THE MIGRATION PATTERNS OF QUELEA QUELEA IN AFRICA

Red-billed Queleas migrate, at the beginning of the wet season, away from their dry-season concentration areas and towards areas where rain started several weeks earlier. Considerable fat deposits are accumulated for this “early-rains migration”. The direction taken by the migrants, the distance they must fly, and the timing of the movement are dependent upon the timing of the rains and the way the rain-front moves. On the return “breeding migration” individuals in breeding condition stop to breed (in large aggregations) wherever they find conditions suitable for the founding of colonies. The location of the colonies can vary greatly from year to year. The migrations performed by several populations, in different parts of Africa, are predicted on the basis of general rainfall patterns, and the predictions tested against the facts available. There is evidence that individual females are able to produce a succession of broods in the same breeding season, at colonies which may be very far apart, and probably with different mates. The adaptive value of this “itinerant breeding” is discussed. Many other bird species, which breed at a particular phase of the wet-season/dry-season cycle, are expected to perform similar “itinerant breeding”.     

THE LEVEL OF RESERVE PROTEIN AS THE PROXIMATE FACTOR CONTROLLING THE TIMING OF BREEDING AND CLUTCH-SIZE IN THE RED-BILLED QUELEA QUELEA QUELEA

Changes in the fat and flight muscle protein reserves of adult Red-billed Queleas Quelea quelea were followed in two colonies in Tanzania and Botswana. At the start of a breeding attempt the protein reserves were higher that at any other time of the year, particularly in females which had heavier flight muscles (non-fat dry weight) than did the (larger) males at that time. The pre-breeding increase in the labile component of the muscle protein (the actual protein reserve) is calculated at 80% for females, but only 14% for males. The fat reserve was only increased slightly at the beginning of the breeding attempt.
In both sexes, though for different reasons, the protein and fat reserves fell rapidly during the first few days of the attempt, in some individuals to dangerously low levels. During the incubation period there was rapid recovery while the situation during the rearing period appeared to vary between colonies.
It is proposed that the proximate control of breeding is provided by the individual's own body condition, and particularly the state of its protein reserves. No environmental releasers are required for the birds to breed at the appropriate time of the year.
Individual females producing two, three and four egg clutches differed in the rate at which their reserves fell during egg formation. The results are used to support the view that in this quelea the actual clutch-size produced on any occasion is the largest the female can produce before becoming too enfeebled. Thus, clutch-size appears to be determined phenotypically downward from a maximum which is indirectly under genetic control.     

THE BREEDING BIOLOGY OF THE BLACK-FACED DIOCH QUELEA QUELEA IN NIGERIA

A study of the breeding biology of Quelea quelea in Nigeria, and particularly at a large breeding colony near Lake Chad, showed that losses of eggs and young were extremely small. 95% of eggs laid hatched successfully, and 87% give rise to fledglings. Nestling deaths were density-dependent and apparently due to starvation.
The incubation period was 10 days or less. By day, eggs were heated to 34°- 37° C. by the sun; at night the females incubated. The nestlings were initially fed mainly on insects, their diet gradually changing to one of seeds—mostly of the grass Echinochloa pyramidalis . The deep body temperatures of young birds were determined. It is suggested that the nestlings left the nest after, on average, 11¹/₂ days to escape intolerable temperature conditions in the nest.
Fat reserves were accumulated by nestlings and fledglings, and were utilized when the young became independent. The adults put on fat during the incubation period and lost it during the time spent feeding nestlings.
It is concluded that the most common clutch-size of Q. quelea , which is everywhere three, corresponds to the largest number of young the parents can normally nourish. This conforms to Lack's theory on the significance of clutch-size, and gives no support to Skutch's opinion that the theory does not apply to tropical birds.     

