Diet of the Red-billed Chough Pyrrhocorax pyrrhocorax in south-east Spain

A sample of 140 Red-billed Chough pellets (35 from each season) was collected from communal roosting sites in south-east Spain. In almost every pellet there were three distinct dietary fractions: animal, vegetable and mineral. The animal faction constituted nearly 50% of the pellet volume in each of the four seasons. Wild grains and cultivated cereals were the most important vegetable elements, while 60% of animal prey (n= 3484) were beetles (mainly Tenebrionidae). There was marked seasonal variation in the composition of both the vegetable and animal fractions, the latter associated mainly with variation in the occurrence of Orthoptera, Lepidoptera larvae and Formicidae. Mixed flocks of Choughs and Jackdaws were common in the study area though agonistic interspecific interactions were never observed. The diets of the two species differ in that Choughs eat more beetles and wild seeds, whilst Jackdaws prefer ants and cereals. These observations support the hypothesis that competition from Jackdaws is not responsible for the reduction in the Chough's range.     

Ecogeographic correlates of morphometric variation in the Red-billed Chough Pyrrhocorax pyrrhocorax and the Alpine Chough Pyrrhocorax graculus

We estimated the magnitude of intraspecific geographic variation in the Red-billed Chough Pyrrhocorax pyrrhocorax and the Alpine Chough Pyrrhocorax graculus from the analysis of external measurements of museum specimens collected throughout the Palearctic ranges of the species. By means of univariate and multivariate techniques we tested the importance of climatic and geographic factors as potential agents that might have shaped Red-billed and Alpine Chough morphology, discussing the dynamics of the interplay between natural selection, gene flow and phylogenetic constraints. Both species exhibited concordance in character differentiation. Bergmann's rule offered a valid explanation of Red-billed and Alpine Chough body size variation with the largest birds being found at higher elevation, or in colder and more arid regions. Shape was also important. The extremities of the body (bill and tarsus) were longer in warmer areas, in line with Allen's rule. In the Alpine Chough, temperature seemed to be the most important cause of body trait variation, whilst in the Red-billed Chough geographic distance among populations (a measure of geographic isolation) and altitude were also significant. In this paper we critically evaluate the validity of subspecific categories quoted in the literature, given that most variation appeared to be clinal.     

Demographic consequences of prey availability and diet of Red-billed Choughs Pyrrhocorax pyrrhocorax

Capsule Variation in prey availability appears to influence Chough fledging success and juvenile survival.

Aims To determine seasonal and annual variations in Chough prey and how these influence fledging success and juvenile survival.

Methods Chough faeces (n = 437, 3905 invertebrates) were collected year-round and analysed to determine diet composition. Seasonal and annual variation in prey abundance in Chough foraging habitat was assessed using pitfall trapping (n = 747, 27 124 invertebrates) between 1996 and 2003. Fledging success was estimated for a population of 12 breeding pairs; juvenile survival was estimated by year-round resighting (n < 2500) of individual birds that were colour-ringed as nestlings.

Results From April to June a high biomass of prey and a great variety of species were observed. Between July and October, both biomass and species diversity were reduced; prey consisted mainly of ants and a few beetle species. From November to March, biomass availability was intermediate, with the diet consisting mostly of Tipulidae larvae, plants and dung beetles. Chough juvenile monthly survival was low in August, November and December. Annual variation in fledging success was correlated with prey biomass availability in May.

Conclusion Seasonal variation in the availability of prey species and their biomass influences Chough demography.     

