Geographical differentiation, acoustic adaptation and species boundaries in mainland citril finches and insular Corsican finches, superspecies Carduelis [citrinella]

Aim In birds, differentiation of acoustic characters is an important mechanism of reproductive isolation that may lead to an ethological–acoustic barrier, resulting in the formation of new species. We examined acoustic variation in mainland citril and insular Corsican finch populations, with the aim of assessing the degree of acoustic differentiation between both members of the superspecies Carduelis [citrinella] and documenting possible variation between local subpopulations that are geographically isolated. Location We chose study sites throughout the geographical ranges of citril and Corsican finches. For the citril finch, we obtained samples from the Black Forest (Germany), the Cevennes (France) and the Pyrenees (Spain); for the Corsican finch, we obtained samples from the islands Capraia and Sardinia (Italy) and Corsica (France). Methods We analysed frequent contact calls and elements of the perch song. Vocalization patterns of the study populations were compared by means of discriminant and hierarchical cluster analyses. Results There were significant differences in vocalization characteristics of perch songs and contact calls, which permitted unambiguous discrimination of citril and Corsican finch populations. However, we also detected significant differences in contact calls between mainland citril finch subpopulations. There was a pattern of clinal variation in vocalization: short, steeply modulated signals in the northern part of the geographical range (Black Forest) and long, shallowly modulated signals in the southern part (Pyrenees). Main conclusions Acoustically, mainland citril and insular Corsican finches separate well in their contact calls and perch songs. However, variation in the two vocalization patterns between subpopulations of mainland citril finches indicates that acoustic characteristics can evolve very quickly, not only on islands but also on the mainland. Local habitat differences may play a crucial role in the rapid evolution of these signals under full or partial isolation of small subpopulations. To judge the importance of signal variation as a pre‐mating isolating barrier, future studies will have to determine whether members of the distinct subpopulations are able to match their signals to each other if they re‐meet, and whether intraspecific species recognition is still possible.     

Inter-locality variation in reproductive success of the citril finch Serinus citrinella

Habitat quality is generally thought to affect breeding success. We tested this effect comparing differences in clutch size and reproductive success between citril finch Serinus citrinella sub-populations closely located (<5 km) but differing in habitat quality, within the Port del Comte mountain, in the Catalonian Pre-Pyrenees. We found that birds in the low quality area (Bofia) showed significantly lower hatching, breeding and nesting success than finches in the high quality area (Vansa). These differences in reproductive success fit well with recently found differences in citril finch body mass, fat score, diet, survival rate and speed of moult between these two localities.     

Seasonal variation in the diet of citril finches <Emphasis Type="Italic">Carduelis citrinella</Emphasis>: are they specialists or generalists?

The seasonal variation of food selection in mountainous citril finches was studied in the Black Forest. citril finches show a strong seasonal variation in quantity and quality of food plants. From November to March, only a few plants have been observed as diet, namely seeds of the germander and the mountain pine (period of food restriction). From April to June, the seeds of a few key food plants such as the dandelion, common sorrel, vernal grass, and mountain pine gain special importance during breeding and the rearing period of the young (period of food specialization). Finally, from June/July to October, citril finches enter into a generalist period with a wide variety of seeds of herbs and grasses (period of food generalization). The changes in food selection are well adapted to the changing resource availabilities and climatic conditions of the Black Forest mountains. In direct comparison to other finches, pure mountain-dwelling species such as citril finches and Syrian serins show a clearly higher seasonal variability in food selection than do lowland species such as goldfinches, linnets, and greenfinches.     

