Macrogeographic variations in food choice of mainland citril finches Carduelis [citrinella] citrinella versus insular Corsican (citril) finches Carduelis [citrinella] corsicanus

We studied variations in diet composition in sub-populations of mainland citril finches Carduelis [citrinella] citrinella in European mountain chains, compared to closely related insular Corsican (citril) finches Carduelis [citrinella] corsicanus on several Mediterranean Islands with a special emphasis on key food plants used during the breeding period. We found that citril finch sub-populations of the Pre-Pyrenees and the Black Forest rely mostly on mountain pine and dandelion seeds as main food resources during the breeding season. In contrast, insular Corsican finches on the Mediterranean islands of Capraia and Corsica fed mainly on various herb species. Finches in Corsica fed predominantly on shepherd’s purse, while birds from Capraia were choosing rosemary as their main food plant during the breeding period. These observations confirmed the previously expected difference in food choice between the two forms due to the observed increased niche breadth on Corsica. However, Corsican finches on Sardinia showed a food choice more similar to that of the citril finch populations, in that they fed predominantly on black pine seeds during breeding season. Thus we were not able to find clear behavioural differences in diet composition between all studied sub-populations of citril and Corsican finches. To conclude, food choice of both forms is highly adaptive and, in the different breeding areas, distinct key plants may be of special importance during the breeding season. The preference for these plants is likely to be linked to their abundance and their energetic and nutritional content.     

Genetic differences among mainland and insular forms of the Citril Finch Serinus citrinella

The Citril Finch Serinus citrinella breeds in several mountains of central and southern Europe and on Corsica, Sardinia and Tuscany islands. Several studies have emphasized differences in phenotype and vocalization, and some authors consider mainland and insular forms to be two distinct species. A genetic approach based on the sequences of a mitochondrial DNA fragment was used to estimate genetic distance separating several populations. Individuals from the Alps and the Pyrenees belong to one group and the individuals from Corsica to the second. These results, discussed together with data on ecology, biometrics and vocalization, suggest keeping only one polytypic species which includes two distinct forms.     

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.     

Patterns of Genetic and Reproductive Traits Differentiation in Mainland vs. Corsican Populations of Bumblebees

Populations on islands often exhibit lower levels of genetic variation and ecomorphological divergence compared to their mainland relatives. While phenotypic differentiation in characters, such as size or shape among insular organisms, has been well studied, insular differentiation in quantitative reproductive traits involved in chemical communication has received very little attention to date. Here, we investigated the impact of insularity on two syntopic bumblebee species pairs: one including species that are phylogenetically related (Bombus terrestris and B. lucorum), and the other including species that interact ecologically (B. terrestris and its specific nest inquiline B. vestalis). For each bumblebee species, we characterized the patterns of variation and differentiation of insular (Corsican) vs. mainland (European) populations (i) with four genes (nuclear and mitochondrial, 3781 bp) and (ii) in the chemical composition of male marking secretions (MMS), a key trait for mate attraction in bumblebees, by gas chromatography-mass spectrometry (GC-MS). Our results provide evidence for genetic differentiation in Corsican bumblebees and show that, contrary to theoretical expectations, island populations of bumblebees exhibit levels of genetic variation similar to the mainland populations. Likewise, our comparative chemical analyses of MMS indicate that Corsican populations of bumblebees are significantly differentiated from the mainland yet they hold comparative levels of within-population MMS variability compared to the mainland. Therefore, insularity has led Corsican populations to diverge both genetically and chemically from their mainland relatives, presumably through genetic drift, but without a decrease of genetic diversity in island populations. We hypothesize that MMS divergence in Corsican bumblebees was driven by a persistent lack of gene flow with mainland populations and reinforced by the preference of Corsican females for sympatric (Corsican) MMS. The impoverished Corsican bumblebee fauna has not led to relaxation of stabilizing selection on MMS but to consistent differentiation chemical reproductive traits on the island.     

Interlocality variation in speed of moult in the Citril Finch Serinus citrinella

The speed of avian moult has been related to body condition, and this to habitat quality. These facts suggest a relationship between habitat quality and moult speed. We looked for evidence of such a relationship in the Citril Finch Serinus citrinella in the Pyrenees, where, because of a Mediterranean influence, there is an important bioclimatic contrast between north- and south-facing slopes of the same mountain. This contrast strongly affects the general body condition of birds there (higher body mass, fat score and survival on north-facing slopes). Citril Finches in the higher quality area moulted more rapidly (measured as residual wing raggedness) than those in the lower quality area, the two sampling localities being only 5 km apart. As the birds initiated moult at the same time in the two locations, this difference in speed cannot have resulted from a differential effect of photoperiod. This stresses the importance of habitat selection, even at very small scales, for the completion of moult.     

