VOCALIZATIONS, SOCIAL ORGANIZATION AND BREEDING BIOLOGY OF THE TWITE ACANTHUS FLAVIROSTRIS

A seven-week study of breeding Twites at the mouth of the Trondheim fjord revealed that they are double brooded. The second clutch is started while the first nestlings are still dependent on both parents. Males defend a moving area around the female which becomes focused on the nest during incubation. Adult vocalizations recorded and analysed fall into seven basic categories. We believe this represents the entire repertoire, which is rather small, and may correlate with the visually open habitat. Nine measures of the tup-up-up flight call reveal that calls of a male and female that are paired match closely and differ from those of other birds in the area. This is taken as evidence that the Twite flight call is modifiable by learning, as in some other cardueline finches.     

Validation of an enzyme immunoassay for measurement of excreted estrogen and testosterone metabolites in the white-crowned sparrow (Zonotrichia leucophrys oriantha)

Over the past few years there has been a growing interest in hormonal analyses, despite the cost and difficulty involved in measuring hormones using radioimmunoassays. Therefore, there is a need for alternate procedures, such as enzyme immunoassays, capable of providing similar data to that provided by radioactive methods. Enzyme immunoassays are a less expensive method of measuring estrone conjugates and testosterone. With further work, the enzyme immunoassay also provides the potential to adapt the enzyme assay for use in the field. The data in this study demonstrate that an enzyme assay can accurately detect both endogenous and exogenous hormonal changes in the droppings of white-crowned sparrows. © 1995 Wiley-Liss, Inc.     

Vervet monkey alarm calls: Semantic communication in a free-ranging primate

Vervet monkeys (Cercopithecus aethiops) at Amboseli, Kenya, give acoustically different alarm calls to different predators. Each alarm evokes contrasting, seemingly adaptive, responses. Animals on the ground respond to leopard alarms by running into trees, to eagle alarms by looking up, and to snake alarms by looking down. In a 14-month field study examining the semantic properties of alarm calls, we played tape-recorded alarms to vervets in the absence of actual predators and filmed the monkeys' responses. Playbacks confirmed observations and showed that (1) alarm length, amplitude and alarmist's age/sex class had little effect on response quality, and (2) context was not a systematic determinant of response. We conclude that vervet alarm calls function to designate different classes of external danger.     

Forebrain arginine vasotocin correlates of alternative mating strategies in cricket frogs.

In cricket frogs, Acris crepitans, sexually active males can switch between calling and noncalling (satellite) mating strategies and injections of the neuropeptide arginine vasotocin (AVT) stimulate calling behavior. We report here that this behavioral variation of animals under field conditions is associated with variations in AVT-immunoreactive (AVT-ir) staining in distinct brain nuclei. In both calling and satellite males, one AVT-ir brain region was found in a continuous string of cells between the medial amygdala and the nucleus accumbens (ACC). Satellite males possessed significantly more AVT-ir staining in the brain (cells and fibers) than calling males at the level of the ACC, although not in the medial amygdala. This difference in AVT-ir staining in the ACC can, in part, be explained by differences in the density of staining within the cells and in cell size. In addition, satellite males had significantly higher AVT-ir staining in the fibers medial to the ACC than calling males. Because other studies have demonstrated that AVT stimulates calling behavior, a plausible hypothesis is that calling males are releasing more AVT from neurons in the ACC, depleting reserves within the cells, and that the released AVT elicits calling behavior. AVT immunoreactivity levels are also higher in the ACC in both calling and satellite males than in female cricket frogs, which do not call. Satellite males may therefore have AVT reserves that might allow them to call depending on the social conditions.     

Species song discrimination in choice experiments with territorial male swamp and song sparrows

Playbacks of synthetic and normal songs were used to determine what song parameters are important to species song recognition by territorial male swamp sparrows (Melospiza georgiana) and song sparrows (Melospiza melodia). Syllable morphology influences the discrimination of conspecific song from song sparrow song in adult swamp sparrows, but temporal pattern does not; this result duplicates that found in studies of song learning of the young in this species. Species song recognition is influenced by both syllable morphology and temporal pattern in adult song sparrows, in contrast to the situation in young sparrows, which seem not to distinguish their own species' song from that of swamp sparrows on either cue.