Geographic variation in female preference functions and male songs of the field cricket Teleogryllus oceanicus.

Male crickets (Teleogryllus oceanicus) produce a complex call consisting of two elements, the long chirp (three to eight sound pulses) followed by a series of short chirps (each with two sound pulses). There is significant geographic variation in the temporal structure of calls, and the long chirp is selected against by acoustically orienting parasitoids in some populations. Here we examine geographic variation in female preference functions for the amount of long chirp. In general, females prefer calls with greater proportions of long chirp, although the strength and nature of selection varied across populations. Variation in preference functions did not match variation in call structure. There was a mismatch between the proportion of long chirp produced by males in a population and the proportion of long chirp preferred by females. The convergent preferences of predators and females are likely to maintain genetic variation in song traits in parasitized populations. The apparent mismatch between preference and trait is discussed in relation to theoretical models of preference evolution.

Temporal and spatial variations in the behavior of shrubsteppe birds.

We documented patterns of activity and microhabitat use by breeding male Sage Sparrows (Amphispiza belli) and Brewer's Sparrows (Spizella breweri) in the semiarid shrubsteppe of northwestern U.S.A. to determine how their behavior varies in space and time and how these variations relate to environmental features. In analyses of several sites with multiple plots that were studied for 2-4 yr, the frequencies of activities and substrate use varied significantly with year, plot, and location. The major activities, foraging and singing, varied inversely with one another. Thus, although the general structure of the activity budgets of these species was stable (i.e. foraging and singing were always the most frequent activities), there was considerable variation in the quantitative details of their behavior in space and time. Using stepwise regression, we related these variations in behavior to variations in environmental features such as the densities of the same or other species, the number of species in the community, and coverages of the different substrate types. Few patterns emerged, and those that did were generally not in accord with our expectations. In particular, patterns of substrate use were not related to variations in coverages of those substrates. Sage Sparrows, for example, increased their use of sagebrush and grass with increasing grass coverage and with increasing densities of Sage Sparrows. Responses to both variables suggested nonlinear threshold patterns.We interpret the variations in behavior as indicating a loose coupling between behavior and proximate environmental conditions for these species. In such situations, the variability of behavior complicates attempts to test ecological hypotheses (e.g. behavioral niche partitioning) with data from a limited number of locations or years.