Temperature‐correlated shifts in the timing of egg‐laying in House Finches Haemorhous mexicanus

Although temperature‐correlated shifts in the timing of egg‐laying have been documented in numerous bird species, the vast majority of species examined to date have been those that breed in Europe and have an animal‐based diet during breeding. However, given that the timing of breeding can be driven, either in the proximate or in the ultimate sense, by seasonal fluctuations in food availability, the relationship between temperature and laying may differ with diet. Here, we report on patterns of reproductive timing in House Finches Haemorhous mexicanus, a North American species that breeds on a primarily seed‐based diet. Analysing nest records from House Finches in California spanning more than a century, we found that egg‐laying occurred significantly earlier in warmer springs. We also found that although the timing of egg‐laying does not show long‐term changes in most of California, in the hottest region of the state (the southeast desert basin) it has advanced significantly.     

On humans and wildlife in Mediterranean islands

Aim To investigate the effects of human‐induced landscape changes in Mediterranean islands on the ecological and evolutionary responses of bird communities and populations. The combination of mass extinction of large mammals and massive deforestation by humans was hypothesized to produce new selection regimes to which organisms were likely to respond. Habitat selection and niche breadth have been investigated at the scale of species, and phenotypic variation at the scale of local populations. Location The study was carried out along habitat gradients and in habitat mosaics at different spatial scales on the island of Corsica and in areas of similar size and structure in continental France. Methods Two sets of gradients have been used for investigating habitat selection and niche breadth: gradients of altitude, and gradients of vegetation structure. Population studies focused on the blue tit, Cyanistes caeruleus. Large samples of breeding attempts by this species in 10 habitats provided detailed data on phenotypic variation of fitness‐related traits both on Corsica and on the mainland. Results The extent of niche space used by birds differed substantially depending on which habitat gradient was considered. Many species have been found to contract their habitat niche along the elevation gradient on Corsica compared with the mainland, whereas all species in the vegetation gradient broadened their niche on the island. Breeding patterns of the blue tit differed considerably depending on whether they settle in deciduous oaks (Quercus humilis) or in evergreen sclerophyllous oaks (Quercus ilex). Phenotypic variation of breeding traits was much higher on the island, where more populations were correctly timed for the best breeding period than on the mainland, a pattern that is likely to result from lower dispersal of organisms on the island. Main conclusions The differences in observed niche breadth between the two series of habitat gradients is explained both by the species‐specific ecology of the species and the human‐induced environmental history of Corsica. Large‐scale landscape changes provided new opportunities for island colonization by non‐forest species, which are isolated as small, ‘fugitive’ local populations. In both gradients, forest species that are typical components of the Corsican bird fauna definitely expanded their niche and occupied a wider range of habitats on Corsica than on the mainland. At the population scale, landscapes included habitat patches with contrasted selection regimes, which resulted in high phenotypic variation for many fitness‐related traits. Reduced dispersal of birds on the island resulted in a much higher degree of local differentiation on Corsica than on the mainland.     

Competition for resources mediated by intrinsic social dominance in sympatric finches

Gouldian Erythrura gouldiae and Long‐tailed Finches Poephila acuticauda are morphologically and ecologically similar sympatric species, for which social dominance relationships are likely to determine access to critical limiting resources. Building on previous research showing that Long‐tailed Finches dominate competition for nest‐sites, I staged dyadic contests for food between the two species in captivity in order to test social dominance dynamics under controlled conditions. Long‐tailed Finches were likely to dominate interactions with Gouldian Finches and expressed higher levels of aggression while competing for access to food. These results suggest a stable dominance relationship between the two species which could be affecting Gouldian Finches' access to food resources in the wild, potentially constraining their ability to recover from recent population declines.     

Why do Corsican Blue Tits Cyanistes caeruleus ogliastrae not use nest boxes for roosting?