Breeding ecology and nest site selection in allopatric mainland Citril Finches Carduelis[citrinella] citrinella and insular Corsican Finches Carduelis[citrinella] corsicanus

The breeding ecology and nest site selection of mainland Citril Finches and insular Corsican Finches have been studied throughout their limited range. For many years both endemic forms were considered to be two sub-species; however, based on evidence from more recent molecular studies they have been split into two species. This study provides data on the variations in breeding ecology and nest site selection in the different sub-populations of these little studied species. A secondary aim was to search out evidence of ecological differentiation between mainland Citril Finches and insular Corsican Finches. We found that the studied sub-populations of both species largely overlapped in breeding ecology. Our data confirms the close similarity of Citril Finches and Corsican Finches, both which are, similar to mountain birds, well adapted to the local habitat conditions of their different mountain systems. Several differences were identified within the studied sub-populations of the two (sub-) species with respect to nest site selection, probably caused by environmental conditions and local predators. One of the main differences between the two species is that Citril Finches breed mainly in half-open conifer forests (especially pine forests), while Corsican Finches breed in the more open scrubby mountains of the Mediterranean islands dominated mainly by the Tree Heath as an adaptation to the different landscapes on the islands. In contrast to Citril Finches, this preference of the Corsican Finches for Tree Heath as nesting plants – even if suitable pines are available – is typical of the species. These behavioural changes result in a niche expansion into open habitats at lower altitudes. We suggest that the observed niche expansion and behavioural variations are not suitable criteria for taxonomic status, a proposal in contrast to that of Sangster [Ibis 142:487–490 (2000)]. We further suggest that the few ecological differences found in this study between the two (sub-)species are the result of the so-called insular syndrome, which includes changes in life history traits such as morphology, demography and behaviour.     

Microgeographic variation in citril finch <Emphasis Type="Italic">Carduelis citrinella</Emphasis> abundance as a consequence of resource availability and ancient landscape cultivation

The avifauna of mid-European mountains has for a long time been influenced by the intensive activities of man. As a consequence, the ancient cultivation in the formerly wooded Black Forest has led to a typical semi-open to open cultural landscape (heath land) on the mountain summits dominated by extensive pasturing with cattle and goat. Within several species of semi-open landscapes, especially citril finches profited from this development. However, during the last decades pasturing and transhumance activities ceased drastically, and continuous natural and artificial reforestation began. Due to these changes, several characteristic bird species of this semi-open landscape decreased strongly or became extinct. In this thematical context I studied microgeographic habitat selection in citril finches as a consequence of resource availability at mount Schliffkopf in the Northern Black Forest. As expected, citril finches are especially drawn to man-made habitat structures in this area and seem to react directly to the continuous reduction of these structures in the last centuries. Its recently observed population decline is characteristic for a couple of other bird species of semi-open landscapes in mid-European mountains, such as woodlarks and nightjars.     

Nestling diet variation in an insular Mediterranean population of blue tits Parus caeruleus: effects of years,territories and individuals

Mediterranean evergreen forests of Corsica are characterized by relatively high species diversity of arthropods with low population densities. Food is never superabundant for Corsican blue tits Parus caeruleus. This study focused on the composition of the food of blue tit nestlings and especially on two main components, caterpillars and spiders. The nestling diet was studied for two years using 8-mm cameras that automatically took photographs of adult birds with food. The diet was composed of c. 50% caterpillars and c. 30% spiders. There were between-year and between-individual differences in these proportions. In both years of the study the proportion of caterpillars declined during the course of the breeding season. Individual and time effects on prey sizes were also observed. Pairs and individuals were fairly constant in the proportions of prey over the feeding period. Different food items were not brought in runs. These findings suggest that strong food limitation exists on Corsica, which can considerably influence life-history traits of the blue tit.     

Seed set in Sorghum stipoideum,and not fire,determines the timing of breeding by Gouldian finches (Erythrura gouldiae)

