Great Reed Warbler Acrocephalus Arundinaceus Research Articles

Behavior of radio-tracked Common Cuckoo females during the breeding season in Japan

ABSTRACT The breeding behavior of Common Cuckoo Cuculus canorus females was studied in detail by individual marking, radio-tracking, and automatic recording of radio signals. A total of 132 female cuckoos was captured, and radio transmitters were attached to 44 of them. The female cuckoos parasitised three different types of hosts: Azure-winged Magpies Cynopica cyane, Great Reed Warbler Acrocephalus arundinaceus and Bull-headed Shrike Lanius bucephalus. Female cuckoos using magpie hosts were radio-tracked for a total of 131.1 hours, and females using warbler hosts were radio-tracked for a total of 142.1 hours. The total time for cuckoos using shrike hosts was 12.6 hours. Female cuckoos were found to have distinct breeding and feeding areas, which they commuted between every day. Dominant females maintained strict breeding site tenacity throughout the breeding season. Each female specialized on one host type, knew almost all of the host nests in their breeding areas, and laid eggs selectively among the nes...

Sjeldne fugler i Norge i 2004 - Rapport fra Norsk sjeldenhetskomité for fugl (NSKF)

This is the 28th annual report and the 29th announcement from the Norwegian Rarities Committee (NSKF). Most of the records treated here are from 2003, but older records are also included. The systematic list of accepted records is set out in the following system: (1) The bird’s Norwegian name, (2) scientific name, (3) the numbers in brackets, e.g. (30/32 - 1), refers respectively to the total number of records/total number of individuals up to and including 2002, and in 2003, (4) any limitations given of (3), (5) any breeding, (6) year, (7) county, (8) number of individuals, age (1K = first calendar year etc.), sex (if known) and sometimes circumstances («ringmerket» means that the bird was ringed), (9) site and municipality, (10) date, (11) * indicates if the record was complemented by positive evidence, and type of the evidence (F = photo, V = video-recorded, L = tape-recorded, D = found dead), (12) observers names in brackets, main observer is specified first and emphasized with *, (13) roughly gives the species general distribution and (14) comments concerning the records. General trends: This year was the second best in the history of NSKF concerning number of accepted records. Several species reached record numbers. Most significant were the influxes of Water Pipit Anthus spinoletta (17 records) and Hume’s Warbler Phylloscopus humei (10 records) during autumn. Five records of Black-necked Grebe Podiceps nigricollis , two records of Black-browed Albatross Thalassarche melanopris , four records of Balearic Shearwater Puffinus mauretanicus , six records of Bittern Botaurus stellaris , nine records of Red Kite Milvus milvus , two records of Sharp-tailed Sandpiper Calidris acuminata, six records of Mediterranean Gull Larus melanocephalus , two records of Caspian Gull Larus cachinnans and five records of Red-rumped Swallow Hirundo daurica were all maximum records for one single year. Four records of White-rumped Sandpiper Calidris fuscicollis and two records of Isabelline Shrike Lanius isabellinus were equal to previous maximum number of records. New accepted records from 2002 resulted in an increase in the maximum number of records for Great Reed Warbler Acrocephalus arundinaceus (9 records) and Blyth’s Reed Warbler Acrocephalus dumetorum (7 records). Pallid Harrier Circus macrourus (6 records), M ontagu’s Harrier Circus pygargus (6 records), Pectoral Sandpiper Calidris melanotos (12 records), Olive-backed Pipit Anthus hodgsoni (4 records) and Pallas’s Leaf Warbler Phylloscopus proregulus (20 records) were also recorded in relatively high numbers. Species and subspecies new to the Norwegian list: Two species were added to the Norwegian category A list: Yellow-legged Gull Larus michahellis and Ovenbird Seiurus aurocapillus . A record of Masked Wagtail Motacilla alba personata added a new subspecies to the Norwegian list. A record of Lammergeier Gypaetus barbatus was placed in category D and a record of Turkey Vulture Cathartes aura from 2002 was placed in category E. With these new records the official Norwegian bird list consists of 466 species. In 2003, Black-necked Grebe Podiceps nigricollis was recorded breeding in Norway for the first time with one brood successfully raised, and Pink-footed Goose Anser brachyrhynchus was recorded breeding for the first time on the Norwegian mainland excluding Svalbard).

