bluuebunny/crossref_metadata_2025 huggingface dataset:
Breeding biology of the Barn Owl Tyto alba in central Mali
Authors: WILSON R. T. , WILSON M. P. , DURKIN J. W.
Published: April 2008

Data were obtained on 178 clutches of African Barn Owls in central Mali from four breeding seasons during 1979–1983. Significantly more clutches were laid in 1979–1980 and significantly fewer in 1980– 1981 than the average for the 4 years and there were significantly more clutches laid in the middle period of the annual breeding season. The egg volume was significantly smaller at the beginning of the breeding season and significantly larger in the middle than the overall mean with eggs of second clutches being larger than those of first clutches. The clutch size was 605 eggs of which 479 hatched. The number of young fledged per successful nest was 319 and was 1 83 for all nesting attempts. The month was the only variable shown to affect significantly the clutch size, eggs hatched and fledging rate, the highest success rates being associated with the middle of the breeding period. The average interval between the hatching of eggs was 2–31 days. Survival rates (47'1%) to fledging were significantly affected by year (1981–1982 being the least) and month (mid‐season birds the best). The order of hatching significantly affected age at death or disappearance, the first‐hatched birds surviving the longest. The year significantly affected age at fledging, the young from the year in which most clutches were laid leaving the nest at the youngest age and those associated with the year having the least number of clutches remaining in the nest the longest. The month of hatching also affected fledging age, birds at the extremes of the breeding season fledging at older ages. The discussion compares these data with those from elsewhere.
Song characteristics and response to playback of male and female Robins Erithacus rubecula
Authors: HOELZEL A. RUS
Published: April 2008

Male and female Robins, from a population occupying deciduous woodland habitat, were recorded during autumn, winter and spring. Song characteristics were compared between individuals with respect to sex and reproductive success. For the parameters measured, male song did not vary with reproductive success; however, male song was more complex and less redundant than female song. Furthermore, male song in response to playback was more complex in response to female than to male song. Both males and females could discriminate between male and female song. Males approached playback of male song more readily in the autumn than in the spring. The possible significance of these results is discussed.
The spread of the House Sparrow Passer domesticus in Bolivia
Authors: DOTT H. E. M.
Published: April 2008

Bolivia lies within the Tropics and contains extremes from desert to jungle and from low to high altitudes. House Sparrows entered the south of Bolivia from Argentina about 1930 and have now spread to towns and villages scattered through about half of the country. These are principally in the semi‐arid Andean descents of south and central Bolivia and in the lowlands in Santa Cruz city and certain nearby towns. In the high altiplano they have reached only two cities and are not numerous in either. They appear to be absent from the humid Andean slopes and from most of the eastern and northern lowlands, with the exception of two isolated towns which they could have reached either from Brazil or from elsewhere in Bolivia. House Sparrows do not occur away from human settlements in Bolivia.
The breeding of the Wedge‐tailed Eagle Aquila audax in relation to its food supply in arid Western Australia
Authors: RIDPATH M. G. , BROOKER M. G.
Published: April 2008

The breeding of the Wedge‐tailed Eagle Aquila audax was investigated in four areas of the arid zone of Western Australia from 1968 to 1976, with some supporting data from the adjacent Mediterranean zone. Breeding was dependent on, and geared to, the occurrence of a minimum level of available prey. In the arid zone the seasonally most regular occurrence of the low rainfall, combined with greatest diversity of vegetation and prey, was associated with the most regular breeding and the greatest annual productivity of young per pair. At the other extreme, where an identical mean annual rainfall was distributed more erratically between seasons and years and was combined with a less diverse flora, the prey available to eagles was restricted to virtually one species–the introduced European rabbit Oryctolagus cuniculus. In this situation there were gaps of up to 4 years between the breeding of eagles, because of major fluctuations in the size of the population of its rabbit prey. Their density was actually greatest in those areas where the widely fluctuating food supply occasionally allowed them to breed with considerable success; however, this did not compensate fully for the irregularity of breeding. Where the prey available was thus restricted to a single species and was least stable, the area may have been unable to support a population which could maintain itself without recruitment from outside.

Breeding success in the Mediterranean zone was higher than in the arid zone. The Wedge‐tailed Eagle's breeding strategy is conservative (with ’k‐selected‘ characteristics), but this study shows that it is ecologically successful in both zones, although least so where the climate is extremely erratic.
Comparative ecology of the six albatross species breeding on the Crozet Islands
Authors: WEIMERSKIRCH HENRI , JOUVENTIN PIERRE , STAHL JEAN CLAUDE
Published: April 2008

Six species of albatrosses breed sympatrically at the Crozet Islands. The population size, masses and measurements of adults, nesting habitats and coloniality, laying, hatching and fledging dates, duration of incubation and brooding shifts are compared. The growth of chicks, diets and feeding methods of the six species are reviewed. Their distribution in the south Indian Ocean is described in relation to the feeding frequency of chicks. Various aspects of ecological isolation among the species are analysed. Overlaps exist in the timing of breeding in the small albatrosses and to a lesser extent in their diet. Differences in the foraging zones at sea appear to be the most important factor in reducing interspecific competition. It is shown that the effective division of resources results from a relative scarcity of resources around the Crozet Islands. Finally the close interrelationship between foraging strategy, breeding biology, diet, chick growth and breeding frequency in the small albatrosses is demonstrated.
Sensory capacities and the nocturnal habit of owls (Strigiformes)
Authors: MARTIN GRAHAM R.
Published: April 2008

