Bunting

Abstract: Habitat loss and fragmentation have led to a widespread increase in the proportion of edge habitat in the landscape. Disturbance-dependent bird species are widely assumed to benefit from these edges. However, anthropogenic edges may concentrate nest predators while retaining habitat cues that birds use to select breeding habitat. This may lead birds to mistakenly select dangerous habitat—a phenomenon known as an ''ecological trap.'' We experimentally demonstrated how habitat shape, and thus amount of edge, can adversely affect nest site selection and reproductive success of a disturbance-dependent bird species, the Indigo Bunting (Passerina cyanea). We did so within a landscape-scale experiment composed of equal-area habitat patches that differed in their amount of edge. Indigo Buntings preferentially selected edgy patches, which contained 50% more edge than more compact rectangular patches. Further, buntings fledged significantly fewer young per pair in edgy patches than in rectangular patches. These results provide the first experimental evidence that edges can function as ecological traps.

Abstract: Songs of the Indigo Bunting, Passerina cyanea, mostly from Kentucky and Michigan, were analyzed for species-consistent characteristics. These were compared to sampled Lazuli (P. amoena) and Painted (P. ciris) Bunting songs to identify genus-consistent characteristics and possible directions of behavioral evolution. Playback experiments tested song organization in terms of the species-recognition function. The initial three to six figures in Indigo song appear to be specialized in structure and function. Average frequency ranges and durations of song figures progressively increase at the beginning of the song, while silent intervals between figures progressively decrease. These characteristics appear to have developed at different times. Another initial specialization is the presence of "introductory" figure types that are only found in the first or second figure position in the song, while all other figure types are likely to appear at any position in the song. Introductory figures form separate identifiable peaks in distributions of figure frequency and duration. They have fewer subsegments (unidirectional frequency modulations) than other figures. A playback experiment suggested that the structural specializations of the first few figures are functional in gaining attention of the species. In addition to the initial attention process, two other separate processes apparently take place. A playback experiment showed that stimuli releasing the strong territorial defense behaviors are different from those attracting the Indigos. Since the fine detail of the figures is probably distorted across the territory, grosser structures of the song are thought to be responsible for the attraction process. These apparently involve many of the most species-consistent parameters of bunting song. Included are the frequency ranges of Indigo and Painted Bunting figures and whole songs, as well as the absolute position of the frequency range of Indigo figures. Some frequency characteristics of successive figures were found to be species-consistent in all three species of Passerina. Yet, particular figure types are not consistently found to be associated with one another in Indigo Bunting songs. Figure durations are very similar for the Painted and Lazuli Buntings, but the two individual Indigo population samples are different, even from each other. Silent intervals between Indigo Bunting figures are species-consistent and distributed into two significantly different groups: the intervals between repeated figure types and the intervals between different figure types. Lazuli Bunting intervals are not significantly different in this respect. The roles of different species-consistent factors were tested in three playback experiments. They involve figures that were different from wild Indigo figures in various respects, and yielded almost no responses from Indigo Buntings. A playback experiment demonstrated that territorial display and attack behaviors are dependent upon the fine structure of the Indigo Bunting figures. Other playback experiments in which the fine detail of Indigo figures had been manipulated, indicated that the cues which release strong territorial behavior are highly redundant. Consequently, the figure details were examined for species-consistent tendencies. These tendencies include the relationship between frequency and duration of the figure subsegments of all three Passerina species, and the number of subsegments per figure for the Indigo. Of special note is the distribution of Indigo Bunting subsegment durations, which tend to peak at 0.89 centiseconds and multiples of that value. A theoretical model of song organization, development, and evolution is based upon these species-consistent subsegment durations.

Abstract: 1 An earlier paper related bird species richness to hedgerows and other field boundary attributes including adjacent land use The study was over several years (winter and summer) at two sites, Huntingdon and Swavesey, in East Anglia UK 2 The present paper deals with similar relationships, but the bird variables used are the abundance of individual species, of groups of species (all finches, all raptors, etc) and of all birds, as well as Simpson's index of diversity This required extensive modelling - 105 models for Huntingdon and 174 for Swavesey 3 The results of all 279 models are presented in a condensed form, highlighting the importance of given field boundary attributes to particular species or groups of species 4 Like bird species richness in the earlier paper, the abundance of many species was strongly influenced by the land use, and by the main vegetation variables (tree height and number, hedgerow length, height and width) Land use was important to a larger majority of species, the exceptions being carrion crow, pheasant, reed bunting and wren 5 Verge width appeared important for small insectivores (blue tit) and was particularly important for seed eating birds, eg most finches and buntings, red-legged partridge in summer, and carrion crow and skylark in winter 6 Ditch dimensions were associated with the abundance of some seed eaters (linnet, reed bunting and goldfinch) and insectivores (blackbird, great tit, skylark, song thrush and wren) Kestrel and the groups raptors, corvids, waders and aquatics were associated with large ditches 7 Though the general management prescriptions to benefit the majority of farmland birds were found to be similar to those in the earlier paper, the detailed species specific modelling made it possible to examine the habitat requirements of particular species 8 Ecological evaluation of the results from the two studies are presented in a form considered to be of value for practical management Bird species and groups of birds are categorised with respect to their likely requirements of particular attributes of the field boundaries