Seeds of native grasses are an important food source for granivorous finches throughout the tropical savannas of northern Australia. The iconic Gouldian finch (Erythrura gouldiae), a threatened species endemic to these savanna grasslands, relies almost exclusively on the grass seeds of annual Sorghum spp. when breeding, and appears to time breeding with the availability of these seeds. Fire is common throughout the savanna grasslands of northern Australia and has the potential to alter Sorghum spp. seed germination and plant reproductive phenology which in turn could alter the Gouldian finch breeding phenology window. This study examines if the temporal relationship between breeding by Gouldian finches in the north‐east Kimberley region of Australia relates to fire and Sorghum stipoideum seed phenology. The availability of S. stipoideum seed was monitored at Gouldian finch breeding sites in association with local fire history and Gouldian finch breeding data. The effect of experimental fire (heat and smoke) on S. stipoideum seed dormancy and germination was also investigated. We found that the first heavy rainfalls preceded germination of S. stipoideum in November/December. Synchronous seed set by S. stipoideum plants the following March/April coincided with the start and duration of the Gouldian finch breeding season. The timing of dry season fires had no relationship with seed dormancy or the phenology of seed germination and seed set. Nor did the effects of smoke or heat affect seed dormancy and germination. These findings support the importance of the seed phenology of annual grass species, such as S. stipoideum, to breeding Gouldian finches, and also suggest that the occurrence of fire at a breeding site in the previous year does not alter the S. stipoideum seed or finch breeding window. The implications of these results for threatened Gouldian finch ecology and management are discussed in relation to previously published fire impacts on S. stipoideum seed nutrition and finch breeding site selection.     

Spatial and behavioural measures of social discrimination by captive male zebra finches: Implications of sexual and species differences for recognition research

All bird species reproduce sexually and individuals need to correctly identify conspecifics for successful breeding. Captive zebra finches are a model system for studying the factors involved in species recognition and mate choice. However, male zebra finches’ behavioural responses in a spatial preference paradigm to a range of estrildid finch species, other than domesticated Bengalese finches, remain unknown. We investigated spatial and display responses of male zebra finch subjects to stimulus females between conspecific and four phylogeographically relevant finch species, in addition to female Bengalese finches. Surprisingly, male subjects did not show consistent spatial association with conspecific over heterospecific females. Overall, as predicted by sexual selection theory, the spatial proximity responses of males were less discriminatory compared to female zebra finches’ responses tested previously using the same paradigm. However, male subjects showed consistently more behavioural displays towards female conspecifics than heterospecifics which were positively related to the behavioural display rates of the respective female stimuli. Some male behavioural responses, other than song, also showed significant differences between the different stimulus species and consistently differed across individual test subjects, with the most individual subject variation seen in choice trials between female conspecific and Bengalese finch stimuli. The results are important for the design and interpretation of future behavioural and neurobiological experiments on species recognition systems using the zebra finch as a model species.     

Rhodopechys obsoleta (desert finch): a pale ancestor of greenfinches ( Carduelis spp.) according to molecular phylogeny

The evolutionary history of three out of four birds traditionally classified into the genus Rhodopechys birds has been studied by comparing their mitochondrial cytochrome b DNA sequence with that of greenfinches and other genus Carduelis finches. The desert finch (Rhodopechys obsoleta) or a sister extinct species seems to have existed about 6 million years ago in Asian and perhaps African desert-like areas. This bird has no molecular relationship with other Rhodopechys birds and seems to have given rise to the greenfinches radiation, probably by allopatry of marginal or isolated groups; the latter would have evolved to green plumage colours and more simple song modulations (i.e., greenfinches). The possible role of assortative mating and the newly postulated acquired phenotypic characters in greenfinches speciation are discussed.     

Comparison of whole wood and cellulose carbon and oxygen isotope series from Pinus nigra ssp. laricio (Corsica/France)

Stable isotopes in tree rings have widely been used for palaeoclimate reconstructions since tree rings record climatic information at annual resolution. However, various wood components or different parts of an annual tree-ring may differ in their isotopic compositions. Thus, sample preparation and subsequent laboratory analysis are crucial for the isotopic signal retained in the final tree-ring isotope series used for climate reconstruction and must therefore be considered for the interpretation of isotope–climate relationships. This study focuses on wood of Corsican Pine trees (Pinus nigra ssp. laricio) as this tree species allows to reconstruct the long-term climate evolution in the western Mediterranean. In a pilot study, we concentrated on methodological issues of sample preparation techniques in order to evaluate isotope records measured on pooled whole tree-ring cellulose and whole tree-ring bulk wood samples. We analysed 80-year long carbon and oxygen chronologies of Corsican Pine trees growing near the upper tree line on Corsica. Carbon and oxygen isotope records of whole tree-ring bulk wood and whole tree-ring cellulose from a pooled sample of 5 trees were correlated with the climate parameters monthly precipitation, temperature and the self-calibrating Palmer Drought Severity Index (sc-PDSI). Results show that the offsets in carbon and oxygen isotopes of bulk wood and cellulose are not constant over time. Both isotopes correlate with climate parameters from late winter and summer. The carbon and oxygen isotope ratios of cellulose are more sensitive to climatic variables than those of bulk wood. The results of this study imply that extraction of cellulose is a pre-requisite for the reconstruction of high-resolution climate records from stable isotope series of P. nigra ssp. laricio.     