We compared winter roosting behaviour of Blue Tits Cyanistes caeruleus in the mainland of southern France and on the island of Corsica in small-holed nest boxes. While in southern France Blue Tits use nest boxes for roosting, Corsican Blue Tits do not. We suggest that this behaviour is innate because Corsican wild-caught as well as F1 and F2 birds born in captivity do not use nest boxes in aviaries even when kept adjacent to mainland tits that sleep in boxes. We suggest that the cost/benefit balance differs between mainland France and Corsica: in Corsica, the costs of roosting in the canopy are less than in mainland France because (1) predators, e.g. owls, are rare in Corsica while abundant on the mainland, (2) the permanent evergreen foliage of the dominant tree in Corsica, the holm oak, could be preferred to nest boxes which are not risk-free, and (3) the costs of using cavities for roosting could be higher in Corsica because of increased mammal predator pressure and higher ectoparasite load than on the mainland.     

陕西红碱淖同域分布遗鸥与棕头鸥巢址选择比较

2009—2011年4—7月在陕西红碱淖对同域分布的遗鸥和棕头鸥巢参数特征、巢群空间分布和巢址生境选择进行了对比分析。结果表明:巢外径、巢深、巢高等参数均存在显著差异,这主要是与营巢生境和巢址空间分布上有关;从巢群空间分布上来看,两者均选择于湖心岛上营巢繁殖,巢群呈斑块状分布,但彼此没有混巢现象,有时甚至通过压缩种间巢间距来达到共存,由于遗鸥繁殖群体数量占优势,遗鸥总是占据最佳的巢域,棕头鸥巢群通常被排挤至湖心岛边缘部分;在巢址生境选择上,植被类型、植被高度、植被盖度、巢离水面高度和巢距最近水边距离均存在显著差异。这表明两者巢址生境选择上具有特异性,这种特异性使得巢址生境选择上存在生态位差异,促成了遗鸥和棕头鸥能在同一湖心岛上营巢繁殖因素之一。     

Local breeding experience and the reproductive performance of Tree Swallows

ABSTRACT The potential advantages of repeated breeding at a particular location should improve reproductive performance in long‐lived species of birds. However, for short‐lived species, natural selection should favor individuals that most quickly develop competency in reproduction. Therefore, we hypothesized that local breeding experience beyond the first breeding attempt at a particular location would have little effect on subsequent reproductive performance of Tree Swallows (Tachycineta bicolor), a species where about 50% of adults breed only once in their lives. We tested this hypothesis using data collected from Tree Swallows in Michigan from 1993 to 2002. Because we were specifically interested in examining the effects of local breeding experience on reproductive performance, we restricted our analyses to after‐second‐year (ASY) females and their mates that we first encountered as breeders. Consistent with our hypothesis, we found no relationship between repeated local breeding experience and the reproductive performance of ASY female Tree Swallows and their mates as measured by clutch size and number of fledged young. However, pairs with more combined total local experience tended to lay eggs earlier in the season. These results suggest that Tree Swallows may benefit from breeding site fidelity, not because repeated local experience improves reproductive performance as measured by the production of fledglings, but because returning individuals acquire nest cavities earlier and are able to begin breeding earlier, providing time to renest in case of early nest failure.     

Nest site availability and niche differentiation between two cavity‐nesting birds in time and space

Niche differentiation is a key concept in the field of ecology and refers to the process by which competing species within an ecological community partition utilization of environmental resources to achieve coexistence. The existence of niche differentiation is uniquely difficult to prove on account of the fact that historical interaction among species, which plays a key role in elucidating the current state of coexistence among species, is not well known. We created continuous niche gradients in nest‐site resources between two sympatric secondary cavity‐nesting birds, the green‐backed tit (Parus monticolus) and the russet sparrow (Passer cinnamomeus), and investigated whether nesting site is a factor contributing to limiting breeding overlap by regular inspection and 388,160 min of film recording. Our results indicate that although we manipulated nest site availability to be uniformly high along the habitat gradient, the two bird species have little overlap in nest sites and rarely compete for them. Furthermore, the green‐backed tit possessed a wide range of fundamental niche that covered that of the russet sparrow, while their reproductive time was largely segregated. The sparrow was more aggressive and outcompeted the tit in their overlapped range. These results suggest that even though nesting sites are crucial to the reproduction of cavity‐nesting birds, some other factor plays a more important role in limiting niche overlap between sparrows and tits in space and time. Given that these two cavity‐nesting birds continued to use different habitats and breed in segregated time after our manipulation, their relationship is better explained by the ghost of competition past theory.     

