bluuebunny/crossref_metadata_2025 huggingface dataset:
Movements of radio‐tagged Grey Herons Ardea cinerea during the breeding season in a large pond area
Authors: VESSEM JANIKE VAN , DRAULAKS DIRK , BONT ANTOON F. DE
Published: April 2008

This paper describes the strategies of resource utilization in the course of the breeding season by five radio‐tagged Grey Herons Ardea cinerea. The seasonal changes in exploitation of the environment by two breeding adults, one non‐breeding adult and two non‐breeding first‐year birds were studied from March to August 1982, near Zonhoven in Belgium.

Two adult breeding birds could be followed continuously from the end of March until the middle of June. During the first month they explored an extended area all around the colony, but each concentrated its search in a specific direction. From the end of April until the beginning of June, most probably from egg‐hatching until the end of breeding activities, each bird spent a very large proportion of its time at a particular feeding site, from which other herons were actively excluded. In the first part of June they again visited different sites, each maintaining its preferred direction. From the middle of June onwards they seemed to have left the fish‐pond area.

The pattern of movements of the first‐year birds differed markedly from that of the breeding adults. In April, although both non‐breeding and breeding birds explored large areas, only the areas used by non‐breeders were centred on the colony. From the end of April onwards, probably after general egg‐hatching in the colony, the non‐breeders very rarely revisited the colony, and from May till August their ranges became more and more restricted to very small areas at an increasing distance from the colony. They were never observed defending particular sites.

The results are discussed with regard to recent speculations about the evolution of colonies as an adaptation for the exploitation of food resources. Breeding herons seem to explore a large part of the environment during incubation and defend a particular site while feeding their young. Choice of feeding site by non‐breeding birds may be influenced by the site defence of the breeding birds. Non‐breeding birds exploit a large area when breeding birds occupy feeding territories. Perhaps they are forced to forage in less suitable places at this time. Colonies might have evolved as a strategy to minimize effort in resource esploitation as, especially at the beginning of the breeding season, the colony could act as an assembly point in the exploration of the environment. However, its importance as an assembly point diminishes in the course of the season, as non‐breeding birds no longer visit the colony and adults defend territories.
The moult of the Little Stint Calidris minuta in the Kenyan rift valley
Authors: Pearson D. J.
Published: April 2008

Moult data were collected during 1967–80 from some 6900 Little Stints in the southern Kenyan rift valley.

Adults typically moulted from summer to winter body and head plumage during September and early October, soon after arrival. The complete pre‐winter wing and tail moult began in most adults between mid‐September and early October. Some birds finished by December, but others continued until February and March. Individual duration was usually between 100 and 150 days. Adults which completed this moult early often remoulted outer primaries between January and early April.

Young birds acquired first‐winter body plumage during October and early November. Some 90% had a complete pre‐winter wing and tail moult. This usually began between December and early February, and finished during March or early April, taking about 70–100 days. In about 10% of young birds, flight feather moult was restricted to the outer primaries and inner secondaries. Birds adopting this strategy typically began moult late, during January or February. Short periods of suspension were common during pre‐winter wing moult, particularly in adults. The difference in moult speed between adult arid first‐winter birds was attributable in the primary, secondary and tail tracts to differences in numbers of growing feathers.

Practically all birds completed a pre‐summer moult involving the entire body and head plumage, most of the tertials, some or all of the tail feathers and many wing coverts. Most birds began this moult between early February and late March, and finished between mid‐April and early May. It was typically later and more rapid in first‐year birds than adults. In late birds, the onset of pre‐summer moult was linked to the final stages of pre‐winter moult.

The wing moult of the Little Stint in different wintering areas is discussed. First‐winter moult strategy is compared with that in other small Calidris species.
The microclimate of the nests of waterfowl
Authors: Howey P. , Board R. G. , Davis D. H. , Kear Janet
Published: April 2008

A sophisticated radiotelemetry system was used to monitor continuously the temperature, relative humidity and the incidence of parental movement sufficient to admit light to, or turn the eggs in, the nest cup of (number of days recordings m parenthesis): Black Swan Cygnus atratus (68); Barnacle Goose Hrantal leucopsis (70); Whooper Swan Cygnus cygnus (28) and Greylag Goose Ansev anser (26). The following features were common to all the nests: (1) a slow rise in the temperature of the nest cup with the onset of incuhation; (2) a temperature gradient in the vertical plane of the nest cup throughout incubation; (3) a diurnal rhythm in the temperature and humidity of the nest cup, this being caused by bird behaviour rather than the ambient environment; (4) nesting materials dried out during incubation thereby accentuating the steepness of the diffusion gradient between a real egg and the atmosphere of the nest cup; (5) the eggs, which were turned between 0.594.95 times an hour, were rotated mainly around their long axes.
A population study of the Rook Corvus frugilegus in Leon Province, northwest Spain
Authors: Ena Vicente
Published: April 2008