Behavioural studies show that in the eye of the Tawny Owl Strix aluco both absolute visual sensitivity and maximum spatial resolution at low light levels are close to the theoretical limit dictated principally by the quantal nature of light and the physiological limitations on the structure of vertebrate eyes. However, when the owl's visual sensitivity in relation to naturally occurring ligh levels is analysed, it is concluded that at night there will often be occasions when vision can only be used to control the owl's behaviour with respect to large objects.

Owls are capable of detecting and catching prey by hearing alone. However, absolute auditory sensitivity is not superior to that of mammals (including Man), but does appear to have reached the absolute limit on sensitivity in the aerial environment, which is dictated by the minimum ambient sound level.

An explanation of the owl's ability to be active at night based only upon high sensory sensitivity is thus untenable. Many features of the natural behaviour of the Tawny Owl (e.g., the high degree of territoriality, prey catching technique, dietary spectrum) may be interpreted as reflections of an additional requirement for the nocturnal habit beyond high sensory sensitivity: detailed knowledge of local topography.
Sex ratio variation in birds
Authors: CLUTTON‐BROCK T. H.
Published: April 2008

Significant variation in the sex ratio at hatching is unusual in birds. In contrast, sex differences in juvenile mortality have been found in a variety of species, especially when food is scarce‐ In some cases, these differences may be a consequence of reduced viability of males when food is scarce but, in others, the available evidence suggests that parental manipulation is involved.
A Ploceus sp. nov. from Uganda
Authors: ASH J. S.
Published: April 2008

A new species of weaverbird, Ploceus victoriae, is described from Entebbe, Uganda. Its nearest relatives are Ploceus taeniopterus of northeast Zaïre, Sudan, Ethiopia and northwest Kenya, and Ploceus velatus, widespread through East Africa and across the Sahel to the Atlantic, but it differs in several morphological and behavioural characteristics.
Piping as a display of dominance by wintering Oystercatchers Haematopus ostralegus
Authors: ENS B. J. , GOSS‐CUSTARD J. D.
Published: April 2008

Although Oystercatchers Haematopus ostralegus wintering in the Exe Estuary performed the piping display in any type of aggressive encounter, it was predominantly observed in two contexts. ‘Solitary piping’ occurred when one individual piped without an obvious opponent being in the immediate vicinity. In ‘piping ceremonies’, two or more individuals piped at each other for prolonged periods at close distance. Prolonged contests over mussels were usually won by the individual that had initially started piping. The most aggressive and successful birds (the dominants), engaged most often in solitary piping and piping ceremonies, using up to 10% of their time this way. This suggests that the behaviour was associated with dominance rank. The hypothesis is that the two birds are likely to start piping if their relative status has not already been established, so that a quick end to a dispute over a mussel or feeding site is not achieved. A dominant individual performs solitary piping from a distance to suppress the aggressive activities of other birds within its feeding range. If this signal fails, the dominant may join the ceremony, explaining why three was the most frequent number of birds involved in piping ceremonies. The ‘butterfly’ flight, used mainly by apparently dominant birds as they arrived on the feeding grounds, may signal their high status to birds already there.

The outcome of several piping ceremonies involving birds of known dominance was consistent with this explanation. The location of piping ceremonies involving only two birds (interpreted as piping ceremonies not joined by dominants) at the extremities of the feeding ranges of the most dominant individuals is also consistent with this hypothesis, because this is where their dominance would be expected to decline and would therefore be more likely to be contested. This explanation of piping and butterfly displays assumes that individuals can recognize other individuals or quickly assess their dominance. Since dominant individuals were attacked less often than subdominants and attacking birds were rebuffed less than would be expected if recognition did not occur, we suggest that some form of dominance or individual recognition did exist. The width of the white collar did not correlate with dominance, but the individual variations in this feature may enable birds to distinguish each other and thus learn their relative status. It is intriguing that the diplomatist posture, which is typically used to rebuff misguided attackers, seems almost designed to give the opponent a particularly clear view of the white collar.
Evidence of itinerant breeding of the Red‐billed Quelea Quelea quelea in the Ethiopian Rift Valley
Authors: JAEGER M. M. , BRUGGERS R. L. , JOHNS B. E. , ERICKSON W. A.
Published: April 2008

This paper provides evidence for itinerant breeding by Red‐billed Quelea Quelea quelea in the Ethiopian Rift Valley. Queleas were mass‐marked with aerially applied fluorescent particles in two separate nesting areas in southwestern Ethiopia during June 1981. Marked adults from both areas were recovered from nesting colonies in the Awash River Valley during August and September, up to 100 days post‐spray and between 500 and 700 km to the north of the spray sites. In the Awash colonies, the presence of marked adults in breeding plumage with interrupted primary wing‐moult, together with two age classes of juveniles, suggests that this was the second nesting. The progress of both the post‐breeding and post‐juvenal primary moults was consistent with an earlier breeding in May and June. The timing of the arrival and departure of birds from these nesting areas also supported the occurrence of double breeding by the same birds. Furthermore, the composition of black facial mask types of adult males was more similar between samples from the southern Ethiopian Rift and Awash Valley than between samples from either of these areas and samples from outside the Rift, providing additional evidence that the same population of birds bred in these two areas of the Rift Valley.