A comparative analysis of the diets of the Chough Pyrrhocorax pyrrhocorax and the Alpine Chough Pyrrhocorax graculus coexisting in the Alps

The diets of the Chough Pyrrhocorax pyrrhocorax and the Alpine Chough Pyrrhocorax graculus coexisting in the western Italian Alps have been compared by faecal analyses. A total of 1581 fresh droppings (405 of the Chough and 1176 of the Alpine Chough) were collected in the pastures of the Rhêmes Valley, Aosta, Italy, from June to November 1992 and analysed in the laboratory, and a mean volume percentage for each item was calculated. Both species were omnivorous, including animal, vegetable and mineral dietary fractions. There was no overlap in the vegetable part of the diet since the Chough fed virtually exclusively on Yellow Gagea Gagea fistulosa bulbs (dug out from the soil), which were not taken at all by the Alpine Chough. Conversely, the Alpine Chough fed on berries and hips from September to November, but these were virtually ignored by the Chough. Even though animal items were collected by both species, their preferences were different. In June, Alpine Choughs largely collected cranefly (Tipula) larvae whilst Choughs mainly fed on Lepidoptera larvae. From July onward, Alpine Choughs mainly consumed grasshoppers while Choughs also collected Tipula pupae, Lepidoptera and fly (Bibionidae) larvae and beetles (Scarabaeidae and Staphylinidae). Interspecific morphological and behavioural differences may be partly responsible for the segregation observed. Chemical composition and caloric contents of the food items suggest that the balance between costs of collecting and benefits of consuming may also contribute to diet differentiation. Both species took a broad spectrum of food, and there was no clear indication that the different population densities of the two Choughs in the Alps were directly correlated with diet, even though some data suggest that during autumn the Alpine Chough might have a diet better adapted to the high mountain environment than the Chough.     

A comparative analysis of the foraging behaviour of the Chough Pyrrhocorax pyrrhocorax and the Alpine Chough Pyrrhocorax graculus coexisting in the Alps

The foraging behaviour of the Chough Pyrrhocorax pyrrhocorax and the Alpine Chough Pyrrhocorax graculus was studied during summer and autumn in the western Italian Alps. We assessed feeding times, feeding rates and foraging techniques associated with different foraging habitats. The Alpine Chough is mainly a ground surface feeder, stays for a rela-tively short time at a feeding site (on average 2.1 min) and feeds quickly (on average 9.2 items/min). In contrast, the Chough is almost exclusively an undersurface feeder (digger and prober), stays at a feeding site twice as long as the Alpine Chough (5.4 min) and feeds four times as slowly (2.2 items/min). These differences suggest that the degree of actual ecological overlap is almost as low as possible for two species using the same Alpine pastures as foraging sites. Interspecific coexistence has occurred through a clear differentiation of foraging strategies and diets. The foraging efficiency (in terms of feeding rate)of the Alpine Chough was always higher than that of the Chough in all habitats where they occurred together. The Alpine Chough was more variable in the use of foraging techniques and more diversified in the use of foraging habitats than the Chough. In both species, juveniles fed less efficiently than adults; the foraging behaviour of the Chough is probably more difficult to learn than that of the Alpine Chough. Other data have also shown that the Alpine Chough is more opportunistic than the Chough in using seasonally available food. Considering the above, we suggest that the foraging behaviour of the Alpine Chough is more flexible and, perhaps, better adapted to the high mountain Alpine environment than that of the Chough. Two hypotheses concerning the ultimate reason why the Alpine Chough and the Chough have evolved divergent beak morphology are discussed.     

Captive Husbandry and Socialization of the Red‐Billed Chough (Pyrrhocorax pyrrhocorax)

Since the 1970s, Paradise Park Wildlife Sanctuary in Cornwall, United Kingdom, has built up a captive flock of red‐billed choughs Pyrrhocorax pyrrhocorax and over 30 years has developed successful methods of keeping, breeding, and appropriately socializing them in captivity. A total of 77 nests reached the egg stage with 27 nests producing at least one young and 48 young fledging in total. Several components are important in achieving successful breeding and socialization. Provision of live food, especially ant's eggs and small mealworms and crickets, in the first days after hatching is essential, improving the condition of adults and survival of nestlings. Situating aviaries in quiet areas, away from public view, is important. Socialization in family groups during the winter months and allowing choughs to choose partners induces better compatibility. Introduction of nest cameras greatly improved young survival through early identification of health problems enabling treatment of young between hatching and 10‐days old, when mortality is otherwise highest, and enabling precautionary medication shortly after hatching. We show that clutch size increases significantly with female age and that direct intervention such as artificial egg incubation and hand rearing can be successful and worthwhile, but its requirement is reduced by closer monitoring. Red‐billed choughs provide a good model species to further develop captive management and release techniques that can then be applied to critically endangered species that show similar social and long‐learning behaviors. Captive breeding programs can play an important role in such work through provision of suitable birds and supporting avicultural expertise. Zoo Biol. 31:725‐735, 2012. © 2012 Wiley Periodicals, Inc.     