人工巢箱条件下两种山雀鸟类的同域共存机制

种间竞争会导致鸟类对自身的生存策略进行多方面调整,将多种因素结合起来分析不同鸟类的同域共存机制具有十分重要的意义.2009-2011年的3-7月,在辽宁省东部山区以悬挂人工巢箱的方法招引杂色山雀(Parus varius)和大山雀(Parus major),通过比较这两种鸟类在繁殖时间、繁殖参数和巢址选择上的差异,分析其繁殖期的栖息地选择及繁殖对策,探讨这两种鸟类同域共存的机制.结果表明,生态位的部分分离是大山雀和杂色山雀能够长期共存的基础.两者都是在繁殖期到来立即开始繁殖,均出现两次繁殖高峰,采用消减窝卵数的对策来适应环境质量的下降.对繁殖参数的分析表明,两种鸟类的繁殖对策都为k-选择,但大山雀略偏向r端,大山雀倾向高窝卵数、低繁殖成功率的繁殖策略;杂色山雀倾向低窝卵数、高繁殖成功率的繁殖策略.两种鸟类都选择在林龄较长的森林中筑巢,但是大山雀较注重巢址的安全性能,巢距地面较高,周围乔木密集;杂色山雀较为注重植被类型的选择,巢址多选择在植被多样、灌木生长茂盛的针阔混交林中,推测可能与杂色山雀的食物构成有关.     

Aspects of breeding ecology of the eastern olivaceous warbler (Hippolais pallida)

The breeding ecology of eastern olivaceous warblers Hippolais pallida is poorly known. In this study, we provide data on nest site selection and breeding parameters of the species in a population in northwestern Bulgaria, the only one known to be regularly and heavily parasitized by the common cuckoo Cuculus canorus (hereafter cuckoo). Eastern olivaceous warblers only bred within human settlements of the study area, avoiding seemingly suitable habitat outside them. Nests were built in a wide range of plant taxa but ailanthuses Ailanthus altissima and mulberries Morus spp. were most frequently used (21%). After taking into account the availability of vegetation, there was an apparent preference for several plant taxa but not for mulberries. Mean nest height was 1.65 ± 0.98 (0.53–7.60) m, n = 217, and it varied significantly among different types of nesting substrate. Laying date and clutch size of first breeding attempts averaged 10 June ± 0.98 days, n = 101 and 3.9 ± 0.07 (2–5) eggs, n = 72, respectively. Hatching success, fledging success, and breeding success were 42.5, 86.4, and 36.7%, respectively. The main sources of nest mortality were predation and cuckoo parasitism, with no significant difference in the proportion of nests lost to each. Cuckoo parasitism seemed responsible for the relatively low hatching success in this population.     

Can variation in risk of nest predation explain altitudinal migration in tropical birds?

Migration is among the best studied of animal behaviors, yet few empirical studies have tested hypotheses explaining the ultimate causes of these cyclical annual movements. Fretwell’s (1980) hypothesis predicts that if nest predation explains why many tropical birds migrate uphill to breed, then predation risk must be negatively associated with elevation. Data from 385 artificial nests spanning 2,740 m of elevation on the Atlantic slope of Costa Rica show an overall decline in predation with increasing elevation. However, nest predation risk was highest at intermediate elevations (500–650 m), not at lowest elevations. The proportion of nests depredated by different types of predators differed among elevations. These results imply that over half of the altitudinal migrant bird species in this region migrate to safer breeding areas than their non-breeding areas, suggesting that variation in nest predation risk could be an important benefit of uphill migrations of many species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Conspecific-only experience during development reduces the strength of heterospecific song discrimination in Zebra Finches (Taeniopygia guttata): a test of the optimal acceptance threshold hypothesis

Conspecifics during development provide the most reliable sensory cues for species recognition in parental bird species. The Zebra Finch (Taeniopygia guttata) is a sexually dimorphic model species used for investigations of the behavioural cues and neurobiological substrates of species recognition. Regarding acoustic conspecific cues, theory predicts that exposure to both con- and heterospecific vocalisations and other environmental sounds results in more accurate auditory species discrimination, because diverse vocal cues during development shift optimal conspecific acceptance thresholds to be more restrictive to yield fewer acceptance errors. We tested the behavioural preferences of female and male Zebra Finches raised in an outdoor environment (Control) and female and male Zebra Finches reared in an indoor colony with exposure to Zebra Finches only (Restricted), to playbacks of songs of Zebra Finches, Zebra Finches cross-fostered by Bengalese Finches (Lonchura striata var. domestica), and Bengalese Finches. Several behavioural measures revealed minimal sexual dimorphism in discrimination but showed that Control subjects preferred conspecifics’ songs over either the songs of cross-fostered Zebra Finches or Bengalese Finches. Restricted Zebra Finches in contrast did not discriminate behaviourally between the three song types. These results support the concept of a shift in the species acceptance threshold in the restricted treatment resulting in more acceptance errors. We discuss future work to test the role of exposure to diverse vocal cues of both con- and heterospecifics in the ontogeny of song perception in this important laboratory model species for social recognition research.     