Nesting colonies in both areas were scattered in time and space. Colonies in the Awash were distributed for more than 300 km and were established over a two‐month period, which coincided with local differences in the timing of the seeding in grasses. This wide distribution probably increases nesting success in such areas of locally variable rainfall. This contrasts with a stategy of mass migration, where concentrated breeding occurs where and when suitable conditions are first encountered.

Knowledge of the location and timing of previously successful nesting areas may increase the success of itinerant breeding, as Queleas seem to use the same areas in successive years if conditions are favourable. Recoveries of marked birds in the Awash were segregated according to both spray site and sex, suggesting some degree of group cohesion by sex from the first to the second nesting. We speculate that post‐nesting group cohesion of adults may provide a means to maintain the integrity of collective group information on seasonal movements. Group cohesion may be facilitated by the high degree of nesting synchrony within colonies.
The vocal systems of two nocturnal burrowing petrels, the White‐chinned Procellaria aequinoctialis and the Grey P. cinerea
Authors: BROOKE M. de L.
Published: April 2008

I studied the calls of White‐chinned Petrels Procellaria aequinoctialis and Grey Petrels P. cinerea at the Prince Edward Islands in the Southern Ocean. White‐chinned Petrels gave two calls. One, the Wheezy call, was usually given from within breeding burrows, was given in response to playback of strange (= non‐mate) calls, and probably served a burrow defence function. The other call, the Rattle call, was uttered roughly as often on the ground as from within the burrow. This call was mostly given by males and probably served as sexual advertisement. The one identified call type of the Grey Petrel was given in the same circumstances as the Wheezy call of the White‐chinned Petrel.

In both species there was evidence of mate recognition of calls. Birds tended to remain silent to the playback of the mate's call, whereas they responded vocally to strange calls.

This vocal system, where both sexes share two call types but where sexual dimorphism in call is absent, has not been described before for petrels. Possible reasons for the variation in petrel vocal systems are discussed.
Retrieval of stored seeds by Marsh Tits Parus palustris in the field
Authors: STEVENS T. A. , KREBS J. R.
Published: April 2008

The retrieval of stored food by Marsh Tits was documented using Hall‐plate detectors to register visits to storage sites by marked individuals. In each experimental session a marked bird was allowed to store up to 50 radioactively labelled half‐peanuts. By placing detectors next to each stored item that we located it was possible to show that birds attempt to retrieve about 25% of their stored food. Most of the retrieval is within one or two days (confirming Cowie et al. 1981) and the proportion of recorded retrieval attempts that are successful declines to zero after about three days. By this time storage sites have already been emptied by cache robbers. There may be a tendency for retrieval to occur in the afternoon.
The diet and foraging behaviour of the Dunnock Prunella modularis in a hedgerow habitat
Authors: BISHTON GLENN
Published: April 2008

The diet and foraging behaviour of a population of Dunnocks inhabiting hedgerows was studied between November 1981 and December 1983 at Nedge Hill, Shropshire. Invertebrates were most abundant in hedgerows and adjacent vegetation during the summer when the diet of the Dunnock was largely insectivorous. Beetles (Coleoptera) were the main taxa in the diet, with weevils (Curculionidae) and rove beetles (Staphylinidae) predominating. Arachnids were important, and snails (Gastropoda), earthworms (Oligochaeta), springtails (Collembola) and flies (Diptera) were taken. Seeds were available in the study area from July and featured in the diet from August to April. Nettle Urtica dioica comprised the main seed in the diet. Other important seeds included Yorkshire fog Holcus lanatus, elder Sambucus nigra and dock Rumex obtusifolius. Stomach stones were most common in the faeces in winter. The Dunnocks were predominantly ground feeders and mainly used a hop‐picking technique. Some seeds and invertebrates were picked directly off plants by Dunnocks above the ground. Most feeding occurred in hedgerows, which formed a small proportion of the study area. Overgrown hedgerows were the most important of the five hedgerow types. Nettle patches were an important feeding habitat. Dunnocks usually foraged alone or in pairs and rarely fed in association with other bird species. The highest proportion of time spent feeding was in January and the lowest in May.
Social rank in winter flocks of Willow Tits Parus montanus
Authors: HOGSTAD OLAV
Published: April 2008

