bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal variations in feeding range and flock structure of the Rook Corvus frugilegus in eastern Ireland
Authors: MACDONALD R. A. , WHELAN J.
Published: April 2008

The feeding range and flock structure of Rooks showed temporal variations caused mainly by the dispersion of food and reproductive behaviour.

Feeding range was restricted in spring, autumn and early winter when food availability was high and Rooks were reproductively active. A large feeding range occurred in late summer and late winter, when food availability was either generally low or locally distributed and when Rooks were reproductively inactive. The occurrence of flocks common to several rookeries mirrored variations in feeding range; mixed rookery flocks were more common in late summer and late winter. Similarly, the size of the rookery (as measured by the number of nests) was related to feeding range only when Rooks were reproductively inactive and at such times larger rookeries had greater feeding ranges.

Flock structure showed similar seasonal variations; small widely spaced flocks predominated in summer, autumn, early winter and spring, whereas large dense flocks occurred in late winter. Diurnal variations in flock structure occurred within any one season. Both seasonal and diurnal variations in flock structure may be determined by the dispersion of the prey and the feeding strategy used to obtain it, reproductive behaviour and the risk of predation.
Reproduction and survival of polygynous and monogamous Blue Tit Parus caeruleus
Authors: DHONDT ANDRÉ A.
Published: April 2008

In a seven‐year study of Blue Tits in optimal habitat near Antwerp, Belgium, 45 polygynous broods involving 22 males out of 667 successful first broods were found. In another 43 nests no male was found, although a major effort was made to trap all adults. The estimated proportion of polygynous males is 3.4%, if only confirmed cases are considered, but 10.8% if all possible cases are included. One male was paired simultaneously to three females.

Primary females (laying earliest in a triangle) were as successful as monogamous ones. Secondary (laying later in a triangle) and deserted females (nests in which no male was trapped), although still quite successful, raised fewer young and in one plot had a lower probability of recruiting offspring.

Both in males and females, the frequency of polygyny was independent of age. Adult survival did not differ between monogamous and polygynous males. Among females no effect of pairing status on survival was found in one plot, but in a second plot monogamous females survived better than others. It is concluded that in any study of Blue Tits in optimal habitat one could expect to find polygyny.
Do Great Tit Parus major parents gear their brood defence to the quality of their young?
Authors: CURIO E. , REGELMANN K.
Published: April 2008

Parental investment theory suggests that animals should increase their reproductive success by investing more heavily in higher‐quality offspring than in lower‐quality offspring. Great Tit Parus major nestlings of higher body weight have been shown to enjoy a higher survival rate after fledging. We examine for the first time whether Great Tit parents invest more heavily in heavier nestlings as measured by defence (six variables) against a Pygmy Owl Glaucidium perlatum, similar to G. passerinum, which is a predator of both adult and nestling birds including hole‐nesters like the Great Tit. Thirty‐two parent Great Tit pairs in a wood‐ and parkland study area in Essen‐Stadtwald did not vary their antipredator behaviour in relation to nestling weight; between‐brood variation of weight was similar to that found in different populations and in different years. However, parental defence behaviour varied, as expected, with parent's sex and nestling number, though overall responsivity of parents to many other independent variables appeared lower than found previously.
Breeding success of the Great Bustard Otis tarda in Zamora Province, Spain, in 1984
Authors: ENA VICENTE , MARTINEZ ANA , THOMAS DAVID H.
Published: April 2008

Great Bustards are still fairly abundant (5‐2 nests/1000 ha) in Zamora. Overall fecundity was high (92% of adult females attempt to nest; 2–47 eggs/clutch; 89% egg fertility), but pre‐ and post‐hatching mortality were also high (50% of eggs laid; 57% of nestlings hatched), due mainly to agricultural machinery but also to natural predators. Calculated annual yields per 100 adult females were: 227 eggs, 102 hatchlings, 44 fledglings. Production of 44 fledglings/y could sustain a stable adult population (mortality approx. 8%/y) if mortality of immatures is not more than 18–22%/y.
A quantitative analysis of habitat preferences of Woodcock Scolopax rusticola in the breeding season
Authors: HIRONS GRAHAM , JOHNSON T. H.
Published: April 2008

In Britain, prior to breeding, Woodcock Scolopax rusticola switch from feeding on pastures by night to feeding in woodland by day. Their major food is earthworms (Lumbricidae). In April and May 1985, vegetation structure and composition and soil parameters including earthworm numbers (30 habitat variables) were recorded for quadrats containing 50 feeding locations of six radio‐tagged birds, seven nests and 50 random locations in Whitwell Wood, northeast Derbyshire.

Significantly different mean values between feeding and random sites were found for 11 habitat variables. Feeding sites were in younger stands, with a higher percentage ground cover of dog's mercury Mercurialisperennis and consistently high values for pH. Earthworm biomass was on average 82% greater than in random plots. Areas of beech Fagus sylvaticus were avoided. A discriminant function based on six habitat variables correctly classified 85‐5% of the feeding and random sites; 70% of the feeding locations were correctly classified by a jack‐knife procedure. The important factors determining where feeding occurs are probably safety from avian predators and high availability of earthworms.