A resident population of Kooks Corvus frugilegus in Leon, Spain, decreased by 247; from 197679. Migrant Rooks appear not to enter the range of this population which is unique in the Iberian Peninsula. During the breeding seasons colonies are attacked by man: 17–19% of birds failed to breed and only 0.5‐0.7 young per nest survived to fly. The trees chosen for nesting are in plantations subject to regular cropping, after which colonies are scattered. Adult mortality was 16–26% annually. Young formed 17.6–23% of the population in June; 11–15.6% of birds in March were in their first year and many of these bred successfully. Communal roosts were used only from mid‐July to mid‐October.
Breeding seasons and laying patterns of the southern African Ostrich Struthio camelus
Authors: JARVIS M. J. F. , JARVIS C. , KEFFEN R. H.
Published: April 2008

Wild Zimbabwe Ostriches Struthio camelus were studied during four successive years. Information on breeding seasons and laying patterns was compared with that of domesticated South African hybrid Ostriches in Bophuthatswana. In wild populations laying occurred mainly from July to December or early January, while domesticated birds continued until at least the end of February. Domesticated birds normally laid about 16 eggs in succession, one every second day. There was marked synchronisation of laying and the middle of each successive peak in egg production was about 6 weeks from the preceding peak. Wild birds laid up to eight eggs in any one nest, and normally clutches were contributed by three females, the average combined clutch being 12 or 13 per nest. Circumstantial evidence suggests that individual females may lay in more than one nest during a single laying sequence. Comparisons between rainfall patterns and laying rhythms proved inconclusive.
Reproductive success of the Kittiwake Rissa tridactyla: the roles of clutch size, chick growth rates and parental quality
Authors: COULSON J. C. , PORTER J. M.
Published: April 2008

Kittiwake growth rates and breeding success are examined in relation to survival between fledging and breeding and to adult survival rates. High chick growth rates lead to increased survival after fledging. Broods of three (the maximum brood size) did not suffer lower fledging success than broods of two and clutches of three fledged appreciably more chicks per pair than did clutches of two or one. On average, the a‐ and b‐chicks in broods of three grew at a faster rate and had a higher survival before breeding than those from smaller broods. Chicks from broods of two with experienced female parents grew at a faster rate than those of inexperienced female parents. Female parents which laid three egg clutches had a higher survival rate than those which laid clutches of two or one. We contend that three egg clutches were laid by higher quality individuals. We believe that clutch size indicates the condition of the Kittiwakes forming the pair. This condition probably has a genetical component, but is modified by environmental factors.
Brood reduction in the Blue‐eyed Shag Phalacrocorax atriceps
Authors: SHAW P.
Published: April 2008

Brood reduction is common in a population of Blue‐eyed Shags on Signy Island, South Orkney Islands. This paper describes possible adaptations which may reduce the brood. In clutches of three, the last egg was smaller, and hatched 2.4 days later than its siblings. Whilst 78–84% of first and second (‘A’ & ‘B’) chicks fledged, only 11 % of ‘C’ chicks did. In a sample of artificially synchronized broods chick survival was as high as in normal asynchronously hatching broods, but there were more cases of total brood loss. The age at which the C chick died was related inversely to the length of the A‐C hatching interval. Relative differences in sibling weights were highest during the first 12 days, when most of the C chick deaths occurred. At this age the daily food requirements of each brood of three was one‐tenth that of each brood of two just prior to fledging. It is suggested that C chicks were unable to compete effectively for a food supply which was limited by the parents, rather than by the environment. The asymptotic weight attained by A chicks was inversely related to brood size, and was greater than that of B or C chicks. Normal asynchronous broods produced at least one heavy (A) chick and one medium weight (B) chick, whilst in synchronized broods the asymptotic weight attained was similar to that of B chicks in normal broods.
Selection of nest sites by a hole‐nesting duck, the Goldeneye Bucephala clangula
Authors: DOW HILARY , FREDGA SVEN
Published: April 2008

Nest site preferences were examined for a population of Goldeneye Ducks breeding in nest boxes in Värmland, central Sweden. Some nest boxes were occupied more often than others even if females returning to the same nest box were excluded from the analysis. Nest boxes located higher up trees were occupied more often than those close to the ground and some spatial ‘cluster groups’ of boxes were occupied more often than others. Otherwise nest site prefernces were not related to any measured physical attributes of the boxes. Prefernces for nest boxes seemed to be based mainly on a tendency for females to select those that had been occupied by other females in the preceding year, especially if they had bred successfully. As a result of this, the occupancy of nest boxes was not random over years but rather progressed in a series of runs; a period of consecutive years in which a box was occupied was followed by a period of years in which it was empty.

