bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal reproductive success of the Moorhen Gallinula chloropus: the importance of male weight
Authors: GIBBONS DAVID WINGFIELD
Published: April 2008

During a three‐year study of 82 pairs of Moorhens Gallinula chloropus, seasonal reproductive success (SRS) varied greatly between pairs. Pairs on big territories had a higher SRS than pairs on small territories, probably because clutch survival was higher on big territories. Pairs that began breeding early had a higher SRS than pairs that began late because early breeders laid larger clutches and could attempt more broods. Pairs with heavy males had bigger territories and began breeding earlier than pairs with light males. Heavy males therefore had a higher SRS than light males. Female weight did not affect territory size, timing of breeding, or female SRS. Assuming SRS to be a good predictor of lifetime reproductive success, selection should favour heavy males but not heavy females. Male Moorhens are significantly heavier than female Moorhens. Finally, pairs with breeding experience had a higher SRS than pairs without, because they had bigger territories and began breeding earlier. However, males in inexperienced pairs were not lighter than males in experienced pairs, so it is not clear why they defended smaller territories or laid later.
Variation in the correction factor used for converting counts of individual Guillemots Uria aalge into breeding pairs
Authors: HARRIS M. P.
Published: April 2008

The correction factor k (breeding pairs/total count of birds) was measured for two nesting groups of Guillemots Uria aalge over 6–7 years. The value varied between different subgroups but there were no significant differences between groups or between years. These results, and those from other studies, suggest that a value of 0–67 is applicable to a range of colonies. Values of k for Razorbills Aha tarda were more variable. A plea is made for the presentation of original counts rather than ‘corrected’ figures in published work.
Responses of the Bush Warbler Cettia diphone to artificial eggs of Cuculus cuckoos in Japan
Authors: HIGUCHI HIROYOSHI
Published: April 2008

Artificial eggs of six different colours and control eggs of Bush Warblers Cettia diphone were introduced into nests of Bush Warblers, a host of both Little and Himalayan Cuckoos Cuculus poliocephalus and C. saturatw in Japan. All control (chocolate‐brown) and artificial red eggs were accepted; all grey and all white eggs were rejected. The rejection rates of orange, pink and orange spots on grey eggs were 8%, 369; and 55%, respectively. Bush arblers are more likely to reject eggs the more dissimilar they are from their own. The results strengthen the possibility that the chocolate‐brown eggs of Little and Himalayan Cuckoos may have evolved through the discriminative ability of Bush Warblers and their intolerance towards dissimilar eggs.
Sexual maturation and moult in juvenile Starlings Sturnus vulgaris in response to different daylengths
Authors: WILLIAMS T. D. , DAWSON A. , NICHOLLS T. J.
Published: April 2008

Starlings, like most other species, show no gonadal development until spring of the year after they hatch, even though they hatch and attain full body size during long days. This could be because they develop in a physiological state analogous to that of photorefractory adults and so need to experience short days in order to activate the reproductive system. To test this possibility, young were hand‐reared under different photoperiodic regimes. Young raised under constant long days showed no gonadal development, nor did birds initially raised under short days and then transferred to long days at 3 weeks of age. However, birds transferred from short to long days at 10 weeks of age did show gonadal development, followed by gonadal regression, while birds raised under constant short days showed slow continual gonadal development. This last group, unlike the other three groups, did not moult into adult plumage. Since 4 weeks of long days are required to terminate photorefractoriness in adult Starlings, these results demonstrate that the reproductive system of young birds is in a similar state to that of photorefractory adults, and hence that puberty is analogous to the termination of photofractoriness.
The social organization of non‐breeding Magpies Pica pica
Authors: EDEN S. F.
Published: April 2008

The social behaviour of non‐breeding individuals in a colour‐marked population of Magpies was studied. In early autumn most non‐breeders began to forage in a common area, the ‘Non‐breeding Flock Area’. A few individuals remained on their natal territories away from the flock area as solitary non‐breeders. Most non‐breeders were first‐year birds, but some were second years or adults which no longer held a territory. Birds foraged in groups, their food intake rate differing with both group size and location. It appeared that the area in which birds foraged had a significant effect on food intake rate; foraging groups tended to form at sites rich in food. There was a dominance hierarchy amongst non‐breeders; an individual's foraging behaviour, survivorship and chances of breeding were status dependent, with subordinates feeding less in groups and being less likely to survive and breed. Solitary individuals' chances of breeding were similar to those of high status birds, although their survivorship to breeding age may have been lower. Non‐breeding Magpies are compared with non‐breeders of other species and the factors which may influence their social behaviour are discussed. It is suggested that remaining as a solitary non‐breeder is a viable alternative to becoming a low‐status flock member for some birds.
A multifactorial explanation for variation in breeding performance of Brent Geese Branta bernicla
Authors: EBBINGE BARWOLT S.
Published: April 2008