Discriminant analysis of the habitats used for feeding by solitary birds, broods and for nesting produced significant functions which correctly classified 84% of sites. Nests were in areas with a high percentage cover of brambles Rubus spp. and more open ground vegetation. Broods and solitary birds used similar areas characterized by denser ground vegetation than nest sites.

The results of this study indicate that both habitat structure and food availability influence the distribution of Woodcock in the breeding season.
Foraging energetics of Grey‐headed Albatrosses Diotnedea chrysostoma at Bird Island, South Georgia
Authors: COSTA D. P. , PRINCE P. A.
Published: April 2008

At‐sea metabolism (CO2 production) and water turnover of six breeding Grey‐headed Albatrosses Diomedea chrysostoma were measured, using the doubly labelled water method, at Bird Island, South Georgia, Mean food consumption (estimated from a water influx rate of 1.01 1 d‐1 and data on dietary composition) was 1200gd‐1 or 50.4 W. At‐sea metabolism (derived from a rate of CO2 production of 3.98 1 h‐1) was 27.7 W, 2.5 times the estimated basal metabolic rate (BMR). On average the birds ingested nearly twice as much food energy as they expended to obtain it. The metabolic rate during flight (estimated from at‐sea metabolism and activity budget data) was 36.3 W (range 34.7–39.0 W) or 3.2 (range 3.0–3.4) times the predicted BMR. This is the lowest cost of flight yet measured, but consistent with the highly developed adaptations for economic flight shown by albatrosses. These results are briefly compared with data for other polar vertebrates (penguins, fur seals) exploiting similar prey.
Survival of Mallard ducklings Anas platyrhynchos and competition with fish for invertebrates on a flooded gravel quarry in England
Authors: HILL DAVID , WRIGHT ROSALIND , STREET MICHAEL
Published: April 2008

The survival of Mallard Anas platyrhynchos ducklings was studied on a complex of flooded gravel quarries in England and their weight changes in response to invertebrate predation by fish were studied by experiment. The majority of duckling loss occurred during the first 12 days after hatching but those feeding on the river where fish were scarce survived better than those feeding on lakes where fish density was high. Duckling mortality was higher in broods with large home ranges. In the experimental trials an increase in fish density was related to a reduction in both the number of emerging invertebrates and the biomass of aquatic macrophytes. Ducklings feeding in these ponds travelled further and gained less weight than on the pond with a low fish density where the number of emerging invertebrates was higher.
Parental care and the transition to independence of Spanish Imperial Eagles Aquila heliaca in Doñana National Park, southwest Spain
Authors: ALONSO JUAN CARLOS , GONZALEZ LUIS MARIANO , HEREDIA BORJA , GONZALEZ JOSE LUIS
Published: April 2008

The behaviour of five broods of radio‐tagged Spanish Imperial Eagles Aquila heliaca adalberti was studied in Doñana National Park, Spain during the post‐fledging period. The distance between perching sites and nest, the mean flight duration and distance, the percentage of time spent flying and the home range all increased exponentially with age. As the young got older, the parents spent less time in their vicinity. Young were not seen hunting, but depended on their parents for food. They begged and chased their parents throughout the post‐fledging period, with higher intensity at the end. Nevertheless, the adults became progressively more reluctant to feed them, as reflected in the decrease in feeding frequency and in the number of approaching flights towards the young. At the end of the post‐fledging period, adults often performed aerial displays and frequently chased their offspring. The age of independence of the different young studied varied between 123 and 145 days. The correlations between individual independence and the dates when the young were last fed by their parents, and when the highest intensity of parental aggressive behaviour occurred, were higher than correlations with the variables related to the maturation of flying. Therefore, it is suggested that parental ‘meanness' and aggressive behaviour may be the factors determining the date of juvenile independence and dispersal from the home territory.
Radar observations of the stoop of the Peregrine Falcon Falco peregrinus and the Goshawk Accipiter gentilis
Authors: ALERSTAM THOMAS
Published: April 2008

Measurements in 10‐s intervals by a tracking radar showed average speeds of about 25 ms‐1 for a Peregrine Falcon Falco peregrinus and a Goshawk Accipiter gentilis during four stoops lasting 40–110 s, with angles of dive between 13o and 64o, and involving height losses between 450 and 1080 m. Maximum speeds during 10‐s intervals were between 31 and 39 ms‐1 in the Peregrine Falcon, and close to 30 ms‐1 in the Goshawk. The observed speeds are well below the maximum possible terminal speeds in steep or vertical dives according to theoretical estimation. By adopting a moderate stooping speed, raptors may gain in hunting precision.
Age effects on clutch size and laying dates of individual female Lesser Snow Geese Anser caerulescens
Authors: HAMANN JEAN , COOKE FRED
Published: April 2008