There were reproductive consequences for these prefernces in that females occupying preferred boxes were less likely to lose their clutch to a predator. These females also bred earlier in the year and produced larger clutches and broods than females breeding in other boxes.
The comparative breeding biology of Adelie and Chinstrap Penguins Pygoscelis adeliae and P. antarctica at Signy Island, South Orkney Islands
Authors: LlSHMAN G. S.
Published: April 2008

Adélie Penguins and Chinstrap Penguins breed in abundance at Signy Island, South Orkney Islands, which is near the northern breeding limit of the former but in the centre of the latter's breeding range. During the 1980–81 and 1981–82 breeding seasons daily checks were made to record laying date and interval between laying, egg weight and volume, incubation period and shifts by each parent, hatching date and interval between hatching, the date on which the young first creched and their age at the time, and fledging date and age. This was done for the eggs and chicks from 60 marked nests of each species. Adelies started breeding about one month before Chinstraps and showed other adaptations which may relate to early breeding and probably to the presence of ice around the breeding site. These adaptations included longer incubation shifts and a heavier and larger first egg which may promote more rapid brood reduction. Chinstraps had shorter incubation shifts and both eggs had similar weights and volumes. Although the later breeding of Chinstraps meant that chick rearing coincided with the availability of a better food source than that utilized by Adelies, Chinstraps were unable to cope with persistent heavy ice conditions in 1980–81 and were no more successful than Adelies in 1981–82. All previous breeding data for both species are reviewed and it is suggested that early breeding by Adelies may be a consequence of competition for food with Chinstraps but, by retaining adaptations to harsh environmental conditions, Adelies are well able to breed successfully. Conversely, Chinstrap Penguins appear mainly adapted to milder environmental conditions and it is unlikely that they could compete successfully with Adelie Penguins at breeding sites on the Antarctic Continent.
Reproductive performance of the Bald Ibis Geronticus calvus in relation to rainfall and grass‐burning
Authors: MANRY D. E.
Published: April 2008

Reproductive performance of the Bald Ibis Geronticus calvus was studied during three consecutive nesting seasons (1978–80) at a single large breeding colony in Natal, South Africa. A focal sample of 22 nest sites (out of a total of 60 in the colony) was inspected at frequent intervals to determine clutch sizes, egg survival, hatching success, nestling mortality and fledgling production in each year. Mean clutch size was slightly lower in 1980, compared to the two previous years, although survival and hatching success of eggs were similar in all three years. However, nestling mortality was significantly higher in 1980, largely as a result of parental nest desertion and nestling starvation, so that the proportion of breeding pairs producing at least one fledged offspring, and the average brood size at fledging, were lower compared to 1978 and 1979.

The 1978 and 1979breeding seasons were both preceded by 12 months of above average rainfall, and Bald Ibises fed extensively on small invertebrates obtained in burnt grassland in the study area during the nesting period. By contrast, the onset of nesting in 1980 followed 11 consecutive months of sub‐normal rainfall. As a result of the drought, and the consequent lack of controlled burning by landowners in the study area in 1980, very little burnt grassland was available during the Bald Ibis' breeding season, and the birds fed primarily in cultivated pastures during the customary burning period. The lower reproductive performance of Bald Ibises at the study site in 1980 is discussed in relation to the possible effects of drought on the abundance of invertebrate prey and the extent of controlled burning in the species' grassland biotope.
The survival of gamebird (Galliformes) chicks in relation to pesticide use on cereals
Authors: RANDS M. R. W.
Published: April 2008

Field experiments were carried out to test the effects of cereal pesticides (herbicides, fungicides and insecticides) on chick survival of Grey Partridge Perdix perdix, Red‐legged Partridge Alectoris rufa and Pheasant Phasianus colchicus. On fields in experimental plots the outer 6 m of cereal (the headland) were not sprayed with pesticides from 1 January 1984, whereas control plots were fully sprayed. Gamebird brood counts were carried out after the cereal harvest. In addition, nine Grey Partridge broods were radio‐tracked for 21 days after hatching (four in sprayed plots and five in unsprayed plots) to determine their movements, home range size and survival in relation to pesticide spraying.

The mean brood size of Grey Partridge and Pheasant was significantly higher on plots where field edges were unsprayed than on fully sprayed control plots. Data for Red‐legged Partridge were inconclusive. The survival of individually marked Grey Partridge broods was negatively related to the distance moved between successive nocturnal roost sites. Survival was significantly higher, the distance moved between roost sites significantly shorter and the proportion of home range including headland significantly greater for broods feeding in spring barley fields with unsprayed field edges compared with broods feeding in fully sprayed fields.
Habitat exploitation and interspecific competition of moulting geese in East Greenland
Authors: MADSEN JESPER , MORTENSEN CHRISTIAN EBBE
Published: April 2008

Jameson Land, East Greenland is a moulting area of c. 5000 non‐breeding Pink‐footed Geese and 5000 Barnacle Geese. Breeding populations of both species in the area are small and scattered. The moulting Pinkfeet originate from Iceland, and the Barnacle Geese from other parts of East Greenland. Both species arrive in the area at the end of June and moult their remiges in July.

