Visual and Auditory Conspicuousness in a Woodland Bird Community: a Quantitative Analysis.

Abstract

Summary.1. Quantitative observations were made in a Berkshire copse throughout a breeding season. Monthly coefficients of relative conspicuousness are given for each species, together with the coefficients for the previous year's study; it is therefore possible to present a mean coefficient from two seasons' work in the same habitat.2. The counts from which the coefficients are computed have been subjected to analysis and give the relative position of each species in the woodland stratum, being illustrated by a diagram showing the vertical graduation of the different niches. Closely related species obtain their food from different strata; the male inhabits a higher stratum than the female.3. It is shown how a coefficient of sexual conspicuousness can be obtained from the observed sex ratio.4. Song lends itself to quantitative treatment. Persistency varies less than might be expected, among the few examples given. A direct relation between song intensity and size of territory in monogamous territorial birds is suggested. It is shown how population density can affect conspicuousness.5. No attempt is made to ascribe a function to each aspect of coloration. It is suggested that birds are conspicuous in the spring rather than inconspicuous in the summer,