bluuebunny/crossref_metadata_2025 huggingface dataset:
Density‐dependent effects on productivity in the Griffon Vulture Gyps fulvus: the role of interference and habitat heterogeneity
Authors: FERNANDEZ CARMELO , AZKONA PAZ , DONAZAR JOSE A.
Published: April 2008

Griffon Vultures Gyps fulvus in northern Spain were studied between 1969 and 1994. The number of breeding pairs increased from 221 in 1969–1975 to 1395 in 1994. The annual population growth rate decreased in the last 5 years, and this may reflect population regulation through density‐dependent phenomena. Breeding success was monitored in 1994 and examined in relation to colony size, density of breeding pairs within a radius of 25 km (regional density), climate, human disturbance and food availability. We also recorded whether the year of first occupation of each nest site was before 1989 or after 1989 and whether or not the nest had a rocky shelter. The probability of successfully raising young declined as the regional density increased, which suggests that resource limitation would take place at foraging sites because the Griffon Vulture scavenges socially and no permanent feeding hierarchies are established. The other significant variable was the year of occupation of the nest; nests occupied after 1989 had a lower probability of raising a chick. The increase in the regional density of Griffon Vultures produced a decrease in the productivity at both optimal and suboptimal nest sites. This suggests that density‐dependent regulation of breeding success operates through interference and that all the individuals in a colony are similarly affected. In birds of prey, prevalence of interference or habitat heterogeneity may be dependent on the social strategy of each species in space exploitation.
Global dispersion of nesting Hen Harriers Circus cyaneus; implications for grouse moors in the U.K.
Authors: POTTS G. R.
Published: April 2008

In the U.K., a full recovery of Hen Harrier Circus cyaneus breeding numbers is prevented by illegal culling by some gamekeepers who fear the species threatens the future of grouse moors. This study's main purpose was to estimate how many more Hen Harriers there would be in the U.K. if this culling were to cease. A review of 33 studies of the Hen Harrier in nine countries showed that the densities of nesting females decreased strongly as the size of the areas studied increased and also that such information could not be used to estimate the potential density over a large area, such as the U.K. Correcting for the size of the areas studied showed that the potential density of nesting Hen Harriers on grouse moors could be predicted from studies overseas. Estimates of the densities of Hen Harriers in occupied areas globally were therefore used to estimate the density appropriate for the U.K. If all potential habitats were occupied, present numbers could more than double, to an estimated 1660 nesting females. This estimate represents an average of one nesting female per 2 5 km2 of habitat, a density which would cause little or no significant economic damage on grouse moors. However, because Hen Harriers tend to aggregate, they would not spread out evenly but would nest in relatively high densities on a number of moors. The economic impact on Red Grouse Lagopus lagopus would not be a function of overall numbers, rather it would arise from the uneven dispersion of nesting Hen Harriers.
Effects of clutch size and egg‐laying order on the breeding success in the Little Tern Sterna albifrons on the Nakdong Estuary, Republic of Korea
Authors: HONG SOON‐BOK , WOO YONG‐TAE , HIGASHI SEIGO
Published: April 2008

Survivorship of Little Tern Sterna albifrons eggs and chicks was followed on an islet in the Nakdong Estuary, Republic of Korea, in 1995 and 1996. Mean egg size and incubation period were significantly different between the 2 years. The maximum clutch size was three eggs, and the second egg in the clutch often hatched earlier than the first, while most of the third eggs hatched last. In 1996, when the fate of 249 eggs from 106 nests was followed for 40 days, hatching success, fledging success and breeding success were 77%, 40% and 31%, respectively. High mortality occurred in the early chick stage, mostly because of rain and predation by Weasels Mustela sibirica. The breeding success per egg was 14% in one‐egg clutches, 28% in two‐egg clutches and 34% in three‐egg clutches. This difference was mainly attributed to the lower hatching success in the smaller clutches. In three‐egg clutches, the third egg showed significantly lower breeding success than siblings. The main foods of the Little Tern were Tridentiger obscurus, Engraulis japonicus, Hyporhamphus intermedius, Acanthogobius flavimanus (all fish), Palaemon sp. and Crangon affinis (shrimps). The feeding frequency was, apparently, not affected by time of day and age of chicks but was probably influenced by weather conditions. Newly hatched chicks failed to eat 25% of the prey brought to them, although this decreased with the age of the chicks.
Movements of radio‐tagged Buzzards Buteo buteo in early life
Authors: WALLS S. S. , KENWARD R. E.
Published: April 2008