It is well known in many species of birds that mean clutch size increases and laying date advances with increasing age of the female. This has been interpreted widely as being due to some maturation process in which the performance of individual birds improves as they age. There are two alternative explanations, however. Birds which lay small clutches and lay late may have a higher mortality and be under‐represented in the later year samples, or birds with a propensity to lay large and early clutches may enter the breeding population at a later age. In an attempt to discriminate between these alternatives, the reproductive performances of individual Snow Geese were examined over a series of years. Clutch size increased and laying date advanced for these individuals as it did for the population as a whole, thus confirming the maturation hypothesis.
Energetics of the annual cycle of Dippers Cinclus cinclus
Authors: BRYANT D. M. , TATNER P.
Published: April 2008

Time‐activity budgets and energy expenditure of Dippers Cinclus cinclus were studied in all months of the year and for every stage of the annual cycle. The commonest daytime activity was feeding (54%), then resting (43%) and flying (4%). On a 24‐hr day basis the most marked changes in activity followed from changing daylengths. DEE (Daily Energy Expenditure), derived from time‐activity budgets through the year and laboratory estimates of metabolism, averaged 201 kj d ‐1 in females and 228 kj d ‐1 in the larger males. Over a more restricted range of circumstances, direct estimates of DEE obtained from 77 Dippers using the doubly labelled water technique averaged 205 ± 43 kj d‐1 and 251 ± 55 kj d‐1 in females and males, respectively. Overall, the correspondence between these largely independent estimates of energy expenditure was reasonably close. DEE was highest during breeding (laying‐females; rearing‐males) and in late winter for both sexes. The lowest energy expenditures occurred during moult, amongst juveniles and in early winter. Incubating females and mate‐guarding males also had low energy costs. Across all stages of the annual cycle body size, activity patterns, ambient temperature and river flow had significant effects on energy expenditure. The rate at which food was gathered to meet these changing energy demands varied widely. While some of this variation was imposed by a seasonal environment, it was also likely to reflect adaptive shifts in rates of food gathering, in some cases consequent upon the changing fitness benefits of various non‐feeding activities.
Food selection, food‐seeking patterns and hunting success of captive Goosanders Mergus merganser and Red‐breasted Mergansers M. serrator in relation to the behaviour of their prey
Authors: SJÖBERG K.
Published: April 2008

Food selection and food‐seeking behaviour of hand‐raised Goosanders Mergus merganser and Red‐breasted Mergansers M. serrator were tested in experimental situations. When different combinations of two species of fish were presented simultaneously to hungry birds in a small trough where the prey was easily and equally available, neither duck species showed any preferences in prey selection. However, when these same fish species were presented to satiated birds, they showed definite preferences; the most preferred species were baltic salmon and brown trout followed in decreasing order by minnow, whitefish, sculpin, burbot and river lamprey. This was also the case when combinations of five to seven species were presented. However, under semi‐natural conditions in a stream tank, the number of each species offish caught was related to their escape behaviour, not to the previously determined predator preferences. When salmon and minnows of different size were presented to hungry birds, they selected the larger fish regardless of species. In contrast, when satiated, they preferred small fish over large fish. Under the experimental conditions, the use of certain elements of foraging behaviour clearly differed between the two bird species: Mergus serrator spent more time hunting underwater than did M. merganser. Results are discussed in relation to the predator‐prey situation existing under natural conditions in northern Swedish rivers.
The pelagic ecology of the Grey and Red‐necked Phalaropes Phalaropus fulicarius and P. lobatus in the Bay of Fundy, eastern Canada
Authors: BROWN R. G. B. , GASKIN D. E.
Published: April 2008

The outer Bay of Fundy, eastern Canada, is an important feeding area for migrant Grey and Red‐necked Phalaropes Phalaropus fulicarius and P. lobatus in late summer. The birds feed on copepod‐sized zooplankton, brought to the surface by the passage of strong tidal streams over shallow, rocky ‘ledges’, and concentrated there in upwelling and convergence ‘streaks’. Feeding phalaropes are significantly more abundant in the ‘streaks‘ than in adjacent ‘contro’ areas. Red‐necked Phalaropes are the more common species; they prefer the New Brunswick shore, where copepod biomass is high and the species‐community is dominated by large, Stage VI‐V Calanus finmarchicus. Grey Phalaropes occur mainly on the Nova Scotian side of Fundy, where the copepod biomass, and the dominant species, are smaller. The feeding habits of both species, and their non‐breeding distributions, are reviewed. It is concluded that upwellings, convergences, and other oceanographic phenomena that concentrate zooplankton at the surface are the principal factors influencing the pelagic ecology of phalaropes.
Selection of incubation mound sites by the Australian Brush‐turkey Alectura lathami
Authors: JONES DARRYL
Published: April 2008

Environmental characteristics associated with siting of the incubation mounds of the megapode, the Australian Brush‐turkey Alectura lathami were investigated in three rainforest locations in southeast Queensland. Seventeen environmental variables were measured for 52 mounds and 137 non‐mound sites. Most mounds were constructed on top of old mounds which had not been used during the previous year. A Discriminant Function Analysis obtained a clear separation between mound and non‐mound sites, based primarily on three variables: (1) the number of saplings growing within the mound or centre of the site: this was considered to be a result of the germination of seeds raked in earlier years; (2) the proportion of Lantana camara thicket occupying the site. Approximately half of the mounds constructed during a season were abandoned by their constructor due to expulsion by a neighbouring male. Brush‐turkeys could more easily establish mounds next to thickets since the efficiency of defence by other males was reduced in these areas; and (3) the openness of the canopy. Areas with greater canopy cover provided two important mound resources: a good supply of leaf litter, and protection of the mound from dessication.
Advantages of social foraging of Willow Tits Parus montanus
Authors: HOGSTAD OLAV
Published: April 2008