The dramatic differences in annual breeding success of Dark‐bellied Brent Geese Branta b. bernicla are generally interpreted as being caused by variable conditions on the arctic breeding grounds. The recently revived discussion on this issue mentions, in particular, the cyclic variation in abundance of lemmings, resulting in cyclic variation of predation pressure on bird nests by arctic foxes, as the main factor determining whether Brent Geese are able to breed successfully or not. New data on the spring condition of Brent Geese in Western Europe and wind conditions during migration from the spring staging areas to the breeding grounds show that these factors also influence breeding output.
The hunting habitats of Goshawks Accipiter gentilis in boreal forests of central Sweden
Authors: WIDÉN PER
Published: April 2008

Radio‐tracking was used to study the habitat utilization of hunting GoshawksAccipiter gentilisin central Swedish boreal forest. Data were collected during September‐June, in 1977–1981. There was no major difference between autumn, winter or spring in any aspect of habitat preference, despite seasonal differences in prey composition. Despite the strong reversed sexual size‐dimorphism, no habitat segregation between the sexes was found. It is argued that this is due to the lack of prey segregation between the sexes. Goshawks showed a strong preference for mature forest, which was chosen twice as often as would be expected from its prevalence in the environment, whereas the younger successional stages of the forest were under‐used. Goshawks preferred large habitat patches, and showed no major preference with respect to tree species composition of the forest. Kills made by radio‐tagged Goshawks showed the same habitat‐ and patch‐size distribution as did Goshawk locations in general. It is argued that the profitability of different hunting habitats, and thus habitat preferences, is not only determined by prey density in the habitats, but also by other habitat features influencing the Goshawk's ability to hunt there. Winter home‐ranges averaged 5700 ha, considerably larger than Goshawk ranges recorded in areas with richer prey supply.
The presence of non‐territorial males in Willow Warbler Phylloscopus trochilus populations–a removal study
Authors: HOGSTAD OLAV
Published: April 2008

A total of six (unmarked) and 24 (individually colour‐ringed) male Willow Warblers Phylloscopus trochilus were removed from their territories in two study areas: subalpine birch and lowland mixed forest, respectively. The removals were made during three separate periods throughout the breeding season: (1) pair‐formation and egg‐laying; (2) early incubation; and (3) middle and second half of the incubation period. During Period 1 all of the males removed (n= 10) were quickly replaced by new males, while during Period 2 eight of the 11 males removed were replaced. The new males defended basically the same territorial borders as the males they replaced. During Period 3 only one of the nine males removed was replaced. Since the replacements occurred within a few hours of the removals, it is suggested that the new settlers were non‐territorial males that were already present in the respective areas before the experimental removals were made. The mean wing‐lengths of the two groups of males indicated that the initial occupants of the territories were 2 years old or older in both study areas, whereas the new settlers in the subalpine birch forest (mean Willow Warbler density: 55 territories/km2) were 1‐year‐old birds, and two years old, or older, in the mixed forest area (mean Willow Warbler density: 133 territories/km2).
Weight loss of the female during the first brood as a factor influencing second brood initiation in Great Tits Parus major and Blue Tits P. caeruleus
Authors: LAET JENNY F. DE , DHONDT ANDRÉ A.
Published: April 2008

We tested the hypothesis that the weight lost by female Great and Blue Tits Parus major and P. caeruleus while raising their first brood influences their ability to start a second brood. The evening weight of female parents was recorded when the nestlings were 5 and 13 days old, in different years and habitats. Several predictions were tested: (1) both species lose weight while raising nestlings and Great Tit females which start a second brood lose less weight than females which do not; (2) differences in the average weight lost between years and areas correlate with differences in the proportion of second broods; (3) the relative weight loss in Blue Tits, which only rarely undertake second broods, is higher than in Great Tits in which second broods are more common. Other factors also are related to the probability of undertaking a second brood: more second broods are undertaken by more successful females, adult females and females that lay earlier.

The comparison of Great and Blue Tits suggests that the two species use different reproductive strategies.
Golden Eagles Aquila chrysaetos: land use and food in northeast Scotland
Authors: WATSON A. , PAYNE S. , RAE R.
Published: April 2008

This paper contrasts changes in breeding numbers and breeding success of Golden Eagles Aquila chrysaetos on four areas with different land uses. On land primarily used for deer stalking but also for grouse shooting, and supporting abundant prey, the number of eagle pairs was steady in 1944‐80. On deer land with fewer prey, the number of pairs declined greatly in the 1960s, when deer carrion became scarcer following increased shooting of red deer. On grouse moors incorporating deer stalking, the number of pairs declined in the 1950s due to persecution by gamekeepers, and then largely recovered as this lessened. On grouse moors with little or no stalking, the number of pairs fell after 1946 and remained low due to persecution, which has continued since then. Eagles on grouse moors bred poorly due to persecution. On deer land they were seldom persecuted by estate staff, and bred well. On an area of deer land, the mean annual number of young reared per undisturbed clutch in summer was related to the estimated weight of prey in the spring of the same year. The eagles have remained fairly pesticide‐free, and bred well in 1963‐65 when more contaminated birds in west Scotland bred poorly.
A comparison of the song and territorial behaviour of a long‐distance migrant, the Marsh Warbler Acrocephalus palustris, in summer and winter
Authors: KELSEY M. G.
Published: April 2008

