bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of food supply on the breeding ecology of Kittiwakes Rissa tridactyla in Shetland
Authors: HAMER K. C. , MONAGHAN P. , UTTLEY J. D. , WALTON P. , BURNS M. D.
Published: April 2008

We measured the breeding performance, body condition, time budgets and foraging ranges of Kittiwakes Rissa tridactyla at Sumburgh Head, Shetland, in two years of contrasting food availability. Kittiwakes in Shetland generally feed their young almost entirely on sandeels, and fisheries data indicated that stocks of sandeels in Shetland waters were at least ten times higher in 1991 than in 1990. Fledging success of Kittiwakes was nil in 1990 and 68% of eggs laid in 1991, although clutch‐size and hatching success were no different between years. Post‐hatching foraging trips in 1991 were of comparable duration to those recorded at other colonies in conditions of good food supply (2–3 h), while trips recorded during incubation or post‐hatching in 1990 were approximately three times longer on average than at corresponding stages of the breeding season in 1991. Radio‐tracking data indicated that adults generally stayed within 5 km of the colony in 1991 but flew more than 40 km from the colony on each trip in 1990. Eggs were apparently not left unattended in either year, despite the fact that this required adults to incubate for periods in excess of 44 h in 1990. The extent to which adults were able to increase trip durations, foraging ranges and incubation shift lengths between years, while maintaining hatching success, indicates the degree to which Kittiwakes are normally buffered against adverse feeding conditions during incubation. Reduced nest attendance and lower body‐condition of adults post‐hatching in 1990, in conjunction with complete post‐hatching breeding failure, indicate that adults were beyond the limits of their buffering capacity during chick‐rearing in 1990.
Information parasitism in foraging Bar‐tailed Godwits Limosa lapponica
Authors: LARSEN TORE
Published: April 2008

Foraging behaviour of sympatric Bar‐tailed Godwits Limosa lapponica and Whimbrels Numenius phaeopus was studied in the period prior to egg‐laying. Godwit females preferred wet bogs, while godwit males and Whimbrels foraged on dry palsas in the bogs. Habitat overlap between godwit males and Whimbrels was larger than intersexual overlap in the godwits. Observations of scanning behaviour of foraging godwits showed that the vigilance level of males was not affected by the presence or absence of their mates. Female vigilance levels, however, dropped significantly when females fed near their mate, and—in the absence of the mate—near Whimbrels. While female godwits benefited from associating with Whimbrels, males seemed to avoid close proximity to this species. Whimbrels chased godwit males more often than females, presumably because they used the same foraging habitats.
Fat, hydration condition, and moult of Steppe Buzzards Buteo buteo vulpinus on spring migration
Authors: GORNEY EDNA , YOM‐TOV YORAM
Published: April 2008

Physical condition of migrating Steppe Buzzards Buteo buteo vulpinus was determined during spring migration at Elat, southern Israel, 1984–1988. An index based on measurements of body mass, wing‐length and culmen was used to estimate fat content, based on fat extraction from nine buzzards. In addition, hydration condition was measured in 1988 and moult was checked in 1985–1988. More immatures (1001) than adults (459) were trapped, and a greater percentage of immatures (19.8%) than adults (8.4%) was retrapped during the same season. Adults had significantly greater fat reserves (4.5% of body mass) than immatures (3.8%). Most adults were in some stage of interrupted moult: however, active primary moult was noted only in immatures (10%). These findings suggest that different age groups use different migration strategies. Most of the buzzards trapped in this study could not have completed their entire migration using only stored fat: thus, hunting was probably necessary to replenish their energy reserves. No indication of water stress was found in the spring of 1988.
Influence of growth rate retardation on time budgets and energetics of Arctic Tern Sterna paradisaea and Common Tern S. hirundo chicks
Authors: KLAASSEN MARCEL , HABEKOTTÉ BEREND , SCHINKELSHOEK PETER , STIENEN ERIC , TIENEN PIET VAN
Published: April 2008

Time budgets of free‐living chicks of Arctic Terns Sterna paradisaea and Common Terns S. hirundo throughout development are presented with special reference to changes in time allocation when growth rate varies. Chicks of both species were inactive most of the time observed (87%). Time allocated to the different behaviours changed during development and was generally better correlated with body mass than age. Slower growing nestlings were brooded more and allocated more time to quiescence and less time to locomotion, preening, begging and attacking (the latter two significant only for the Arctic Tern). The energetic implications of variation in time budgets with age and growth rate were considered. Parental brooding resulted in an average energy saving of nearly 40% of an individual nestling's thermoregulatory costs. Whereas thermoregulatory costs remained nearly unchanged in Arctic Tern chicks, these were negatively correlated with growth rate in Common Terns. Tentatively, we estimated a 30% reduction in a nestling's total energy requirement for a 50% reduction in average growth rate for both species.
The effects of food abundance on breeding performance and adult time budgets of Guillemots Uria aalge
Authors: UTTLEY J. D. , WALTON P. , MONAGHAN P. , AUSTIN G.
Published: April 2008