The relationship between introduced European Starlings and the reproductive activities of Mountain Bluebirds and Tree Swallows in British Columbia,Canada

The European Starling Sturnus vulgaris is an introduced species in North America and is an aggressive competitor for tree cavity nest‐sites. Starlings are commonly considered to influence nest‐site selection and reproductive success of native cavity‐nesting species negatively. We examined the relationship between Starling nest density and the fecundity of two native secondary cavity‐using passerines, Mountain Bluebird Sialia currucoides and Tree Swallow Tachycineta bicolor. We monitored a total of 622 nests (approximately equal numbers for each of the three species) in woodpecker‐excavated and naturally occurring cavities in 29 small forest groves in central British Columbia, Canada, between 2000 and 2009. The dimensions of cavities used and the timing of nest initiation overlapped for all species, although Starlings initiated clutches earliest. Mixed‐effects models were used to assess whether nest abundance, clutch size or nest success were affected directly by Starling nest abundance, or indirectly via a shift in cavity selection or timing of breeding. Starlings and Mountain Bluebirds showed inverse trends in nest abundance. Mountain Bluebird clutch sizes were smaller if they were initiated later in the breeding season. There was weak evidence that Tree Swallow clutch size decreased with cavity depth when Starling nests were abundant, and increased with cavity depth where there were few Starling nests. We conclude that despite the aggressive nature of this exotic cavity‐nester, the influence of Starlings on native secondary cavity‐nesting passerines is modest where cavities are abundant.     

Risk-taking behavior of bull-headed shrikes that recently colonized islands

Individuals which have invaded urbanized environments are reported to engage in riskier behaviors, possibly influenced by the scarcity of predators in urbanized areas. Here, we studied the risk-taking behavior of birds which had invaded a new natural environment, rather than an artificial urban environment, using recently established populations of the bull-headed shrike Lanius bucephalus, which naturally colonized three subtropical islands in Japan. We compared flight initiation distance (FID), the distance at which an individual approached by a human initiates flight, between the islands and the temperate mainland. FID was longer for the insular shrikes compared with the mainland shrikes after controlling for other factors, indicating that the individuals which had invaded a new natural environment had a lower propensity for risk-taking. A possible explanation for these results is that low risk-taking behavior might be adaptive on the islands due to predation by the black rat Rattus rattus, an unfamiliar predator not found in shrike habitats on the temperate mainland. Further studies are needed to examine the nest predation rate, predator species, and nest site selection of these insular shrike populations.     

HANDEDNESS, HOLDING AND ITS POSSIBLE TAXONOMIC SIGNIFICANCE IN GRASSQUITS, TIARIS SPP

The use of the foot to hold down nest material or food items was studied in two species of grass-quits. Two Cuban Olive Finches used only their left foot, and seven others used predominantly or exclusively their right foot. An Olive Finch from Costa Rica used mostly its left foot. Cuban Melodious Finches infrequently used the foot to hold down items. This difference in behaviour probably reflects differences in feeding ecology. The incidence of holding supports arguments for affinity between Tiaris spp. and geospizines.     

Colony and nest site fidelity of the rock shag ( Phalacrocorax magellanicus )

The rock shag (Phalacrocorax magellanicus) is an endemic species from southern Argentina and Chile. In Argentina, the population is distributed along the Patagonian coast in 143 small colonies (5–377 pairs). We studied colony and nest site fidelity of rock shags at Punta Loma, Patagonia, Argentina. We banded 37 adults from December 2001 to June 2003, during two breeding and two non-breeding seasons. Nest site fidelity was extremely high during consecutive breeding and also non-breeding seasons. The high percentage of banded birds residing in the colony in consecutive seasons suggests that rock shags are highly faithful to breeding sites and supports the idea of low post-breeding dispersion.