Radio‐tags were used to track 146 Buzzards Buteo buteo during 1990–1996. Each bird was tracked for up to 4 years; of 74 Buzzards tagged since 1992, 72% were monitored for more than 3 years. Among the 87 Buzzards tracked for more than 1 year, 46% settled after one dispersal movement, 37% dispersed and then changed their ranges, 17% did not disperse and one Buzzard alternated between a summer and a winter range. Natal dispersal occurred in two waves, one in the first autumn and the second in the following spring. Initial dispersal distances in the autumn were significantly greater than those in the spring. For 73 Buzzards that dispersed in their first autumn, 96% settled within 100 km of their natal nest, and their distances were similar to 76 records from ringing. After their second spring. Buzzards rarely changed ranges and were significantly more often to the east than the west, especially those that had dispersed more than 20 km. Buzzards that had dispersed farthest were most likely to be detected returning towards their natal area each spring and returned earlier as they got older. However, none was detected returning once it had started to breed. Nine early breeders were significantly farther from their natal nests than 44 nonbreeders.
Spring migratory routes of eight trans‐Saharan passerines through the central and western Mediterranean; results from a network of insular and coastal ringing sites
Authors: PILASTRO ANDREA , MACCHIO STEFANO , MASSI ALBERTO , MONTEMAGGIORI ALESSANDRO , SPINA FERNANDO
Published: April 2008

Detailed information on spring migration routes of songbirds across the Mediterranean is still scanty. Results are presented here from a study on the occurrence of eight Palaearctic‐African migrants across the western and central Mediterranean based on ringing data collected during the Progetto Piccole Isole, a co‐ordinated project based on standardized mist netting at 21 islands and coastal stations. The species were Melodious Warbler Hippolais polyglotta, Icterine Warbler Hippolais icterina,Bonelli's Warbler Phylloscopus bonelli, Wood Warbler Phylloscopus sibilatrix, Pied Flycatcher Ficedula hypoleuca, Collared Flycatcher Ficedula albicollis, Red‐backed Shrike Lanius collurio and Woodchat Shrike Lanius senator. Their capture frequencies were expressed as the frequency of each species relative to the total number of migrants ringed at each station in order to correct for differences in capture effort between stations. For most species, the detailed, quantitative results confirmed the scanty information available so far, whereas in the case of Melodious Warbler and Bonelli's Warbler, evidence of undescribed and unexpected migration routes was found. These results suggest that standardized mist netting provides an important method for studying the migratory routes of small birds, in particular for those species which are not frequently ringed in their breeding and wintering grounds.
Barlow's Lark: a new species in the Karoo LarkCerthilauda albescenscomplex of southwest Africa
Authors: RYAN PETER G. , HOOD IAN , BLOOMER PAULETTE , KOMEN JORIS , CROWE TIMOTHY M.
Published: April 2008

The Karoo LarkCerthilauda albescenscomplex, endemic to southwest Africa, is characterized by regional phenotypic variation. Recent consensus has been to recognize two species, Dune LarkCerthilauda erythrochlamysand Karoo LarkCerthilauda albescens, but intermediate forms around the mouth of the Orange River have resulted in some authors treating it as a single polytypic species complex. We reexamined the status of taxa in this group by sequencing a segment of the mitochondrial DNA cytochrome b gene. Most samples were from the area around the mouth of the Orange River, where there is considerable local phenotypic variation. Our results indicate that the complex comprises three species, Karoo Lark, Dune Lark and Barlow's LarkCerthilauda barlowi, separated by 1.9‐5.5% sequence divergence. There were no sequence differences among described subspecies, but there was limited variation among Dune Lark individuals (sequence divergence values 0.2‐0.4%). The Red LarkCerthilauda burrais closely related to the Karoo Lark complex; indeed, it may be that Karoo Lark is the ancestral form. There was morphological (biometrics and plumage) and behavioural (male display song structure) support for the recognition of Barlow's Lark as a separate species. Species ranges within the complex are allopatric or narrowly parapatric, and they occur in different habitats and climatic conditions. Discriminant function analysis correctly identified 99% of skins assigned to taxa based on range, but a few individuals collected in the contact zone between Karoo and Barlow's Larks exhibited intermediate phenotypes, and further investigations are warranted to search for evidence of hybridization. The newly recognized Barlow's Lark has a maximum range of 18,000 km2. It appears to have disappeared from heavily grazed farms around Aus, southern Namibia, and occurs almost exclusively in diamond mining areas, where domestic livestock are excluded. Changes to land use practices which reduce vegetation cover could seriously impact this species.
Food resource matching by foraging tits Parus spp. during spring‐summer in a Mediterranean mixed forest; evidence for an ideal free distribution
Authors: DÍAZ MARIO , ILLERA JUAN CARLOS , ATIENZA JUAN CARLOS
Published: April 2008