Within-year nest reuse in open-nesting, solitary breeding passerines

During fieldwork at Lake Sic (46°57’N, 23°54’E), Romania, in the summer of 2003, we observed a strange incident of nest reuse in the Great Reed Warbler Acrocephalus arundinaceus . After first laying a complete clutch of five eggs and then ejecting an experimentally added parasite egg together with two of its own eggs, a new clutch was initiated in the same nest. In Tana (70°16’N, 28°19’E), Norway, in June 2003, we observed a similar incident in the Brambling Fringilla montifringilla . In a nest that was completely depredated when 3-4 eggs had been laid, a new clutch was initiated 8-9 days later. This is as far as we know the first time nest reuse has been documented in Great Reed Warblers and Bramblings.

Common cuckoos (Cuculus canorus) lay eggs with larger yolk but not more testosterone than their great reed warbler (Acrocephalus arundinaceus) hosts

The relatively small common cuckoo Cuculus canorus hatchling evicts its host's propagules, then begs intensively to elicit sufficient parental care. The proximate mechanisms of these behaviours are still obscure. Recent intraspecific studies on avian broods revealed higher competitive ability of nestlings that hatched from eggs with a greater yolk testosterone level. Greater maternal investment in yolk steroids may provide an explanation for the vigour of parasitic chicks. Unexpectedly we found no evidence of higher yolk T concentration and absolute amount of T in cuckoo eggs compared to those of its host, the great reed warbler Acrocephalus arundinaceus. The yolk mass of cuckoo eggs, however, was significantly greater than that of the host, despite egg volumes being similar between these two species. Relatively larger yolks of cuckoo eggs indicates differential maternal investment strategies by parasites as more yolk may contain additional macronutrients to increase the vigour of parasitic young during the early days of its life and/or to enhance its begging display to elicit care from foster parents.

Break-down of arms race between the red-backed shrike (Lanius collurio) and common cuckoo (Cuculus canorus)

AbstractThe red-backed shrike Lanius collurio once was parasitised by the common cuckoo Cuculus canorus in low frequency until the late 1960s in Hungary, but no case of parasitism is known from the last three or four decades. The cuckoo most probably abandoned this host species because its arms race had defeated, which may be indicated by the high level egg recognition and rejection ability of shrikes. However, mimicry of the cuckoo eggs in the last known cases of parasitism was significantly lower than between cuckoo eggs and host eggs collected from great reed warbler Acrocephalus arundinaceus nests within the same period. This suggests that red-backed shrikes won the arms race leaving no chance for cuckoos to develop better mimicry for their eggs. We tested these findings with experimentally induced parasitism using two types of real eggs: red-backed shrikes rejected 57.6% of the foreign conspecific eggs, but rejected 93.3% of the real cuckoo eggs transferred form nests of great reed warblers. This high level of rejection against real cuckoo eggs shows that there is no chance for presently occurring cuckoos to reparasitise red-backed shrikes in Hungary. Experimental eggs rejected by shrikes had lower mimicry than the eggs which were accepted, but intraclutch variation did not differ between accepters and rejecters. Hosts' aggression was significantly higher against the stuffed cuckoo than against the control species, the collared dove Streptopelia decaocto, and it was the least against female red-backed shrikes. Red-backed shrikes high aggression against cuckoo dummies also showed a highly developed antiparasite adaptation.

European CuckooCuculus canorusparasitism and host's rejection behaviour in a heavily parasitized Great Reed WarblerAcrocephalus arundinaceuspopulation