The social hierarchies in winter of ten flocks of Willow Tits Parus montanus were studied when the birds were foraging naturally and when visiting feeders. All the flocks consisted of one adult mated pair together with two juvenile males and two juvenile females (probably pairs). All flocks studied had a stable composition and the hierarchies remained constant throughout the study period. The hierarchies were linear and unilateral. The adults of each sex dominated the respective juveniles and within each age group the male dominated the female. The dominance relationships between the age and sex groups were not consistent. Although the males dominated all the females in six flocks, in one flock the adult female dominated both the juvenile males, but only one of them in three other flocks. The degree of aggression between flock‐members was 0.8 encounters per hour, and males initiated 94% of all attacks. Body‐weight explained 77% of the variation in dominance rank. It is suggested that the dominance rank of a male is also a function of his seniority, while the rank of a juvenile female is correlated with the rank of her mate.
Timing of breeding of Tengmalm's Owl Aegolius funereus in relation to vole dynamics in western Finland
Authors: KORPIMÄKI ERKKI
Published: April 2008

Timing of breeding in Tengmalm's Owl was studied in western Finland for 13 years. During 1973‐85, half of the females started laying before 4 April, near the seasonal low of main food abundance (voles), and earlier than in southern Finland or as early as in southeastern Norway. The reason for this latitudinal trend is the shallow snow cover of the study area. The annual variation in the median laying dates was one month and was negatively correlated with the spring abundance of Microtus voles. The mean clutch size was related to the start of laying with early clutches being larger than late ones. These findings accord with the ‘food limitation hypothesis’, which states that laying begins as soon as the female can accumulate enough energy stores for forming eggs. Early breeding is adaptive, since juveniles of early clutches probably survive better during their first winter. In adults, early nesting improves the chances of rearing two broods per year, allows them to moult after breeding and gives more time to accumulate fat reserves to survive the winter. Tengmalm's Owl is one of the earliest breeders among North European birds. This is possible because of its hole‐nesting and resident habits, small body‐size in relation to the main prey and the greatest sexual size dimorphism among European owls.
Differences in the ages, sexes and physical condition of Starlings Sturnus vulgaris at the centre and periphery of roosts
Authors: SUMMERS R. W. , WESTLAKE G. E. , FEARE C. J.
Published: April 2008

The differences between individuals at the centre and at the periphery of social groupings of birds have been demonstrated, but night‐time roosts have received little attention. Here, the effects of age, sex and physical condition on the structure of Starling roosts were investigated. It was found that the dispersion of different age and sex categories was heterogeneous; proportionately more adult males occurred in the centre compared with the periphery, and proportionately more first‐year females occurred on the periphery compared with the centre. Birds in the centre were heavier than peripheral ones irrespective of differences in body‐size. We propose that the centre of the roost is the preferred location and that the observed dispersion reflects dominance.
Sex role partitioning during offspring protection in the Rough‐legged Buzzard Buteo lagopus
Authors: & Staffan Andersson , Wiklund Christer G.
Published: April 2008

Nest defence and sex role partitioning during offspring protection were examined in tests with a human territory intruder as well as a dummy. Five defence responses including warning calls were identified. Except for the warning call, males were more aggressive than females. The most important defence response, the attack, was performed by males only. We suggest that individual and inter‐individual selection work in concert to maintain small male size due to the requirements of great aerial agility during predator deterring actions.
Growth of nestling Barn Owls Tyto alba in central Mali
Authors: WILSON R. T. , WILSON M. P. , Durkin J. W.
Published: April 2008

Data on growth of 276 young Barn Owls were analysed with respect to the effects of year and month of hatching, hatch order and brood order. Growth characteristics considered were weight; lengths of culmen, tarsus, central tail feathers and quill of third outermost primary; standard wing length; and wing span. For weight the growth constant K was 0151 and time t10‐t90 was 32‐2 days. Least‐squares analyses showed that gain in weight and culmen and tarsus length were affected by month of hatching with young hatched in the middle part of the breeding season showing the most rapid growth. Hatch order affected gain in weight. Differences in growth rates of all these characters were not, however, reflected in differences in weight or length at fledging except for the effects of brood on weight with second broods fledging at significantly lighter weights than first ones. Predictive equations for character against age are provided for all linear measurements. All characters examined attained apparent asymptotes before fledging except tail and standard wing length.
Patterns of arrival and departure of Grey Herons Ardea cinerea at two breeding colonies
Authors: VESSEM JANINE VAN , DRAULANS DIRK
Published: April 2008

We attempted to test whether intervals between subsequent departures and arrivals of Grey Herons Ardea cinerea at two breeding colonies were clumped, and whether this could be attributed to birds following each other or not. First of all, however, we made a description of the pattern of flight activity and found that flights were highly clumped in space and in time. We also found among other things that Grey Herons performed nocturnal flights, that both partners of a pair tended to select similar flight directions and that first‐year birds, more than adults, flew in less‐frequently selected directions. The clumping of flights affected the length of the intervals between subsequent flights and most of the variability in frequency distribution of intervals could be explained by variations in the total number of herons flying. We found that both departures and arrivals tended to be clumped, and suggested that clumped departures could easily follow from synchronization of arrivals. First‐year Grey Herons tended to leave the heronry shortly after another bird more than the adults did. Synchronization of activity may facilitate the finding of foraging areas through other mechanisms, apart from ‘following’ successful birds, such as heading into frequently selected directions. We assume based on our results that information transfer, if it occurs, is more common at successful colonies when compared to unsuccessful ones, which contradicts a prediction of the information‐centre models.
Aspects of the reproductive ecology of the Hamerkop Scopus umbretta in central Mali
Authors: WILSON R. T. , WILSON M. P. , DURKIN J. W.
Published: April 2008