Colour‐ringed populations of Marsh Warblers Acrocephalus palustris on breeding and wintering grounds were compared with respect to song and territorial behaviour. Song and territorial defence had a short duration on the breeding grounds, peaking during the period of mate acquisition and mate‐guarding. Some males later showed polyterritorial behaviour. Wintering Marsh Warblers sang and showed defensive behaviour for a longer period which included moult. This behaviour could be described in terms of defence of a short‐term resource (a fertile female) in the summer and long‐term defence of a reliable food resource in the winter.
Male copulation frequency and female competition for fertilizations in a promiscuous brood parasite, the Pin‐tailed Whydah Vidua macroura
Authors: BARNARD PHOEBE , MARKUS MILES B.
Published: April 2008

Male Pin‐tailed Whydahs Vidua macroura copulate infrequently and terminate most courtship displays, even when females are highly receptive. Female sexual interference is aimed at preventing other females from copulating, and is nearly always successful.
Food provisioning lowers inter‐clutch interval in Moorhens Gallinula chloropus
Authors: EDEN S. F. , HORN A. G. , LEONARD M. L.
Published: April 2008

Food supplements were provided to Moorhens Gallinula chloropus during production of their first brood, to test whether food availability limited the number of broods they could rear in a season. Supplemented territories had shorter inter‐clutch intervals when individual differences were held constant, although they did not produce more broods. Because unmanipulated birds with short inter‐clutch intervals produced more broods, food availability may be one of several factors limiting the production of multiple broods and therefore reproductive success.
Turnover and recruitment in a tundra population of Peregrine FalconsFalco peregrinus
Authors: COURT G. S. , BRADLEY. D. M. , GATES C. C. , BOAG D. A.
Published: April 2008

The population dynamics of tundra‐nesting Peregrine FalconsFalco peregrinus tundriuswas studied over 7 years on a 450 km2study area in the Keewatin District of Canada's Northwest Territories. Peregrines showed strong fidelity to nest sites; none of 25 males ringed changed territories, while five of 38 females ringed were recorded changing territories. Such changes usually occurred after nesting failure. Annual turnover of territorial adults was estimated to be 22% (15% for males and 26% for females). Annual mortality of adults was estimated to be 17% (15% for males and 19% for females). If we assumed that territory vacancies, in addition to mate replacements, were indicative of mortality, then maximum annual mortality was estimated at 24% for each sex. Territories were held only by adult Peregrines. The oldest male on territory was at least 7 years old, the youngest was 2. The oldest female on territory was at least 7 years old, the youngest was 3. Territories were held by individuals of each sex for at least 6 years. One pair remained together for at least 4 years. Less than 4% of all young Peregrines produced on the study area in the first 5 years of the study were recruited into the breeding population. More male than female young were recruited despite an even sex ratio among nestlings. Peregrines did poorly in their first breeding attempts. The single young female recruited into the study population dispersed more than three times the median dispersal distance of six recruited males, suggesting that other females probably dispersed beyond the boundaries of the study area.
The effects of improvement of upland, marginal grasslands on the breeding success of Lapwings Vanellus vanellus and other waders
Authors: BAINES D.
Published: April 2008

Data on the breeding success of Lapwings Vanellus vanellus on unimproved and improved grassland, with comparative data for arable land, were obtained from a study on 760 Lapwing clutches. The study was undertaken in the Eden Valley, Cumbria, and Teesdale, Co. Durham, between 1985 and 1987. First clutches were larger on unimproved grassland with a mean of 3.73 eggs compared to 3.61 eggs on improved grassland. In contrast, replacement clutches were larger on improved areas (3.90 eggs) than on unimproved (3.47 eggs). On average, 40% of eggs laid on unimproved pastures hatched compared to only 17% on improved pastures. No significant difference in hatching success was found between unimproved and improved meadows with 32% and 22% of eggs hatching, respectively. Overall, 73% of unsuccessful first clutches were replaced on unimproved pastures, whereas on meadows and improved pastures combined, only 32% were replaced. Survival of small chicks was highest on unimproved areas. Production on unimproved areas was sufficient to replace adult losses and so maintain numbers, whereas on improved land production was too low to maintain existing breeding densities. Hatching success on unimproved areas was similar for the four species of wader considered. On improved areas, Redshank hatching success was relatively high, with 54% of pairs producing chicks, compared to 35% for Lapwing and 23% for Curlew.
Cainism in the Sulidae
Authors: Nelson Bryan
Published: April 2008

Commenting on Simmons' (1988) valuable review of cainism may I suggest for the Sulidae answers to three of his four questions (p.348) concerning the interpretation of two‐egg clutches as insurance policies?
Breeding ecology of the White‐headed Petrel Pterodroma lessoni on the Kerguelen Islands
Authors: ZOTIER RICHARD
Published: April 2008

