bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intraordinal relationships of the Pelecaniformes and Cuculiformes: electrophoresis of feather keratins
Authors: Brush Alan H. , Witt Hans‐H. 
Published: April 2008

Electrophoresis of soluble feather keratins was performed in Gradipore gels under two pH conditions. The taxa of two diverse orders, the Pelecaniformes and Cuculiformes, were compared. Dendograms based on identity indices and genetic distances were constructed by the Fitch‐Margoliash and unweighed pair‐group algorithms (UPGMA). Differences within taxa were influenced by both pH conditions and the algorithm used for analysis.Values of identity indices at each pH were compared within and between taxa. Dendograms for the Pelecaniform consistently group species within genera and placed families within the traditional arrangements. One notable exception was Nannopterum. The Cuculiformes, with many monotypic genera, were more resistant to constant clustering.The problems of relating genetic distance to phylogenies are discussed. The relationship of systematic, ecological and molecular diversity is still unresolved. Genetic distance of feather keratins consistently correlated with other estimates of divergence times. The values indicate the systematic equivalence of taxa within orders.
Ecological character displacement and character release in grebes Podicipedidae
Authors: Fjeldså Jon 
Published: April 2008

The paper is based on measurements of 2925 grebes and extensive field studies on ecological segregation and resource exploitation of the grebes of northern Europe, Colombia, Peru, Patagonia and Australia.In all examined cases where two closely related grebe species overlap locally, one or both showed indications of divergent bill morphology. In two cases there are indications of evolutionary changes during the present century. In the case of the grebes of the Junin and Titicaca basins and for one European species, it was found that the morphological change reduced the interspecific food overlap.There is a statistical tendency for evolution of a quite specific bill (21–26 mm long, 88‐9‐8 mm high, 7‐6‐8‐5 mm wide) in isolated areas with only one grebe species. A close examination of one of these populations suggests that this bill type is an ‘all‐purpose’ one which permits opportunistic fish‐eating without loss of the ability to feed efficiently on tiny arthropods. In the case of two or more sympatric grebes, there appears, on a worldwide scale, to be a compulsory radiation away from the ‘all‐purpose’ bill type.The data suggest the existence of co‐evolution in grebe faunas. Birds living under poor feeding conditions have to exploit all potential foods available, while specialization on optimal foods takes place where it is easy to find. Small individual differences in the trophic organs thus influence the diet only in relatively prolific habitats. Character displacement is therefore most likely to take place in stable environments inhabited by K‐strategists, whose biotic adaptations keep their populations on levels where individual birds generally have more food than the bare necessity.
Long‐term defence of fruit by Mistle Thrushes Turdus viscivorus
Authors: Snow Barbara K. , Snow D. W. 
Published: April 2008

In an area of south‐central England Mistle Thrushes Turdus viscivorus regularly defend fruit‐hearing plants (four kinds of tree, ivy and mistletoe) against intruders from autumn to early spring. Holly Ilex aquifolium is by far the most important of the plants defended. To be suitable for defence, a tree must be free‐standing and of moderate size. Observations were carried out over three winters, one mild, one very severe and one intermediate. During the mild winter hollies were successfully defended until the Mistle Thrushes gave up active defence with the onset of breeding activities. During the very severe winter nearly all defended hollies were overwhelmed by invading flocks of other thrush species during the very cold spells. Mistle Thrushes in possession of a fruit supply conserve it by feeding on undefended fruit near‐by if it is available, and to a large extent on the ground when conditions are suitable. Defended fruit trees are generally avoided by other species living in the vicinity. Hence depletion of fruit from defended trees is much slower than from undefended trees, and consequently the fruit may last for several months and provide a food supply in dry weather in spring and early summer for Mistle Thrushes and other species.Fieldfares and Blackbirds show similar, but less well developed, fruit‐guarding behaviour. Fruit‐defence is clearly related to the bird's size, but other physical and behavioural adaptations may be involved. The most important characteristic of holly fruit making it suitable for defence, apart from the dimensions and spatial relationship of the tree, is its ability to last for many months without significant deterioration.
Morphological and genetic variability of Snow Petrels Pagodroma nivea
Authors: JOUVENTIN PIERRE , VIOT CHRISTOPHER‐ROBIN 
Published: April 2008