In a 4‐year study of Hamerkops in central Mali, territories of breeding pairs overlapped and most clutches were laid in the late rainy or early dry seasons. Clutches averaged 4–8 eggs. Different pairs laid eggs having, on average, different dimensions. Eggs laid in the late rainy and early dry seasons were larger than those laid at other times. Eggs weighed, at 27‐8 g, about 6% of adult female weight. Hatching success was 79% with a fledging rate of eggs hatched of 53%. Successful nests fledged 27 young but for all completed clutches the fledging rate was 0'9. Young hatched early in the sequence had a higher survival rate than those hatched later. Mean age at fledging was 47 days. Pairs fledged between 0–5 and 0–9 young per year.
Food abundance and clutch size of Tree Swallows Tachycineta bicolor
Authors: HUSSELL DAVID J. T. , QUINNEY T. E.
Published: April 2008

We studied Tree Swallows Tachycineta bicolor during eight breeding seasons (1977‐84) at three sites that differed in food availability, which we measured as an index of the biomass of flying insects derived from daily catches in suspended nets. Mean clutch size differed significantly between sites (6.2, 5.8, and 5.6 eggs) and was related to average food abundance at the site. Within two sites, clutch sizes were significantly larger in years when food was more abundant during egg‐laying (r= 0.83 and 0.97 at the high and low food abundance sites, respectively; r= 0.63, not significant, at the medium abundance site). Both clutch size and laying season food abundance were positively correlated with food abundance during the nestling stage at the ‘high’ site, but not at the other two sites. Our results support the hypothesis that female Tree Swallows respond proximately to abundant food during egg‐laying by laying more eggs, but they do not elucidate the ultimate evolutionary factors involved in determining clutch size.
The breeding biology of the Lapland Bunting Calcarius lapponicus in West Greenland during two contrasting years
Authors: FOX A. D. , FRANCIS I. S. , MADSEN J. , STROUD J. M.
Published: April 2008

The breeding biology of the Lapland Bunting was studied in an area of central West Greenland during two contrasting seasons. In the delayed thaw of 1984, male birds arrived on the breeding grounds at the same time as in the more typical spring of 1979, but females delayed arrival by two weeks in 1984 compared with 1979. Mean clutch size was depressed in the latter year and declined through the season; breeding productivity was correspondingly reduced in 1984 compared to 1979. Egg and juvenile predation rates were similar for the two years. Nestlings grew as rapidly in 1984 as in 1979 despite an apparent reduction in detected ground‐dwelling invertebrates known to form an important constituent of the nestling diet. Because they bred later in 1984, females tended to commence moult later in 1984 than 1979 but completed moult by early September in both years. Males also commenced moult later but completed earlier in 1984.
Causes and consequences of egg‐size variation in the European Starling Sturnus vulgaris
Authors: GREIG‐SMITH PETER W. , FEARE CHRISTOPHER J. , FREEMAN ELAINE M. , SPENCER PETER L.
Published: April 2008

Variations in egg‐size (weight, or an index of volume derived from the length and breadth of eggs) were analysed for four years' data from a colony of Starlings in southern England. Variation was much greater among clutches than within clutches. There were no consistent trends for egg‐size to increase or decrease through the laying sequence, but the first‐ and last‐laid eggs tended to be smaller than the clutch mean. Loss of single nestlings (perhaps by starvation) was more frequent if the smallest, or last‐laid egg was particularly small. Effects of egg‐size on the growth of surviving chicks were slight‐most variation in development was attributable to factors such as clutch or brood size, and nestlings' relative weights fluctuated so that they continually changed ranks during the nestling period. In Starlings, egg‐size was inversely correlated with clutch size, but three open‐nesting species (Bullfinch, Song Thrush and Blackbird) showed the opposite pattern. These results are discussed in relation to their implications for understanding the adaptive aspects of egg‐size variation.
Clinical and pathological studies on the Mauritian Pink Pigeon Columba mayeri
Authors: COOPER J. E. , NEEDHAM J. R. , APPLEBEE K. , JONES C. G.
Published: April 2008

Six Pink Pigeons Columba=Nesoenas mayeri from the captive breeding project on Mauritius which showed a range of physical abnormalities were examined clinically and post mortem. Significant findings included a pedal deformity in several birds and cerebellar hypoplasia/aplasia in another. Parasites were not detected and none of the birds showed serum antibodies to Newcastle disease virus, Paramyxovirus or Chlamydia psittaci. The results are of relevance to the captive breeding and management of this endangered species.
Behaviour of birds after release from capture as an indicator of territorial status
Authors: MATTHYSEN ERIK , DHONDT ANDRÉ A.
Published: April 2008