Vocal types in crossbill populations (Loxia spp.) of Southwest Europe

The evolution of crossbills is one of the most fascinating topics in evolutionary ecology. Recent studies have shown an astonishing divergence in terms of vocalisation between morphologically quite similar crossbill populations in the Red/Common Crossbill complex (Loxia curvirostra) of North America and Europe. Some evidence even indicates the existence of “cryptic” species with different vocal types and bill sizes, which are adapted to different conifer species. However, there is so far no strong genetic evidence for the existence of separate species, although assortative mating occurs with respect to bill size. To understand the role of vocalisation in the speciation process of crossbill taxa, basic studies that assess the distribution of vocal types of crossbills and the use of different habitats and resources are needed. In our study, we investigated the occurrence of crossbill vocal types in Southwest Europe. In addition to the well-known vocal types described first by Robb (Dutch Birding 22:61–107, 2000) for the Benelux and Great Britain, we discovered at least six more vocal types in the Mediterranean area. Some vocal types were found exclusively in rather small areas, e.g. in the Pyrenees, the Sierra de Cazorla, Sierra de Javalambre and on Corsica, and appeared to be tightly linked to certain habitat types and pine species. Overall, vocal types in the Mediterranean had a more local occurrence than vocal types from northern populations, which were more widely distributed. This might reflect the nomadic behaviour of northern European crossbills, which feed, in contrast to Mediterranean crossbills, mostly on rather unstable food sources, especially spruce seeds. Furthermore, the vocal types of Mediterranean crossbills show at least some similarities to the vocal types of the rather sedentary crossbills of North Europe (L. pytyopsittacus, L. scotica), which are as well adapted to pine seeds. This might reflect a common ancestry of crossbills adapted for pines. We therefore suggest the existence of two main groups of crossbills in Europe: one group that is rather sedentary and feeds mainly on pine seeds (L. pytyopsittacus, L. scotica and the Mediterranean forms), and another group in Central, Northern and Eastern Europe that is highly nomadic and mostly feeds on spruce seeds (L. curvirostra). Further studies are needed to unravel the consistency of vocal types and the genetic relationship between the different forms, and to provide more evidence for the degree of assortative mating of crossbills with distinct vocalisation breeding in sympatry.     

Habitat selection of the Corsican Nuthatch (Sitta whiteheadi) after a fire

The Corsican Nuthatch Sitta whiteheadi is a bird endemic to Corsica Island and has a very small population. Its habitat, Corsican pine Pinus nigra laricio forest, is currently restricted to less than 16,000 ha and is threatened by forest fires. In this article, we aim (1) to evaluate the effects of a large wildfire on a Nuthatch population, and (2) to identify the habitat features that influence the presence/absence of the Nuthatch after fire, so as to promote appropriate forestry practices after fire. The study has been conducted on a study plot of 300 ha which is part of a larger area severely burnt in August 2003. Habitat characteristics have been investigated on 39 plots of 1,225 m² occupied by the bird, and 22 randomly chosen plots without the Nuthatch. We observed a decrease of 37.5% in Nuthatch abundance the first spring after the fire, but the impact showed great local variation as a function of fire severity. Logistic modelling showed that the presence of Nuthatch mainly depended on the degree of crown alteration: the Nuthatch tended to be present when at least one pine had less than 2.5 m of crown burned. We have no evidence of any direct fire-induced mortality, but several effects of fire can explain this population decrease, namely, the reduction of canopy volume, the decrease of the amount of pine seeds, and the reduction of nest-site availability. These results permit us to propose a simple criterion that can help in choosing the plots to be cut where salvage logging is necessary.     