Moulting flocks of the two species seldom mix. Pinkfoot flocks are common along coastlines, in wide rivers and on lakes with open views to all sides, while Barnacle Geese predominate in smaller rivers and on lakes with surrounding hills. During moult the geese, and especially the Pinkfeet, are extremely wary and depend on a safe area of water serving as a refuge with nearby food supplies (sedge‐dominated marshes). Barnacle Geese graze in a zone 0–100 m from the refuge, Pinkfeet up to 200–250 m from the refuge. The moulting sites fill up with geese according to available marsh areas, and the grazing pressure on average amounts to 594 goose‐days per ha during the moulting period. Food intake is estimated at 149 g and 138 g organic material per 24 h by Pinkfeet and Barnacle Geese, respectively, [n 1984, which was sunny and warm, net above‐ground primary production of a Carex subspathacea marsh (the prime feeding ground during moult) from the beginning of growth to the end of July was 13–15 g dw m2, and it is estimated that the geese consumed 60–69% of the production. In 1983, which was cold, geese probably consumed the entire production. Goose grazing did not affect productivity, but nutrient levels were high in grazed compared with ungrazed shoots, and peaked in early July.

When separate, the diet of both species comprises sedges and grasses. Where the species co‐exist the amount of mosses in the diet increases, especially in Barnacle Geese. With respect to nutrient and fibre contents, moss is a suboptimal food compared to sedges and grasses. When separate, the geese spend 41–46% of the 24 hr grazing. Where they co‐exist, Barnacle Geese spend 62% of the time grazing, while Pinkfeet seem unaffected by the presence of Barnacle Geese.

It is argued that carrying capacity for moulting geese is reached. Geese compete for resources, the Barnacle Goose suffering from the presence of the other. The observed distribution pattern is suggested to result from (1) Pinkfeet being limited to certain sites due to extreme wariness, and (2) Barnacle Geese trying to avoid competition by utilizing sites which Pinkfeet are reluctant to use. The experience of older Barnacle Geese of stress when settling with Pinkfeet may be the segregation mechanism.

Moult coincides with the onset of growth and peak nutrient levels in the vegetation. It is suggested that the geese undertake moult migrations to Jameson Land both to avoid competition for resources with breeding geese and because they gain advantage from a growing, nutritious vegetation.
A comparison of breeding and moult cycles and life histories in two tropical starling species: the Blue‐eared Glossy Starling Lamprotornis chalybaeus and Rüppell's Long‐tailed Glossy Starling L. purpuropterus
Authors: DITTAMI JOHN P.
Published: April 2008

The Blue‐eared Glossy Starling Lamprotornis chalybaeus and Rüppell's Long‐tailed Glossy Starling Lamprotornis purpuropterus were investigated in the field and in aviaries at Lake Nakuru National Park, Kenya for seasonality in reproductive activity and moult. The former species was found to be a seasonal breeder which nests after the onset of the heavy rains in April. Although some birds had large gonads prior to the rains in the dry season no nesting occurred. The rains were contemporary with increases in gonadal size and the plasma titres of LH, testosterone (T) in males and estradiol (E2) in females. These hormones are associated with the initiation of breeding activity. As breeding ceased in July and the moult began, the plasma titres again decreased. There was a bimodal breeding pattern which paralleled a change in biotope preference for nesting. Early nests, in the heavy rains, were on the open savanna and later nests were in the acacia forest. Late nesting birds also had delayed peaks in gonadal size, plasma titres of LH, T and E2 and a delayed moult onset. Data on individual captive birds demonstrate that these annual cycles have a distinctly individual character superimposed on the seasonal trends.

In Rüppell's Long‐tailed Glossy Starlings no seasonality in breeding was found although the flight feather moult commenced and was completed in all individuals at about the same time. The moult extended over about ten months, so a great deal of breeding‐moult overlap was present. The absence of seasonality in field birds was reflected in the aviary birds, which had no pronounced cycles in the reproductive parameters measured (gonadal size, LH, T and E2 plasma titres). Breeding in field birds was regulated on a pair basis and correlated with increases in duetting. The striking differences in the seasonal organization between this species and Blue‐eared Glossy Starlings were presumably due to the different biotope preferences and social behaviour of the two species.
Notes on the behavioural ecology of the Magnificent Frigatebird Fregata magnificens
Authors: TRIVELPIECE WAYNE Z. , FERRARIS JOAN D.
Published: April 2008

The Magnificent Frigatebird population breeding on Man‐o‐War Cay, Belize in 1980 laid their single eggs between mid‐December and early April, and had a mean hatching date of mid‐ to late April. There were no differences between the sexes in the percent of time spent incubating eggs or brooding small chicks (males 48%, females 52%). However, males were not observed to feed larger (75–100 d) chicks. All 81 feedings of juvenile (approximately 1 year old) frigatebirds observed during 126 hr of observations were by females, and the majority of these feedings occurred at midday (46%) when approximately equal numbers of females and juveniles frequented the study area. Our data confirm Diamond's (1972, 1973) reports of unequal roles in chick rearing and post‐fledging care between male and female F. magnificens, and support the hypothesis that males and successful females may breed at one‐ and two‐year intervals, respectively.
Frugivory, external morphology and digestive system in mediterranean sylviid warblers Sylvia spp
Authors: JORDANO PEDRO
Published: April 2008