The breeding season of the White‐headed Petrel Pterodroma lessoni on Mayes Island off the Kerguelen archipelago was studied between December 1985 and February 1987. The birds returned to land in November, and the chicks hatched at the end of January and fledged in May. These incubation and fledging periods are among the longest known in the family Procellariidae. Successful birds normally bred every two years, which has not previously been reported for any member of this family. The breeding ecology is compared to that of other gadfly petrels from sub‐antarctic and tropical waters, and the breeding frequency is discussed.
The relationship of spring and summer weather with density and breeding performance of the Buzzard Buteo buteo, Goshawk Accipiter gentilis and Kestrel Falco tinnunculus
Authors: KOSTRZEWA A. , KOSTRZEWA R.
Published: April 2008

The density of territorial pairs, laying pairs and the breeding performance of three raptor species, Buzzard Buteo buteo, Goshawk Accipiter gentilis and Kestrel Falco tinnunculus, were investigated in relation to rainfall and temperature during the breeding cycle. In all species the density of territorial pairs was not related to spring rainfall and temperature. In the Buzzard the percentage of pairs that bred unsuccessfully was significantly related to May rainfall. The number of young fledged was negatively correlated with rainfall in April and May. In the Goshawk the percentage of laying pairs was negatively correlated to rainfall in March and April. Success in terms of number of young fledged was related mostly to May temperature. In the Kestrel the density of territorial pairs was dependent on March‐April rainfall. The number of young fledged per successful pair was highly correlated with May and June temperature. All these relationships showed that the hatching period and the subsequent two weeks were most important for chick survival.
Time budgets of Nuthatches Sitta europaea with supplementary food
Authors: ENOKSSON BODIL
Published: April 2008

Individual time budgets during winter and spring were studied in a population of Nuthatches Sitta europaea in south‐central Sweden. In late winter birds spent about 90% of daytime foraging, males feeding somewhat less than females, possibly due to male dominance. In early spring, foraging time decreased to about 65% of daytime activity, and sex‐related differences became more pronounced. Males then increased time spent resting and singing. Females were nestbuilding, spent less time resting and also devoted more time to foraging than did males. Prior to the observation periods, food density for part of the population was experimentally increased by supplying sunflower seed. In spite of this, time budgets in the experimental group were similar to those of the control group. It is possible that the intensity of foraging, rather than actual time devoted to it, was influenced by food density and that, as a result, birds in the experimental group were able to maintain a higher level of vigilance. Also, an increase in food supply may be less important to a hoarding bird such as the Nuthatch. However, the result remains that Nuthatch time budgets in winter and spring are not readily influenced by an increase in food density.
Acquisition of food by fledgling Egyptian Vultures Neophron percnopterus by nest‐switching and acceptance by foster adults
Authors: DONAZAR JOSÉ A. , CEBALLOS OLGA
Published: April 2008

In a dense population of Egyptian Vultures Neophron percnopterus in northern Spain, nest‐switching occurred between nearby nests. Fledglings obtained more feeds by intruding and pirating than by remaining in their own nests during the same period. Intruder fledglings showed the same behaviour with Foster adults attacked intruder fledglings significantly less than they attacked alien adults and immatures but more frequently than they attacked their own fledglings. Effective rejection behaviour by foster adults to intruders may not have evolved as Egyptian Vultures usually nest at lower densities than that found in the study area.
The effect of human observers on the intensity of nest predation
Authors: MAJOR RICHARD E.
Published: April 2008

Disused nests containing eggs from aviary birds were used to determine the effect of human observers on the intensity of nest predation. Nest predation was significantly higher for nests visited daily than for nests visited only at the end of a typical incubation period. Care should be taken by nest observers to minimise the number of visits to nests of ground‐nesting birds. The average distance of nests from the edge of the supporting plant was greater for unsuccessful than successful nests, implying that the position of nests is an important factor affecting their survival. Predation rates on active nests of White‐fronted Chats Ephthianura albifrons visited daily over the same period were similar to those of experimental nests, suggesting that ‘artificial’ nests may be a useful tool for studying nest predation.
Incubation routines and foraging‐trip regulation in the Grey‐faced Petrel Pterodroma macroptera gouldi
Authors: JOHNSTONE ROBIN M. , DAVIS LLOYD S.
Published: April 2008

In Grey‐faced Petrels Pterodroma macroptera gouldi parental care during the 55‐day incubation period is mainly achieved by three long shifts (two by the male) when one partner is ashore while the other forages at sea. This situation would seem to carry high risks of parental desertion and failure of the hatching chick to receive a meal before its yolk sac is exhausted. We examined incubation routines of 51 pairs of Grey‐faced Petrels to investigate factors implicated in parental desertion and in the duration of the final foraging trip before hatching. The duration of the final long foraging trip (by the female) during incubation is not predicted by the time spent fasting on the nest but by the time elapsed since laying. Desertions accounted for 6.5% of egg losses. Eggs were deserted not after the delay of the foraging bird to return to the nest, but when the incubating bird departed early in the incubation spell. Desertions were not a response to critically depleted energy reserves.
Changes in adult annual survival rates in a western European population of the White Stork Ciconia ciconia
Authors: KANYAMIBWA S. , SCHIERER A. , PRADEL R. , LEBRETON J.D.
Published: April 2008