The breeding performance, food fed to chicks and adult time budgets of Guillemots Uria aalge were examined in a year of high and a year of low food availabiIity. There was no difference between the 2 years in reproductive success, although the rate of chick feeding, chick weight and fledging success were greater in the year of high food availability. On average, chick prey items were larger in the poor food year, but this was insufficient to compensate for the lower feeding frequency. Chick feeding frequency did not differ between days in the good year but did increase later in the season in the poor food year. Compared with the high food availability year, adult Guillemots in the year of low food availability spent much less time resting at the breeding colony. and their foraging trips were twice as long. Foraging birds tended to make several successive trips before resuming brooding duties from their mates when food supplies were good, but in the low food availability year single trips were the norm. These results demonstrate that predators experiencing reduced food supply may mitigate the effects on their reproductive output by shifting their time allocation such that more time is available for foraging.
Time and energy budgets of breeding males and females in sandgrouse Pterocles species
Authors: HINSLEY SHELLEY A. , FERNS PETER N.
Published: April 2008

The investment of time and energy in reproduction by male and female sandgrouse (genus Pterocles) was studied. Energy expenditure was estimated using time budgets and laboratory measurements of metabolism. Female parental expenditure was greatest during laying and incubation. Females took the larger share of daytime incubation, which reduced their time available for foraging (3.6 h compared with 4.8 h for males). To remain in energy balance, they required a higher food intake rate than males (97 kJ/h compared with 79 kJ/h, respectively) and consequently were likely to lose condition during incubation. Male parental expenditure was greatest during chick‐rearing, especially when the young were well grown but still dependent on the male for water. The role of males as water carriers increased their energy expenditure and decreased their time available for foraging. Males also took the greater share of time spent in vigilance on behalf of the young, which further reduced their foraging time (3.2 h compared with 4.9 h for females). To remain in energy balance, males with young required a higher intake rate than females (62 kJ/h compared with 44 kJ/h, respectively).
Variability and stochasticity of meal size and feeding frequency in the Little Sheanvater Puffinus assimilis
Authors: HAMER K. C.
Published: April 2008

The pattern of chick feeding in Little Shearwater Puffinus assimilis on Selvagem Grande was examined by weighing chicks at 4–h intervals throughout eight successive nights and daily for a further 11 days (19 days in all). Individual meals fed to chicks averaged 23.2 g (s.d. ±4.7) or 13.6% of adult mass. Mass increments over 24 h (NET) were linearly related to the sum of positive mass increments over 4–h intervals during the night (SUM) by the equation NET = 0.36SUM ‐ 5.89 (r2= 0.60). Using this relationship, I estimated that over a period of 18 nights, a mean of 95% of chicks were fed each night, and the mean interval between feeds was 1.05 nights, with a maximum of three nights. There was no significant day‐to‐day variation in feeding rate. These results were not compatible with the prevalent idea that the purpose of large fat deposits in Procellariiformes is to tide chicks over periodic fasts resulting from poor feeding conditions. On average, chicks required 16 g of food per day to maintain constant mass and converted 33% of their intake of food above this requirement into biomass. Meal size and feeding frequency were independent of chick size and body condition (body‐mass corrected for body‐size), and the masses of food received by individual chicks each night varied in direct proportion to previous values. These results suggest that the rate of food supply to chicks was not regulated by adjustment according to chicks' nutritional requirements. To some extent, this supports the hypothesis that lipid accumulation among Procellariiformes is related to stochastic variation in food supply rate, resulting from an absence of regulation of feeding. However, feeding was not stochastic, in that adults tended to deliver consistent amounts of food to their chicks, and the pattern of feeding among even the worst‐fed chicks was inconsistent with a need for large lipid stores based upon chance variation in food delivery.
Interrelationships between breeding frequency, timing and outcome in King Penguins Aptenodytes patagonicus: are King Penguins biennial breeders?
Authors: HEEZIK Y. M. VAN , SEDDON P. J. , COOPER J. , PLÖS A. L.
Published: April 2008

King Penguin Aptenodytes patagonicus chick growth is interrupted by a winter fast which extends the length of the breeding cycle (laying to chick independence) to 14–16 months, so that continuous annual successful breeding appears to be impossible. The 3–month laying period imposes further constraints with respect to timing of breeding attempts in relation to the onset of fasting. By the frequent resighting of individually marked birds at Marion Island, we examined the frequency of breeding and the relationships between timing, outcome and frequency in the same and in consecutive years. A total of 3101 adult King Penguins were banded between 1984 and 1991, yielding continuous breeding histories spanning a maximum of 5 years. Most penguins attempted to breed in consecutive years, although the likelihood of taking a year off increased with the number of consecutive attempts. In any one season, about 19% of potentially breeding adults did not breed. Early breeders were more likely to succeed than late breeders and comprised 84% of breeding attempts of known timing. Successful birds in one season usually bred late in the following season, whereas failed attempts were usually followed by an early attempt. Non‐breeding was more likely to occur after a successful outcome than a failed one, and after a year off 93% of birds bred early. It is incorrect to refer to the King Penguin as a biennial breeder.
Effects of male removal on the behaviour and reproductive success of female Eastern Bluebirds Sialia sialis
Authors: MEEK SUSAN B. , ROBERTSON RALEIGH J.
Published: April 2008