Correlated changes in male plumage coloration and female mate choice in cardueline finches

The coevolution of extravagant male traits and female mate preferences is a central tenet of sexual selection theory. In lineages in which males have developed more elaborate sexual characters, females favour the most extreme expression of the trait. In some taxa, however, ornamental displays have evolved from more to less exaggerated states. Under these circumstances, it is unclear whether females show preferences for an ancestral male condition or for the current, less elaborate display. Here, we tested female mate preferences relative to male ornamental coloration in two species of cardueline finch (the American goldfinch, Carduelis tristis, and pine siskin, Carduelis pinus) that have evolved less elaborate carotenoid-based colour displays from more elaborately coloured ancestral states. We presented females of each species with a choice of males having either large patches of red colour (the elaborate, ancestral condition) or with species-typical patches of yellow colour (the less elaborate, derived state). Female goldfinches and siskins showed consistent preferences for the natural colour displays of males, and not for the more elaborate, ancestral colour pattern. Previous research on another cardueline finch taxon (a subspecies of the house finch, Carpodacus mexicanus griscomi), however, showed that females prefer more elaborate, ancestral coloration to the current form of reduced colour expression. The lack of congruence between male trait expression and female trait preference in the lineage with the most recently derived reduction in trait expression suggests that there may be evolutionary lags in the correspondence between male traits and female preferences. A shift in the expression of male coloration appears to be the first step towards the evolution of reduced colour displays in these finches.     

Preference and performance of the sawfly Diprion pini on host and non-host plants of the genus Pinus

The sawfly, Diprion pini L., is a pest of Pinus in Europe and is mainly found on P. sylvestris L. and P. nigra laricio Poiret. The relative importance of female oviposition capacity and behaviour, egg development, and larval survival on a new host plant was measured on 11 pine species. Five were natural host plants and six non-host plants, five of which are not indigenous to Europe. Oviposition choice tests showed that females discriminated between the pine species. Egg and larval development also differed between pine species. However, the female choice was not linked with hatching rate and larval development. Results of biological tests clearly indicated that there were different response patterns of D. pini life stages in relation to pine species, and these patterns were the same with insects of four different origins. We discuss the importance of each potential barrier to colonisation of a new host.     

Polymorphic microsatellite loci from the American goldfinch (Carduelis tristis) and their cross‐amplification in a variety of passerine species

Cardueline finches have become important models in studies of sexual selection. Here I describe eight polymorphic microsatellite loci isolated from the American goldfinch (Carduelis tristis) that are useful in parentage and heterozygosity studies. The number of alleles per locus ranged from eight to 38 based on 252 goldfinches. The markers are polymorphic in at least four other Cardueline finch species, and several amplify in nonfinch passerines including red‐winged blackbird (Agelaius phoeniceus), black‐throated blue warbler (Dendroica caerulescens) and tufted titmouse (Baeolophus bicolor), indicating they should be useful in paternity and population studies of a variety of species.     

Discovery of the Large Blue Flycatcher Cyornis [banyumas] magnirostris breeding in northern Kachin State (Burma/Myanmar) and taxonomic implications for the Cyornis-group

The little-known taxon Cyornis [banyumas] magnirostris has long been treated as a race of the widespread Hill Blue Flycatcher C. banyumas, with which it was thought to be allopatric during the breeding season. On the basis of morphology, magnirostris has lately been considered a full species, endemic as a breeder to northeastern India. Our recent field work during migration and the breeding season (September 2005 and June–July 2006) has, however, resulted in the first records of magnirostris from northern Burma/Myanmar, establishing that its breeding range broadly overlaps the range of C. banyumas whitei. We demonstrate how historical factors, sources of error, including fraud, errors of omission and commission, and inferences based on lack of data have all negatively affected assessment of species limits and conservation status in this speciose group of flycatchers. We also provide evidence that the taxon C. [banyumas] lemprieri is highly distinct and should be treated as a full species.     