The population of the White Stork Ciconin ciconia in Alsace (northeastern France) has decreased considerably since 1961. Using recent captureerecapture models, we analysed resighting data on ringed birds resulting from a long‐term ringing programme carried out in 1947–1985. Time‐dependence and age‐dependence in annual survival rates are examined with reference to environmental variables in the Sahel wintering area. Our results show a decrease in adult annual survival rate linked to the severity of the drought in the Sahelian zone.
Acquisition of foraging skills by Heron Island Silvereyes Zosterops later alis chlorocephala
Authors: JANSEN AMY
Published: April 2008

Age‐related differences in foraging efficiency and behaviour were investigated in a population of colour‐ringed Silvereyes Zosterops lateralis. First‐year birds were less efficient foragers than older birds with second‐year birds being intermediate. First‐ and second‐year birds had lower success rates than older birds overall, and for most capture techniques and substrates. First‐year birds never attempted breeding while about half of the second‐year birds and all of the older birds did. Both learning and selection effects may have been involved in causing the age‐related differences in foraging behaviour. Foraging skills appear to improve during the first 2 years of life and selection could remove the least efficient foragers from the population in winter when food is short. That second‐year birds, some of which had already attempted breeding, were not significantly more efficient foragers than first‐year birds suggests that reproduction is not delayed until adult levels of foraging efficiency have been attained.
Integrated population monitoring of breeding birds in Britain and Ireland
Authors: BAILLIE STEPHEN R.
Published: April 2008

Effective wildlife monitoring schemes identify changes in population variables that require conservation action. This must be based on an understanding of normal patterns of population variability. Monitoring schemes ideally provide data on the stages of the life cycle at which changes are taking place and indications of the probable causes of change.

The Integrated Population Monitoring Programme of the British Trust for Ornithology aims to fulfil these requirements for British birds. It encompasses existing BTO projects that measure population size, productivity and survival rates, principally the Common Birds Census, Waterways Bird Survey, Nest Record Scheme, Constant Effort (mist‐netting) Sites Scheme and the Ringing Scheme. Integrated analyses of long‐term BTO data are being used to study the population dynamics of individual species. Relationships established through such analyses will be used to construct models that will predict population performance, and against which observed performance can be compared.

A simple application of Integrated Population Monitoring is presented using data for the Song Thrush (Turdus philomelos), a species which has been declining throughout most of Britain since the mid 1970s. No reduction in reproductive performance was detected and the decline appears to have been brought about through reduced survival rates. Factors responsible for much of this decline were identified from a multiple regression model involving winter weather conditions.
Lapwings Vanellus vanellus on aerodromes and the birdstrike hazard
Authors: MILSOM T. P.
Published: April 2008

Habitat selection by Lapwings Vanellus vanellus varies seasonally, with aerodromes comprising a preferred habitat in late summer and again in late autumn and winter. The presence of flocks of Lapwings on aerodromes poses a flight safety problem but management of the aerodrome habitat, especially the grass areas, combined with scaring, can minimize the hazard. The consequences of displacing large numbers of Lapwings from aerodromes to other habitats are reviewed in relation to the declines in breeding populations that have occurred as a result of changes in agricultural practices.
The damage‐conservation interface illustrated by geese
Authors: OWEN MYRFYN
Published: April 2008

Changes in legislation, in public attitudes and in shooting practices, both in Britain and overseas, have allowed populations of geese which winter in Britain to increase in numbers. Since 1960 the number of individuals in the seven populations that come into conflict with agriculture has increased almost fivefold.

There are serious conflicts between geese and farmers in some localities, where damage is alleged to growing grass, cereals and high value cash crops. Despite extensive studies over 20 years, it has proved impossible to devise precise and cost‐effective methods of assessing the damage caused by geese and to provide a fair and workable system of compensation

Farmers and their representatives are calling for a co‐ordinated cull to reduce population sizes substantially. There are, however, a number of political and practical problems in undertaking population control, except perhaps in the feral populations of GreylagAnser anserand Canada GeeseBranta canadensisin England.

Proposals are put forward for each species, which take into account the international responsibility of each country to safeguard the populations of migratory birds, and which provide solutions to the local serious problems of farmers. These proposals involve the setting aside of land for geese, either by the creation and management of reserve areas or by making payments to farmers to tolerate the birds on their land.
The effects of changing agricultural practice upon Woodpigeon Columba palumbus numbers
Authors: INGLIS I. R. , ISAACSON A. J. , THEARLE R. J. P. , WESTWOOD N. J.
Published: April 2008

The Woodpigeon Columba palumbus population in a 1070 ha study area in East Anglia was studied from 1961 to 1986. This paper relates variations in Woodpigeon numbers to changes in the areas and types of crops grown.

In the early 1960s the mean Woodpigeon population fluctuated between 60 and 112 birds per 50 ha during the winter months. Subsequently there was a steady decline until the population levelled out in the early 1970s at around 30 birds per 50 ha. From a very low point in 1977, the numbers of birds increased reaching in 1986 a mean of 55 birds per 50 ha.