We removed male Eastern Bluebirds Sialia sialis to examine the importance of male parental care and the behavioural responses of unaided females to loss of male assistance. Unaided females fed young significantly more than control females (females with male assistance) fed young, but young in experimental nests were fed significantly less frequently in total than young in control nests. Unaided females had significantly lower nesting success (fledged at least one young) than control females. At control nests, males defended the young more strongly than did their mates. Unaided females defended their young as strongly as control females. Unaided and control females spent the same amount of time brooding young, and there was no tradeoff between feeding and brooding young. Most early season experimental nests failed, but late in the season many unaided females were as successful as pairs. Unaided females were able to match the feeding rat'e in control broods at late nests but not at early nests, where control nestlings were fed at a higher rate. In our population, male bluebirds played an important role in provisioning young, and early in the season unaided females were unable to provide sufficient bod to raise any young to fledging.
Seasonal patterns of sperm storage in the Yellow‐headed Blackbird Xanthocephalus xanthocephalus
Authors: BRISKIE J. V.
Published: April 2008

The seasonal pattern of sperm storage was examined in a wild population of Yellow‐headed Blackbirds Xanthocephalus xanthocephalus by collecting females at eight different stages of their breeding cycle. Sperm storage tubules (SSTs) were present in simiktr numbers throughout all stages of the breeding season, from arrival on the breeding grounds to departure for winter. In contrast, the size of SSTs varied enormously over the season, reaching maximum size just prior to clutch initiation, when SSTs were more than three times the length of those found in post‐breeding birds. The amount of sperm stored also varied over the season, in parallel with the growth and regression of SSTs. Sperm were first observed in SSTs approximately 2–5 days before laying and increased rapidly in abundance until clutch initiation. The amount of sperm stored then decreased gradually during the egg‐laying period so that by clutch completion approximately 70% of stored sperm had disappeared from the SSTs. The rapid seasonal development and subsequent regression of SSTs in the Yellow‐headed Blackbird contrast sharply with the pattern found in domestic poultry, where the imposition of continuous laying regimes has; led to the maintenance of SSTs at maximum size for extended periods of time.
Storage of stones by Jays Garrulus glandarius
Authors: CLAYTON N. S. , GRIFFITHS D. , BENNETT A. T. D.
Published: April 2008

The aims of this study were to test whether or not Jays Garrulus glandarius store stones and, if so, to examine the conditions under which they store stones. By directly observing the behaviour of five captive Jays that were housed individually in flight cages, we found that stones were stored only in the absence of food items or when food items were no longer available to store and that there was a strong preference for storing stones that resembled acorns in both size and appearance (in terms of colour, shape and smoothness of the surface) and were undamaged rather than heavily chipped. These results are discussed in terms of Tinbergen's classic ethological model in which animals respond selectively to certain key features and ignore other features of the stimulus.
The effects of daylength and testosterone on the initiation and progress of moult in Starlings Sturnus vulgaris
Authors: DAWSON A.
Published: April 2008

The effects of daylength and of testosterone implants, before and after the beginning of moult, on the timing and rate of primary moult have been quantified. Female Starlings Sturnus vulgaris were moved from natural daylength in February to 13 h or 18 h of light per day (13L: 11D or 18L: 6D). Some of the birds on 18L: 6D were left on 18L: 6D throughout the experiment and others were transferred to 13L: 11D after 6 weeks, before moult had begun, or after 12 weeks, after moult had begun. Birds kept on 18L: 6D began to moult before birds kept on 13L: 11D, but the subsequent rate of moult was the same in both groups. A decrease in daylength before moult started slightly advanced the onset of moult. A decrease after moult had begun increased the speed of moult. Castrated male Starlings on 18L: 6D were given testosterone implants for different periods before or after the beginning of moult. Testosterone treatment which ended before moult would normally have started had little effect. Treatment extending beyond the normal start of moult considerably delayed or even prevented the onset of moult. Moult was arrested in birds which received testosterone after moult had begun. On removal of testosterone implants, moult began again from the point where it had stopped, but in some birds, all of the feathers which had been regrown recently were dropped again and regrown. These results are discussed in relation to the different patterns of moult seen amongst different species.
THE FIRST ALFRED NEWTON LECTURE Presented at the “Bird Conservation in Action” conference, April 1994
Authors: NEWTON I.
Published: April 2008

