No description available.

No description available.

The breeding and feeding ecology of the Swallow, Hirundo rustica, and the Sand Martin, R. riparia, in Central Scotland is described, with particular reference to the constraints imposed by environmental conditions. The time and energy investment in reproduction was examined for all stages of the breeding season in a wide variety of environmental conditions. Brood sizes were manipulated to change the investment of each parent in the brood. The D2018 technique was used to measure flight costs (0.0848 kcal g-l h-1 for the Swallow, 0.1288 kcal g-l h-1 for the Sand Martin) and the rate at which each species collected food under a variety of conditions was examined (mean values were 0.14 assimilable kcal min-1 for the Swallow, 0.05 assimilable kcal min-1 for the Sand Martin). These data, along with measurements of the nestlings' daily energy requirements, were used to investigate energy balance and the consequences for the timing and level of each breeding attempt. It is suggested that the Swallow lays later than the Sand Martin because (a) it takes larger insects and does not lay until these become abundant and (b) the female Swallow incubates alone whereas both Sand Martin sexes incubate, hence the Swallow defers laying until the risk of encountering bad weather during incubation is low. On 65% of the days on which measurements were made Sand Martins were unable to feed adequately a brood of five or more nestlings (31% of days for the Swallow) because foraging rates were depressed by bad weather. The risk of encountering bad weather is thus likely to limit the upper level of brood size. Energetics data are used to show that parents feeding nestlings maximise the net intake rate of energy rather than that of nutrients (protein, sulphur or calcium). The Swallow's diet includes nonpreferred small items, especially when these are relatively abundant, even when the preferred large items are available - contrary to predictions of optimal foraging models. It is shown, however, that foraging effiency is high when small items are taken. In agreement with central place foraging theory the bolus size of Sand Martins is mainly determined by the distance travelled to the feeding site. This is not always the case, however, since patch and prey quality and the search methods employed have a greater influence on the bolus size of the Swallow. Overall, the study allowed the scope for breeding activity for hirundines under different conditions to be defined and showed the importance of each species' reproductive and foraging strategies in optimising the number of offspring produced.

This thesis investigates the ecology, taxonomic affinities and conservation management in Sierra Leone of a threatened West African forest bird, the White-necked Picathartes Picathartes gymnocephalus, which has not been previously studied in detail. The incubation and nestling periods (20 and 25 days) respectively were longer than is usual for most tropical passerines. In most cases, one clutch of two eggs was laid between June and December, immediately followed by moult between January and May (the dry season). Peaks in egg laying occurred 1-2 months after the maximum monthly rainfall. Both parents cared for the young and fed nestlings disproportionately more earthworms, frogs, millipedes and earwigs in relation to their abundance in the environment. Nestlings fledged when still as much as 30% below adult size. Food abundance peaked in both forest and farmbush (forest regrowth) habitat at the start of the wet season and in the early part of the dry season; coinciding with the period immediately prior to egg-laying and with dispersing fledglings respectively. Potential Picathartes prey were more abundant in farmbush than forest habitat. The proportion of eggs laid that resulted in fledged young was 22.9% and productivity was 0.22 chicks per adult. Nest predation was the main cause of nest failure but infanticidal behaviour played a significant role. A substantial number of non-breeding birds were apparently present in populations and infanticidal behaviour may have been a consequence of competition for limited nest sites. Population density was estimated as 0.37 individuals km-' and the total population in Sierra Leone as about 1100. Local populations in forest reserves are close to the theoretical minimum for long-term viability in all cases but populations are apparently stable or declining only very slowly. Abandonment of colonies was associated with habitat degradation but there was also evidence that Picathartes may be fairly tolerant to disturbance in some areas. Phylogenetic analysis using mitochondrial DNA of the cytochrome b gene suggests that Picathartes is more closely related to the thrush-babbler assemblage than the crows.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Frank Johnson, Florida State University, College of Arts and Sciences, Department of Psychology. Title and description from dissertation home page (viewed June 16, 2004). Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains vi, 57 p. : ill. Includes abstract. Includes bibliographical references.

No description available.

No description available.

The predation strategies of four species of aerial feeding bird, the Swallow, Hirundo rustica, Sand Martin, Riparia riparia, House Martin, Delichon urbica and Swift, Apus apus, are examined during their breeding season in Britain. The abundance of aerial insects upon which they feed increases in April and reaches a plateau in May which is maintained until September. Aerial insect density is higher nearer the ground, the spring rise in abundance occurs earlier, a greater proportion of larger insects are available and insect numbers fluctuate less than at higher levels. The arrival times of the different predator species into the breeding area are staggered and this is linked to their preferred prey and feeding station, and to the distribution of aerial insects. Throughout the breeding season the four species of bird are ecologically isolated with respect to feeding station in the air-space and various characters of the insect prey, primarily size and mobility. It is suggested that to coexist they segregate along a combination of axes of the feeding niche, although segregation in air-space may be the most effective. Morphological adaptation to feeding niche is shown for tail shape, wing-length and bill shape, which respectively influence manoeuvrability, mode of flight and prey handling ability of the predators. Both Sand Martin and Swallow show increases in their prey size and mobility niche breadths in favourable feeding conditions whilst all four species simultaneously show decreases in air-space niche breadths. It is postulated that both within and between species there is a tendency to switch between patch specialisation and prey specialisation. Current theories of optimal patch and prey choice are discussed in relation to this hypothesis. Under very adverse conditions prey size overlaps are small and, when they increase, air-space overlaps simultaneously decrease. This suggests competition between aerial feeding birds in adverse conditions. Swallows deliver more meals per unit time to larger broods, with an increase in the feeding rate of the male most evident. Males also increase their feeding rate to second broods, but these receive the same amount of food as first broods indicating a seasonal decline in meal size. There is a seasonal decline in size of prey items even though a higher density of available large (> 5 mm body length) insects occurs during second brood feeding. It is shown that the largest insects are in patches too far from second brood nests to be profitable. For first and second broods an optimal foraging strategy is to choose patches with the largest mean insect size, if the patches are within a given distance from the nest. Selection of an optimal size for fast-flying taxa is influenced by time and energy costs of pursuit. It is suggested that rearing larger than normal broods is constrained by the requirement of equal parental investment and the extra reproductive cost likely to be incurred by the male bird. Based on a very small sample of nests it is tentatively suggested that in colonial nesting Sand Martins there is an advantage in nesting early, with more birds feeding communally to aid location of food concentrations. Because individuals with centrally placed burrows are more able to minimise time spent deterring predators, and because early centre nesters suffer less time loss through competition at the nest-site, these same individuals have more time for locating other feeding birds and food concentrations. Thus the early season, centre colony nesters may collect more food per unit time and raise more off-spring. Comparison of aerial feeding bird communities in three zoogeographical regions indicates that selection for characters contributing to mode of flight and manoeuvrability are more important than selection for bill character. In Africa the Palearctic species maintain essentially the same feeding stations as in their breeding season although the air-space niche breadths show contraction and overlap is reduced except between Swift and House Martin. The indigenous species have different feeding stations and small air-space niche breadths, and where overlap is high the species involved apparently do not breed during the "winter" of the Palearctic species, possibly because of food shortage. The prey size niche breadth of the Swallow, H. rustica is very similar between Britain and Africa. With many more species utilizing this niche axis, compensation is likely along another axis, probably air-space.

Thesis (M.S.)--University of Wyoming, School of Renewable Natural Resources, 2005. / Title from screen (viewed on April 18, 2008). Includes bibliographical references. Also available via World Wide Web.