An unusually high frequency (64%) of European CuckooCuculus canorusparasitism was found in Great Reed WarblerAcrocephalus arundinaceusclutches in central Hungary. Sixty‐four per cent of the parasitized clutches contained one Cuckoo egg, 23% contained two, 10% had three and 3% had four. This means that 58% of the Cuckoo eggs were found in multiply parasitized clutches. In multiple parasitism the laying second Cuckoo removed an egg from the clutch randomly, so preferred neither the host eggs, nor the concurrent Cuckoo egg. Host response towards the parasitic eggs showed 66% acceptance, 12% ejection, 20% desertion and 2% egg burial. We found great variation in both the host and the parasitic egg colour and pattern. This reduces the chance that the parasitic egg's appearance matched that of the hosts’ but, in spite of this, almost perfect mimesis was found in 28% of the Cuckoo eggs. Poorly mimetic Cuckoo eggs were more frequently rejected by Great Reed Warblers than parasite eggs that were very similar to the host eggs. This high level of mimicry sometimes makes it difficult for the observer to identify the parasitic egg, especially when it is similar in size to the host eggs. It is also difficult for the host, as shown by the relatively high recognition error and ejection cost.

Predictors of natal dispersal in great reed warblers: results from small and large census areas

For most species, it is currently not known whether individual characteristics and population parameters affecting dispersal distances within the local population are also affecting dispersal of individuals emigrating longer distances. We evaluated this in the great reed warbler Acrocephalus arundinaceus by analysing data of natal dispersal distances within (1) the local hatching area in southern Central Sweden and (2) the species’ whole breeding range in Sweden. The different scales gave conflicting results. Site of birth was the main predictor of natal dispersal distance in the local census area, whereas in the larger census area the dispersal distance differed significantly between hatching years. Previous studies have shown that the recruitment rate of great reed warblers within the local study area differs between hatching years and also that it declines during the course of the breeding season. It was not known, however, whether these relationships reflected variation in survival or dispersal. The results from the present study suggest that the differences in local recruitment rate between hatching years is partly caused by annual variation in emigration rate, whereas the decline in local recruitment rate with season mainly reflects mortality of late‐hatched nestlings. Our study shows a twofold advantage of a large census area when studying dispersal. First, predictors of longer‐distance dispersal will be revealed and, second, the variation in local recruitment rate can be separated into the two components, survival and dispersal.

ADAPTATIONS BY GREAT REED WARBLERS TO BROOD PARASITISM: A COMPARISON OF POPULATIONS IN SYMPATRY AND ALLOPATRY WITH THE COMMON CUCKOO

Abstract Egg rejection behaviour, as an antiparasite defence against brood parasitism was compared in two great reed warbler Acrocephalus arundinaceus populations. In central Hungary the host population lives in sympatry with the common cuckoo Cuculus canorus, and it is heavily parasitised (ca 66%). In central Greece the great reed warbler occurs in allopatry with the cuckoo, so it is not parasitised at all. Experimental parasitism with poorly mimetic (often called 'non-mimetic') artificial cuckoo eggs revealed a 100% rejection rate towards the foreign eggs in the Greek population, but the Hungarian hosts accepted 29.4% and rejected 70.6% of the model cuckoo eggs. No other rejection type than ejection was observed. The significantly higher level of rejection in Greece than in Hungary suggests that the Greek great reed warbler population is an abandoned host population of the cuckoo, which kept its egg recognition ability. A computer-based image analysis of host's clutches revealed that interclutch variation in egg colour was greater than intraclutch variation in the Hungarian population, but not in the Greek population. Spottedness of eggs were similar in both populations. Generally, a tendency for a higher interclutch variation was found in Hungary. Intraclutch variation was more similar in the two populations, but for the colour variables it showed a lower value in Hungary than in Greece. The heavy cuckoo parasitism in Hungary is suggested to be the main cause for the increased interclutch variation in relation to intraclutch variation in egg appearance among great reed warbler clutches. The high interclutch variation reduces the chance that the parasite egg's appearance matches that of the hosts', which facilitates hosts' egg discrimination.