THE FOOD AND FEEDING HABITS OF GOLDENEYE BUCEPHALA CLANGULA IN GREAT BRITAIN

The food and feeding habits of Goldeneye Bucephala clangula are described, based on the analyses of 51 stomach contents and a brief review of the literature. The type of food taken depends on the type of habitat being used, the availability and size of the food items and on the methods of feeding—though animal material largely predominates.
In estuarine and coastal areas, small crustaceans and in particular Carcinus maenas figured highly in the diet, with some molluscs and small fish. In two brackish-water feeding birds, seeds formed the bulk of the food, some caddis-fly larvae also being taken. In freshwater feeding birds insects predominated, particularly Trichoptera larvae, chironomid larvae and the adults of Corixa spp. Some crustaceans ( Asellus, Gammarus ) and small molluscs were taken and occasionally small fish. A small amount of plant material was taken in the form of seeds, mainly Potamogeton spp.
The relation between Goldeneye and fishing interests is briefly discussed and it is concluded that fish normally form a small part of the diet and it is unlikely that any serious depredation of fish stocks is common.     

Assessment of territory quality and its effects on breeding success in a migrant passerine, the Wheatear Oenanthe oenanthe

This paper examines how a returning migrant assesses the quality of an area as a breeding territory before the period of peak food demand and how effective the assessment is in terms of breeding success. Male Wheatears Oenanthe oenanthe return from Africa to choose territories in the Breckland of eastern England about March, females arriving shortly after males. The food supply was predictable: prey densities during the breeding period (egg-laying to chick independence) were strongly correlated with prey densities at the same sites during the period of arrival and territory establishment. Prey densities were also related to vegetation structure, averaging highest on short turf. Male arrival date and territory size were not significantly related to prey density but were strongly related to vegetation structure, implying that birds used vegetation as an indirect clue to prey availability. Neither territory size nor nest spacing appeared to affect nest losses caused by predators. The major variations in number of young fledged (other than predation) were caused by the number of nestlings hatched and presence of a second brood. Both early arrival and an early first brood improved first-brood success and were necessary for a second brood. Not all birds which arrived early bred early enough for a second brood. First-brood hatching date was strongly negatively correlated with pre-breeding prey availability but not significantly related to vegetation structure. Thus by using vegetation as a clue to habitat quality, some pairs suffered reduced breeding success. This result implies that birds may not be able adequately to assess prey density directly at the time of territory establishment. The critical period for food availability may not be the period of peak demand (nestling period), when food is relatively abundant, but is probably the pre-breeding period when females must accumulate reserves for eggs and when the food supply is poor. Food supply during this period may determine the timing of breeding and the ability to rear a second brood, and may thus have a greater effect on breeding success.     

A RADAR STUDY OF TERN MOVEMENTS ALONG THE COAST OF GHANA

During spring and autumn 1970 and 1971 the movements of terns off the coast of Ghana near Accra were studied by radar. In autumn, dense movements were recorded within 22 km of the coast both day and night from July to early December. Fluctuations in the magnitude of the movements suggest that the terns were on passage through the Gulf of Guinea. Simultaneous to these movements were roosting flights into shore roosts and both movements appeared independent.
In contrast, no spring movements along the coastline were detected either by radar or visually from the land. Although small tern flocks probably moved westwards within 22 km of the coast, but outside their detectable radar range, the results suggest that the majority of terns return through the Gulf of Guinea by a different route from that taken in autumn.
The difference between spring and autumn movements correlates well with the seasonal variation of the terns' food sources. In autumn, upwellings result in an abundant fish supply (sardines) in the surface waters close to land, whereas in spring, fish is abundant only well off shore such as at fronts (convergences) and upwellings (divergences) both of which have been located as far as 600 km from the coast.     