Marked changes occurred in the types of cereals grown in the area. In the 1960s spring‐sown barley was the major crop with winter‐sown wheat occupying most of the remaining area. Throughout the 1970s winter wheat was increasingly grown and winter‐sown barley replaced the spring‐sown variety. Although the area of permanent pasture did not change significantly, the area of clover ley was reduced markedly in the late 1960s. In the mid 1970s silage and oilseed rape were introduced and the cultivation of peas was expanded. On the basis of the crop types grown, the study period was divided into two 11‐year blocks 1961–1971 and 1975–1985. Crop preferences of Woodpigeons were calculated for each month within each of these 11‐year periods. A series of stepwise regressions was then conducted on both of the 11‐year periods in order to see how well the areas of preferred crops in a particular month could account for the mean population size of that month.

In the winters 1961/62 to 1971/72 the winter Woodpigeon population size was influenced by two crops. The area of cereal sowings largely determined how many birds remained in the area in December. The availability of clover ley, which depended upon both the area of clover ley and the amount of snow cover, controlled the population size in January and February.

In the winters 1975/76 to 1985/86 the population size was again affected by two crops. In November the amount of grain on both stubbles and sowings influenced how many young birds stayed in the area. The area of oilseed rape in December then set the population size which changed very little throughout the rest of the winter.

The change in the pattern of population regulation has profound implications for the likely success of shooting Woodpigeons in winter as a means of reducing local numbers.
Synthetic bird calls and their application to scaring methods
Authors: AUBIN T.
Published: April 2008

This paper suggests means of synthesizing efficient signals for bird scaring and examines five ways in which synthetic signals may be more efficient: the coding/decoding process, transmission through the environment, interspecificity, habituation and broadcasting techniques. Examples are taken from our own studies comparing natural and synthetic distress calls.
Plant chemistry and bird repellents
Authors: CROCKER D. R. , PERRY S. M.
Published: April 2008

Research into chemical bird repellents is reviewed. The feeding preferences of Bullfinches Pyrrhula pyrrhula for bud extracts of 26 pear cultivars were established in the laboratory and correlated with underlying biochemical differences between extracts. A group of phenolic compounds was identified as aversive. Some of these compounds proved to be powerful inhibitors of protease activity in uitro, supporting theories about the role of phenolics as plant defences against herbivores. A larger study, however, failed to demonstrate a correlation between their biochemical reaction with digestive enzymes and their ability to deter feeding by feral pigeons Columba livia. Nevertheless, cinnamamide was identified as a promising bird repellent, although its mechanism of action is unclear.
Ornithology and integrated pest management: Red‐winged BlackbirdsAgelaius phoeniceusand corn
Authors: DOLBEER R. A.
Published: April 2008

Red‐winged BlackbirdsAgelaius phoeniceus, the most abundant bird in North America, annually destroy over 360 000 tonnes of field corn and substantial amounts of sweet corn. This loss, representing <1% of North American corn production, is localized within 8 km of wetlands where Red‐winged Blackbirds roost in late summer. Red‐winged Blackbirds are often initially attracted to corn fields to feed on insect pests during the 2–3 week period between silking and kernel development. An ideal resolution of the conflict between corn farmers and Red‐winged Blackbirds is to couple the birds' beneficial feeding habits in silking‐stage corn with management techniques to reduce subsequent damage to kernels. Once birds switch from feeding on insects to feeding on corn, protective measures to reduce damage are more critical in the early (milk) stages of kernel development than later because the damage potential is much higher at this time. Birds must eat three times more kernels at 20 days after silking than at 40 days in order to receive the same corn biomass. The use of bird‐resistant cultivars of corn, the deployment of frightening devices during the critical damage period, and the provision of alternative feeding sites are important components of an integrated management programme. The goal is to accommodate Red‐winged Blackbirds as a part of the wetland‐agricultural complex in North America.
An analysis of clutch‐size in New World passerine birds
Authors: KULESZA GEORGE
Published: April 2008

Variation in clutch‐size among New World passerine birds was analysed with respect to four variables: body‐mass, geographic latitude, the frequency of nest predation, and the structure of the nest. Data were analysed separately by averaging traits at three taxonomic levels: species, genus, and subfamily. Allometric scaling with body‐mass did not account for significant variation in clutch‐size regardless of the taxonomic level of analysis. Latitudinal effects on clutch‐size were highly significant at all taxonomic levels. For species building small‐pensile nests and open‐cup nests, nest predation had a significant partial effect on clutch‐size, with latitude held constant. When nest predation and latitude were held constant, clutch‐size was significantly different among species building small‐pensile nests, open‐cup nests, and domed nests. These results suggest that New World passerine clutch‐size is related to at least three variables: latitudinal effects, nest predation, and nest structure.
Energetic demands during brood rearing in the Wheatear Oenanthe oenanthe
Authors: TATNER PAUL
Published: April 2008

Daily energy expenditure of Wheatears Oenanthe oenanthe during the brood rearing period was measured using the doubly‐labelled water technique. The average daily metabolic rate (ADMR) (± 1 s.d.) for 24 individuals was 6.24 ± 1.17 cm3 CO2/g/h, which corresponds to 95.3 ± 17.0 kJ/day (RQ = 0.75) for a bird of average mass (24.3 g).