Fruit consumption was assessed in six species of Sylvia warblers and compared to variation in external morphology and digestive system. Variation in the use of fruit was determined primarily by external morphology (body‐size, gape‐width and hindlimb characteristics). Variation in digestive traits (intestine‐length, gizzard and liver‐weight) did not account for a significant fraction of variation in frugivory across species. Relative to other non‐frugivorous Muscicapidae, Sylvia spp. exhibit digestive adaptations specific to fruit processing; however, variation in external morphology constrains the degree of dependence on fruit within the genus.
Kleptoparasitic interactions of Arctic Skuas Stercorarius parasiticus and Black Guillemots Cepphus grylle in northeastern Hudson Bay, Canada
Authors: BIRT V. L. , CAIRNS D. K.
Published: April 2008

Kleptoparasitic behaviour of Arctic Skuas was studied at a Black Guillemot colony in northeastern Hudson Bay, Canada. Skuas procured fish in 7‐2% and 19‐9% of attacks, and Black Guillemots lost fish in 7‐2% and 21‐2% of chases in 1982 and 1983, respectively. In 1983 chase outcome was related to distance between birds at the end of a chase and number of skuas in pursuit. The skuas' foraging efficiency (energy intake/energy expended during hunting) was estimated at 45 for 1982 and 5–8 for 1983, and total daily energy expenditure was estimated at 2–4 and 2‐1 × b.m.r. for these years. Energetic calculations suggested that skuas obtained sufficient food to meet their daily needs in 3–6 h of hunting in 1982 and 2–7 h in 1983. The absence of intensive kleptoparasitic activity by breeding skuas in North America is attributed to the paucity of colonies suitable for both feeding (due to available host species and colony topography) and nesting (due to presence of arctic foxes and/or polar bears).
Species differences in diet and the development of seed digestion in partridge chicks Perdix perdix and Alectoris rufa
Authors: GREEN R. E. , RANDS M. R. W. , MOREBY S. J.
Published: April 2008

Chicks of both the Grey and the Red‐legged Partridge feed on arthropods and plant material, mainly leaves and seeds. Fully grown partridges are mainly herbivorous and the proportion of plant material eaten increases rapidly during early life in both species, but plant material predominates in the diet of the Red‐legged Partridge from an earlier age than for the Grey Partridge. Red‐legged Partridge chicks are also able to disrupt grass seeds efficiently during passage through the digestive tract from an earlier age (2 days) than Grey Partridge chicks (10 days). It is suggested that the difference in timing between species in the development of herbivory is associated with this difference in digestive ability.
Parental care of the Common Tern Sterna hirundo
Authors: WIGGINS DAVID A. , MORRIS RALPH D.
Published: April 2008

Parental care activities of male and female Common Terns Sterna hirundo were recorded over two breeding seasons. Males and females exhibited distinct parental roles throughout a breeding bout. Courtship feeding by males was extensive prior to and during egg‐laying, but declined with the onset of incubation. Females performed significantly more incubation behaviour than males although both sexes spent equal time attending at the nest site. During the chick stage, females spent significantly more time on the territory than did males. Chick feeding was largely the responsibility of the male; males fed chicks at a rate approximately three times higher than that of females. In addition, whereas females showed no trend in the size of fish delivered to chicks relative to chick age, the size of fish delivered by males increased with chick age. Courtship feeding activities and extensive chick feeding contributions by male Common Terns appear to outweigh parental contributions by females, contrary to predictions for a monogamous species.
Offspring quality and the evolution of cainism
Authors: SIMMONS ROBERT
Published: April 2008

Obligate siblicide, known as ‘cainism’ in large raptors, is a taxonomically widespread avian phenomenon that remains inexplicable as a simple consequence of food stress: two young can be raised to independence in experimentally manipulated nests, and food supplements do not decrease sibling aggression.

A review of the Falconiformes identified 23 species in which obligate and facultative cainism is regular. All species have small clutches and deferred acquisition of adult plumage. Obligate cainists in particular are large, long‐lived species characterized by extreme subadult mortality and intense competition for breeding sites. Hence, it can be suggested that early sibling conflict, in the absence of food stress, is the end result of selection for quality (survival) and competitive ability. Cain's domination or killing of Abel insures (1) an increase in Cain's chances of survival through the high‐risk, pre‐breeding period via improved nestling weight gain, and/or (2) domination of surviving sibs, enhancing Cain/s competitive abilities and thereby increasing the probability of achieving breeding status. Only among long‐lived species can the benefits of enhanced survival and competitive ability outweigh the major costs of sibling loss.

Facultative cainists. which in more than 10% of cases raise more than one young (despite aggression and sibling hierarchies), not only lay larger, more variable clutches, but on average attain adult plumage earlier than obligate cainists. Their shorter lives and higher population turnovers are consistent with their less extreme siblicidal tendencies. Similar life‐history traits and cainistic habits in other avian orders parallel those in the Falconiformes, indicating several independent evolutionary pathways to cainism.