STUDIES OF THE DIEDERIK CUCKOO CHRYSOCOCCYX CAPRIUS IN THE TRANSVAAL

The migrant Diederik Cuckoo Chrysococcyx caprius was studied on a 72–acre area near the Klein Jukskei River near Johannesburg from 1955–1958. The birds first arrive in early October, after which the males take up territories and call continually until February; subsequent calls up to April are probably made by young birds.
Courtship displays, which involve courtship feeding, and egg-laying follow the birds' arrival by about a month. The Red Bishop Euplectes orix was the species most commonly parasitized, with smaller equal numbers of Cape Sparrows Passer melanurus and Masked Weavers Ploceus velatus . The cuckoos' eggs differ according to the host species and in two cases hatched between ten and 14 days after laying. The chicks normally evict their hosts' offspring on the second or third day after hatching. The fledging period appears to be roughly 19–20 days, and there is a period of post-fledging care lasting between 17 and 38 days, during which the chicks are fed different foods by different host species (grass seeds by bishops; insects of different sizes by weavers and sparrows).
The fact that the eggs and the calls of the chicks vary according to their host species suggest the existence of three separate host-specific strains in this area. The incidence of brood parasitism in Red Bishops' nests varied from 7–50% and averaged 25%.     

COMMUNAL ROOSTING BEHAVIOUR OF THE AUSTRALASIAN HARRIER CIRCUS APPROXIMANS IN NEW ZEALAND

The Australasian Harrier Circus upproximans habitually roosts communally in New Zealand but not in Australia. As many as 100 birds can occupy a roost in a small area of swamp. They start to assemble about one hour before dark and communal aerial displays in the vicinity of the roost are an integral part of the roosting behaviour. Roosts may be occupied all the year round, non-breeding birds continuing to roost communally throughout the summer. In New Zealand the habit is neither connected with migration nor is it an anti-predator device. It is considered that the abundance of food caused by the spread of introduced mammals and the large increase of habitat created by European settlement has built the harrier population up to such a size that the number required to elicit the response of communal roosting occurs at all times of year in most districts. Numbers within individual roosts fluctuate throughout the year and it is suggested that communal displays before roosting may provide the necessary feed-back for the initiation of population adjustments.     

鸟类夜栖地选择研究进展

夜栖地可以为鸟类提供安全、舒适、温暖的夜间栖息场所。昼行性鸟类夜间视觉能力较差,对夜栖环境中潜在的威胁感知程度较低,导致其夜栖时常常处于被动和危险的环境中。鸟类通过选择适宜的夜栖地,进而达到充分利用夜栖地空间资源的目的。本文从鸟类夜栖地选择的行为适应性以及保温性、食物因子和安全性(隐蔽性)等3个影响因素,对国内外鸟类夜栖地选择相关研究进行综述,为今后该领域的研究提供更多思路。     

Long-term hoarding in the Paridae: a dynamic model

Using stochastic dynamic programming we modeled the hoardingand foraging behavior of tits and chickadees, Pandas, that areresident in the boreal forest at high latitudes. Here autumnshave a rich supply of seeds and temperatures are relativelymild, while winters are cold with short days and a low foodsupply. We assumed that parids have a memory of limited durationand that forgotten seeds accumulate in a bank that adds to thegeneral food supply in the hoarder's territory. Our model predictsthat birds should start "high-intensity" hoarding in early autumn,but not before that. Because of mass-dependent costs the birdswill keep their fat levels low during the autumn. When winterarrives they will carry more body fat, both for the long winternights and to hedge against the large effects of weather variationsin winter. After increasing the fat level at the start of winter,fat should gradually increase even more, to compensate for thediminishing food supply. Most hoarding occurs in autumn as away of building up the supply of long-term stores. Remembered,or short-term caches, may hedge against stochastic events inthe environment. Even though conditions are not beneficial forhoarding in winter, the birds still stored in winter to maintainlarger short and long-term hoards if environmental variationincreased. Almost all time in winter that not was spent foragingwas spent perching, mainly to avoid predation     

Spatial pattern of dry rainforest colonizing unburnt Eucalyptus savanna

Abstract The spatial pattern of dry rainforest and savanna tree species was analysed in a 1.56‐ha plot within an unburnt eucalypt savanna woodland in north Queensland, Australia. Rainforest colonization constituted only 1.3% of the basal area and mostly consisted of individuals less than 3 m high. The distribution of rainforest trees was highly clumped around the large savanna eucalypt trees. Ecological mechanisms generating the clumped distribution are discussed in light of evidence from this study and the literature. Herbaceous biomass was not reduced under trees, suggesting that relief from grass competition has not favoured rainforest colonization under tree crowns. Edaphic facilitation through nutrient enrichment under savanna tree crowns appears to be only minor on the moderate fertility soils of the area. The highly clumped pattern of colonizing dry rainforest may be a consequence of seeds dropped from birds roosting in savanna trees.     