Snow Petrels vary greatly in size, the largest birds being over twice as heavy as the smallest. Two morphological types have been distinguished, but the Adelieland population alone shows continuous variation spanning the complete range of the species. There is no evidence of size‐related assortative mating. Size variation cannot be attributed to nest site location nor to individual age, nor is the large sexual dimorphism sufficient to account for the situation. The great individual variation in size is accompanied by an important genetic variability as revealed by a starch gel electrophoretic study.Comparisons of wing length data from many localities around the Antarctic Continent suggest a cline, with a peak at the Balleny Islands. Taking into account the extent of size variation at breeding places only, it appears that morphological variability is low at Balleny Islands, where only large form birds are known, and at Antarctic localities inhabited exclusively by small form birds. In contrast, several localities on the continent in the vicinity of Balleny Islands, and especially Adelieland, exhibit a high degree of variability.We propose that during the quaternary glaciations, the Antarctic continent provided no refugia for this species, but, when glaciation ended, Snow Petrels re‐established colonies, coming from two refugia, a low latitude one inhabited by small birds Pagodroma nivea nivea, and one in higher latitudes characterized by large birds P. n. major. Reproductive isolation broke down, and a hybridization zone was created. The high proportion of polymorphic loci exhibited by the Adelieland population is then attributable to the mixing of two previously isolated genetic pools.
The relationship between dominance behaviour, bill size and age group in Greater Sheathbills Chionis alba
Authors: SHAW P. 
Published: April 2008

A dominance hierarchy developed within a wintering flock of Greater Sheathbills which fed regularly at a concentrated artificial food source. Each bir's dominance position was determined from the proportion of interactions in which it was displaced, and from the number of other birds which it was seen to displace.Most dominant birds were known to be over 6 or 7 years of age. They had larger bills than their subordinates had and initiated displacement interactions more often. After each interaction the displacer resumed feeding more quickly than the bird it displaced. Although dominant birds had a higher average peck rate, they did not maintain a higher body mass throughout the winter, nor did they show a higher survival rate than their subordinates.
Prey profitability for adult Grey Herons Ardea cinerea and the constraints on prey size when feeding young nestlings
Authors: MOSER M. E. 
Published: April 2008

Patterns of handling time and profitability are examined for adult Grey Herons feeding on carp, eels and catfish. Handling times generally increased with prey size but were influenced markedly by the morphology and behaviour of the prey. Profitability was highest for carp (max. 0.9 g/s for 15–20 cm fish), lowest for catfish (max. 0.05 g/s) and intermediate for eels (max. 0.1 g/s). Nestlings were unable to ingest the sizes of fish most profitable for the adults to consume until aged 20 days; by the age of 30 days, they could consume the full size‐range of prey taken by the adults. In order to feed their young chicks, adults must therefore either select smaller prey, or break their large prey into smaller pieces. The diet of nestling Grey Herons in the Camargue is examined for evidence to support or refute the former hypothesis.Young nestlings (≤20 days) regurgitated smaller carp than old nestlings (> 20 days). Comparison of prey types in the diet of the two groups showed that small prey species occurred significantly more often in the diet of young chicks, while the converse was true for larger prey species. The occurrence of particular prey types in the diet only of young chicks suggests that adults may forage in more marginal, shallower water (where small prey are probably more abundant) to meet the requirements of their brood during the early part of the nestling phase. The second hypothesis, that the adults break down large prey into smaller pieces, was not examined, although evidence from other studies suggests that this does occur; both mechanisms may therefore be important.
The breeding biology of White‐tailed Tropicbirds Phaethon lepturus at Cousin Island, Seychelles
Authors: PHILLIPS N. J. 
Published: April 2008