Retention of the second egg by obligate cainists, usually explained as insurance against failure, may instead allow parents adaptively to track population stability. Thus when breeding places are numerous (habitat saturation and competition low), parents laying two eggs and rearing two young may achieve greater fitness than single‐young parents. When populations become saturated (competition high), selection should favour high‐quality, competitive young and levels of siblicide should increase. Aproximate mechanism is proposed linking population saturation with the incidence of cainism, based on demonstrable population characteristics found in several long‐lived species.
Competition for food between Neotropical vultures in forest
Authors: HOUSTON DAVID C.
Published: April 2008

Carcasses were provided at a gallery forest site in Venezuela to compare the feeding methods of four vulture species. Turkey Vultures or Lesser Yellow‐headed Vultures were always the first species to arrive. Black Vultures were most likely to arrive at large carcasses or those in open situations and were the only species to form large feeding groups. King Vultures were equally likely to arrive at small or large carcasses. There were marked differences in feeding technique, food selection, rate of feeding and bill morphology between Turkey, Black and King Vultures, and the level of aggression between species was low compared to intra‐specific aggression.
Comparative day and night feeding strategies of shorebird species in a tropical environment
Authors: ROBERT MICHEL , McNEIL RAYMOND
Published: April 2008

A study was carried out in northeastern Venezuela to determine whether or not shorebirds feed at night in tropical environments. Results show that some Neotropical residents and Nearctic winter migrants feed during darkness. During daylight, Black‐winged Stilts Himantopus himantopus, mexicanus group, were predominantly visual foragers (75% attempts were pecking), performing a tactile type of feeding technique (immersion of the whole head and portion of the neck while searching for food through soft mud) on other occasions. During night‐time, they were almost equally visual (pecking) and tactile (multiple scythelike sweeps) foragers. Greater and Lesser Yellowlegs Tringa melanoleuca and T. flavipes foraged visually during daylight and tactilely (sidesweeping) at night. Short‐billed Dowitchers Limnodromus griseus were tactile feeders (probers) both by day and by night while Semipalmated Plovers Charadrius semipalmatus during daylight and at night and Wilson's Plovers C. tvilsonia by night were sight feeders (peckers). Prey abundance was higher at night than during daylight. Black‐winged Stilts and yellowlegs seemed to feed at night on food items at least partly different from those they fed upon during daylight.
Population fluctuations and survival of Great Tits Par us major dependent on food supplied by man in winter
Authors: ORELL MARKKU
Published: April 2008

The 16‐year data of a Great Tit population, breeding and overwintering in a nest box area at Oulu, northern Finland, were studied to reveal the factors governing the annual fluctuations in density and local survival. The breeding density at Taskila was high after a cold spring (March‐April) and a warm August the year before was also followed by a large breeding population. A similar relationship resulted for the local survival of fledglings, and there was a tendency for immigrant yearlings to settle to breed in large numbers when the spring was cold. In the north, Great Tits cannot survive the winter in the forests but gather around feeding tables near human settlements. A cold spring evidently suppresses the birds' dispersal before the breeding season. For a population which is time‐limited, it is adaptive to remain in order to breed nearby instead of searching for territories out in the forests when conditions become favourable late in the spring. Thus, the negative correlation between spring temperature and the size of the following breeding population may be the result of a spatial distribution of juveniles achieved by behavioural responses to unfavourable conditions. The causality behind the high survival of resident juveniles after a warm August may be attributable to food availability during the time when the birds undergo their postjuvenile moult, which is an energy‐demanding process. The survival rate of breeding adults was highly dependent on the intensity of nightly predation upon individuals roosting in nest boxes. Stoats Mustela erminea, the prime predators, preyed on tits when the populations of their main prey species, small rodents, were low. When the effect of predation was eliminated, the density‐dependent survival of adult birds disappeared. During low predation years the adult survival rate was negatively related to the number of fledglings produced per pair; this suggests that investment in descendants is a substantial survival cost for reproducing individuals.
Breeding biology and current status of the Amsterdam Island Albatross Diomedea amsterdamensis
Authors: JOUVENTIN P. , MARTINEZ J. , ROUX J. P.
Published: April 2008

A small population of the ‘Great Albatrosses’ has been discovered on Amsterdam Island (Indian Ocean) and described in 1983 as a new species: Diomedea amsterdamensis (Roux et al. 1983). We present here data on the biometry, plumage variability and preliminary results of a long‐term study on the breeding cycle and population dynamics of this relict population. The current population is estimated at 65 birds including 21 breeding pairs.
The reproductive biology of the Red Shining Parrot Prosopeia tabuensis on the island of ‘Eua, Kingdom of Tonga
Authors: RINKE DIETER
Published: April 2008