How to hatch from an egg of great structural strength. A study of the Common Cuckoo

Brood parasitism represents a unique mode of avian reproduction that requires a number of adaptations. For example, to reduce chances of puncture ejection of their eggs by small hosts, brood parasites may have been selected for laying eggs of unusually great structural strength. However, great structural strength of eggshells should hinder hatching. The goals of our study were to establish if chicks of the Common Cuckoo Cuculus canorus have more difficulty with hatching out of their strong eggs than chicks of species with eggs of similar size, and whether they possess any mechanisms facilitating hatching. To achieve these goals, we compared hatching pattern and selected body characteristics of chicks of the Common Cuckoo with those of another altricial species with eggs of a similar size, the Great Reed Warbler Acrocephalus arundinaceus. Although the rate of pecking was similar in the two species, the Common Cuckoo chicks started pecking earlier in relation to their emergence and consequently required more time and a greater cumulative number of pecks for breaking open their eggs than did young Great Reed Warblers. The two species also differed with respect to the pattern of opening their shells; in contrast to the warbler chicks, which enlarged the original pip circularly, the cuckoo chicks opened the egg by systematically creating a long narrow slit until they emerged. Finally, our study of hatched young revealed several differences; the Cuckoo hatchlings were significantly heavier, had a longer forearm, and their egg tooth was located significantly farther from the tip of the beak. The edge used for cutting through the shell was also significantly longer than that of hatchling Great Reed Warblers. To conclude, our data suggest that hatching is more difficult for a Cuckoo than for a Great Reed Warbler and that Cuckoos possess several mechanisms to overcome the problems of hatching from a structurally strong egg.

Effect of nest and nest site characteristics on the risk of cuckooCuculus canorusparasitism in the great reed warblerAcrocephalus arundinaceus

The risk of cuckooCuculus canorusparasitism for great reed warblerAcrocephalus arundinaceusnests was evaluated in respect to nest and nest site structure in the reedbeds along canals in central Hungary, In total 90 nests were analysed, from which 31 remained unparasitised. 37 were single parasitised and 22 multiple parasitised. Multiple discriminant analysis, based on eight structural variables, separated well the unparasitised clutches from the cases of single and multiple parasitism, but the latter two categories also showed a weaker separation. Nests close to cuckoo vantage points are most vulnerable to parasitism. The variable “distance from nest to closest available cuckoo perch site” (tree or electric wire) played the most important role in the risk of parasitism. It showed highly significant differences among the groups: lowest distances were found in the case of multiple parasitism, and the highest distances were measured when nests remained unparasitised. Additionally, “nest visibility” also showed significant differences among the three groups: a more visible nest is more likely to be parasitised. Risk of parasitism affects on the host on two levels: 1) female cuckoos search for nest‐building hosts from a perch site, but 2) when they are in the act of parasitism, they can find more visible nests in the reed. Besides the robust effects of the variables “distance to cuckoo perch site” and “nest visibility”, the variable “distance from nest to open water” may reduce, but “nest volume” increases the risk of multiple parasitism. Differences between cases of single and multiple parasitism are weak, mainly affected by chance. We explain it by the high abundance of the cuckoo, the parasitism rate was 65.6% (59/90), Cuckoos parasitised almost all of the available nests in the close vicinity of potential perch sites. There was no evidence that great reed warblers nested closer to each other when risk of parasitism was high.

Effect of nest and nest site characteristics on the risk of cuckoo Cuculus canorus parasitism in the great reed warbler Acrocephalus arundinaceus

Effect of nest and nest site characteristics on the risk of cuckoo Cuculus canorus parasitism in the great reed warbler Acrocephalus arundinaceus

Studies of Sex Allocation in Birds and Molecular Tools for Sex Identification

The recent development of molecular methods for sex identification makes large-scale studies of sex allocation in birds possible. This review identifies three types of sex allocation studies of birds. These relate either to the population primary sex ratio, the facultative manipulation of the sex ratio, or to sex-skewed provisioning. Many recent studies have suggested that facultative sex ratio manipulation may be more widespread among birds than has previously been considered. In contrast, only a few studies have been made of the population primary sex ratio, and of sexskewed provisioning. Despite all these studies, the mechanism for adjusting the sex ratio remains a mystery. In particular, estimating the cost of making sex ratio adjustments is indispensable for quantitative predictions of sex allocation. The relationships between the three aspects outlined above have not yet been sufficiently clarified. In both Budgerigars Melopsittacus undulatus and Great Reed Warblers Acrocephalus arundinaceus, fathers provide extra-feeding for a certain sex of offspring, while mothers manipulate the primary sex ratio. I suggest that the distinction between the sexes in terms of providing extra-feeding or manipulating the sex ratio, may in fact affect the population primary sex ratio and cause a bias towards the sex for which fathers provide extra-feeding.