We analysed whether patterns of microhabitat use by Blue Tits Parus caeruleus, Great Tits Parus major and Crested Tits Parus cristatus inhabiting a mixed forest consistently matched the patterns of food availability experienced by foraging birds during spring‐summer. The use of five microhabitats by each bird species (the foliage of three tree species, shrubs and ground) and the availability of food in trees during the prebreeding, breeding and post‐breeding periods of the birds' annual cycle were measured. All three tit species foraged mainly in the outer part of tree canopies (small branches and leaves or needles). Tit distributions between tree species matched food resource distributions irrespective of overall food resource levels, which varied four‐fold between the study periods, and tit species. Tits also exploited secondary microhabitats (shrubs and ground) in periods of low food availability; Blue Tits tended to use shrubs, whereas Great and Crested Tits foraged on the ground. Between‐trees distributions fitted that expected from an ideal free distribution, suggesting that food availability and intraspecific exploitative competition were the main factors governing tree use by tits. In contrast, patterns of use of secondary microhabitats (shrubs and ground) seemed to indicate a role for the species‐specific morphological configurations of each tit species since Blue Tits are better adapted to hang and tended to forage in shubs, whereas Great and Crested Tits are better adapted to feed on horizontal surfaces and tended to forage on the ground. No evidence of interspecific interactions was observed. Overall, the results pointed to an independent exploitation of Mediterranean mixed forest by each bird species, food availability and food accessibility being the main factors affecting microhabitat use by foraging tits.
Behavioural and morphological correlates of variation in the extent of postjuvenile moult in the SiskinCarduelis spinus
Authors: SENAR J. C. , COPETE J. L. , MARTIN A. J.
Published: April 2008

Siskins Carduelis spinus show great variation in the acquisition of adult plumage, so that yearling birds can be classified as either “delayed” (i.e. still showing yearling plumage) or “advanced” (i.e. with an adult plumaged appearance). The extent of moult in males is related to the size of their black bib, which in turn is highly correlated with their social dominance rank. Autumn male body mass is higher in advanced than in delayed moult birds, but by winter the relationship is reversed, suggesting a trade‐off between investment in moult and subsequent body condition. Results were similar in Spain and Britain. A possible cost of advancing moult is suggested by an analysis of aggressive interactions at bird feeding tables which showed that adult males discriminate between delayed and advanced birds, directing most aggression towards adult‐looking yearling males. The results suggest that the variation in the extent of postjuvenile moult is not only related to energetic constraints but has other important behavioural and ecological implications.
Diet and habitat use of moulting Greylag Geese Anser anser on the Danish island of Saltholm
Authors: FOX A. D. , KAHLERT JOHNNY , ETTRUP HENNING
Published: April 2008

The diet and habitat use of moulting Greylag Geese Anser anser were studied at the recently established moulting site on the island of Saltholm, between Denmark and Sweden. Classification of the vegetation in the area most used by Greylag Geese during their moult showed that the geese selected low saltmarsh habitats which were richest in Common Saltmarsh‐ grass Puccinellia maritima and that dropping density was highly correlated with Puccinellia cover. Geese showed slowest step rates and highest peck rates in vegetation types rich in Puccinellia. Examination of faecal material confirmed that the geese fed almost exclusively on PuccineEia during the main moult period, despite its limited spatial distribution. Puccinellia maritima exhibited the highest levels of protein of any of the graminoid species present except for the belowground lower stem base of Sea Club‐rush Scirpus maritimus, which offers a nongrowing food resource which is difficult to extract and consume. The results of this study suggest that the statement that the “limited data available for moulting waterfowl indicate no active selection for proteinaceous foods; i.e., birds are selecting foods in proportion to their availability” does not hold for Greylag Geese moulting on Saltholm.
Habitat use and selection by Red‐crowned Crane Grus japonensis in winter in Yancheng Biosphere Reserve, China
Authors: MA ZHIJUN , WANG ZIJIAN , TANG HONGXIAO
Published: April 2008

We report the distribution and habitat selection by the Red‐crowned Crane Grus japonensis in winter in the Yancheng Biosphere Reserve, China. Including original wetlands and artificial habitats, six types of habitat are used by the species: saltworks (salinas), fish ponds, reed beds, Wormwood Artemisia halodendron beaches, tidal grasslands and wheat fields. We compared the habitat availability with habitat use in each type. In winter, Red‐crowned Crane preferentially used tidal grasslands and fish ponds. Saltworks, Wormwood beaches and wheat fields were avoided. The distribution of Red‐crowned Crane in different types of habitat changed with the distribution of freshwater and with human activities.
Vigilance during food handling by OystercatchersHaematopus ostralegusreduces the chances of losing prey to kleptoparasites
Authors: GOSS‐CUSTARD JOHN D. , CAYFORD JOHN T. , LEA STEPHEN G.
Published: April 2008

OystercatchersHaematopus ostralegusperiodically pause while handling musselsMytilus edulisto make visual scans. This paper presents evidence that scanning is associated with the high incidence of intra‐specific food stealing among mussel‐eating Oystercatchers. Scanning increased in frequency as bird density ‐ and the risk of being attacked for mussels increased and the duration of attacks decreased. Additionally, among a sample of individually marked adults, the aggressive dominant birds spent half as much time scanning as the less aggressive subdominants and were also less likely to be attacked. Whereas detecting an attack made no difference to the success with which the dominants defended their mussels, subdominants increased their chances of retaining the mussel if they detected and carried the mussel away from the approaching attacker. The extra time which the less aggressive birds spent in vigilance seems best understood as a tactic for reducing food loss to kleptoparasites.
Individual breeding decisions and long‐term reproductive strategy in the King Penguin Aptenodytes patagonicus
Authors: JIGUET FREDERIC , JOUVENTIN PIERRE
Published: April 2008