Vocalizations and morphology: interpreting the divergence among populations of Chough Pyrrhocorax pyrrhocorax and Alpine Chough P. graculus

Capsule Differences in vocalizations among populations are mostly explained on morphological bases, but historical factors may have played a significant role in differentiation processes.

Aims To investigate the relationships among vocal and morphological variation in two corvids: Chough and Alpine Chough.

Methods We used data from 11 populations of Chough and seven populations of Alpine Chough spanning the Palearctic distribution of the two species. Three data sets (morphometry, spectrotemporal parameters of trill calls and acoustic repertoire) were analysed and their variation compared with uni- and multivariate techniques.

Results In both species, morphological differences among populations were correlated to spectro-temporal variation of trills; in particular, frequencies of calls were negatively correlated to wing length (an indicator of body size). By considering only co-existing populations of the two species, the magnitude of morphological and spectrotemporal divergence was similar.

Conclusions In both species, birds from populations with similar morphology uttered similar call types and trills with close spectrotemporal features. In particular, larger-sized populations, as expressed by wing length, emitted lower pitched calls. However, the fact that dissimilarities in repertoire and morphology were correlated cannot be explained only by appealing to functional explanations, as the observed intraspecific morphological variability does not seem to be high enough to promote consistent changes in the pool of calls. In this case, historical factors might have contributed to the present pattern of differentiation.     

A comparative analysis of the breeding biology of the Red-billed Chough Pynhocorax pyrrhocorax and the Alpine Chough P. graculus coexisting in the Alps

We compare the breeding biology of a small population of Red-billed Chough Pyrrhocorax pynhocorax with that of the Alpine Chough P. graculus coexisting in the western Italian Alps. The analysis focused on nest site choice, timing of breeding, reproductive success and parental effort (assessed by means of behavioural indices such as food provisioning rates and time budgets inside and close to the nest). The Alpine Chough nested in a greater variety of sites: natural cliffs, windows of a dam, pot-holes and abandoned buildings; the Red-billed Chough used only natural cliffs. Laying dates also differed significantly, with the Red-billed Chough breeding one month earlier than its congener. Differences in the feeding ecology of those species might be responsible for the observed temporal partitioning, thus facilitating coexistence. Breeding success and reproductive behaviour were similar, and the species differed in only one out of eight breeding parameters. It is suggested that similar strong constraints on breeding behaviour have resulted in the similarities in behaviour seen in these species.     

Linking territory quality and reproductive success in the Red-billed Chough Pyrrhocorax pyrrochorax: implications for conservation management of an endangered population

As changes in land use have been identified as the main factor explaining the decline in Red-billed Chough Pyrrhocorax pyrrochorax populations across western Europe, a study was carried out in Ouessant (western France) in order to assess the relationship between territory quality and reproductive success. As such an approach could be hindered by the fact that the birds' reproductive performance could be influenced by their breeding experience, we analysed both inter- and intranest-site variation in fledging success. Territory quality was quantified, combining habitat selection, territory size, the amount of feeding area and distance between nest and feeding area. Feeding habitats selected positively by Red-billed Choughs were characterized by a mean sward height of less than 5 cm. Foraging area was on average 21 557 m². Feeding areas (i.e. feeding habitat within foraging area) close to the nest were used preferentially. Fledging success appeared to be influenced neither by the total area of feeding sites in a Chough territory, nor by the mean feeding flight distance. However, fledging success adjusted to nest-site and year appeared to be influenced by feeding area close to the nest: one additional fledgling was expected for each additional 10 000 m² of feeding habitat within 300 m of the nest. These first results allowed us to consider recommending landscape management measures to ensure a favourable conservation status of local Chough populations.     