There were no significant differences in daily energy expenditure between the sexes, nor between first‐year and older birds. Individual males with longer tarsi had lower ADMR but raised larger broods. The ADMR increased at lower ambient temperatures, but this effect disappeared when the positive correlation with rainfall was taken into account. There was no relationship between the natural brood‐size and parental daily energy expenditure. A positive correlation between ADMR and the time spent hopping and pecking suggests that foraging activity may account for some of the variability between individuals. The daily change in body‐mass was not related to either the individual's age or its sex, and overall was not correlated with the level of daily energy expenditure. For birds examined on the same day, individuals with a higher ADMR had a greater loss of body‐mass, which appears to be a high risk strategy. However, Wheatears also exhibited an ability to increase body‐mass in conjunction with a drop in their daily energy expenditure.
Reproductive interactions of the Shiny Cowbird Molothrus bonariensis and the Yellow‐hooded Blackbird Agelaius icterocephalus in Trinidad
Authors: CRUZ ALEXANDER , MANOLIS TIMOTHY D. , ANDREWS ROBERT W.
Published: April 2008

The reproductive interactions of the Shiny Cowbird Molothrus bonariensis, a brood parasite, and the Yellow‐hooded Blackbird Agelaius icterocephalus, a host of the cowbird, were studied In Trinidad, West Indies. We gathered information on the breeding biology of the Shiny Cowbird and the Yellow‐hooded Blackbird, the frequency of use of the host species, and the effects of brood parasitism on host breeding success. Yellow‐hooded Blackbirds are polygynous for the most part; males build nests and attempt to attract females to lay in them by means of song and visual displays directed towards the nests. This behaviour probably makes it easy for cowbirds to locate breeding birds and their nests. Cowbird eggs were found in 153 of 377 (40–3 %) blackbird nests located before the nestling stage. Shiny Cowbird parasitism of the Yellow‐hooded Blackbird had little negative impact on host reproductive success, whereas predation accounted for the majority of nest failures. Vigilant nest defense by male blackbirds combined with colonial breeding apparently also minimized the extent of host egg damage and removal by cowbirds, and the parasitized and unparasitized nests were equally successful at producing blackbirds. Cowbirds most frequently parasitized the first or only nesting attempts in blackbird territories, and first or only nests were also successful more frequently than subsequent nests.
A new species of shrike (Laniidae: Laniarius) from Somalia, verified by DNA sequence data from the only known individual
Authors: SMITH EDMUND F. G. , ARCTANDER PETER , FJELDSÅ JON , AMIR OSMAN GEDOW
Published: April 2008

A new species of bush‐shrike is described on the basis of the only known individual. The bird was captured in a disturbed Acacia thicket near the town of Bulo Burti by the Shabeelle River in central Somalia. Believed to represent a species near extinction, the bird was kept alive, studied in captivity and then released. The type material comprises moulted feathers, blood samples and DNA extracted from feather quills. For comparison, DNA from other bush‐shrikes was obtained from old museum skins and three live birds. Comparisons of base sequences from the cyt‐b gene of mitochondrial DNA support the judgement that the bird represents a full species and is not a colour morph or hybrid of examined taxa. This procedure confirms that, in situations where collecting is not desirable, tissue from live individuals can be used to define taxa, and for comparisons with DNA from museum specimens of other taxa.
Intraspecies variation in avian energy expenditure: correlates and constraints
Authors: BRYANT DAVID M. , TATNER PAUL
Published: April 2008

Data on energy expenditure by 553 individuals of 28 species of small bird (10–150 g) are presented. All estimates of energy expenditure were obtained using the doubly‐labelled water technique. Intraspecies variation in daily energy expenditure was found to be positively correlated with brood provisioning rates, percentage of time flying and the frequency of non‐resting activity. Correlations were also shown with body‐mass, body‐size and several environmental factors. Published data on basal metabolic rates (BMR) sometimes differed substantially from estimates either made specifically as part of the studies considered here or calculated from allometric equations. For the purpose of interspecific comparisons, specific estimates of BMR are to be preferred. When expressed as a function of BMR, energy expenditures of free‐living birds ranged from 1 + to 7 + times BMR with a mode at 3 +. Values of daily energy expenditure exceeding 4 times BMR were found in up to 48% of species and 30% of individuals, so that, contrary to earlier suggestions, 4 times BMR is not a universal upper limit to the sustained work rate of small birds. Observed upper limits tended to be higher in species with energy‐expensive foraging habits. Energy expended by breeding birds is likely to involve a balance between the benefits a greater expenditure has for offspring production and any fitness penalty associated with the high level of energy expediture which nest provisioning involves.
The effect of social dominance on foraging by the Three‐toed Woodpecker Picoides tridactylus
Authors: HOGSTAD OLAV
Published: April 2008