Although studied for 35 years, knowledge of the reproductive biology of the King Penguin Aptenodytes patagonicus remains incomplete. The chick requires more than 12 months of care, which extends the breeding cycle, including moult, to more than one year, i.e. the King Penguin is neither annual nor biennial. In an attempt to resolve ambiguities in the literature and to elucidate the long‐term breeding strategy of the species, we studied breeciing frequency at the individual level, considering the decision to breed in relation to breeding history over the previous few years. Although adult birds attempted to breed annually (0.83 breeding attempts per year), successful rearing occurred, at best, every two years only (maximum of 0.41 fledged chick per pair). Comparing successive years, the number of breeding birds in the colony was stable but the number of fledged chicks varied from 29 to 278 over eight years. These results suggest that King Penguins adopt (as individuals) an opportunistic reproductive strategy, in that they usually lay an egg every year, even when failure is certain. Nevertheless, the decision to breed was not entirely blind, and we identified groups of birds that invested differentially in breeding attempts. The decision to breed was related to the previous breeding frequency, i.e. 81% of the birds that had bred continuously in the past started a new breeding attempt, but only 67% of birds that had missed a year did so. In intermittent breeders, birds that had bred frequently, more often started a new breeding attempt than birds that had largely missed years (71% versus 57%, respectively). Classes of breeders could correspond to age classes, to birds of different breeding quality or to alternative breeding strategies coexisting in the species. Testing the hypothesis that reproductive effort increases with age should be possible in future.
Parental behaviour in the Lapwing Vanellus vanellus
Authors: Liker András , Székely Tamás
Published: April 2008

Parental behaviour of monogamous and polygynous Lapwings was studied during incubation and brood care. Both parents attended the nest in 86% of monogamous pairs (n= 29 pairs). In 14% of pairs, only the male parent continued incubation until the eggs hatched, whereas the female deserted the clutch before or at the end of incubation. There was a clear division of parental roles during incubation. Females spent more time incubating (64% of time) than their mates (27%), whereas males spent more time defending the nest (3%) than females (>1%). Time spent incubating did not differ between monogamous and polygynous males. However, polygynous females spent more time incubating (primary females: 95%; secondary females: 97%) than monogamous females. Biparental care was the most common pattern of post‐hatching care, although in some broods either the male or the female parent deserted before the chicks fledged. Division of sex roles was less pronounced in brood care than during incubation. Females spent more time brooding (21%) than males (3%), and females attended their chicks more closely than males. Nevertheless, males and females spent similar amounts of time defending the brood from predators and conspecifics. We suggest that the apparent division of parental roles may be explained by sexual selection, i.e. the remating opportunities for male Lapwings might be reduced if they increase their share in incubation. However, the different efficiency of care provision, for example in ability to defend offspring, may also influence the roles of the sexes in parental care.
Territory acquisition during winter by juvenile Willow Tits Parus montanus
Authors: Hogstad Olav
Published: April 2008

Willow Tits Parus montanus live within exclusive territories in non‐kin winter flocks with a dominance hierarchy in which males dominate females and adults dominate juveniles. Because they live in habitats that are saturated with dominant territory owners, the options of subordinate juveniles surviving the winter are: (1) to become a dominant owner of a vacated territory, (2) to stay in an occupied territory and hope for ownership or (3) to leave the area and hope for territory acquisition elsewhere. Removal experiments during December to February revealed that particularly the most dominant of the juvenile pairs left their own flock territory and replaced birds experimentally removed from a neighbouring flock, if by doing so they increased their own dominance position. It is suggested that juvenile Willow Tits updated their information about the composition and dominance structure of adjacent winter flocks by regularly visiting these territories and attempted to become dominant owners during winter, thereby increasing their chances of breeding.
Temporal variation in the annual survival rates of six granivorous birds with contrasting population trends
Authors: Siriwardena Gavin M. , Baillie Stephen R. , Wilson Jeremy D.
Published: April 2008

To identify the environmental changes responsible for the declines in abundance shown by many granivorous bird species, the demographic mechanism through which the changes have acted must be determined. Ring‐recovery data were used to estimate the annual survival rates (since 1962) of six seed‐eating bird species with contrasting population trends to identify whether variations in survival could have been the mechanism behind population change. The survival rates of Bullfinch Pyrrhula pyrrhula, Chaffinch Fringilla coelebs, Goldfinch Carduelis carduelis, Greenfinch C. choris, Linnet C. cannabina and House Sparrow Passer domesticus were estimated using models allowing age‐ and time‐specificity in survival (reporting rates could be assumed to be constant). Three tests of the importance of variations in survival in determining population trend were conducted: (1) simple population models with constant productivity showed whether temporal changes in survival were sufficient alone to explain observed trends in abundance, (2) survival models incorporating changes in abundance as a covariate identified whether annual survival rates were associated with population changes, and (3) mean survival rates found in objectively identified periods of increase, decline and stability in each species' population trend were compared. These analyses suggested that environmental change has led to the observed population trends for Goldfinch and House Sparrow largely through effects on survival. Weaker relationships between variations in survival and population trend were found for Bullfinch, Chaffinch and Linnet, but other factors such as breeding success are likely to have been at least as important for these species, and also for Greenfinch. Checking analyses incorporating density‐dependence did not alter these conclusions.
Song strophe‐length and reproductive success in a non‐passerine bird, the Hoopoe Upupa epops
Authors: Martín‐Vivaldi Manuel , Palomino Jose Javier , Soler Manuel , Martínez Juan Gabriel
Published: April 2008