On Eua, Red Shining Parrots Prosopeia tabuensis breed in the cool and dry season, i.e. from May to October. Climate is the main factor timing the breeding season, which gives additional evidence for an assumed origin of the genus from temperate regions. Two or three eggs are laid in cavities of forest trees; the incubation time is about 24 days. Only females were observed brooding and feeding the young. Nestlings were fed three times a day independently of age. Single nestlings and older siblings received almost twice as much food per feeding as younger siblings. Growth constants are presented for weight, the width of the upper mandible, and wing‐length. The fledging age is reached after 7 weeks but none of the observed nests fledged young due to predation by man. Breeding success was calculated at more than 50% for those nestlings that would have fledged without human interference. The reproductive biology of the Red Shining Parrot does not, apparently, show island‐specific adaptations such as a reduced clutch‐size or a prolonged nestling period.
Determination of the absolute visual threshold of a nocturnal seabird, the Common Diving Petrel Pelecanoides urinatrix
Authors: BROOKE M. DEL.
Published: April 2008

Many of the smaller burrowing petrels are active at their colonies during the night. How they find their nesting burrows in the open terrain of an oceanic island or in the even more visually‐taxing gloom under a forest canopy (Grubb 1974 and references therein) is a feat which has long intrigued naturalists (Lockley 1942). There is experimental evidence that vision is important in burrow location by the Manx Shearwater Puffinus puffinus (Brooke 1978, James 1986), while olfactory homing by Leach's Petrel Oceanodroma leucorhoa has also been suggested by Grubb (1974).

Additionally it seems likely that a number of petrel species catch a significant fraction of their food at night (Imber 1973, Prince & Francis 1984). Many of the squid presumed to be caught then are not bioluminescent (Imber 1973, Clarke et al. 1981), so their detection presumably demands good night vision. In the context of these observations, the dearth of information on the visual abilities of petrels is remarkable.

The present study investigated the absolute visual threshold of the Common Diving Petrel Pelecanoides urinatrix. Probably because the species is small (c. 130 g) and so vulnerable to predators such as Sub‐antarctic Skuas Catharacta antarctica, it is strictly nocturnal at breeding colonies (Thoresen 1969, Payne & Prince 1979). It nests in burrows that are often located under tussock grass Poa spp. Whether the birds catch their crustacean prey (Payne & Prince 1979) by day or night is not known.
Movements of Eiders Somateria mollissima on the east coast of Britain
Authors: BAILLIE S. R. , MILNE H.
Published: April 2008

Movement patterns, sex differences in natal dispersal and breeding dispersal, and interchange of birds between colonies were studied in the population of Eiders Somateria mollissima breeding on the east coast of Britain. First‐winter Eiders reared at the Sands of Forvie, Grampian, remain at or close to the colony, while most adults move about 100 km south to winter on the Firths of Forth and Tay. A proportion of the Forvie population is sedentary. Eiders which breed in Northumberland either move north to winter on the Tay and Forth estuaries or remain close to their breeding areas. Eiders breeding in Fife are sedentary. Recoveries of British‐ringed Eiders in Scandinavia indicate that some British‐born males join the Baltic breeding population, probably by pairing with Scandinavian females wintering in Britain. There is extensive natal dispersal of males from Forvie, with more than twice as many Forvie‐bred females as males returning to the colony to breed. The breeding dispersal of males is also twice that of females. Dispersal of males from the relatively sedentary Forvie wintering population is less than that from the breeding population. Previous work suggested that at Forvie sedentary birds nesting close to the estuary were genetically isolated from migratory ones nesting along the coast. This situation is less clear cut than had been supposed previously, with many migrants nesting close to the estuary. It is unlikely that the genetic differences between females nesting in different parts of the Forvie colony will remain stable in the long term, due to the natal and breeding dispersal of males.
Miocene hawk converges on Secretarybird
Authors: FEDUCCIA ALAN , VOORHIES MICHAEL R.
Published: April 2008

A falconiform Miocene fossil bird from North America, represented by a nearly complete tarsometatarsus with phalanges in place, is that of a hawk that converged on the living Secretarybird Sagittarius serpentarius. It is described as a new genus and species, Apatosagittarius terrenus. The palaeoenvironment indicates a Miocene setting similar to the present day habitat of the living Secretarybird, characterized by extensive grasslands and savannas.
Feather eating in Great Crested Grebes Podiceps cristatus: a unique solution to the problems of debris and gastric parasites in fish‐eating birds
Authors: PIERSMA THEUNIS , EERDEN MENNOBART R. VAN
Published: April 2008

The occurrence of feathers in stomachs of 407 Great Crested Grebes Podiceps cristatus from Lake IJsselmeer, The Netherlands, is described. Only four of the 8718 identified stomach feathers originated from a species other than Great Crested Grebes. In all, 68% were breast and belly feathers and 19% were flank feathers. Flank feathers were positively selected from those becoming available during moult, and also occurred more in the ejected feather pellets than expected from the intake. This suggests that flank feathers, which are long and curved and have a black tip, may be especially suited for the formation of pellets. Feather ingestion was more than balanced by feather production. Feathers were most abundant in stomachs in autumn and were least numerous in winter. Most of this variation can be explained by seasonal differences in the intensity of body moult. In addition, the type of prey was related to the number of ingested feathers. When the diet consisted of smelt, which leave little indigestible matter, more feathers were eaten than with a diet of perch and pikeperch, which leave more fish debris. We suggest the hypothesis that ingested feathers, in the absence of other indigestible matter, contribute substance to the stomach content, enabling the formation of pellets that can be ejected. The habit of regularly ejecting the stomach contents minimizes the chance that any serious population of gastric parasites will build up in the upper part of the alimentary tract.
The significance of clutch overlap in Great Tits Parus major
Authors: SMITH HENRIK G. , KÄLLANDER HANS , NILSSON JAN‐ÅKE
Published: April 2008