Flock size and habitat-dependent food and energy intake of foraging Goldfinches

Summary During the breeding season Goldfinches (Carduelis carduelis L.) feed on milky ripe seeds of about 20 food plants. Individual Goldfinches joining a flock reduce the time spent vigilant with increasing flock size. Therefore birds feeding in flocks get an increased intake of kernels per time unit. This was measured for five different food plants (Dactylis glomerata (Gramineae), Knautia arvensis (Dipsacaceae), Senecio vulgaris, Taraxacum officinale, Tragopogon pratensis (Compositae)). In large-sized flocks, birds fed up to 2.3 times more kernels, than when feeding solitarily. In addition, visibility in the vegetation leads to a further increase of kernel intake. Thus feeding under good conditions as in recently mown areas, can raise kernel intake to the seven fold per time unit as compared to solitary feeding. The maximum ingestion rate of kernels was 98 per min which implies a head up-and-down movement every 0.6 s. The calculated energy intake of birds per time unit is lowest in Senecio and highest in Tragopogon. Thus the birds, when feeding on Tragopogon in larger flocks, can gain an energy intake 16 times higher than that reached when feeding on Senecio, despite of a higher kernel intake rate. The energy intake individual Goldfinches gain at the particular plant species is markedly increased with flock sizes up to eight birds, with larger flocks the intake increases only slightly.     

Reproductive success and nestling diet in the Lesser Spotted Woodpecker ( Picoides minor ): the early bird gets the caterpillar

Populations of Lesser Spotted Woodpecker (Picoides minor) are decreasing in size, necessitating management strategies. However, data on the reproductive biology of this species are scarce. The aim of this study was to investigate the influence of timing of breeding and nestling diet on the reproductive success of the Lesser Spotted Woodpecker and thereby contribute to an understanding of the determinants influencing its reproductive success. During 6 study years between 1996–2003, we investigated various variables of reproductive success in a Lesser Spotted Woodpecker population in the Taunus low mountain range, Germany. We observed nestling feeding at breeding holes to assess the composition of nestling diet and how it changes during the season. Clutch size, number of fledglings as well as body mass of the nestlings declined with the start of egg laying. Pairs composed of individuals that had breed together in previous years started egg laying earlier than newly established pairs. Nestling diet consisted mainly of aphids, caterpillars, craneflies and wood-living larvae. The composition changed considerably within the breeding season in both early and late broods. However, early broods were provided with caterpillars more frequently, whereas late broods received wood-dwelling larvae more often. Our results suggest that Lesser Spotted Woodpeckers time their breeding so as to coincide with the early nestling stage with the highest availability of caterpillars, since this is the time of highest energy demand. Moreover, food availability declines during the breeding season, and the decline in reproductive performance seems to be an effect of this development.     

Dynamics of Mycoplasmal Conjunctivitis in the Native and Introduced Range of the Host

In 1994, Mycoplasma gallisepticum, a common bacterial poultry pathogen, caused an epidemic in house finches in the eastern part of their North American range where the species had been introduced in the 1940s. Birds with mycoplasmal conjunctivitis were reported across the entire eastern United States within 3–4 years. Here we track the course of the Mycoplasma gallisepticum epidemic as it reached native, western North American populations of the house finch. In 2002, Mycoplasma gallisepticum was first observed in a native house finch population in Missoula, MT, where it gradually increased in prevalence during the next 2 years. Concurrently, house finches with conjunctivitis were reported with increasing number in the Pacific Northwest. In native populations of the host, the epidemic expanded more slowly, and reached lower levels of prevalence than in the eastern, introduced range of the species. Maximal prevalence was about half in the Missoula population than in local populations in the East. Although many factors can contribute to these differences, we argue that it is most likely the higher genetic heterogeneity in western than in eastern populations caused the lower impact of the pathogen.     

Use of spatial and colour cues by foraging pine siskins (Carduelis pinus): A field study

Pine siskins (Carduelis pinus) frequently forage at known high quality food supplies such as backyard feeders. In this field study, pine siskins visited backyard feeders of differing colour and spatial position. The three feeders contained varying amounts of food in a ratio of 3:2:1. The birds quickly distributed their visits in this ratio to the three feeders. During unbaited tests, two feeders on a given day had their positions swapped. The siskins appeared to primarily use both large-scale spatial or distal cues when foraging as well as local colour cues.