The breeding densities of birds could be limited by resources, such as food and nest sites, or they could be held at a lower level by natural enemies, such as predators and parasites. In this paper, I review the experimental evidence for each of these limiting factors affecting bird breeding densities. Of 18 experiments involving winter food provision (mostly on tits, Paridae). 11 led to increased breeding densities compared with control areas. Of four involving summer food depletion (all on forest insectivores), none led to decreased breeding densities. In experiments with Red GrouseLagopus 1. scoticus, fertilizing areas of heather moor led to increased densities during a period of population increase but did not prevent a later decline. Of 32 studies on tree‐cavity nesters, the provision of nestboxes led to increased breeding density in 30 (95%) studies, each involving one or more species of hole nesters. Of 15 experiments involving predator removal (mostly on ducks and gamebirds), at least 14 led to increased hatching success, four out of eight led to increased post‐breeding numbers, and six out of 11 led to increased breeding density. In one experiment, the removal of strongyle parasites from a Red Grouse population prevented a cyclic decline on five out of five occasions. Taken together, these experiments confirmed that all main potential external limiting factors have affected breeding density in one bird species or another. They also confirmed that the same species has been limited by one factor in certain areas or years and by another factor in different areas or years.
Bird interactions with utility structures: collision and electrocution, causes and mitigating measures
Authors: BEVANGER KJETIL
Published: April 2008

The causes of collision and electrocution accidents involving birds and power lines, and measures to mitigate such accidents, are reviewed. It is convenient to group the causes according to (1) biological, (2) topographical, (3) meteorological and (4) technical aspects. As regards collisions with power lines, the important biological variables are connected with the morphology, aerodynamic capability, physiology, behaviour and life‐history strategies of birds. To understand the electrocution problem, the relationship between body size and electrocuting installations must be considered.

Removing earth wires (and modifying earthing methods). modifying line, pole and tower design, installing underground cables and conspicuous marking of lines, poles and towers are important measures for tackling the problems. The route planning process should include careful mapping of (1) topographical features which are leading lines and flight lanes for migrating birds and/or are important for local movements of resident species, (2) topographical elements such as cliffs and rows of trees that force birds to fly over power lines, (3) primary ornithological functions or uses of the area to avoid key areas for birds and avoid separating these areas and (4) local climatic conditions (including seasonal variations) like fog frequency and prevailing wind direction. The outcome depends largely on a combination of these factors.

Objective assessment of the effects of mitigating measures, in particular wire marking, is required. The mitigating efforts should be directed against species known to be potential collision victims, and their design should be the result of a careful analysis of the biology and ecology of the target species.

Because of the cumulative effects of negative impacts on bird populations today and the alarming number of species with endangered or vulnerable status being killed in connection with utility structures, the problem deserves increased general awareness.
Recent changes in the food of the Grey Heron Ardea cinerea in central‐west Spain
Authors: Peris S. J. , Briz F. J. , Campos F.
Published: April 2008

As far as we know, there are no data on how changes in the freshwater fauna within the same area affect the feeding preference of the Grey Heron Ardea cinerea. We present data on the diet of the bird during the breeding seasons of 1990 and 1991 in central‐west Spain and compare these data with those obtained from the same colonies in 1986–1987.
Survival, site and mate fidelity in South Polar Skuas Catharacta maccormicki at Anvers Island, Antarctica
Authors: PIETZ PAMELA J. , PARMELEE DAVID F.
Published: April 2008

In 1974–1975, 34 adult South Polar Skuas Catharacta maccormicki were colour‐ringed on 18 nest territories at Bonaparte Point, Anvers Island, near Palmer Station along the Antarctic Peninsula. Subsequently, the area was searched for these birds during the austral summers of 1975–1976 to 1984–1985 and in 1987–1988 and 1989–1990. Fifty‐three percent were seen in 1984–1985, 32% in 1987–1988 and 21% in 1989–1990. Annual survival rate averaged 95% from 1974–1975 to 1984–1985; no sexual differences were detected (n = 28 of known sex). Strong territory and mate fidelity were apparent: 34 skuas averaged 1.1 nest territories and 1.7 mates each in 16 years. Only 4 of 34 individuals (all females) were known to change territories, and each territory change involved a change of mates. Although males showed higher territory fidelity than females (P < 0.01), most females (four of five) retained their territories when previous mates failed to return. Seventeen of 34 birds changed mates a total of 24 times; at least 20 mate changes followed the death or disappearance of the former mate. Males showed slightly higher mate fidelity than females (P < 0.04). Female South Polar and Brown Skuas Catharacta lonnbergi did not differ in territory or mate fidelity. From 1974–1975 to 1984–1985, 120 South Polar Skua chicks were ringed on 18 nest territories on Bonaparte Point: 17 were resighted in the Palmer area when they were 3–10 years old. All 15 returnecs were found within 3 km of their natal nest sites, and four of them occupied nest territories on Bonaparte Point.
Seasonal differences in habitat selection by Black Grouse Tetrao tetrix in the northern Pennines, England
Authors: BAINES DAVID
Published: April 2008

Between‐season differences in habitat use by Black Grouse Tetrao tetrix were studied on four moors in the northern Pennines between 1989 and 1992. Heather moor and bogs were preferred at all times of the year, apart from during the breeding season. In spring, large quantities of Cotton‐grass Eriophorum vaginatum flowers were consumed, whereas in autumn and winter Heather Calluna vulgaris was more important. Enclosed fields on the edge of the moors were regularly used in autumn and winter by large flocks of cock birds, and hens were found in smaller groups. Where present, overgrazed grass moorland was generally avoided, apart from during the summer. Similarly, enclosed rough grazing allotments rich in rushes were favoured during the summer months by breeding hens and moulting cocks.
Morphometrics of falconets and hunting behaviour of the Black‐thighed Falconet Microhierax fringillarius
Authors: KEMP ALAN C. , CROWE TIMOTHY M.
Published: April 2008