HoopoeUpupa epopsmales produce a very simple song, with a repertoire size of one, in which the main difference between different strophes of a male and between the songs of different males is the number of elements they include (strophe‐length). In several passerine species it has been shown that strophe‐length is a sexually selected trait that reflects male quality and correlates with reproductive success. Here we analyse whether in a non‐passerine, the Hoopoe, strophe‐length of males is correlated with several variables of their reproductive success. Females paired with males singing long strophes laid their first clutch earlier, produced larger first clutches and laid second clutches after a successful first one more frequently than those paired with males singing short strophes. Moreover, males with long strophes produced more fledglings in their first clutches and in the whole season, partly because they brought more food for the brood than males with short strophes. The relationships found are not mediated by age effects. Previously we have shown that Hoopoe females in the early spring are attracted preferentially to songs with long strophes. Here we show that males singing long strophes also obtain postpairing benefits in terms of reproductive success, and that females paired with these males obtain direct benefits because these males provide greater feeding effort in the second half of the nestling period. These findings support the hypothesis that in the Hoopoe, strophe‐length is a sexually selected cue under direct selection.
Molecular analysis off the phylogeny off 11 genera off the Corvidae
Authors: Cibois Alice , Pasquet Eric
Published: April 2008

Phylogenetic analysis of 11 genera of Corvidae has been undertaken using a sequence of 925 bp of the cytochrome b gene of the mtDNA. Both maximum‐parsimony and maximum‐likelihood analyses were performed, and different weighting schemes have been used according to the saturation observed in the data (mostly at the third codon position). The cytochrome b data provide good evidence for the monophyly of the Corvidae, including the Piapiac Ptilostomus afer in spite of its aberrant morphology. In all analyses, the choughs are the first lineage emerging in the family; this result conflicts with the traditional chough‐crow group, as well as the hypothesis of the ancestral position of the jays. The monophyly of the American jays is well supported by the molecular data, unlike the Palearctic jays, which are not closely related. The other intergeneric relationships are not strongly supported by bootstrap proportions, and are not congruent in all different weightings and methods, except for groups of species of the same or very closely related genera.
Population density and the intensity of paternity assurance behaviour in a monogamous wader: the Curlew Numenius arquata
Authors: CURRIE DAVE , VALKAMA JARI
Published: April 2008

We compared paternity assurance behaviour and related displays in high (1.6 pairs perkm2) and low (6.7 pairs per km2) density populations of the Curlew Numenius arquata breeding on arable farmland in western Finland. There was little evidence of individuals pursuing extra‐pair copulations or males exhibiting paternity assurance behaviour. Furthermore, there was no variation in the frequency of intrusions or in the intensity of paternity assurance behaviour relative to lay date. However, intrusions and approaches to the pair female by extra‐pair males were more frequent at high breeding density, and pair males remained closer to their female, followed her more and exhibited a higher frequency of copulatory behaviours in the high‐density population. Therefore, high breeding density appeared to increase opportunities for individuals to copulate outside the pair‐bond and resulted in more intense male paternity guards. Male song flight displays were also more frequent in the high‐density population. Territorial absences by males were infrequent in both areas. The increased frequency of intrusions and interactions between non‐pair individuals (male‐male and male‐female) at high density were probably the major factors in explaining area differences in the intensity of paternity assurance and territorial behaviour.
Lunar synchrony in the reproduction of the Moluccan Megapode Megapodius wallacei
Authors: BAKER GILLIAN C. , DEKKER RENÉ W.R.J.
Published: April 2008

The Moluccan Megapode Megapodius wallacei uses heat generated by the sun to incubate its eggs. It buries the eggs deep in the sand of sun‐exposed beaches and open sandy areas on islands in the Moluccas, Indonesia. The eggs are laid at night and left to incubate for two to three months without parental care. We present evidence that the Moluccan Megapode exhibits lunar synchrony in the timing of egg‐laying, its spatial distribution of egg burrows and in its behaviour at communal nesting grounds. More Moluccan Megapodes visit the nesting grounds on bright nights than during the new moon. Data collected on the spatial distribution and depth of egg burrows also exhibit lunar periodicity. On moonlit nights, the birds excavate burrows in communal groups and spend longer at the nesting ground digging deeper burrows. Lunaphilia and lunar periodicity of reproduction are rarely documented in birds. We discuss possible explanations for these behaviours in the Moluccan Megapode.
Effects of body mass on the foraging behaviour of subordinate Coal Tits Parus ater
Authors: BARBOSA ANDRÉS , BARLUENGA MARTA , MORENO EULALIA
Published: April 2008