Movements, Space Use and Social Organization of Radio-tracked Common Cuckoos during the Breeeding Season in Japan

The movements, space use, and social organization of a colour-marked Common Cuckoo Cuculus canorus population were investigated during the 1984-1993 breeding seasons in central Japan. Of 333 captured cuckoos, 81 had radio transmitters attached to them. Excluding unknown birds (8.7%), the male : female ratio was 1.25 : 1.00. Radio-tracking showed that each cuckoo had a distinct breeding area and a distinct feeding area, and commuted between them every day. Birds spent most early mornings in host-rich habitats such as the Chikuma River, and then visited neighboring mountains or suburbs for foraging. The average time spent in the breeding area was 9.0 ± 0.8 hours per day (58.2 % of the daytime hours) for males and 8.7 ± 0.7 hours (56.3 %) for females. All males visited their breeding areas just after dawn, but the peak time for females was one hour later. After the early morning peak, the rate decreased gradually until early afternoon and increased again in the late afternoon with both sexes. The main activity of males in the breeding area was singing, and they sang between 19.8 % and 40.2 % of the total time they spent there. Each male sang in a restricted area and the average size of the song area was 40.9 ± 4.9 ha. However, male song areas had a large overlap, especially at the groves of acacia trees around which were many host nests. Males sometimes made short visits outside their song areas. The average size of males' breeding area, including these short visits, was 67.5 ± 8.9 ha. There were three types of females corresponding to three major hosts: the Great Reed-warbler Acrocephalus arundinaceus, the Bull-headed Shrike Lanius bucephalus and the Azure-winged Magpie Cyanopica cyana. Each female cuckoo in this study specialized on a single host species. The breeding areas of females overlapped considerably both "inter" and "intra" between different female groups. The average size of the females' breeding areas was 63.6 ± 8.5 ha. However, magpie-cuckoo females had significantly larger areas than warber-cuckoo females. The cuckoos rarely fed in their breeding areas. During their absence from the breeding area, most cuckoos visited nearby mountains, but some cuckoos, breeding at sites far from the mountains, visited suburbs for feeding. The average size of a feeding area in the mountains was 23.7 ± 5.7 ha for males and 27.6 ± 6.8 ha for females. By contrast, a female which foraged in the suburbs had a large feeding area (327.0 ha). The number of visits per day was related to the distance between the breeding area and feeding area. Cuckoos foraging at more distant sites visited these sites only once per day, while cuckoos foraging at closer sites visited them more frequently. There was a positive relationship between distance to feeding area and mean times spent per visit. There was a negative relationship between distance to feeding area and total feeding time per day. Cuckoos roosted solitarily in both their breeding and feeding areas. Roosting sites in the mountains changed almost every day, but some cuckoos roosting at the river or in the suburbs often used the same sites repeatedly. Roosting in the breeding area was more commons with males than with females, but it decreased in both sexes as the season progressed. The average size of a home range was 3.02 ± 0.28 km2 for males and 3.26 ± 0.40 km2 for females. In this paper, we discuss the following three points: (1) The separation of the breeding area and the feeding area is a common characteristic of the cuckoo and it is closely related both to the cuckoo's parasitic breeding and to its special feeding habits; (2) There are costs attendant with leaving the breeding area in order to visit a feeding area.

Female Mating Status and Reproductive Success in the Great Reed Warbler: Is there a Potential Cost of Polygyny that Requires Compensation