Samples of up to ten study skins for each of five species of Microhierax, two species of Polihierax, one species of Spiziapteryx and 23 species of small Falco were measured for 24 dimensions of the head, wings, tail and feet. The logarithmic (log10) valucs of the means of each mcasurcmcnt for each species, and for each sex where dimorphic, were compared using cluster and factor analyses. Microhierux falconets are most similar to the African Pygmy Falcon Polihierax sernitorquatus but are morphometrically distinct from all other falconets and small Falco species. The five species of Microhierax falconets are morphometrically similar, sexually dimorphic and probably replace one another ecologically, since all are allopatric or differ in proportions and habitat where parapatric (two species). Prelim[nary observatioris on the hunting behaviour and social organization of the Rlack‐thighed Falconet Microhierux fringillarius indicate that the genus has morphological and social specializations for aerial capture of large forest insects.
Lack of allozyme variation in the Spanish Imperial EagleAquila adalberti
Authors: NEGRO JUAN JOSÉ , HIRALDO FERNANDO
Published: April 2008

The breeding population of the Spanish Imperial EagleAquila adalbertiis reduced to 126 pairs located in the southwestern quadrant of the Iberian Peninsula. Protein electrophoresis was used to determine levels of genetic variation in the seven extant subpopulations of the species. Seventeen proteins encoded by 22 putative loci showed no variation among all the individuals which were analysed. The population crashed at the beginning of this century, but the long generation time of the species makes it improbable that a population bottleneck was the only cause of the lack of genetic variation. As an alternative explanation, a natural background of low variation cannot be discounted.
Philopatry and colony fidelity of Shags Phalacrocorax aristotelis on the east coast of Britain
Authors: AEBISCHER N. J.
Published: April 2008

Shag Phalacrocorax aristotelis colonies from the Firth of Forth south to the Fame Islands (SE Scotland and NE England) were surveyed in 1982 and 1983 for nesting Shags ringed as chicks or adults in the previous 20 years. On average, 5% of 863 Shags ringed as chicks were breeding away from their natal colony, and only 1% of 401 marked adults had left their breeding colony. The proportion p of chicks that settled at or beyond distance D from the natal colony followed the relationship p= 0.263D‐0.771, implying that more Shags moved 10 km or beyond to breed than expected from diffusion models or a constant‐rate dispersal model; adjusted for birds that settled outside the study area, the relationship was p = 0.314D‐0771. There was no effect of colony size on emigration rate, but females showed a greater tendency to settle away from the natal colony than did males. At the natal colony, more males (69%) than females (47%) nested within 300 m of their birthplace. Two mechanisms appear to determine where a Shag settles to breed: a navigational one governing the return to the natal colony, plus the competitive process of nest‐site establishment.
The Sooty Falcon Falco concolor on the Red Sea coast of Saudi Arabia: distribution, numbers and conservation
Authors: GAUCHER PHILIPPE , THIOLLAY JEAN‐MARC , EICHAKER XAVIER
Published: April 2008

Ground and aerial surveys of breeding Sooty Falcons Falco concolor were conducted along the western coast of Saudi Arabia and its offshore islands from August to October 1991 and 1992. An estimated population of 260–381 pairs was found. The known world breeding population is still below 1000 pairs. Most rocky islands were occupied except the largest islands of the Farasan archipelago. Among the many low islets surrounded with mangrove, only one small group near Al Lith harboured breeding Sooty Falcons. The distribution pattern, density and breeding success of the falcons seemed to be strongly influenced by food availability (autumn migration of small and medium‐size birds) and the deterring presence of terrestrial predators. Human disturbance and trapping are still of local importance.
Polygyny in the Willow Warbler Phylloscopus trochilus in Swedish Lapland
Authors: NEERGAARD RAIMO , ARVIDSON BENGT A.
Published: April 2008

The breeding sex ratio of Willow Warblers Phylloscopus trochilus in a subalpine birch forest was strongly female biased. Very few territorial males remained unmated and most became polygynous. Bigyny was the rule, but some males probably had three females. Male assistance at secondary nests varied and was probably dependent on temporal distance between the females' nests. There was no significant reduction in reproductive output for these females. Variation in the sex ratio of breeding birds can be explained, at least partly, by variation in the timing of male settlement.
Do all Blackcaps Sylvia atricapilla show winter site fidelity?
Authors: CUADRADO MARIANO , SENAR JUAN CARLOS , COPETE JOSE LUIS
Published: April 2008