Several mechanisms can explain individual differences in foraging behaviour, such as variation in predation risk between patches, variation in the ability of individuals to detect or escape from predators, variation between individuals in their requirement for food, the quality and abundance of food in different patches, phenotypic variation giving rise to differences in resource use (exploitation hypothesis) and interference competition such as the exclusion of subordinate individuals by dominants. Subordinates can develop compensation mechanisms. One of these mechanisms is morphological differentiation. However not every change in morphology can account for the same variation in behaviour, since some morphologies can be ecologically more plastic than others (i.e. some morphs can exploit a broader niche than other morphs). Under controlled conditions in the Coal Tit Parus ater, we tested whether (1) differences in resource use were explained by either the exploitation hypothesis or by the interference hypothesis, and (2) the presumed costs of subordination can be reduced through different ecological plasticities associated with different morphologies. Our results support the interference hypothesis as there are no differences in hanging behaviour between dominants and subordinates when foraging solitarily; while in the presence of other individuals, we observed differences in foraging behaviour that varied with social status. Our results also show that body mass influenced foraging behaviour; lighter birds can exploit patches where hanging postures are needed more easily than heavier birds. Moreover, this relationship varied among individuals, as predicted by the ecological plasticity hypothesis. Lighter subordinate individuals used hanging postures more frequently than heavier ones, differentially reducing the costs of subordination. We propose that differences in the breadth of ecological niche due to differences in morphology can reduce the costs of subordination.
Growth and provisioning strategies of Northern Fulmars Fulmarus glacialis
Authors: PHILLIPS RICHARD A. , HAMER KEITH C.
Published: April 2008

Growth and foraging strategies in procellariiforms show a great deal of variation, but the fulmarine petrels are notable in that chicks are fed frequently and develop unusually rapidly. This study examined age‐related and daily variation in provisioning of the Northern Fulmar Fulmarus glacialis throughout the chick‐rearing period at Fair Isle in 1997. In common with many other petrels, meal mass showed an initial rise with age, probably because of a gradual increase in chick gut capacity, but then levelled off. By comparison, feeding frequency showed little age‐specific variation until chicks reached the oldest age‐class, when the number of meals declined to less than a third of the previous level as chicks underwent mass recession prior to fledging. Compared with the limited day‐to‐day variation in mean provisioning rates for the whole sample, food delivery to particular chicks was much more variable, suggesting that differences in feeding rates were determined by stochastic factors influencing the feeding success of individual parents. The caloric density of feeds and their size in relation to adult mass were lower in Northern Fulmars than in most other Procellariiformes. This implies that adults are not heavily dependent on stomach oil formation to raise the energy content of the payload, but rely on a high feeding frequency to maintain adequate rates of energy transfer to chicks.
Invertebrate diet of the Houbara Bustard Chlamydotis [undulata] macqueenii in Abu Dhabi from calibrated faecal analysis
Authors: TIGAR BARBARA J. , OSBORNE PATRICK E.
Published: April 2008

The ecology of the Houbara Bustard Chlamydotis [undulata] macqueenii is poorly known and populations are declining due to hunting and habitat loss. As wintering populations in Abu Dhabi may be limited by habitat and food, we studied the diet using calibrated faecal analysis. Prey were categorized into 16 groups and fed to captive birds under controlled conditions. We calculated the recovery rates of prey following digestion and identified consistent fragments for each group. Wild Houbara Bustard faeces were collected and examined for key fragments, and initial prey intake was calibrated. Plant remains were identified and their contribution was estimated. Fewer than 28% faeces contained >50% plant material by volume and only 12% contained 95% or more. Numerically, the most important prey were: ants (64%), large nocturnal tenebrionids (14.5%), small climbing tenebrionids (12%) and diurnal tenebrionids. However, the Tenebrionidae contributed 97% of the animal biomass. The relative proportions of prey in the diet were similar to relative abundance as assessed by pitfall trapping. Estimates of the energetic value of the prey suggested that on average Houbara Bustards must consume around 670 desert invertebrates/day to meet energy needs. The effort required to catch these prey may vary at least ten‐fold seasonally. On average plants could provide a further 6.4–14% energy but more work is needed on this. Whether Houbara Bustards wintering in Abu Dhabi are prey‐limited depends on prey densities and renewal rates which remain unknown.
Bipedal locomotion in ratites (Paleognatiform): examples of cursorial birds
Authors: ABOURACHID ANICK , RENOUS SABINE
Published: April 2008