The mean number of Willow Tits Parus montanus in single‐species flocks was significantly larger than in mixed‐species flocks of Willow and Coal Tits P. ater. Both flock size and the tendency of Willow Tits to join mixed‐species flocks were negatively correlated with ambient temperature, probably because each bird, when the metabolic rate of the birds increased, could allocate more time to foraging due to improved predator detection by many eyes. The vigilance time of Willow Tits decreased with flock size and was determined by the total number of individuals in a flock rather than by the number of Willow Tits in mixed‐species flocks of Willow and Coal Tits.
On the advantages of crossed mandibles: an experimental approach
Authors: BENKMAN CRAIG W.
Published: April 2008

The importance of the crossed mandibles to crossbills for foraging on conifer cones was studied by removing most of the crossed portion of the mandibles of two Red Crossbills L. curvirostra. The foraging rate of these two bill‐altered crossbills on the cones of three species of conifers was compared to their rates prior to bill alteration and to two controls. The mandible crossing proved essential for extracting seeds from closed cones. However, as cones open the bill crossing becomes less critical. The mandible crossing appears to be one of several adaptations of crossbills that have extended the period during which conifer seeds can be exploited effectively.
A model for avian primary moult
Authors: UNDERHILL LES G. , ZUCCHINI WALTER
Published: April 2008

The regression methods frequently used to estimate the parameters associated with primary moult in birds are unsatisfactory. Results obtained using least squares regression, and various ad hoc adaptations, are so obviously incorrect that many authors have fitted lines ‘by eye’ (Newton 1968, Thomas & Dartnall 1971, Elliott et al. 1976, Morrison 1976, Appleton & Minton 1978). In a comparison of seven regression methods, estimates of the average starting date varied between 29 June and 31 July, completion date between 2 and 24 October, and duration of moult between 72 and 109 days for the Redshank Tringo totonus, in spite of the very large sample of 1482 observations (Summers et al. 1983). In this paper we present a new approach to the analysis of primary moult and develop a mathematical model specifically designed for moult data.
A promiscuous mating system in the Blue Bird of Paradise Paradisaea rudolphi
Authors: PRUETT‐JONES S. G. , PRUETT‐JONES M. A.
Published: April 2008

We studied nesting behaviour, spatial dispersion of display areas and home range dynamics in the Blue Bird of Paradise Paradisaea rudolphi. We found that (1) females carried out nesting duties alone; (2) males displayed from solitary and dispersed sites; (3) female home ranges overlapped, and (4) males had access to and displayed to numerous females. These data suggest a promiscuous mating system in the Blue Bird of Paradise and resolve earlier controversy over this issue.
Mate choice by hen Red Grouse Lagopus lagopus with an excess of cocks—role of territory size and food quality
Authors: MOSS R. , WATSON A. , PARR R.
Published: April 2008

In a breeding population of Red Grouse the ratio of cocks to hens was about 2:1. Cocks with hens had bigger territories and richer feeding sites than unmated cocks. Despite this, the size of a cock's territory was inversely related to the level of nitrogen in his food. The idea that this was because cocks defend a territory just big enough to meet the pair's food requirements seemed inapplicable, since territories were much bigger than this. In addition, it was inferred that hens took longer to choose a cock on a part of the area that had relatively poor feeding sites. Whether hens chose the cock or his territory was uncertain, but both probably played a part.
Egyptian Vultures Neophron percnopterus and Ostrich Struthio camelus eggs: the origins of stone‐throwing behaviour
Authors: THOULESS C. R. , FANSHAWE J. H. , BERTRAM B. C. R.
Published: April 2008

Experiments were carried out on wild and hand‐reared Egyptian Vultures to investigate the origins of the stone‐throwing this species uses to break into Ostrich eggs. There was no evidence of cultural transmission for stone‐throwing through copying experienced birds. A naïve captive‐reared bird threw stones once an Ostrich egg had been linked with a food reward. The origins of aimed stone‐throwing are probably related to the unaimed throwing of small eggs, since the actions are similar, and all tested birds strongly preferred to throw rounded or egg‐like stones, rather than jagged ones, at Ostrich eggs.
Subordination in mixed‐age bird flocks–a removal study
Authors: HOGSTAD OLAV
Published: April 2008

During the winters of 1979 to 1986, flocks (7–17 per season, 78 total) of Willow Tits Parus montanus (generally consisting of an adult pair and four juveniles) were studied in a subalpine mixed forest in Central Norway. The mean survival rate between December and early April for juveniles (0.32) was significantly lower than that found for adults (0.74). As it has previously been found that adult Willow Tits, being dominant, prevent the juveniles in a flock from using preferred foraging sites, a removal experiment was made to see if the survival of juveniles improved when living in flocks with no adults present. After removal of the adult pair from 13 flocks in early January, the juveniles from these flocks survived significantly less well, up to early April, than either the juveniles in 11 flocks in which the adults were present (controlled for flock size) or those in 14 flocks consisting of an adult pair and four juveniles. Despite a skewed access to the resources in favour of dominant adults, the cost of being a subordinate juvenile is probably outweighed by the improved predator evasion and improved food finding efficiency due to the greater experience of the adult pair possessing the territory.
Breeding site fidelity and natal philopatry in the Redshank Tringa totanus
Authors: THOMPSON PATRICK S. , HALE W.G.
Published: April 2008

This paper presents the results of a study carried out on breeding Redshank in the Ribble Marshes, Lancashire, England.