Fidelity to previous wintering areas (i.e. site fidelity) has important ecological and evolutionary implications. However, since the percentage of recaptures of ringed birds at the same wintering area in subsequent years does not allow the estimation of the proportion of birds alive that exhibit site fidelity, previous studies on different passerine species have failed to show the true extent of this site fidelity. Here we use a recent approach, based on the comparison of survival rate estimates from capture‐recapture data at single field stations with recovery data from a much larger area. The idea is to determine the proportion of birds still alive that return to the area. The study was carried out on the Blackcap Sylvia atricapilla, comparing the capture‐recapture data of two field stations (Pilas [SW] and Tiana [NE]) situated 1000 km apart in Spain with the complete winter recovery data of the Spanish Ringing Office. Totals of 1936 and 3976 Blackcaps were ringed at Pilas (1981–1986) and Tiana (1975–1986), respectively, and the numbers of recaptures in subsequent winters were 94 and 34. The pooled annual survival rate estimation based on the two sites is 0.40 (s.e. = 0.05). The annual survival rate estimated from the Spanish ringing recovery data was 0.48 (s.e. = 0.08), which is not significantly different. We can conclude, therefore, that migrant Blackcaps in Spain, if alive, tend to return year after year to the previous wintering site.
Prolonged copulation, sperm reserves and sperm competition in the Aquatic Warbler Acrocephalus paludicola
Authors: SCHULZE‐HAGEN KARL , LEISLER BERND , BIRKHEAD TIM R. , DYRCZ ANDRZEJ
Published: April 2008

The Aquatic WarblerAcrocephalus paludicolahas a quasi‐promiscuous mating system with high levels of multiple paternity and, thus, intense sperm competition. The duration of copulation in the Aquatic Warbler is unusually long. In hand‐reared, captive birds the duration of mounting was 23.7 ± 11.8 min (mean ± s.d.). On average, six cloacal contacts (inseminations) occurred during each copulation. Between inseminations the male remained in contact with the female, either on top of or directly behind her. Protracted copulation may be a form of contact mate guarding, a behaviour not previously recorded in birds. Copulation was most frequent during the evening and early morning. Male Aquatic Warblers also exhibit extreme morphological adaptations of their reproductive system compared with otherAcrocephalusspecies and other birds: their testes, cloacal protuberance and seminal glomera (which contain 198 × 106spermatozoa) are all relatively large. Frequent insemination during protracted copulation and contact mate guarding may be alternatives to paternity guarding found in other birds.
The winter feeding ecology of Avocets Recurvirostra avosetta on intertidal areas. I. Feeding strategies
Authors: MOREIRA FRANCISCO
Published: April 2008

The behaviour of Avocets Recurvirostra avosetta feeding on emerged intertidal areas in a major wintering area, the Tagus estuary (Portugal), was studied during 2 years.

Avocets used four different feeding strategies. By far the most common was the Normal Feeding Strategy, in which the median sweeping rate was 28 sweeps per min and the percentage of swallowing movements (ingestions) was very high (median = 90%). No prey were visible in the bill while birds were using this strategy. Another less common feeding strategy was the Worm Feeding Strategy, in which the sweeping rate was higher (median = 46 sweeps/min) and the percentage of swallowing movements was much lower (median = 6%). While using the Worm Feeding Strategy, Avocets preyed on ragworms Nereis diversicolor. The Mixed Feeding Strategy and Scrobicularia plana Siphons Feeding Strategy were rarely observed.

In a detailed study on the use of the mudflats by Avocets, it was found that the density of birds on the upper shore was much higher than on the lower shore. There were differences in feeding behaviour between these two areas, although the same feeding strategy was used. On the lower shore, where there was a lower biomass of prey available, sweeping rates were higher and aggressive behaviour did not occur. On the upper shore, sweeping rates were lower and aggressive behaviour was frequent, with some birds defending territories. Nevertheless, estimated food intake rates were 1.5 times higher on the upper shore.
The winter feeding ecology of Avocets Recurvirostra avosetta on intertidal areas. II. Diet and feeding mechanisms
Authors: MOREIRA FRANCISCO
Published: April 2008

The diet and feeding methods of Avocets Recurvirostra avosetta using the most common feeding strategy (Normal Feeding Strategy) on emerged intertidal areas in the Tagus estuary, Portugal, were studied during two winters.

Avocets using the Normal Feeding Strategy fed non‐selectively in the top 20 mm of sediment, ingesting prey bigger than a minimum threshold dimension of around 1.5 mm. Some mud was also ingested whilst feeding. Prey were captured by the mechanical action of the bill, and the estimated number of items captured per sweep was quite high (mean = 10.9 worms). Most of the biomass ingested by Avocets consisted of oligochaetes, spionid worms, Capitella capitata and small ragworms Nereis diversicolor.

The estimated intake rate of Avocets suggested that the energy ingested during daylight hours did not represent a significant percentage of the daily requirements. Thus, feeding on emerged intertidal areas is probably a secondary component of their daily gross food intake, unless night feeding yields higher intake rates due to increased prey availability.
Day and night feeding territoriality in Willets Catoptrophorus semipalmatus and Whimbrel Numenius phaeopus during the non‐breeding season in the tropics
Authors: McNEIL RAYMOND , ROMPRE GHISLAIN
Published: April 2008

This study was carried out to determine whether or not, and under what conditions, Willets Catoptrophorus semipalmatus and Whimbrel Numenius phaeopus continue to defend and use their daytime feeding territories at night in a tropical environment. The study was conducted in coastal Venezuela by registering, by night and by day, the behaviour and the position of colour‐marked and radio‐tagged birds. Night observations were made with the use of a light intensifier.