红嘴山鸦青藏亚种鸣声的初步探讨

2006 年10月,在四川省若尔盖县铁布自然保护区,对红嘴山鸦鸣声进行了记录并将其主要鸣声进行了声谱分析.非繁殖期红嘴山鸦具有联络、呼唤、应答、报警、惊叫和集群觅食鸣声6种叫声,其中联络和报警声最为常见,呼应声和应答声是一个连续的过程;获得了联络、呼唤、应答、报警、惊叫和集群觅食鸣声6种叫声的语谱图及其频谱特征.初步探讨了红嘴山鸦的鸣声与其相应行为之间的关系.     

The relationship between Red-Billed Chough Pyrrhocorax pyrrhocorax (L) breeding populations and grazing pressure on the Calf of Man

A link between the numbers of Loghtan Sheep Ovis aries var. and breeding pairs of Red-Billed Choughs Pyrrhocorax pyrrhocorax has been described for the Calf of Man, Isle of Man, UK, through the analysis of data from 1969 to 1982. Recent research has included further data on populations of Choughs and Sheep grazing, as well as data on brood sizes, Rabbit Oryctolagus cuniculus populations and summer rainfall. Data from 1969 to 1994 show a significant relationship between Sheep and Chough numbers, although data for the period 1983 to 1994 in isolation show no significant association. The mean (± se) brood size ringed in the nest in the period 1959–94 was 2.91 ± 0.011. Between 1972 and 1994, as Sheep numbers peaked, mean brood size decreased, only to rise again as Sheep numbers declined. High Rabbit populations correspond statistically with large Chough broods and increased fledging success. Declines in the Chough breeding population appear to be most closely linked to declines in Rabbit numbers due to outbreaks of myxomatosis, even during periods when Sheep numbers were maintained. The recovery of the Chough population after 1970 corresponds with a change in the effects of myxomatosis outbreaks. Rabbit grazing appears to be equally as important as Sheep grazing in the maintenance of the sward characteristics favoured by breeding Choughs. Combined data on Sheep and Rabbit grazing describe the fluctuations observed in Chough breeding success more fully than data for either grazer alone.     

Effects of nest-site availability and distribution on density-dependent clutch size and laying date in the Chough Pyrrhocorax pyrrhocorax

We compared the breeding phenology and clutch size of Choughs Pyrrhocorax pyrrhocorax in three Spanish areas that differed in feeding habitat, breeding environmental conditions and the distribution and availability of different nesting sites (cliffs or artefacts). The variation in the timing of laying seemed to be related to differences in climatic conditions determined by the altitude. The variation in clutch size was associated with the different use that Choughs made of the feeding areas because of the contrasting availability and distribution of their nesting sites. Within southeastern Madrid, clutch size of the Chough decreased and its variance increased at high nest densities on cliff sites, suggesting that density dependence in fecundity arises from habitat heterogeneity rather than by interference. At high densities, individuals, territories, nest sites or a combination of these may differ in quality, thus promoting differences and increasing the variance in the initial investment of reproductive effort. The syncronization of the onset of laying at increased breeding densities suggests that social influences arising from communal foraging or avoidance of predation by early warning and predator swamping may be acting also. We suggest that nest-site availability and distribution have a major influence on the social organization of Choughs through their breeding and foraging strategies.     

Social structuring at a communal roost of Choughs Pyrrhocorax pyrrhocorax

The social structure of a communal roost of Choughs Pyrrhocorax pyrrhocorax was studied between July and September 1985. Different age classes within the roost were spatially segregated. Third-year birds were significantly more likely to attack another Chough and roosted in the densest part of the roosting flock. First-year birds roosted significantly lower down the roost cliff and on the periphery of the flock.     

Capercaillie Tetrao urogallus in Scotland - demography of a declining population

Capercaillie Tetrao urogallus numbers declined in Scottish forests between 1992 and 1997, although the rate (mean 16% per year, 95% CL 1–30%) differed among forests. Hens declined more quickly than cocks despite the sex ratio in chicks favouring females. A probable explanation is that adult cocks lived longer. Juvenile survival was less than adult survival, largely because juveniles were more likely to die from hitting fences. Although poor reproduction was probably the main cause of the decline, this might not have occurred had fence strikes been substantially fewer.     