Territorial Nuthatches which are captured and released within their territory generally start to call within a few seconds after release. Birds released outside of their territory and non‐territorial individuals rarely call. This behavioural rule is found in both males and females throughout the year, and was tested experimentally by moving birds from the site of capture and releasing them elsewhere. Birds captured and released near the border of the territory show a higher tendency towards weak or undetermined responses. The generality of the behaviour makes it useful for detecting changes in territorial status of known individuals, or predicting status of unknown individuals. Some hypotheses are presented to explain the functional significance of calling after release.
Nest predation and nest site selection among EidersSomateria mollissima:the influence of gulls
Authors: GÖTMARK FRANK , AHLUND MATTI
Published: April 2008

Hooded Crows Corvus cornix, Great Black‐backed GullsLarus marinusand Herring Gulls L. argentatus were the main nest predators in an Eider population in southwest Sweden. The clutch sizes of Eider nests within gull colonies did not differ from those outside gull colonies. The proportion of Eider nests destroyed by predators was significantly lower within than outside gull colonies, especially on islands with Lesser Black‐backed Gulls L. fuscus. Although the difference was not significant, the survival time of simulated Eider nests was higher within than outside gull colonies. On Eider islands with gull colonies, foraying crows spent more time within the colony area than expected by chance. However, crows apparently avoided an area around each gull nest, and we suggest that the colonies, to some extent, protected Eider nests against predation. The density of Eider nests was higher on gull islands than on gull‐ free islands, and higher within than outside the gull colonies. However, the association with gulls was weak compared to that displayed by some other waterfowl.
The Musculus splenius capitis of hummingbirds Trochilidae
Authors: FRITSCH ELISABETH , SCHUCHMANN KARL‐L.
Published: April 2008

The peculiar crossover origin of the cervical Musculus splenius capitis was studied in 32 hummingbird species. In this avian family the cruciform neck muscle exhibits extreme intra‐ and interspecific variations independent of age, thus taxa clustering for phylogenetical purposes according to the muscle's distinctive features is impossible. It is argued that the Musculus splenius capitis serves primarily to control precisely fast sideward head movements of hummingbirds while they are preying on insects.
The breeding biology of Guillemots Uria aalge on the Isle of May over a six year period
Authors: HARRIS M. P. , WANLESS S.
Published: April 2008

The breeding of Guillemots was studied in five areas of different breeding density and habitat type on the Isle of May in 1981‐86. Prior to 1981 numbers were increasing at 5 6° per annum but during the study the rate of increase slowed down and from 1983 to 1986 numbers were fairly constant. Adult survival was high, with a mean minimum annual adult survival of 930% (s.e. = 03). Observations in 1986 suggested that the percentage return of colour‐marked immature birds was low, with only l‐6% and 5.5% of second and third year birds being seen. We suggest that poor recruitment was responsible for the levelling off in numbers at the colony.

The timing of laying was constant from year to year in 1981‐85 but was later in 1986. It was significantly and inversely related to sea temperature the previous March. There was a consistent ranking in median laying dates amongst the areas, with area 1 (the highest density of birds) always earliest. However, there was no significant difference in synchrony between the areas. Overall breeding success was high (0–71‐0‐82 young fledged per pair). There was no consistent ranking of breeding success with breeding density, habitat type or laying synchrony.

The only aspect of Guillemot biology which changed significantly was the daily food intake of a chick which approximately halved during the study period. However, this reduction in food intake had no detectable effect on either the weight of chicks with wing lengths greater than 60 mm or the amount of time off‐duty breeders spent at the site. Both of these parameters were still consistent with conditions being favourable in 1986.
Regional, seasonal and annual variations in the structure of Purple Sandpiper Calidris maritime populations in Britain
Authors: NICOLL M. , SUMMERS R. W. , UNDERHILL L. G. , BROCKIE K. , Rae R.
Published: April 2008

Samples of Purple Sandpipers were captured around the coasts of Britain. Analysis of their bill‐length distributions enabled the sex ratios and percentages of ‘long‐billed’ and ‘short‐billed’ birds at each locality to be estimated. The sex ratio for the ‘long‐billed’ population was estimated to be one female to 2–11 males, and one female to 1 ‐34 males for the ‘short‐billed’ population. During winter, proportionately more ‘long‐billed’ birds occurred in northern and western Scotland, Wales and southern England, whilst ‘short‐billed’ birds predominated from Kincardine to Yorkshire. The total sizes of the ‘long‐’ and ‘short‐billed7’ populations were c. 15 000 and 4000, respectively. ‘Short‐billed’ birds started arriving from Norway in early July. ‘Long‐billed’ birds did not arrive until late October. Their origins are as yet unknown. No annual variations in the population structure were detected.
Sparrowhawks Accipiter nisus affect the spacing behaviour of wintering Turnstone Arenaria interpres and Redshank Tringa tetanus
Authors: WHITFIELD D. PHILIP
Published: April 2008

The presence of a Sparrowhawk induces short‐term abandonment of territories by wintering Redshank and increases both the density within flocks and the ranging behaviour of wintering Turnstone. The latter effect is thought to be due to the disturbance caused by hawk attacks, and the results suggest benefits for flocking beyond predator detection.
Crop selection, feeding skills and risks taken by adult and juvenile Rooks Corvus frugilegus
Authors: EAST M.
Published: April 2008