In Willets, both territorial and non‐territorial birds were observed. The use and defence of territories was observed only on sandy mud areas where Fiddler Crabs Uca cumulanta were plentiful; the soft mud sites were used only by non‐territorial birds. All Whimbrel were territorial. Individuals of both species defending a given space during daytime continued to occupy and defend the same area during the night. The proportion of birds foraging at night was higher on moonlit than on moonless nights. Territorial defence involved alert postures, parallel walks, calls and the chasing of intruders. Agonistic encounters between Willets and Whimbrel and other species were rare. Willets were territorial at all states of the tide except when high tides flooded the territories. Tide had no effect on the time of feeding in Whimbrel. Moonlight was clearly the factor conditioning the occurrence of nocturnal foraging on territories by both species. Foraging strategies and the type of prey and substrata explain why the incidence of night foraging varied with moonlight in territorial Willets and Whimbrels and not in non‐territorial individuals.
Movements of radio‐tagged Common Buzzards Buteo buteo in their first year
Authors: WALLS S. S. , KENWARD R. E.
Published: April 2008

The movements of 96 radio‐tagged juvenile Common Buzzards Buteo buteo were studied during 3 years in Dorset, southern England. Contrary to previous studies which implied that Common Buzzards are territorial, we found that 39% foraged within 1 km of the nest during their first winter, presumably within their parents' home range. Most (72%) of those that did not disperse were recorded making brief excursions during August and September, before opting for a “stay‐at‐home” strategy. There was no significant difference between the sexes in the tendency to make excursions or disperse, but females dispersed further than males. Buzzards which dispersed early tended to settle significantly farther from their nests than did late dispersers. Long‐term radio‐tracking has shown that 72% of the dispersing birds returned towards their natal area in the following breeding season. Such philopatry may be an important hindrance to avian recolonization following local extinctions.
Nest site characteristics of four sympatric species of hornbills in Khao Yai National Park, Thailand
Authors: POONSWAD PILAI
Published: April 2008

Characteristics of nest sites, nest trees and nest holes were documented for four sympatric species of hornbills in Khao Yai National Park: the Great Buceros bicornis. Wreathed Rhy‐ticeros undulatus, Oriental Pied Anthracoceros albirostris and Brown Hornbills Ptilolaemus tickelli. Nearly all hornbills nested in cavities in the trunks of at least 13 different genera of living trees. Sixty percent of the 80 nests found were in two tree genera, Dipterocarpus (34%) and Eugenia (26%), which comprised only 7% and 3%, respectively, of all large trees in 302 sample plots. Hornbills tended to prefer holes high in large, emergent trees for nesting, except for the Brown Hornbills, which preferred nest holes within or below the main forest canopy (15–25 m high). Most nest sites were between 700 and 800 m a.s.l. (79% of the total of 80 nests). Brown Hornbill nests were located in areas with a significantly higher altitude than were those of the Oriental Pied Hornbill. Hornbills tended to select nest entrances according to their body size, and all four hornbill species used oval to elongated nest entrances, with the Great Hornbill preferring the most elongated entrances. Hornbills did not select a specific nest entrance orientation.
Utilization of offal and discards from “finfish” trawlers around the Falkland Islands by the Black‐browed Albatross Diomedea melanophris
Authors: THOMPSON K. R. , RIDDY M. D.
Published: April 2008

Multinational fisheries operating in the vicinity of the Falkland Islands currently take c. 90,000 tonnes of true fish (“finfish” as opposed to squid) per annum, including hakes Merluccius spp., Southern Blue Whiting Micromesistius australis, Hoki Macruronus magel‐lanicus and Red Cod Salilota australis, and generate substantial quantities of fisheries waste in the form of discards and offal. This paper examines the use made of this waste by scavenging Black‐browed Albatrosses Diomedea melanophris which breed in the Falklands. The various types of waste produced are described and their consumption by scavenging albatrosses is quantified. The results indicate that Black‐browed Albatrosses obtain c. 8000 tonnes of food per annum from this source, of which two‐thirds is offal and the remainder whole discards. The energy content of this waste is equivalent to 4.4% of the estimated total annual energy requirements of the Falklands Black‐browed Albatross population. However, as the fishery is a greater predator of finfish stocks than are the albatrosses, its long‐term impact may be detrimental to these birds.
The ecology of mangrove forest birds in Peninsular Malaysia
Authors: NOSKE RICHARD A.
Published: April 2008

