As Qause's hypothesis suggests on theoretical grounds, ditrerenoes oan be shown to exist in the habitat, feeding niche, and in the nature and she of food taken by the British finches. Under experimentgl conditions, ohangem occur in the adult's seed choice which tend to inaream the proportion of lmge seeds in the diet. DSerenoe-9 in the extent and rapidity of these changea exist between the s p i e s , those with large bills changing more quickly than others.Development of seed husking technique WBB studied in the ch&chee and followed early mandibulation of the feathers. Experiments showed ditrerences in the time taken by adult chffiches to husk various eeeda, and in amount of kernel obtained from eaah for the -me husking effort.Compariaona were made by timing seed-husking in other species. Large-billed species husked the large seeds quickly and more effioiently than the small-billed birds. It is suggested that demonstrated differencea between the speaie-9 in seed seleotion depend largely on differences in bill structure that condition learning in the individual. Other faotors effecting food selection are age, seesonel change, diet restriction and soaial experience.

No abstract

No abstract

No abstract

A sophisticated radiotelemetry system was used to monitor continuously the temperature, relative humidity and the incidence of parental movement sufficient to admit light to, or turn the eggs in, the nest cup of (number of days recordings m parenthesis): Black Swan Cygnus atratus (68); Barnacle Goose Hrantal leucopsis (70); Whooper Swan Cygnus cygnus (28) and Greylag Goose Ansev anser (26). The following features were common to all the nests: (1) a slow rise in the temperature of the nest cup with the onset of incuhation; (2) a temperature gradient in the vertical plane of the nest cup throughout incubation; (3) a diurnal rhythm in the temperature and humidity of the nest cup, this being caused by bird behaviour rather than the ambient environment; (4) nesting materials dried out during incubation thereby accentuating the steepness of the diffusion gradient between a real egg and the atmosphere of the nest cup; (5) the eggs, which were turned between 0.594.95 times an hour, were rotated mainly around their long axes.