Production and perception of birdsong critically depends on early developmental experience. In species where singing is a sexually dimorphic trait, early life song experience may affect later behavior differently between sexes. It is known that both male and female songbirds acquire a life-long memory of early song experience, though its function remains unclear. In this study, we hypothesized that male and female birds express a preference for their fathers’ song, but do so differently depending on the developmental stage. We measured preference for their father’s song over an unfamiliar one in both male and female Bengalese finches at multiple time points across ontogeny, using phonotaxis and vocal response as indices of preference. We found that in males, selective approach to their father’s song decreased as they developed while in females, it remained stable regardless of age. This may correspond to a higher sensitivity to tutor song in young males while they are learning and a retained sensitivity in females because song is a courtship signal that is used throughout life. In addition, throughout development, males vocalized less frequently during presentation of their father’s song compared to unfamiliar song, whereas females emitted more calls to their father’s song. These findings contribute to a deeper understanding of why songbirds acquire and maintain such a robust song memory.

Differential cross sections have been measured for nucleon-isobar production and elastic scattering in p -p interactions from 6.2 to 29.7 GeV/c in the laboratory angle range 8 < O , ,

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others. The total cross section for production of observable strange particles by protons increases more rapidly with A, from C to Pb, than in the case of production by pions. The lower cross section and more rapid variation with A indicate that indirect production of strange particles by intermediate pions accounts for a significant fraction of all strange particles produced by protons, even in carbon. An estimate of the total protonnucleon direct production of observable strange particles (A 0 , 0i°, 2^->Tr ± +n) giving a reasonable fit to the observed cross sections is 0.09±0.06 mb.A comparison of the cloud chamber results with the 7-ray yields observed at 90° from points downstream from Cosmotron targets indicates satisfactory agreement between the results of the two entirely different techniques of observing strange particle production. This strengthens the evidence that the y rays are indeed the result of strange particle decays. The observed A dependence is in good agreement, giving greater weight to the cloud-chamber evidence that strange-particle production increases more rapidly with A than the total inelastic cross section from C to Pb.It is hoped that the angular and momentum distributions will serve as a guide to those who contemplate experiments making use of strange particles produced by -3-Bev protons. Preliminary results from a Monte A new measurement of the branching ratio (TT + -> e + +v)/(ir + ->/JL + -{-V) has been completed. A doublefocussing magnetic spectrometer was used to observe the spectra of electrons emitted in -K decay and in ix decay. The scintillation pulses from the pion and its decay electron were recorded on a travelling-wave oscilloscope. Timing and pulse-height measurements were used to distinguish good events from accidentals. The total number of n-e events recorded in this experiment was 1346, of which 6% were accidentals and 5% were ir-jji-e contamination. The branching ratio obtained from an analysis of the data over the ir-e and \x-e distributions and corrected to include all decay electrons was (1.21 ±0.07) X10~4. This is close to the result expected for a universal V-A interaction. Kinoshita's calculation, taking into account radiative effects, gave 1.23 X10" 4 . Our data also gave for the mean life of w decay r 7r = (25.6±0.8)X10~9 second.