Redshank tend to return to the same breeding area year after year. There was no detectable sex bias in return rates. Experienced birds were more site faithful than inexperienced birds, with previously successful birds exhibiting the highest degree of breeding site fidelity. Older, more experienced birds were more successful at hatching eggs than inexperienced birds.

Breeding dispersal was the same both within and between years. Faithful pairs and males nesting with a new mate dispersed significantly shorter distances than females nesting with a new partner. Dispersal distances in female Redshank were affected by breeding success: unsuccessful females, nesting with a new mate, dispersed significantly farther than successful females. A pair's breeding success influenced the following year's mate fidelity. However, other factors such as overwintering survival and date of return may also have influenced mate fidelity.

Redshank were highly faithful to their natal area; a high proportion of birds that survived post‐fledging mortality returned to breed in their area of birth. No sex bias in natal dispersal was detected. Approximately 50% of Redshank breed in their first year of life.
Provisioning of nestling Cuckoos Cuculus canorus by Reed Warbler Acrocephalus scirpaceus hosts
Authors: BROOKE M. de L. , DAVIES N. B.
Published: April 2008

Reed Warblers Acrocephalus scirpaceus fostering a single nestling Cuckoo Cuculus canorus bring food to it at roughly the same rate as they do to an average‐sized brood (three or four) of their own young. The food brought, mostly flies and beetles, is also similar. We conclude that the Cuckoo does not provide a supernormal stimulus. We show that Reed Warblers, given experimentally‐enlarged broods of seven or eight, can substantially increase their feeding rate. This raises the question of why the young Cuckoo does not exploit this ‘spare’ feeding capacity of the Reed Warbler hosts. We offer three explanations', (i) that the increased begging necessary would attract predators, (ii) that the young Cuckoo is unable to grow faster, and (iii) that it would not be to the advantage of a young Cuckoo, dependent on its foster parents for about 5 weeks (cf. 3 weeks for Reed Warbler young), to provoke a feeding rate that the warblers could not sustain.
The effect of old age on the reproduction of Great Tits Parus major and Blue Tits P. caeruleus
Authors: DHONDT ANDRÉ A.
Published: April 2008

The results from two data sets show that in Great Tits Parus major and Blue Tits P. caeruleus reproduction is influenced by age. In both species, laying dates become earlier while clutch‐ and brood‐size increase between the ages of 1 and 2, but there is no change in nesting success or post‐fledging juvenile survival. Great Tits aged 5 or older are ‘old’ in that laying starts later and nesting success, brood‐size and post‐fledging juvenile survival decrease. Blue Tits become ‘old’ 1 year earlier than Great Tits: females aged 4 or older lay later, have a lower nesting success and smaller brood‐size, and their young show a decreased post‐fledging survival. The effect on laying date, in the Blue Tit, becomes apparent only for females aged 6 and older. It is concluded that ageing in small passerines is to be expected more generally, but that no extrapolations can be made as to the timing of the effect from one species to another.
Nesting biology and mating system in an alpine population of Temminck's Stint Calidris temminckii
Authors: BREIEHAGEN TORGRIM
Published: April 2008

A colour‐marked population of Temminck's Stint Calidris temminckii was studied in an alpine area of southern Norway over 3 years. Birds arrived from late May until late June, and egg‐laying occurred over approximately 1 month. Each year, one to three males out of about 15–17 males still displayed after the last recorded clutch‐completion date.

There were six documented cases of double‐clutching. Inter‐clutch intervals varied (range 2–8‐9‐1 days), longer intervals probably being caused by weather‐induced food shortage. A successively bigamous mating pattern was recorded in both sexes. A polygynously (bigamously) mated male invariably incubated its first mate's clutch. Females consistently changed mates between layings of successive clutches, the last one incubated by themselves.