During July and August, adult Rooks Corvus frugilegus predominantly foraged on pastures while most juveniles fed on storm‐flattened barley. The rate at which barley grains were consumed by both adults and juveniles increased from early July to late July and August. Adult birds consumed barley at a faster rate than juveniles in early July, but there was no difference in the rate at which barley was consumed by adults and juveniles later in the season. No differences in feeding rates could be detected between adults and juveniles that foraged on pasture. Adult Rooks were more vigilant than juveniles when feeding in barley fields.
The timing of breeding and moult of the Lesser Striped Swallow Hirundo abyssinica
Authors: EARLÉ R. A.
Published: April 2008

The Lesser Striped Swallow seems to have two different breeding populations. The birds south of 10°s breed largely during the spring and summer (July to April) and moult from about April to August. Birds further north breed throughout the year, but mainly during the first seven months of the year. Moult in the birds north of 10°s is from July to February when few birds are breeding. There seem to be two clearly defined moulting populations, with the southern breeding population moulting largely south of 10°s and the east African breeding population moulting largely north of the equator. In both populationsmoult and breeding seem to be separated in time, at least at the individual level.
Growth of nestling Hamerkops Scopus umbretta in central Mali
Authors: WILSON R. T. , WILSON M. P. , DURKIN J. W.
Published: April 2008

Data on growth of nestling Hamerkops Scopus umbretto were analysed with respect to year and season of hatching and to hatch sequence. Quantitative growth characters included weight, culmen, tarsus, tail, third outermost primary quill, standard wing‐length and wing span. The growth constant K of weight was 0.179 and time t10‐t90 was 21.8 days. Least‐squares analyses showed differences in weight gain, culmenlength and tarsus‐length related to year and month but not to sequence of hatching. Predictive equations for character against age are provided for all linear measurements. Characters which attained apparent asymptotes before fledging were weight and culmen and tarsus‐length whilst other characters varied between 80 and 90% of reported adult size. Qualitative indications of growth discussed are crest development, colouration and the disappearance of the egg‐tooth. The rainy and post‐rains seasons appear to offer the Hamerkop the best chances of successful breeding and maximum growth rates.
The effect of nestboxes on breeding populations of birds in broadleaved temperate woodlands
Authors: EAST M. L. , PERRINS C. M.
Published: April 2008

Removal of nestboxes from a semi‐mature, broadleaved woodland caused a decrease in the number of breeding pairs of Great Tits, but did not significantly reduce breeding densities of Blue Tits. Breeding densities of warblers were unaffected by changes in the population of Great Tits. In the absence of nestboxes, intraspecific competition for natural nestholes was more intense amongst Great Tits than Blue Tits. Great Tits tended to occupy larger holes on or near the trunk, while Blue Tits used smaller holes on side branches. Nesting success for both species was lower in natural cavities than nestboxes, due to a higher percentage of total nest failures. The reintroduction of nestboxes did not produce an immediate rise in the breeding population of Great Tits; possible reasons for this are discussed.
Unexpected weight gain in resident Antarctic Terns Sterna vittata during the austral winter
Authors: PARMELEE D. F.
Published: April 2008

Antarctic Terns Sterna oittata (Fig. 1) may display two very different migratory behaviours. According to Cooper (1976), the terns breeding on Tristan da Cunha in the South Atlantic fly thousands of kilometers to the coasts of Africa where they moult. Antarctic Terns that inhabit the more southern and colder Antarctic Peninsula region moult on their breeding grounds. An early account of these seemingly resident peninsular terns (Holdgate 1963) leaves little doubt that at least part of the tern population wintered in the vicinity of Arthur Harbor (64°46′S 64°03′W), Anvers Island, west of the Antarctic Peninsula. Watson (1975) stated that adult Antarctic Terns are generally sedentary around many insular breeding stations, moving only to the nearest open water in winter.

During the year 1975 through 1978, 19 tern specimens of different sexes and ages were collected at Arthur Harbor in the non‐breeding season near U.S. Palmer Station. An additional eight terns were collected at a sea short distance from Anvers Island during the non‐breeding season in 1985 (Pietz & Strong, in press). I found that the adult birds taken at the height of winter weighed significantly more than the 150‐180g of a normal breeding Antarctic Tern. This unexpected discovery prompted me to examine the weights of an additional 34 specimens that had been collected at or near Anvers Island during several breeding seasons. By comparing the weights of adult terns by sex, age, and collection date (Fig. 2, Table 1) I found that both males and females weighed significantly more in the winter non‐breeding season (April‐September) than in the summer breeding season (October‐March) (t24= 6.57, P < 0.001, and t16= 5.71, P < 0.001, respectively). No significant differences were detected between male and female weights in summer(t23=0.76, P >0.20) or winter (t17=1.16, P0.20). In short, it appears that body‐weights of adult terns rise rather dramatically following breeding, attain a peak in mid‐winter, and then fall at the approach of the next breeding season (Fig. 2). I suggest that this increased body‐weight is an adaptation to the austral winter rather than simply a recovery from weight loss due to energetic costs of breeding and moulting.
Energy requirements for growth of Salvin's Prions Pachyptila vittata salvini, Blue Petrels Halobaena caerulea and Great‐winged Petrels Pterodroma macroptera
Authors: BROWN CHRISTOPHER R.
Published: April 2008