During the winter, female Three‐toed Woodpeckers Picoides tridactylus, when unaccompanied by the male, foraged at a lower height above the ground and on tree trunks of greater diameter than when foraging together with a male. Among males, however, no such differences were found between those birds foraging in the absence of, or in company with, a female. The niche breadth of the males was less than that of the females, indicating a higher degree of specialization by the males. The niche overlap between the sexes was less when the birds foraged together in pairs, especially as regards foraging height and foraging site diameter. The intersexual segregation of foraging niche recorded for the Three‐toed Woodpecker is therefore probably not determined genetically, but is due to social dominance by males which obliges the females to occupy the less preferred niche. Both sexes spent less time being vigilant when foraging together, than when alone.
Sperm competition and the reproductive organs of the male and female Dunnock Prunella modularis
Authors: BIRKHEAD T. R. , HATCHWELL B. J. , DAVIES N. B.
Published: April 2008

The morphology of the external and internal reproductive organs of male and female Dunnocks Prunella modularis are described in relation to the intense sperm competition characteristic of this species' mating system. Males have a relatively large cloacal protuberance, seminal glomera (sperm store) and testes. The seminal glomera contain about 1060 times 106 spermatozoa, probably sufficient for numerous copulations. The female's uterovaginal junction comprised 16 primary mucosal folds, each containing an average of 87 sperm storage tubules (SSTs): 1398 in total. SSTs were 370 μm in length and SSTs filled with sperm had an internal diameter of 12.2 μm. The morphology, number, size and storage capacity of SSTs were similar to that for other passerines, despite the female Dunnock's high copulation rate. Sperm ejected during the Dunnock's precopulatory display is thought to originate from the vagina rather than from the SSTs.
The impact of avian predator‐scavengers on King Penguin Aptenodytes patagonicus chicks at Marion Island
Authors: HUNTER STEPHEN
Published: April 2008

While ashore King Penguins Aptenodytes patagonicus are fed upon by a guild of five predator‐scavenger seabirds. During the winter (April‐October) male Southern Giant Petrels Macronectes giganteus killed an estimated 6430 (11.2%) of Marion Island's King Penguin chicks, although most birds only scavenged in the colonies. The rate of predation varied, with peaks in April‐May and in September. The proportion of successful attacks was 22.7%. There was a strong correlation between colony size and the rate of accumulation of chick corpses. Kelp Gulls Larus dominicanus and Lesser Sheathbills Chionis minor also scavenged penguin corpses but Northern Giant Petrels M. halli and female Southern Giant Petrels rarely entered the colonies. During the summer predation was mainly by Sub‐Antarctic Skuas Catharacta lonnbergi which took eggs and small chicks.
Foraging, home range use and social behaviour of a group‐living rainforest raptor, the Red‐throated Caracara Daptrius americanus
Authors: THIOLLAY JEAN‐MARC
Published: April 2008

A stable group of six Red‐throated Caracaras Daptrius americanus was followed over 5 years in a rainforest area of French Guiana and was intensively studied during 52 days in 1989‐90. They bred successfully only twice (1986 and 1990). Communal nest guarding and brood care were observed. Their social behaviour and group‐living habits seem unique among raptors. The 400‐ha all‐purpose, year‐round, group territory was defended by all individuals and was almost fully used. The birds foraged individually, but the cohesion of the group and its coordinated movements were maintained by periodic loud rallying calls. Food sharing of large prey items and even deliberate allofeeding also contributed to the group cohesion. Mature, high, closed‐canopy forest was preferred and 88% of the actively foraging birds were encountered in the understorey, where they had a higher success rate than those hunting in the upper canopy. This may explain why the species' frequency and group size markedly decreased in secondary or disturbed forests. The 12‐hour daily activity period was reduced by an average of 2 hours either by a midday pause (hot weather) or by rains. At least 74% of all food items taken were wasp nests or other insect nests in the foliage, 9% were hard fruits, and the remaining captures were various invertebrates or unidentified items. When the caracaras were raiding a wasp nest, the wasps were kept off probably by a powerful repellent, a striking adaptation unprecedented among birds. Several species of mostly large canopy frugivores regularly formed close associations with the caracaras to forage in the understorey, where they otherwise rarely or never ventured. This new interspecific flocking behaviour is interpreted as an antipredator strategy benefiting from the raptors' warning and mobbing efficiency.
Parental care in Semipalmated Sandpipers Calidris pusilla: brood desertion by females
Authors: GRATTO‐TREVOR CHERI L.
Published: April 2008

Although Semipalmated Sandpipers Calidris pusilla are monogamous, with biparental incubation, most females (86–97%) deserted their broods to the care of their mates, 0–11 days (average 6) after their eggs hatched. Males left the brood an average of 8 days later, shortly before or after the chicks fledged. In several instances, females that deserted in one year remained with the chicks the next year, and vice versa. Females deserted chicks at nests that hatched later in the season at an earlier age than those had hatched earlier (r2> o.6). Since females appeared to have an energy deficit in at least some years, and suffered higher mortality rates than males during breeding, it is possible that females deserted broods in order to take advantage of better feeding conditions at migratory stopovers in northeastern North America early in the season. There was little evidence of higher nesting success or earlier hatching date in reuniting pairs, although if both members of a pair returned to the breeding area, 80% reunited. Increased survival of their mate may be most advantageous to males in ensuring that they obtain a female the following year.