The density, distribution and feeding ecology of birds of mangrove forests in Selangor on the west coast of Peninsular Malaysia were investigated between February and May 1989. Excluding aerial hunters and wading birds, 47 species were recorded from four mangrove forest sites in Selangor, though undoubtedly some rarer species were missed due to the brevity of the study. The estimated density of birds, using fixed‐width transects, ranged from 15 to 26 birds per ha. One quarter of all birds counted belonged to just one species, the Ashy Tailorbird Orthotomus ruficeps. Excluding ground feeders (three species), four foraging guilds were recognized among 17 of the commonest bird species: obligate foliage‐foraging insectivores (seven species), bark‐foraging insectivores (four), facultative nectar‐ivores (five) and aerial hawkers (one). Species within the first and third guilds apparently were partitioned by foraging technique and heights, while those of the second guild (woodpeckers) differed mainly in their selection of plant species. The horizontal distribution of several species corresponded to the zonation of mangroves. Avifaunal differences between sites reflected differences in forest floristics. The greatest number of species occurred at the dry landward edge site, which supported seven bird species not encountered elsewhere in Selangor. This habitat has almost completely disappeared from much of the peninsula owing to land reclamation. Four of the six resident mangrove‐specialized bird species in Selangor were regularly recorded at two or more sites, another (Greater Gol‐denback Woodpecker Chrysocolaptes lucidus) occurred at only one site and the last (Ruddy Kingfisher Halcyon coromanda) was never recorded. Two species of sunbirds probably play an important role in the pollination of several species of mangroves. The colonization of anthropogenic habitats by many mangrove‐dwelling bird species is attributed partly to their generalized foraging niches, which may have evolved in response to regular fluctuations in food availability and the dynamic physiography of mangrove communities.
Breeding and survival of New Zealand Pigeons Hemiphaga novaeseelandiae
Authors: CLOUT M. N. , KARL B. J. , PIERCE R. J. , ROBERTSON H. A.
Published: April 2008

The breeding and survival of New Zealand Pigeons Hemiphaga novaeseelandiae were studied by radiotelemetry at three contrasting native forest sites in the North and South Islands of New Zealand. At each site, mean annual productivity was low (0‐0.12 fledglings/adult) in relation to the mean annual rate of adult mortality (0.18‐0.53). Losses of eggs and chicks to introduced mammals were the main identified causes of nest failure. Causes of adult mortality included episodic predation by introduced mammals and apparent starvation in spring at one site. At the most intensively‐studied site (Pelorus Bridge), where 75 birds were radiotagged over 7 years, there was a marked annual variation in breeding success (0‐0.3 fledglings/adult), including one season (1986–1987) when no breeding activity was detected at all. New Zealand Pigeons were legally hunted in the past, but our results indicate that harvesting is unlikely to be sustainable under current ecological conditions.
Do avian and mammalian nest predators select for different nest dispersion patterns of Fieldfares Turdus pilaris? A 15‐year study
Authors: HOGSTAD OLAV
Published: April 2008

The Fieldfare Turdus pilaris is an open‐nesting passerine that breeds either solitarily or in colonies. The nest‐spacing pattern of this species in a subalpine homogeneous Birch Betula pubescens forest in central Norway (c. 63°N) was studied during the period 1980–1994. Nest‐spacing patterns varied annually, and the number of Fieldfare colonies present (0–6) within a 3.5‐km2 study area was positively correlated with the annual density of small rodents and the birds' fat index and mean clutch size. After the rodent population crashes, prey switching seems to occur among mustelids. The nest‐spacing pattern of Fieldfares in the Birch forest therefore provides indirect support for the alternative prey hypothesis. Since the nest predation rate in Fieldfares is density dependent, and since their use of ejected faeces in communal defence may be detrimental, even lethal, to avian but not mammalian predators, it is suggested that a high density of mustelids results in selection for solitary breeding, whilst a predominance of avian predation risk selects for colonial breeding by the Fieldfare. The physical condition (fat index) of the Fieldfares is apparently a contributing factor in determining their nest dispersion pattern. The proportion of colonial nesting pairs was negatively correlated with the Fieldfare density and indicated a distributional pattern in a patchy habitat in agreement with the ideal free distribution theory.
Site tenacity and survival rates of Wrens Troglodytes troglodytes and Treecreepers Certhia familiaris in a Nottinghamshire wood
Authors: PEACH WILL , FEU CHRIS DU , McMEEKING JOHN
Published: April 2008

Mark‐recapture data from 20 years of standardized mist‐netting were used to investigate site tenacity and adult survival rates of Wrens Troglodytes troglodytes and Treecreepers Certhia familiaris in an English woodland. Within breeding seasons, a high proportion of Wren (but not Treecreeper) recaptures occurred in the same part of the wood as the original capture. Between breeding seasons, a high proportion of recaptures of adult males (but not of adult females) occurred in the same part of the wood as the original capture. Both species experienced exceptionally high mortality during the severe winters of 1978–1979 and 1985–1986, and, in the case of Wren, all or almost all birds which had previously bred in the wood probably died. Outside of these two cold winters, apparent (minimum) adult survival rates of Wrens and Treecreepers showed very different temporal patterns of variation. Wren survival rates were negatively correlated with the number of snow days in winter, whilst Treecreeper survival was negatively correlated with the amount of winter rainfall. After allowing for the influence of winter weather, apparent survival rates of adult Wrens were density dependent, indicating that either mortality or permanent emigration out of the wood was density dependent. There was some evidence from British and Irish ringing recoveries that movements of adult Wrens may be density dependent. The apparent survival rate of adult Wrens was probably an important factor determining the size of the local breeding population.