An excess of nesting females was found, particularly in parts of the study area where nesting started late. This appears to have been caused mainly by a considerable annual immigration of late‐arriving females, having probably laid their first clutch(es) elsewhere, in nesting habitats that were available earlier. I suggest that male availability is relatively unimportant compared with other factors governing female movements between layings of successive clutches; females may increase their reproductive success, either by achieving a longer egg‐laying season (i.e. by moving from nesting habitats/areas available early in the season to those available later) or by being capable of utilizing favourable feeding habitats/conditions in different areas.
Turnover and dispersal in urban Merlins Falco columbarius
Authors: JAMES P. C. , WARKENTIN I. G. , OLIPHANT L. W.
Published: April 2008

Information on the turnover of territorial occupants, the natal dispersal (movements from birthplace to breeding place) and breeding dispersal (breeding place to breeding place) of raptors is very limited, because such data only become available as a result of the long‐term study of marked populations (e.g. Newton 1986). Over the last two decades, Merlins Falco columbarius have colonized urban centres on the Canadian prairies for breeding and wintering (Oliphant & Haug 1985, James et al. 1987a). In Saskatoon, for example, the breeding Merlin population has increased from one pair in 1971 to 27 pairs in 1987 and is still increasing. This population has already achieved the highest recorded nesting density for this species (Oliphant & Haug 1985). Similar urban populations exist in Regina, Moose Jaw, Calgary, and Edmonton. In this paper, we report on the annual turnover, adult mortality, natal dispersal, and breeding dispersal of this population.
Nest intruders, nest defence and foraging behaviour in the Black‐and‐white Casqued Hornbill Bycanistes subcylindricus
Authors: KALINA JAN
Published: April 2008

The female Black‐and‐white Casqued Hornbill Bycanistes subcylindricus uses mud to seal herself into a nest cavity and remains there until the nesting attempt has ended. The male hornbill is solely responsible for food provisioning and external defence of the nest. Data on hornbill nests in a Ugandan rain forest were used to test Martindale's (1982) model of nest defence and central place foraging. As predicted, nest guarding by the resident male hornbill during intrusions by conspecifics altered foraging patterns; the resident male foraged closer to the nest, made a larger number of shorter visits, and brought smaller food loads. There was a significant change in size composition of fruits brought before, during, and after intrusions. For short intrusions, the volumes of food brought per unit time did not change. However, if intrusions lasted for days or weeks, food delivery rates declined. Nest‐sealing by the Black‐and‐white Casqued Hornbill appears to function primarily to protect the nest from conspecifics rather than from interspecific predators.
Breeding season, courtship behaviour, and territoriality of White and Japanese Wagtails Motacilla alba and M. grandis
Authors: HIGUCHI HIROYOSHI , HIRANO TOSHIAKI
Published: April 2008

The breeding ecology of White and Japanese Wagtails, Motacilla alba and M. grandis, was studied along a river in central Japan. The home ranges of the two species greatly overlapped along the river, but no interbreeding occurred. M. grandis spent more time on the river than M. alba and defended territories there. M. alba used the river as part of the entire home range, and did not defend the river areas as territories. Singing activity and breeding started earlier in M. grandis than in M. alba. The early breeding of M. grandis was related to the lack of moulting in spring, less necessity for pair formation due to the existence of pairs in the winter, and the greater dependency on larval than on adult insects. Songs were very different between the two species. The bowing display that preceded the pre‐copulation display was found only in M. alba. During the pre‐copulation display, male M. grandis lifted both wings above the horizontal while male M. alba drooped both wings. The pre‐copulation display of M. grandis was similar to that of Large Pied Wagtails M. maderaspatensis in India, suggesting a closer relationship of the two species than to M. alba.
Flock, pair and group living lifestyles without cooperative breeding by Australian Magpies Gymnorhina tibicen
Authors: VELTMAN CLARE J.
Published: April 2008

The social behaviour of Australian Magpies Gymnorhina tibicen was studied at Linton in the Manawatu district, New Zealand, from June 1978 to November 1982. Territorial magpies defended all‐purpose areas averaging 5 ha in size, and there was no correlation between territory size and the number of occupants. The mean adult survival rate was 0.85, and average annual productivity was 0.96 juveniles per breeding female. Nomadic flocks formed in the spring and foraged on open, treeless pasture. They mainly comprised 1–3‐year‐old magpies which did not breed. Territories were defended by monogamous pairs, and by groups ranging from three to six individuals. Some territorial groups probably originated in the flock, and may therefore have consisted of unrelated birds. Other territorial groups formed when juveniles did not disperse away from the natal territory, and were called family groups. Non‐breeders did not help at the nest in any group, and there was no difference in the production of young by females breeding in group‐defended territories compared with those in pair‐defended territories. The opportunity to disperse into non‐territorial flocks may have liberated Australian Magpies from cooperation.
Foraging by Nightjars Caprimulgus europaeus away from their nesting areas
Authors: ALEXANDER IAN , CRESSWELL BRIAN
Published: April 2008

Radio‐tagged Nightjars Caprimulgus europaeus nesting in conifer plantation clearings and on lowland heath in Dorset travelled an average of 3.1 km away from their nesting areas at night to atypical habitats, presumably to feed. Comparison of habitat availability with use showed that Nightjars preferred deciduous or mixed woodland habitats, while they avoided conifer plantations and arable or improved grassland. Absence from the nesting area was recorded on 72 % of bird‐nights and birds were least likely to be away during the middle third of the night. The use of atypical habitats may have implications for Nightjar conservation.
Nest failures in the Scarlet Rosefinch Carpodacus erythrinus
Authors: BJÖRKLUND MATS
Published: April 2008