During 1981–1983 the population of White‐tailed Tropicbirds Phaethon lepturus at Cousin Island, Seychelles, bred aseasonally and asynchronously. The mean interval between consecutive successful breeding attempts was 273 days. Most individuals nested in the same site, and with the same partner, in successive attempts, but 7‐5% of nest sites were used by more than one pair; 21 % of pairs which lost eggs, and 13% of those which lost chicks re‐nested. Incubation lasted 40–41 days, with a mean incubation shift length of 6‐6 days. Fledging periods varied between 67 and 89 days (mean 76‐5 days). Mean fledging weight was not significantly greater than the average weight of breeding adults.Fledging success was 36%. Many of the 39% of eggs which failed to hatch probably did so as a result of exposure to the sun's heat, following temporary desertion by adults which were themselves heat‐stressed during incubation. Of the 41 % of chicks which died, most died young; many were probably killed by crabs Ocypode spp. Not more than 10% of all nest failures were due to nest site competition. A few chicks probably starved to death.At the time of the study, both food and nesting sites were evidently in excess. A considerable increase in the size of the population will be possible before density‐dependent control mechanisms begin to operate.
The effect of food on laying date and clutch‐size in Tengmalm's Owl Aegolius funereus
Authors: HÖRNFELDT BIRGER , EKLUND ULF 
Published: April 2008

The breeding of Tengmalm's Owl Aegolius funereus was studied at Umeå, Sweden, during the 1984–85. Mean clutch‐size was one egg larger in 1984 than in 1985 despite the later laying in 1984. The difference in clutch‐size was related to a better food supply in 1984. Daily weight increase of females during the prelaying period showed a high negative correlation with laying date in 1985, and a high positive correlation with clutch‐size independently of laying date in 1984–85. This suggested that food eaten before and during laying had a great and direct influence on both laying date and clutch‐size. Many females increased in weight during laying and most others decreased only moderately (relative to egg weight), suggesting that body reserves were not a main source for egg production.Late breeding females were provided with extra food during the prelaying and laying periods in 1985. Fed females weighed more, bred eight days earlier and laid one more egg than controls. At the same laying dates in mid season, and after heavy snow‐fall, clutch‐size and female weight were larger in the fed birds than in controls, but this was not so near the end of the laying season. Although the earliest of the fed late breeders weighed more, and probably were less restricted by food availability just before or during laying, they did not lay more eggs than did early breeders. This result suggested some limitation on clutch‐size that could not be overcome by the supplementary feeding. Weights of females during laying did not show any consistent relationship with clutch‐size during successive laying date intervals, suggesting that clutch‐size was not directly related to body condition.
The occurrence and performance of leucistic Barnacle Geese Branta leucopsis
Authors: OWEN MYRFYN , SKIMMINGS PAUL 
Published: April 2008

The paper reports the occurrence of whitish ‘leucistic’ forms in populations of Barnacle Geese Branta leucopsis. A total of 15 (including 11 in the last 21 years) have been reported in the population breeding in Svalbard and wintering in the Solway Firth, northern Britain, whereas the two other populations, though much larger, have produced only one bird of the same type between them in the last 30 years. Leucism is controlled by a single, recessive allele.The median lifespan of leucistic birds is 2–3 years, compared to 8–10 years for normal plumaged birds. This is because they are sought out by (illegal) hunters. There is no evidence that there is any difference in pairing or breeding performance between white and normal birds, though one male, which is still alive aged 18 years, has produced 13 young; this performance is matched fay less than 2% of normal geese.It is suggested that the Svalbard population was established recently, from a few founders from the Siberian population; if one or two of these carried the allele controlling leucism, this would explain its much higher prevalence in this population than in the other discrete groups of Barnacle Geese.
Scaling nestling energy requirements
Authors: WEATHERS WESLEY W. 
Published: April 2008