The gaits of five Ostriches Struthio camelus, seven Emus Dromaius novaehollandiae, two Greater Rheas Rhea americana, two Southern Cassowaries Casuarius casuarius and one Brown kiwi Apteryx australis were filmed at zoological parks. Locomotor parameters were measured using footprints on sandy tracks and video records. Osteological measurements were made on skeletons of the pelvic limbs. All of these terrestrial birds shift from wallking to running at a relative speed below 1. However, they show two different locomotor patterns: the Brown Kiwi increases its speed by increasing its stride length, mainly by increasing the protraction angle. Its hindlimbs make a flexed jointed chain system, its centre of mass is anterior, its femurs are long and the knees act in yield whereas the distal joints act in propulsion. Other ratites, particularly Ostriches, increase their speed by increasing frequency. Their centre of mass is close to the hip, their hindlimbs have an extended jointed chain system with a short erect femur, maximizing a gravity‐powered system.
Egg size, egg composition and reproductive success in the Oystercatcher Haematopus ostralegus
Authors: JAGER THEO D. , HULSCHER JAN B. , KERSTEN MARCEL
Published: April 2008

We investigated the relationship between egg size and composition and their subsequent effects on hatching and fledging success in Eurasian OystercatchersHaematopus ostraleguson the island of Schiermonnikoog (53d̀30'N, 06d̀10'E) in the Dutch Wadden Sea between 1986 and 1990. Egg size variation was considerable. The ratio in egg volume of the largest over the smallest egg was more than 1.5 in each of five years. Differences between females accounted for, on average, 61% of the total variance of egg volume. Individual females produced similarly sized eggs from one year to another. Nevertheless, average egg volume per clutch declined by 0.2 cm3per year as females aged, but this explains little of the observed variation. Female size and food supplementation had no significant effect on egg volume. In absolute terms, large eggs contain more lean dry matter and lipid than small eggs, but the proportion of both constituents decreases with egg size. Consequently, the combustible energy content of eggs increases less than proportionally with egg size. Hatchability averaged 87% and was not correlated with egg volume. Hatchling weight increased with egg size, averaging 65% of fresh egg weight. Chick survival until fledging did not increase with egg volume. Consequently, within the size range observed, large and small eggs are of comparable quality. Since both the costs and benefits of large eggs compared with small eggs seem small at best, we propose that, within the size range encountered in this population, egg size can be considered an evolutionarily neutral trait.
Satellite tracking of the winter migration of Magellanic Penguins Spheniscus magellanicus breeding in the Falkland Islands
Authors: PÜTZ KLEMENS , INGHAM REBECCA J. , SMITH JEREMY G.
Published: April 2008

Magellanic penguin populations in the Falkland Islands may have decreased over the past decade. The post‐breeding migration may be the period in which the birds are most vulnerable. To investigate this we equipped ten Magellanic Penguins after their moult at Seal Bay (51d̀38'S, 58d̀03'W), East Falkland, with satellite transmitters. The movements of the penguins were tracked for between 15 and 99 days until transmission ceased. All birds initially migrated to the northwest. However, four birds entered Argentinean coastal waters, then headed northeast following the coastline, The other penguins remained offshore, but also changed to a northeasterly course. Two birds migrated beyond 36d̀S with a maximum distance to the colony of more than 1800 km, while the minimum distance travelled was up to 2700 km. Initially, the birds migrated quickly but their speed was reduced and became more variable as time progressed. A high concentration of positional fixes, associated with low travelling speeds, indicated at least four different areas where birds were assumed to forage efficiently. The relevance of these areas is discussed with respect to the diet of Magellanic Penguins and possible interactions with human activities.
Acoustic convergence between two nocturnal burrowing seabirds: experiments with a penguin Eudyptula minor and a shearwater Puffinus tenuirostris
Authors: JOUVENTIN PIERRE , AUBIN THIERRY
Published: April 2008

The evolution of acoustic signals is influenced by environmental constraints. We studied two sympatric but unrelated seabirds: the Little Penguin Eudyptula minor and Short‐tailed Shearwater Puffinus tenuirostris, to examine the degree to which similarities in their ecology had led to convergence in their calls. Both species nest in burrows in Southern Australia and, at night, are highly vocal and territorial. First, we analysed the physical characteristics of the territorial call. Secondly, we studied the transmission of calls through burrows and varying distances through vegetation. Thirdly, we used playback experiments of natural signals to demonstrate that the response disappears between 4–8 m, and of modified signals to understand the coding‐decoding process linked to the territorial function of the call. The structure of the territorial calls of the two species clearly differs, but both species produce a succession of gaps in amplitude and frequency, and a high degree of redundancy. Our experiments show that, to decode the territorial message, birds pay attention only to parameters that are less degraded during propagation and ignore fine details of structure that are quickly degraded, even at relatively short distances (< 8 m). In both species, territorial information is mainly conveyed by the rhythmic succession of two sounds (syllables or subsyllables), birds paying attention to the FM structure of these successive sounds but not to the AM. This convergent coding is adaptive in that it reduces the possibility that the meaning may be distorted by interference from noise and acoustic screening.
Contour feather moult of Ruffs Philomachus pugnax during northward migration, with notes on homology of nuptial plumages in scolopacid waders
Authors: JUKEMA JOOP , PIERSMA THEUNIS
Published: April 2008

