PREY TAKEN BY TAWNY OWLS DURING THE BREEDING SEASON

The diet of Tawny Owls during the breeding seasons 1949-52 in Wytham Woods, near Oxford, was determined (a) from analysis of pellets collected, (b) from observation at night, by the use of a red floodlight, of prey brought to the nest and (c) from records of prey left in the nest made during daily visits to weigh the young.
Analysis of pellets showed an increase in the proportion of moles and beetles (mainly cockchafen) in the diet after the first week of May (the time when, on average, the young owls are about half grown) and a decrease in the proportion of mice and voles.
These changes were confirmed in a more emphatic way from observations of food being brought to the nest and from records of prey left in the nest.
This greater emphasis suggests that tho food brought to the young may differ from that which the adults eat themselves.
The fact that no moles were observed being brought to nests at night, wherean many were recorded as surplus prey in the nest, showed that diurnal hunting is regular during the breeding reaaon.
A true assessment of prey taken by Tawny Owls during the breeding season should be based both on analyeis of pellets cast by the adults and on records of food brought to the nest throughout 24 hours. Such records could best be obtained with an automatic camera and flash and a design of nest-box which is described.     

Studies of oligonucleotide interactions by hybridisation to arrays: the influence of dangling ends on duplex yield.

Effects of dangling ends on duplex yield have been assessed by hybridisation of oligonucleotides to an array of oligonucleotides synthesised on the surface of a solid support. The array consists of decanucleotides and shorter sequences. One of the decanucleotides in the array was fully complementary to the decanucleotide used as solution target. Others were complementary over seven to nine bases, with overhangs of one to three bases. Duplexes involving different decanucleotides had different overhangs at the 3' and 5' ends. Some duplexes involving shorter oligonucleotides had the same regions of complementarity as these decanucleotides, but with fewer overhanging bases. This analysis allows simultaneous assessment of the effects of differing bases at both 5' and 3' ends of the oligonucleotide in duplexes formed under identical reaction conditions. The results indicate that a 5' overhang is more stabilising than a 3' overhang, which is consistent with previous results obtained with DNA overhangs. However, it is not clear whether this is due to the orientation of the overhang or to the effect of specific bases.     

Speciation in monogonont rotifers

Monogonont rotifers are cyclical parthenogens livingin limnic habitats with considerable seasonalvariation and often with island-like features. Theoccurrence of bisexual reproduction in these organismsmakes it feasible to define fields for generecombination, i.e. biological species. In thispaper, we analyze the structure of the diversity inmonogonont rotifers using several data sets: taxonomicand intraspecific diversity as reported inidentification keys, morphological variation reportedin ecological studies, and allozyme and matingbehavior patterns. Our analysis suggests that siblingspecies may be frequent in rotifers. Monogonontrotifers seem to meet conditions for an activespeciation, which might be particularly promoted byseasonal specialization and timing of bisexualreproduction.     

Dye standards, Part II.5: Pararosaniline (CI 42500)

The names and affiliations of the SRMTS members are cited in Part I: terminology and general principles,Histochem. J. (1992)24, 217–19.