Energy expenditures of Salvin's Prions Pachyptila vittata salvini, Blue Petrels Halobaena caerulea and Great‐winged Petrels Pterodroma macroptera during growth were estimated from measurements of oxygen consumption. Total energy expended during growth was calculated to be 6877 kJ and 10206 kJ for the smaller Salvin's Prions and Blue Petrels, respectively, and 22697 kJ for the larger Great‐winged Petrels. A further 2390 kJ, 3067 kJ and 11801 kJ, respectively, was calculated to be accumulated as body tissue. Food requirements for growth, estimated from energy requirements, diets and assimilation efficiencies were estimated to amount to 1519 g and 932 g for Salvin's Prions and Blue Petrels, respectively, and 4577 g for Great‐winged Petrels.
Vocal mimicry of hosts by Great Spotted Cuckoo Clamator glandarius: further evidence
Authors: REDONDO TOMAS , REYNA LUIS ARIAS DE
Published: April 2008

Great Spotted Cuckoo nestlings were shown, after some days in the nest, to have begging calls that differed depending on whether they were being reared by Magpies or Carrion Crows. They also produced calls of a pitch and repetition rate that implied a high level of hunger.
Feeding site selection by Wigeon Anas penelope in relation to water
Authors: MAYHEW PETER , HOUSTON DAVID
Published: April 2008

The feeding sites of European Wigeon Anas penelope are always close to water. Initial studies suggest that this is primarily an anti‐predator behaviour rather than a requirement for drinking and bathing. Vigilance and flock‐size measurements at varying distances from water support this hypothesis. However, birds will feed away from water if grass biomass is greater further away. The end of the shooting season also causes birds to feed further away from water.
Age of first breeding, dispersal and survival of Red Kites Milvus milvus in Wales
Authors: NEWTON I. , DAVIS P. E. , DAVIS J. E.
Published: April 2008

Twenty‐nine Red Kites, that were tagged as nestlings in Wales, bred for the first time at 2–7 years old (mean 3–6). A minimum of 41% of tagged young had entered the breeding population by the 7th year. Individuals moved up to 22 km between birthplace and breeding place and, having bred, most stayed in the same locality from year to year. No differences in these various respects were found between the sexes, though two long movements by territorial birds both involved females. Annual survival of adult breeders was estimated at around 95%.
Distribution and behaviour of passerines around Peregrine Falco peregrinus eyries in western Greenland
Authors: MEESE ROBERT J. , FULLER MARK R.
Published: April 2008

This paper describes the distribution and behaviour of passerine birds within 1 km of Peregrine FalconFalco peregrinuseyries in western Greenland. Passerine populations were censused in 1983 around six cliffs occupied by nesting Peregrines and at six sites on the open tundra, and in 1984 at two unoccupied sites suitable for Peregrine nesting.

Four passerine species accounted for over 90% of birds seen. Within 400 m of Peregrine occupied cliffs, three species, Lapland LongspurCalcarius lapponicus. Northern WheatearOenanthe oenanthe, and Common RedpollCarduelisflammea, were found in lower than average abundance while the fourth, Snow BuntingPlectrophenax nivalis, was found in increased abundance. Our indirect tests suggest that Peregrine presence, rather than direct predation, was responsible for the distributions of the first three species. The Snow Bunting, however, behaviourally adapts to Peregrine presence in order to exploit nesting habitat available at the cliff base.

These results contrast strongly with those reported by other Arctic workers, where increased abundances of potential prey were observed in close proximity to nesting Peregrines.
Habitat preference, breeding success and the effect of primary productivity on Tawny Eagles Aquila rapax in the tropics
Authors: HUSTLER K. , HOWELLS W. W.
Published: April 2008

Breeding success of 176 Tawny Eagle pairs nesting on basalt (4724 km2– 92 pairs) and kalahari sand (9876 km2– 84 pairs) was monitored from 1973 to 1984 in Hwange National Park, Zimbabwe. Flat‐topped trees were preferred for nesting but kalahari sand pairs used round‐crowned trees more often, probably due to tree availability. Mean inter‐nest distances on both biomes were significantly different (3–5 km on basalt, 59 km on kalahari sand). Clutch size and frequency of one‐egg clutches in both biomes were similar and many more one‐egg clutches were laid in the drier period of the study (1979–1984). There was no correlation between laying date and breeding success. More basalt pairs laid synchronously, probably due to the smaller inter‐nest distances. Breeding success in both biomes was similar and significantly more chicks were reared during 1973–1978 than during 1979–1984 (wet and dry periods, respectively). Some districts produced more chicks than others, suggesting good and marginal areas within both biomes. The greater inter‐nest distances and ability to breed successfully in round‐crowned trees by kalahari sand Tawny Eagles resulted in a similar number of chicks reared per breeding attempt as basalt pairs, in spite of the lower primary production of the sand area.