We studied the effects of manipulation of the size of first broods in the Great Tit Parus major on the size and breeding success of second clutches and its relation to the degree of clutch overlap. The rearing of first brood fledglings always overlapped with the laying of the second clutch and in most cases also with the incubation period of the latter. The degree of clutch overlap depended on the size of the first brood, being less when the first brood was large. Clutch overlap also increased with season. Mechanisms affecting the timing of laying of second clutches are discussed. A large first brood imposed reproductive costs. It affected the size of the second clutch by causing it to be delayed; second clutch size decreases with season. It affected the post‐fledging survival of second brood young as, in this population, this decreases with fledging date. The breeding success of second clutches was, however, not affected by the size of the first brood, but instead by the weight of the female when rearing the first brood.
The effect of food supplementation on the reproductive success of Black‐billed Magpies Pica pica
Authors: DHINDSA MANJIT S. , BOAG DAVID A.
Published: April 2008

The effect of supplementary food on the reproductive success of Black‐billed Magpies Pica pica was studied in an urban habitat in the city of Edmonton, Alberta, Canada. We provided supplementary food (pelleted dog food) regularly from August 1986 to June 1988 in a feeder situated outside all known magpie territories. Magpies using the supplementary food showed (i) an advancement of 7 days in the initiation of laying, (ii) no increase in clutch‐size, (iii) higher survival of nest contents (eggs and young) during a spring snow storm, (iv) an increase in rate of nestling weight gain, and (v) an increase in fledging success. Supplementary food did not prompt the fed pairs to select nest sites nearer the feeder in 1988 than in 1987. The feeder did not affect the breeding density because the nearest neighbour distances of fed magpies did not differ from unfed magpies in either year, nor did they differ between the two years for either fed or unfed magpies. This study provided evidence that magpies frequently renest even if their initial nests fail after the eggs hatch—a practice that has been reported to be absent or rare in other studies. Although brood reduction was equally frequent in the nests of food‐supplemented and control pairs, the actual number of nestlings disappearing from the former (1.56 per nest) was significantly smaller than that from the latter (2.60 per nest), suggesting that the availability of food plays a major role in magpie reproductive success.
Foraging differences between white and dark morphs of the Pacific Reef Heron Egretta sacra
Authors: ROHWER SIEVERT
Published: April 2008

Among the species of diurnal herons (Ardeinae) showing light‐dark colour polymorphism in plumage, colour phase is age‐related in one species, closely associated with geography in three species, and found in most populations in three closely related species of reef herons. In Pacific Reef Herons Egretta sacra white‐phased birds sought prey by a flight, land, and freeze hunting style in breaking surf, while dark birds pursued prey by actively walking or running on reef flats. On Mangaia, in the southern Cook Islands, more white‐phased birds used the windward side of the island and more dark‐phased birds used the lee side. On Rarotonga, 204 km from Mangaia, reef herons foraged almost exclusively in shaded streams and no entirely white‐phased bird was encountered. These results provide the first evidence of differences in hunting techniques associated with colour morph and only the second observation of differences in habitat use by white‐ and dark‐phased herons at single localities. As such they support Murton's (1971) idea that colour polymorphism serves herons in their role as predators. For reasons discussed in the text such differences are more expected in reef herons than in most other colour‐polymorphic herons.
Weight loss of Antarctic Fulmars Fulmarus glacialoides during incubation and chick brooding
Authors: WEIMERSKIRCH H.
Published: April 2008

Weight losses incurred by incubating birds of both sexes, and weight changes at the beginning and end of shifts between successive incubation and brooding shifts were studied in the Antarctic Fulmar Fulmarus glacialoides in Adélie Land, Antarctica. The overall rate of weight loss during incubation fasts was 4.46% per day in both sexes but 3.91% per day after the first 2 days of fast once the stomach contents had been digested. Antarctic Fulmars appear to have rates of body‐weight loss significantly greater than the rates of weight loss observed in any other species of albatross or petrel. The validity of methods using the rate of weight loss to estimate incubation metabolic rates is discussed, and it appears that for birds incubating for periods of less than 2–3 days the digestion of the stomach contents can bias the estimation. The absence of change in weight at the beginning of shifts during incubation and brooding, together with the short time spent on foraging trips, suggests that food availability is high and/or food is readily accessible to Antarctic Fulmars. The availability of food allows the Antarctic Fulmar to compensate for the high energy cost of breeding that could be due to the cold Antarctic environment and perhaps also to a higher intrinsic metabolism.