The total energy metabolized (TME) by nestling birds, from hatching to fledging, scales as M1.06, with body‐mass at fledging (M) explaining 97% of the variation in TME. After statistically removing the effects of body‐mass, multiple‐regression analysis reveals that 69% of the variation in TME is explained by nestling developmental rate, expressed as the time to fledging (tfl, days). Together tfl and M explain 99% of the variation in TME for the 30 species considered (M range 9.7 to 3700 g).Peak daily metabolized energy (DME, kJ/day), the maximum rate at which parents must provision their nestlings, scales with fledging mass as M0.78. Body‐mass explains 96% of the variation in nestling peak DME, with 37% of the residual variation being attributable to the time taken to fledge (tfl). Together, tfl and M explain 97% of the variation in peak DME. An examinination of residuals indicates that adaptive modifications in nestling energetics are attained principally through changes in growth rate, which affect TME and peak DME oppositely. Doubling nestling growth rate increases peak DME by 61%, but decreases total nestling energy demand (TME) by 77%. This opposing effect complicates evolutionary interpretations of avian reproductive patterns.
Variation in the abundance of Red‐breasted Mergansers Mergus serrator on a Scottish river in relation to season, year, river hydrography, salmon density and spring culling
Authors: MARQUISS MICK , DUNCAN KEITH 
Published: April 2008

Red‐breasted Mergansers Mergus serrator were counted in the river North Esk, Scotland, and on the sea nearby, 1987–1990. Pairs arrived at the river estuary from early winter, but the main influx to freshwater took place in late April and in May, when breeding pairs dispersed far upriver. Females began incubation from late May. Most young hatched in July and fledged by late September. Males left the river in June and congregated at an offshore moulting site, their numbers peaking in August, and dispersed rapidly in September.Breeding density and total duckling production decreased with increasing distance upstream, decreasing river width and increasing gradient and elevation. The total number of breeding pairs and their distribution on the river were similar from year to year, despite variable numbers killed, suggesting a stable breeding population near the upper limit the habitat would support in those years. It also suggested that killing mergansers in April was an ineffective way to reduce the population. The spatial variation in merganser breeding density was not correlated with the density of their main spring food, parr of salmon Salmo salar, but could have been related to its availability.The production of well‐grown ducklings varied annually and was inversely correlated with river flow during the main period of hatch. It is argued that Red‐breasted Mergansers breed late in the year because the hatching of ducklings in July coincides with an abundance of their food, large aquatic invertebrates and tiny juvenile fish.
Clutch size of passerines at mid‐latitudes: the possible effect of competition with migrants
Authors: YOM‐TOV YORAM 
Published: April 2008

The clutch sizes of the passerines of Israel and the Cape Province, South Africa, which lie at similar latitudinal range, were compared. Mean clutch sizes in Israel and the Cape Province are 4.09 and 2.87, respectively. Mean clutch size of Israeli migrants is larger than that of residents (4.45 and 3.93, respectively), but no such difference exists in the Cape Province.It is suggested that the larger clutch size in Israel is a result of two factors: (1) the higher proportion of wintering birds in Israel in comparison with the Cape Province and the presence of many transients there which may compete with resident birds and cause high winter mortality among them and (2) a higher proportion of migrants in the Israel avifauna, which suffer heavy losses during their trans‐Saharan migration in comparison with Cape Province migrants, which travel shorter routes. The resulting reduced competition for food during the breeding season in Israel enables passerines there to lay larger clutches as predicted by Ashmole (1963) and Ricklefs (1980).
Ranges of males of the Great Hornbill Buceros bicornis, Brown Hornbill Ptilolaemus tickelli and Wreathed Hornbill Rhyticeros undulatus in Khao Yai National Park, Thailand
Authors: POONSWAD PILAI , TSUJI ATSUO 
Published: April 2008

