhinaus werden auch zahlreiche Gelege von den Kuckucksweibchen geraubt. Diese Verluste können viermal so hoch sein wie die durch Parasitierung (s. auch Abb. 3). Beide Arten haben zahlreiche Abwehrmechanismen gegenüber dem Kuckuck, wobei die Eiablehnung durch den Sumpfrohrsänger viel heftiger und effektiver ist als beim Teichrohrsänger. Möglicherweise steht der Sumpfrohrsänger unter einem höheren selektiven Druck für erfolgreiches Brüten.

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Parasitism and egg losses due to the Cuckoo (Cuculus canorus) in Reed and Marsh Warblers (Acrocephalus scirpaceus,A. palustris) in central and western Europe

Summary Both Reed and Marsh Warblers are common Cuckoo hosts. In this paper the frequencies of Cuckoo parasitism in 52 studies dealing with breeding success as well as parasitism in both warblers over a wide range of central and western Europe are analysed. Average parasitism rates are 8.3±7.9 % in Reed and 6.3±6.6 % in Marsh Warblers (tab. 1). Taking the high variation coefficient into consideration the median of Reed Warbler parasitism is 9 % and of Marsh Warbler parasitism only 1.2 %. Due to the uneven distribution of the studies over the region analysed and due to the preference by the researchers for smaller study plots vs large habitats there might be some bias towards higher parasitism figures. Nevertheless, both warblers range on top of the list of Cuckoo hosts and have much higher parasitism rates than other common hosts. Parasitism of the Reed Warbler does occur over the whole region, whereas in the Marsh Warbler it is more unevenly and patchily distributed. Parasitism seems to be higher in the northwestern than in the eastern and southern parts of central and western Europe. Both warblers are ideal hosts due to their high population densities in good habitats. There are indications for an increase of parasitism in both species during the last 30–50 years. Besides parasitism, many clutches of both warblers are predated upon by female Cuckoos. The number of predated nests can be four times as high as the number parasitized (see also Fig. 3). Both species exhibit a broad array of counter-reactions against the Cuckoo. The egg rejection by Marsh Warblers is much stronger and much more effective than in the Reed Warbler. Probably Marsh Warblers are under a higher selection pressure for successful breeding than Reed Warblers or have a different strategy to avoid losses.

     

High prevalence of haemosporidians in Reed Warbler Acrocephalus scirpaceus and Sedge Warbler Acrocephalus schoenobaenus in Spain

Apicomplexan blood parasites (genera Haemoproteus, Plasmodium and Leucocytozoon) prevalence in two related species (Reed Warbler Acrocephalus scirpaceus and Sedge Warbler A. schoenobaenus) was studied in 2006 at the Natural Reserve of Castronu?o-Vega del Duero, Western Spain, a stopover area during the autumn migration. A fragment of the mitochondrial cytochrome b gene of the parasites was amplified, using a nested PCR assay, from avian blood samples. High prevalence of malaria parasites was found in both species, 84.6% in Reed Warbler and 71.8% in Sedge Warbler, and the degree of infection reach 100% of the population that breed at the Reserve, suggesting good conditions for the development of dipteran vectors in this area. By sequencing 464 nucleotides of the obtained fragments, we found four different mitochondrial haplotypes of Haemoproteus or Plasmodium in the two species analysed. Leucocytozoon infection was not detected, in contrast to the high prevalence of this parasite in other avian species in Spain, probably because the water course studied is not an adequate habitat for its vectors.     

Prey abundance and male parental behaviour in Acrocephalus warblers

This study examined the prey abundance at nesting sites of five different Acrocephalus warbler species. Intraspecific variations in prey density were analysed to determine the relative significance of this ecological factor for different mating systems and components of male parental behaviour. The Great Reed Warbler Acrocephalus arundinaceus, a facultatively polygynous species, nested in areas with the highest insect abundance. Its intraspecific variation in prey density (between different territories) was the highest while the male: female offspring feeding ratio was the lowest. At the other extreme, the monogamous Moustached Warbler Acrocephalus melanopogon and Reed Warbler Acrocephalus scirpaceus nested in areas with the lowest prey abundance and lowest intraspecific variation. Males of these species had the highest involvement in feeding young. In the Moustached Warbler and Marsh Warbler Acrocephalus palustris, an intraspecific comparison revealed a negative correlation between insect abundance and the male feeding component; a tendency in this direction was found for the Reed Warbler, while no correlation was evident in the polygynous Great Reed Warbler. These data demonstrate a general pattern relating prey abundance, mating systems and male parental investment on an interspecific level. However, intraspecific correlations revealed a net of complex interdependence. One of the factors which may be important is resource predictability. We found a significant correlation between certain vegetation types and insect abundance. The vegetation composition of territories is further influenced by interspecific dominance relationships whereby the dominant Great Reed Warbler occupies territories with the vegetation type which correlates with high prey abundance while the overlapping Moustached Warbler and Reed Warbler are restricted to areas with lower insect density.