The influence of substrate on the functional response of an avian granivore and its implications for farmland bird conservation

Few studies to date have considered the effect of substrate on the functional response of an organism feeding on prey of varying visibility. Intake rates of lone captive canaries, Serinus canarius L., were measured at varying seed densities on patches of either earth or short grass (<1 cm). Experiment 1, using pale seeds, found intake rates were significantly higher and search times significantly lower on earth than on grass. Two measures of crypticity (contrast in light reflectance as measured using a spectrophotometer and an experiment with humans) found pale seeds to be more visible on earth. The results from experiment 1 could be explained by this difference in crypsis. Experiment 2 used identical seeds to those in experiment 1 except they were dyed to match their backgrounds. The two measures of crypticity both found that black seeds were less visible on earth than green seeds were on grass. However, intake rates were still significantly higher on earth than grass. Seed colour preference, vegetation impeding movement, and differences in vigilance rates or seed accessibility could not explain this result. We discuss three other potentially explanatory mechanisms, the most likely of which was the greater surface area needed for scanning created by the structure of grass. Crucially, regardless of the mechanism(s) involved, many vegetated substrates share similar properties with grass (structural complexity and shiny surfaces which reflect light) and so the outcome of our findings are likely to extend to many natural situations. Conservationists wishing to encourage granivorous birds should consider enhancing food accessibility by providing uniform substrates, such as bare earth, for them to forage on. In addition, behaviour-based models should incorporate the effects of habitat into their equations of the functional response.     

On fruit eating by Scottish Red grouse

Fruit-eating behaviour of Red grouse was studied in the Grampians of Scotland from analyses of bird droppings for seeds and from direct observations of feeding birds. The commonest moorland species with edible fruits are blaeberry, Vaccinium myrtillus L., cowberry, Vaccinium vitis-idaea L., and crowberry, Empetrum nigrum L.
The fruit-frugivore interaction is not species specific, as grouse ate berries of all the fruiting species, but almost all individuals showed high fruit specificity for one type of fruit. Fruit selection is density-dependent and probably depends on the formation by grouse of a search specific image of the commonest fruit available in the feeding area. This is well known in polyphagous predator-prey interactions in animals but has not so far been reported in animal-plant feeding interactions.
We related fruit selection to both relative fruit abundance and plant cover. Some birds were feeding highly selectively on crowberries which were low in fruit abundance but had high relative cover. This indicated that the fruit resource had been large but had become depleted. Such birds would eventually lose their specific searching image and, following a short period of random search, would form new searching images.
The fruit cues and effect of density dependent selection on the evolution of fruiting behaviour was discussed.     

Photoperiodic regulation of food storing and hippocampus volume in black-capped chickadees, Poecile atricapillus

In seasonal environments animals organize their behaviour around annual cycles of resource availability. Wild black-capped chickadees are most likely to hoard food in autumn. At this time of year chickadees are also reported to have a larger hippocampus, a brain area important for spatial memory. This study examined how photoperiodic condition affects these seasonal changes. Captive chickadees were exposed to one of three treatments. Photorefractory birds were held on long days (19:5 h light:dark) and had small gonads. Photosensitive birds were held on short days (LD 9:15 h) and also had small gonads. Photostimulated birds were switched from short to long days and quickly entered breeding condition with large gonads. Photosensitive birds (on short days) stored more seeds than photorefractory birds (on long days). Photostimulated birds stored seeds at a high rate when on short days, but reduced storing when transferred to long days. These results indicate that long days inhibit storing regardless of gonadal condition. There were no differences between groups in hippocampal volume, indicating that photoperiod can produce changes in food-storing behaviour without affecting hippocampal size. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.     