Over a 4‐year period nest failures in the Scarlet Rosefinch Carpodacus erythrinus averaged 36.9%. Distance of a nest from a habitat edge was the only factor influencing probability of failure. Predation of incubating females is considered the most likely explanation of the failures.
A change in the breeding season of Rüppell's Griffon Vultures Gyps rueppellii in the Serengeti in response to changes in ungulate populations
Authors: HOUSTON DAVID C.
Published: April 2008

Breeding by Rüppell's Griffon Vultures Gyps rueppellii is synchronized but the time of breeding of colonies in the Serengeti region of Tanzania has changed by 5 months over the period between 1969–1970 and 1985. During this interval there have been considerable changes in the ungulate populations within the feeding range of the vultures, resulting in an increase to the food supply available to the birds. It is suggested that this species may have two alternative breeding seasons, the selective value of each depending on the magnitude of the food supply.
Comparative foraging adaptations of small raptors in a dense African savanna
Authors: THIOLLAY J. M. , CLOBERT J.
Published: April 2008

Our aim was to investigate how ecologically similar species with different evolutionary adaptations may coexist in a moist Guinean savanna, which is the optimal habitat of the Lizard Buzzard Kaupifalco monogrammicus whereas the Grey Kestrel Falco ardosiaceus and the Grasshopper Buzzard Butastur rufipennis are of more Sudanian origin. Activity budgets, foraging behaviour and success were assessed by focal sampling and were related to habitat parameters and prey availability. Each species had its own daily foraging pattern which seemed to be related to the activity patterns of their main prey, grasshoppers or lizards. Interspecific habitat segregation reflected their morphological and behavioural adaptations and their respective tolerance to grass height, the most important factor in habitat selection. The resident Lizard Buzzard selected the densest woodlands, whereas the Grey Kestrel was restricted to the most open areas and the dry season migrant Grasshopper Buzzard to intermediate, recently burnt, savanna types. The main foraging variables (perch height, inter‐perch distance and frequency of moves) differed significantly between species. Maximum detection distances increased with perch height but decreased with increasing grass cover. Perch height was lower when the grass became too high. When attack rates increased, birds tended to move more often, but for shorter distances, and stayed longer within restricted patches. The highly insectivorous Grasshopper Buzzard had the highest and least variable attack rates, negatively correlated with grass height. It exhibited a behaviour typical of a migrant—superficial and opportunistic exploitation of superabundant, easily accessible, and seasonal food sources. Conversely, the residents were associated with denser, more stable habitats and larger, less abundant, but more predictable prey.
A preliminary assessment of the quantities of Shetland sandeels taken by seabirds, seals, predatory fish and the industrial fishery in 1981–83
Authors: FURNESS R. W.
Published: April 2008

Shetland holds a very high concentration of seabirds that feed to a large extent on sandeels Ammodytes marinus. The available data allow an assessment of the quantity of sandeels consumed by seabirds each year 1981–83, and sensitivity analysis suggests that this figure is accurate to about ±30%. Only very approximate estimates of sandeel consumption by seals and by predatory fish can be made.

From 1981 to 1983 the Shetland fishery catch averaged 45,000 tonnes of sandeels, with an estimated natural consumption of 47,000 tonnes by seabirds (predominantly Guillemots Uria aalge and Fulmars Fulmarus glacialis). Based on sensible guesses and the little data available, consumption may have been about 25,000 tonnes by predatory fish and 9,000 tonnes by seals. The figures suggest that natural mortality of the Shetland sandeel stock in 1981–83 was considerably in excess of the figure used in VPA stock assessments. Further information is required for key variables in order to permit better estimates of sandeel stock dynamics. In particular, we need better data on numbers and diets of seals in Shetland, numbers and diets of predatory fish, diets and foraging distributions of Fulmars, especially out with the chick‐rearing period. In future, sandeel biomass assessments for Shetland should incorporate estimates of predation by seabirds as this is clearly an important part of total mortality for the stock.
The migrations of the Red‐billed Quelea Quelea quelea and their relation to crop damage
Authors: ELLIOTT C. C. H.
Published: April 2008

Recent studies on the migrations of the Red‐billed Quelea Quelea quelea have shown that while the species is capable of long‐distance movements of hundreds of kilometres, the actual migrations probably more often consist of shorter distances with a flexible timing. This flexibility allows adjustments to be made to the rainfall distribution in a particular year. New information comes from studies on the breeding distribution, on the plumage and moult of local populations, and from attempts to apply new techniques such as mass‐marking with fluorescent particles. Breeding has been shown to be both more widespread and more frequent than previously recognized, while local populations can prolong breeding in one place if rainfall continues. Local populations have been identified that are apparently distinct, with limited intermixing with other populations, and some data suggest that intermixing may be reduced by flock or group cohesion. The flexibility of the migrations means that predictions of major influxes of quelea into agricultural areas have proved difficult to make, especially in regions where the rainfall patterns are complex and variable, such as East Africa.
Effects of food variability on growth rates, fledging sizes and reproductive success in the Yellow‐eyed Penguin Megadyptes antipodes
Authors: HEEZIK YOLANDA VAN , DAVIS LLOYD
Published: April 2008

Effects of a change of diet on growth rates and fledging sizes of Yellow‐eyed Penguins Megadyptes antipodes were examined at two breeding areas on South Island, New Zealand, during two breeding seasons. An adverse change in diet was observed in the second season. Evidence for this included depressed growth rates of weight, differential growth of weight and most morphometric parameters between one‐ and two‐chick nests in the second season, lower fledging weights, lower adult body weights, delayed moult, higher chick mortality and higher adult mortality during moult. The change in diet is suggested as being from one including oil‐rich prey species, to one of oil‐poor species.