Among the sandpiper family Scolopacidae, the Ruff Philomachus pugnax combines a large seasonal change in the appearance of the plumage with a very pronounced sexual plumage dimorphism. Studies on the east and south African wintering grounds of Ruffs indicate that before northward migration at least the males moult (part of) their basic (winter) plumage into a kind of alternative plumage. We studied the details of the subsequent moult into a final (supplemental) breeding plumage by quantifying the presence of three feather types—(1) winter (basic), (2) striped (alternate) and (3) breeding (supplemental)—in breast feather samples of 1441 Ruffs captured on staging areas in The Netherlands during northward migration in 1993‐97. Ruffs arriving in March show a mix of winter and striped feathers. In April, the ‘breeding feather’ type appears in both male and female Ruffs, and partially takes the place of winter feathers as well as striped feathers in males, and winter feathers only in females. The presence of three plumages in Ruffs is thus confirmed for males, but also occurs in female Ruffs and in Bar‐tailed Godwits Limosa lapponica. We suggest that striped feathers represent the ‘original’ alternative plumage feather type of the sandpiper family and that the showy feathers of the, in the European literature fortuitously appropriately named, ‘supplementary plumage’ represent an additional feather generation. Such colourful nuptial plumages could thus be derived characters that have evolved independently in several scolopacid genera, presumably under particularly strong sexual selection pressures.
A comparative analysis of the breeding biology of the Red‐billed Chough Pynhocorax pyrrhocorax and the Alpine Chough P. graculus coexisting in the Alps
Authors: LAIOLO PAOLA , ROLANDO ANTONIO
Published: April 2008

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.
Survival, ranging, habitat choice and diet of the Northern Goshawk Accipiter gentilis during winter in Northern Finland
Authors: TORNBERG RISTO , COLPAERT ALFRED
Published: April 2008

The winter ecology of the Northern Goshawk Accipiter gentilis was studied in northern Finland in 1991‐95. The data consist of 26 radiomarked hawks, of which 331 day and 299 night positions were located. Average range size was 9894 ha for males (minimum convex polygon, n= 4) and 6282 ha for females (n= 11). Ranges calculated by the 75% harmonic mean contour gave range areas of 3283 ha for males (n= 3) and 2753 ha for females (n= 11). Harmonic mean centres concentrated near human settlements, implying better food availability there compared with woodland areas. Some Goshawks preyed upon animals living in the city dump in late winter. Goshawks preferred deciduous and mature conifer forests and avoided open areas such as fields and bogs. They also avoided very heterogeneous sites. The winter diet consisted mostly of Mountain Hares Lepus timidus (30.9%), Red Squirrels Sciurus vulgaris (23.6%), Brown Rats Rattus norvegicus (12.7%) and forest grouse Tetraonidae (27.1%), of which Black Grouse Tetrao tetrix was the most important (14.5%). By weight, hares constituted 70% of the biomass consumed.
An updated list and some comments on the occurrence of intraspecific nest parasitism in birds
Authors: YOM‐TOV YORAM
Published: April 2008

This paper presents a list, compiled from the literature, of bird species in which intraspecific nest parasitism (INP) occurs. INP was reported in 234 species: one Struthioniformes, two Tinamiformes, two Procellariiformes, six Podicipediiformes, five Ciconiiformes, one Phoenicopteriformes, 74 Anseriformes, one Falconiformes, 32 Galliformes, eight Gruiformes, 19 Charadriiformes, nine Columbiformes, five Cuculiformes, two Apodiformes, one Coraciiformes and 66 Passeriformes. Hence, INP is very common among precocial species, and less so among altricials. Irrespective of this, most INP birds are colonial.
Flight characteristics of birds:
Authors: BRUDERER BRUNO , BOLDT ANDREAS
Published: April 2008

This is the first part of a study on flight characteristics of birds and presents an annotated list of flight speeds of 139 western Palearctic species. All measurements were taken with the same tracking radar and corrected for wind influence according to radar‐tracked wind‐measuring balloons. Graphical presentation of the birds' air speeds emphasizes the wide variation of speeds within species and allows easy comparison between taxonomic groups, species, and types of flight. Unlike theoretical predictions, speeds increase only slightly with size. The larger species seem to be increasingly limited to speeds close to their speed of minimum power consumption Vmp',. Released birds, apparently reluctant to depart with migratory speed, fly at considerably lower speeds than migrating conspecifics. While large birds seem to be limited to speeds around Vmp', smaller birds seem to be capable of selecting between various speeds, approaching predicted Vmp, when tending to remain airborne at low cost, but flying at much higher speeds when tending to make best progress at low cost (around predicted speed of maximum range Vmr,). Predictions of air speeds by aerodynamic models proved to be too low for small birds because the models do not account for the gain in speed attained by the reduction in profile drag during bounding flight of small passerines. The models predict excessive speeds for large birds because the power output available for flight seems to decline much more with size than previously assumed.