The Effects of Early Feeding Experience on Long-term Seed Choice by Canaries (Serinus canaria)

Early experience has been found to have long-term effects on behaviour such as social imprinting and song learning. In this paper we investigate whether early experience with particular types of food can lead to long-term feeding preferences in canaries. For 8 wk following the onset of independent foraging, two groups of naive fledgling canaries were reared on different diets. One group had a choice of four seed types, while individuals in the other group received only one type of seed. After this training period, all the birds were given a mixed seed diet for a further 15 wk, and then their preference for the original seeds was tested. All six birds that had been given four seeds during the training period showed the same preference, namely: hemp > niger > millet > linseed. However, all the birds that had been trained on one seed type only, still preferred the seed on which they had been trained. After a further 23 wk on a mixed-seed diet, birds from the restricted early diet group showed no further preference for the seed on which they were trained, and their seed choice at this stage was similar to the birds that had received four seeds. We conclude that early experience can affect food choice in canaries for at least 15 wk, but is subordinate to other influences in the longer term.     

Ignorant hooded crows follow knowledgeable roost-mates to food: support for the information centre hypothesis

Communal roosting in birds may function to enhance foraging efficiency as explained by the information centre hypothesis, which predicts that successful foragers return from the roost to the rewarding food patch and that birds ignorant of this food follow knowledgeable roost-mates. We tested these predictions by exposing 34 radio-tagged, free-ranging, flock-living hooded crows (Corvus corone cornix) to a novel experimental set-up mimicking a superfluous food patch with maximum temporal and spatial unpredictability Each replicate lasted two days and was located on a new site. Data were collected during ten replicates over three years. First, a crow was more likely to visit the experimental food patch on the second day when it had been there on the first day. Second, when a crow had not been at this food patch on the first day, it was more likely to visit it on the second day if it had roosted together with a crow that had been there on the first day, but only if this knowledgeable roost-mate returned to the food patch on the second day. Our results support the information centre hypothesis and suggest that communal roosting might function to enhance foraging efficiency in hooded crows.     

THE FOOD AND FEEDING HABITS OF TUFTED DUCK AYTHYA FULIGULA

The food and feeding habits of Tufted Duck Aythya fuligula are described, based on field observations and on the analyses of the stomach contents of 95 birds, all but one of them having fed inland; 57 were collected from a gravel pit near London, 28 from Northern Ireland and 9 from a number of English inland waters, in the shooting seasons 1959-60 and 1960-61.
The London birds in both seasons had fed primarily on molluscs, mainly Dreissena polymorpha. The Northern Ireland birds, where D. polymorpha does not occur, had a more variable diet, again mainly molluscs, but with some crustaceans, insects and plant seeds. The English birds had a similarly variable diet with the emphasis on crustaceans ( Asellus spp.) and with some molluscs, insects and plant seeds. Brief information is given on the food of young birds.
It is suggested that the spread of D. polymorpha may be one of the factors explaining the recent spread of the Tufted Duck in certain areas. It appears that where one particular food such as D. polymorpha is not plentiful a more variable diet is taken, though molluscs always figure prominently. The type of food taken depends on the type of habitat used, the availability and size of the food items and on the methods of feeding.     