Ranges of individual males of three hornbill species were determined by radio telemetry during the breeding and non‐breeding seasons in Khao Yai National Park, Thailand. Two Great Hornbills Buceros bicornis and two Brown Hornbills Ptilolaemus tickelli were studied in both 1988 and 1989, and two Wreathed Hornbills Rhyticeros undulatus were studied in 1989, 1990 and 1991.In the breeding season, the home range of the Great Hornbill was 3.7 km2, similar to that of the Brown Hornbill (4.3 km2), while the Wreathed Hornbill occupied the largest home range (10.0 km2). In the non‐breeding season, the range size of the Wreathed Hornbill (28.0 km2) was greater than that of the Great Hornbill (14.7 km2). Differences in range sizes of different species may be related to differences in diet and breeding strategy. Ranges overlapped within and between the species, and this has implications for the estimation of the minimum area required for the conservation of hornbills within the Khao Yai National Park.
Growth of Stonechats Saxicola torquata from Africa and Europe: an analysis of genetic and environmental components
Authors: STARCK J. M. , KÖNIG S. , GWINNER E. 
Published: April 2008

The postnatal growth of the European subspecies of the Stonechat Saxicola torquata rubicola and the African subspecies Saxicola torquata axillaris and their hybrids was studied to investigate differences in growth rates. Comparisons were made between subspecies, between genetically related chicks within subspecies and between individuals within sibling groups. Genetic and environmental effects on variation and their impact on the growth curves were evaluated. We compared posthatching increase in body mass and wing‐length between chicks raised under identical conditions and between chicks raised under different photoperiod and rearing conditions. Significant differences in body mass increase between the two subspecies were found for all parameters except for the inflection point of the growth curve. Differences in wing‐length occurred during the late posthatching development and were significant only for asymptotic size. However, interactions between independent variables masked the effects on some parameters. Furthermore, our data showed that the components of the total genetic variability are differently attributed to each level of comparison: we found the form of the growth curve and asymptotic size significantly different between subspecies; size at a given day and asymptotic size were genetically different between sibling groups within subspecies; age at the inflection point of the growth curve showed most variability between individuals within groups of related siblings. Cross‐breeding experiments showed that the growth parameters in the hybrids were intermediate, providing further evidence for a genetic basis of the observed differences. In this particular case, the between‐subspecies variability reflects genetically adjusted adaptation rather than phenotypic responses to different ecological conditions.The phenotypic responses of growth to differences in “environment” have been investigated in groups of birds reared under different conditions (hand‐reared v parent‐reared chicks; European v equatorial photoperiod). The rearing method affected only size parameters and not the form of the growth curve of body mass. Significant differences were found for maximum body mass, final body mass and asymptote. Photoperiod had no effect on growth.
Bird fauna of northeast Asia: a summary of the unique biodiversity and the priorities for conservation
Authors: ANDREEV ALEXANDER 
Published: April 2008

The subcontinent of northeast Asia, defined as the region east of the Lena River between 58o and 72oN (and excluding the Kamchatka peninsula), is 3500 km × 1500 km in area (Fig. 1). Influenced by ice‐covered seas, low air temperatures and permafrost, it has a complicated mosaic of habitats, supporting a diverse and unique bird fauna with a number of endemic species and populations.East of the Verkhoyansk range, the northern limit of continuous coniferous forest retreats southwards and is replaced by two vegetation types unique to northeast Siberia: Larch tundra‐forest (sparse Larix cajanderi) and tall bush tundra ecotone (dominated by the Shrub Pine Pinuspumila and Bush Alder Alnus fruticosa). Shrub Pine dominates sub‐alpine altitudes throughout the interior and coastal ranges, descending in places to sea level.Coastal habitats include river deltas, brackish water bays, offshore drift ice fields and leads, lagoons, sand spits, marshes, intertidal mudflats, cliffs. offshore islands, upwellings and surface currents. Warmed by the ground water, the permafrost‐free interior valleys support lush deciduous woods of Poplar Popubs suaveolens and Korean Willow Chosenia macrolepis. Higher in the mountains, dry lichen tundra and rocky deserts occur.