1. Using data from a 9-year study of the great reed warbler Acrocephalus arundinaceus L. carried out in Sweden, I tested the main assumption of the polygyny threshold model (that there is a cost of polygyny) and the main prediction (that this cost is compensated for). The main question was whether a female that chose a mated male (secondary females) experienced the same fitness as a female that at the same time chose an unmated male (primary females). The study includes a total of 192 breeding seasons of 104 individual females of which 40% settled with already mated males. 2. Eight potential correlates of fitness were examined; namely, clutch size, hatching success, hedging success, survival until breeding age, nest survival, mass of fledglings, mass of feeding females and annual survival rate of breeding females. I started each analysis by controlling for four potential confounding variables (year, study site, female age and breeding date). Then I compared the average fitness measure of primary and secondary females. 3. The only detected potential component cost of polygyny was a higher mortality among nestlings if a non-primary position within the harem was retained until hatching. This was supported by a natural experiment. Females that initially chose mated males but which achieved a primary position after failure of the originally primary female's nest enjoyed an increased fledging success, probably because of more male assistance. 4. The number of recruits, controlling for settling dates, for the two categories of females were almost identical (primary females 0 . 53 recruits per year, secondary females 0 . 51 recruits per year). Since secondary and primary females showed similar rates of survival until next breeding season the fitness of the two strategies appears to be equal. These findings strongly suggest that polygyny in the great reed warbler is best explained by the compensation models such as the polygyny threshold model. (Less)

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.

Breeding Biology and Ecology of Different European and Asiatic Populations of the Great Reed Warbler Acrocephalus arundinaceus

A comparison between various populations of the Great Reed Warbler Acrocephalus arundinaceus was made using published and unpublished data. The comparison showed that most differences are consistent with a division into subspecies. The majority of birds from the nominate subspecies go through a complete moult in late autumn in north Africa, and then continue migration to winter quarters south of the equator. The majority of the eastern subspecies moult completely just after the breeding season. In contrast the orientalis birds spent extremely short periods on migration and long periods in the winter quarters. Orientalis also show more habitat tolerance (breeding in bushes, small trees, and no water), higher breeding density, less nestling starvation, and more Cuckoo Cuculus canorus brood-parasitism. However, some of these features may be due to the fact that some of orientalis populations live in extremely changed (man-made) habitats. On the other hand, clutch-size, total nest-losses, eggs hatchability, fledglings production, and nestling diet composition showed interpopulation variation independent of the subspecies division.

Intraspecific Comparison of Ecology and Mating System of the Great Reed Warbler Acrocephalus arundinaceus: Why Different Results from Different Populations?

In the last 20 years intensive studies on the ecology and mating system of the Great Reed Warbler Acrocephalus arundinaceus have been conducted at five different localities in Japan and Europe. Although all the populations showed similar territorial polygyny, the studies showed partly different results and conclusions concerning the evolution of polygyny in this species. Here, we compare ecology and behaviour of the warblers from different populations based on published information, focusing on aspects of territorial polygyny inherent in the polygyny-threshold-model. Breeding results in one of the European populations were unique in that secondary females were far less successful than monogamous females compared to almost equivalent success in other four populations. Although causes of offspring mortality were not the same between populations, the European populations commonly showed higher rates of chick starvation in secondary nests than in monogamous nests, but this was not the case for the Japanese populations. Benefits which compensate for these costs of polygyny were found in three of the five populations. Despite variations in breeding results, all studies showed the existence of a potential cost of polygyny: reduced paternal care in secondary nests leading to a realized cost depending on climatic and ecological conditions. Evidences of female choice based on behavioural observations were available at some populations. In one of the populations the benefit of polygyny was linked to variance in territory quality caused by habitat heterogeneity and habitat partitioning pattern between males. But information on these aspects of ecology has not been collected enough for the other populations. Features of territory differed greatly between populations and it suggests the possibility that different mechanisms work to cause polygyny in different populations. Despite these regional differences, however, the polygyny-threshold-model is generally applicable to this species.

Intraspecif is comparison of ecology and mating system of the Great Reed Warbler Acrocephalus arundinaceus: Why different results from different populations?

Intraspecif is comparison of ecology and mating system of the Great Reed Warbler Acrocephalus arundinaceus: Why different results from different populations?

Breeding biology and ecology of different European and Asiatic populations of the Great Reed Warbler Acrocephalus arundinaceus

Breeding biology and ecology of different European and Asiatic populations of the Great Reed Warbler Acrocephalus arundinaceus

Initiation of remige moult by first‐year Great Reed WarblersAcrocephalus arundinaceus arundinaceusin Europe

Initiation of remige moult by first‐year Great Reed Warblers<i>Acrocephalus arundinaceus arundinaceus</i>in Europe