Growth rates of first‐ and second‐hatched chicks, and of survivors and non‐survivors within a brood were not significantly different in either season, and growth rates of two‐chick broods were only slightly slower than one‐chick broods for some parameters in the second season. This, and synchronous hatching of chicks, equal egg‐size and lack of sibling competition during feeding sessions, suggests that brood reduction is not an option available to Yellow‐eyed Penguins, and that food supply may not be a limiting factor in the majority of breeding seasons.

Few changes in growth rates of morphometric parameters at either breeding area, and similar absolute sizes at fledging, indicate that slowing of growth rates of morphometric parameters only occurs when feeding conditions are so bad as to result in mortality and that, although fledging periods may be longer, patterns of development remain essentially unchanged.
Recognizability of different food types in faeces and in alimentary flushes of Sylvia warblers
Authors: JENNI LUKAS , REUTIMANN PETER , JENNI‐EIERMANN SUSANNE
Published: April 2008

The efficiency of the analysis of faeces and flushes of the digestive tract was examined by feeding captive Garden Warblers Sylvia borin and Blackcaps S. atricapilla with different food types (arthropods, fruits). Faecal analysis underestimated aphids; the analysis of flushes overestimated beetles and underestimated aphids and fruits. Correction factors to remove these biases are given. Flushing free‐living birds showed no noticeable effect on recapture rates and body mass. Methods of calculating the number of prey items from different fragments are evaluated.
The sympatric breeding of Common and Scottish Crossbills Loxia curvirostra and L. scotica and the evolution of crossbills
Authors: KNOX ALAN G.
Published: April 2008

Within the strongly polytypic Red Crossbill L. curvirostra there are many reports of two or more ‘subspecies’ nesting sympatrically, without interbreeding. This 13‐year study examines one such case, in Scotland, where an endemic form is resident and another was thought to occur after irruptions from its main range in continental Europe. Both forms were present in the study area every year; sympatric breeding was proved in 9 years and probably occurred in the other four. There was no suggestion of interbreeding and the Scottish form should be treated as a separate species, L. scotica, the Scottish Crossbill. This is the only endemic species of bird in Britain and one of very few European endemics. The evolution of crossbills in Europe is discussed in the light of recent palynological evidence and the taxonomic status of the Parrot Crossbill L. pytyopsittacus is re‐examined.
Survival of British Sedge Warblers Acrocephalus schoenobaenus in relation to west African rainfall
Authors: PEACH WILL , BAILLIE STEPHEN , UNDERHILL LES
Published: April 2008

Fluctuations in the population levels and annual adult survival rates of British Sedge Warblers Acrocephalus schoenobaenus since the late 1960s are strongly correlated with indices of wet season rainfall in the west African winter quarters. Population changes are unrelated to estimates of breeding productivity in the previous year. Habitat availability in the winter quarters has probably been the main factor limiting the size of the Sedge Warbler population in Britain during the period of study.
Photoperiodic control of testicular regression and moult in male House Sparrows Passer domesticus
Authors: DAWSON A.
Published: April 2008

Testis size, bill colour and moult were monitored in male House Sparrows Passer domesticus kept under a natural daylength regime between February and November. On three occasions (at the summer solstice, 25 days later and 39 days later), groups of birds were transferred to a daylength of 18 h of light and 6 h of darkness per day (18L: 6D), the natural daylength at the solstice. In birds under natural daylengths, the testes had regressed significantly by 2 5 days after the solstice. In those transferred to 18L:6D at the solstice, the onset of regression was delayed by about 4 weeks. Transfer to 18L: 6D after the solstice did not cause recrudescence; the testes continued to regress. In birds transferred to 18L: 6D at the solstice, moult was delayed by 4 weeks and progressed more slowly. These results suggest that photoperiodically induced gonadal regression in this species contains elements characteristic of both absolute and relative photorefractoriness.
The population structure of Greenland Barnacle Geese Branta leucopsis on the wintering grounds on Islay
Authors: PERCIVAL S. M.
Published: April 2008

The population structure of the Greenland Barnacle Goose Branta leucopsis at its main winter haunt, the island of Islay, Scotland, was studied using marked individuals caught at three sites on their breeding grounds in east Greenland and on the wintering grounds on Islay. The distribution of individual geese on Islay was found to be non‐random. Birds were generally faithful to restricted groups of sites on the island, both within a winter and between consecutive winters. These groups of sites on Islay held different proportions of the individuals from the three catch sites in Greenland. Birds caught together in Greenland were associating in winter more than would be expected if their distribution were random.