The dynamics of parental care in Choughs(Pyrrhocorax pyrrhocorax)

Summary The dynamics of parental investment throughout the nestling stage and the factors affecting it were studied in the Chough(Pyrrhocorax pyrrhocorax), a species whose patterns of apportioning parental care are largely unknown. The occurrence of important trade-offs between the sexes, among the different activities of parental care and between parents' survival and current offspring survival were estimated. The parental contributions of both sexes were assessed mainly in terms of food provisioning rate and nest attendance time. Only the female brooded young nestlings while the two sexes contributed equally in food deliveries and nest sanitation. Nestling age greatly affected nest attendance time. The female spent a long time brooding in the first 10 days after hatching. Both sexes increased attendance towards the end of the nestling stage. Conversely, feeding rate and feeding rate per nestling remained approximately constant throughout the nestling period. Nestlings in smaller broods received more feeding visits than those in larger broods. The shape of the per-nestling feeding rate curve was concave-up, supporting Nur's (1984) trade-offs model rather than the Lack-Gibb hypothesis. Maintaining a high feeding frequency in broods already above the modal value might be disadvantageous, implying few benefits and large energy costs (i.e. the reduction of the parents' residual reproductive value). Female brooding time in relation to brood size showed the same decreasing concave-up trend line. Short-term trade-offs proved to be important determinants of the dynamics of parental care. Specifically, the distance from the feeding areas greatly affected the delivery rate: pairs spent a disproportionately longer time foraging in more distant patches than in closer ones. Diurnal variations and changes owing to weather conditions were also examined.

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Die Dynamik elterlicher Investition bei der Alpenkrähe(Pyrrhocorax pyrrhocorax)

Zusammenfassung Der elterliche Aufwand und die geschlechtliche Verteilung des Brutaufwandes bei Alpenkrähen ist weitgehend unbekannt. Ziel der Arbeit war es deshalb, die verschiedenen Aktivitäten der elterlichen Brutversorgung und deren Konsequenzen für die Überlebensverhältnisse der Eltern und des Nachwuchses näher zu untersuchen. Die Fütterung der Brut und die Anwesenheit und Betreuung am Nest standen im Mittelpunkt. Während nur das Weibchen brütete, teilten sich die Eltern die Jungenaufzucht und die Pflege des Nestes etwa gleichmäßig, wobei das Nestlingsalter einen erheblichen Einfluß auf die Nestversorgung hatte. In den ersten 10 Tagen huderte das Weibchen intensiv. Beide Eltern steigerten ihre Brutpflege zum Ende der Nestlingszeit. Dagegen blieben die Fütterungsrate und die Anzahl Fütterungen je Nestling über die gesamte Nestlingszeit in etwa konstant. Junge in kleineren Bruten erhielten mehr Fütterungen als solche in großen. Der Verlauf der Abhängigkeit der Fütterungen je Nestling von der Brutgröße stützt mehr die Hypothese von Nur (1984) als die von Lack und Gibb. Die Aufrechterhaltung einer hohen Fütterungsrate auch bei großen Bruten dürfte nachteilig sein, da sie nur wenig Nutzen bei einem hohen Aufwand (Beeinträchtigung der späteren Brutmöglichkeiten) bringt. Der Huderaufwand des Weibchens zeigt in etwa denselben Zusammenhang mit der Brutgröße. Kurzzeitige elterliche Entscheidungen scheinen eine wichtige Rolle in der Regulation der elterlichen Brutpflege zu spielen. Dabei kommt gerade der räumlichen Lage der Nahrungsplätze eine große Bedeutung zu: an weiter entfernt gelegenen Nahrungsplätzen verbrachten die Eltern unverhältnismäßig mehr Zeit als an nahen Futterplätzen. Daneben haben die Tageszeit und das Wetter einen Einfluß auf die elterliche Brutfürsorge der Alpenkrähen.