THE FOOD AND FEEDING HABITS OF SHELDUCK TADORNA TADORNA

The food and feeding habits of Shelduck Tadorna tadorna are described, based on the analyses of the viscera of 30 birds collected under special licence, and of 18 birds found dead or dying during the cold weather of 1963, on faecal material from eight incubating birds, on field observations and on the literature. The birds came from a number of different localities and from each month of the year, apart from July.
The mollusc Hydrobia ulvae (Pennant) was found in all 46 birds which contained food, and it is quite obvious, and this is confirmed by the literature and by faecal analyses, that this is the most important food item during much of the year and in many different localities. Other species eaten included the bivalve Macoma balthica , the amphipod Corophium volutator , the ragworm Nereis sp., the alga Enteromorpha , and occasionally the seeds of various plants.
The importance of H. ulvae is examined in the light of its distribution and numbers, which may be a strong controlling factor in concentrating Shelduck in certain areas at certain times of the year.
The feeding behaviour of Shelduck, and a number of other birds, is apparently closely related to the cyclic behaviour pattern of the main food species, H. ulvae .
It seems that Shelduck have a rather fixed type of feeding behaviour which exploits only one feeding niche and therein mainly one food item. Any event (prolonged gales or very cold weather) which prevents the bird from using that niche can be the cause of heavy mortality.     

Space use and agonistic behaviour in relation to sex composition in large flocks of laying hens

Some authors have found indications of subgroup formation when domestic fowl are forced to live together in large flocks, while others have not. In this study experiments were carried out to test the hypothesis that hens in large flocks have home ranges in parts of the pen and that they form subgroups. We also studied if this is influenced by males. In a tiered aviary system (density averaged 16 hens/m(2) of floor area) eight flocks of 568+/-59 ISA Brown laying hybrids were kept in pens. Half of the pens contained 1 male per on average 24 females (mixed flocks). At peak production (36-53 weeks of age) four females roosting closely together for about 14 days and four females roosting far apart from each other were taken out from each flock and put together in separate groups in small pens. Their agonistic behaviour was studied for 2 days before they were put back. This was repeated with new birds, resulting in 16 small sample groups being studied. At 70 weeks, three groups of 10 females per flock roosting closely together in different parts of the pen were dyed with different colours and their locations were observed for 2 nights and 2 days.The incidence of aggressive pecks during day 1 among birds that had been roosting close to each other tended to be lower (P=0.05) than among birds that had been roosting far apart. This effect was not significant among birds from all-female flocks, but among birds from mixed flocks (P<0.05). However, this indicates a recognition of roosting partners and possibly also a rebound effect of the males' reduction of female aggressiveness towards strangers. Irrespective of sex composition in the flocks, birds marked while roosting at the ends of the pens were significantly more often observed within these areas than in other areas of the pen during daytime and came back to the same roosting sites at night (P<0.05-P<0.001). This was not the case for birds from the middle of the pens, where the distribution in the pen in most cases did not differ from random. These results show that laying hens in large groups are rather constant in their use of space, which indicate the presence of home ranges. However, environmental features that facilitate localisation may be important. In summary, we think that these findings indicate the existence of subgroup formation.     

DIFFERENTIAL GROWTH AND BODY COMPOSITION IN ALTRICIAL PASSERINES

The differential development of various body organs and of fat, water, and other constituents was studied in three species with altricial nestlings—Blue Tit, House Martin and House Sparrow.
In all species resources available at each stage of the nestling period were allocated to those components of most use to the nestlings at the time, although due regard was paid to future needs. Components associated with the ingestion and assimilation of food, such as the mouth, gizzard, intestine and liver, developed early in the nestling period whilst locomotory components, such as wings and pectoral muscles, developed late. Similarly, body plumage needed for insulation developed ahead of the locomotory remiges and rectrices, but only after much of the nestlings' growth in size had been completed.
The water index (water content/lean dry weight) provided a consistent index of tissue and nestling maturity amongst young of different nutritional status. This index was very similar for all three species when age was expressed as a fraction of the nestling period.
Both absolute fat content and the fat index (fat content/lean dry weight) increased with age. The adaptive value of these trends and of interspecific differences in fat index is discussed.
The results are seen as consistent with both the physiological bottleneck models of avian growth rates. It is suggested that the growth patterns of birds may be dominated more by ecological considerations affecting all aspects of the development mode than by internal physiological constraints affecting growth rates alone.