Effects of off-road vehicles on coastal foredunes at Fire Island,New York,USA

The effects of off-road vehicles (ORVs) on the dune system of Fire Island National Seashore, New York, USA, were examined through a detailed, two-year field study. The experimental approach was adopted in order to evaluate the environmental effects of ORVs in this zone. Adjacent control and impact sites were established in two locations. Vehicle impacts were applied at the equivalent rate of one vehicle pass per week. Monitoring of foredune vegetation through sequential quadrat surveys and construction of sea-ward limit maps showed a significant loss of vegetation resulting from ORV impacting. Loss of vegetation resulted in an alteration of the natural foredune profile, which could increase dune erosion during storm wave attack.     

Biological monitoring and environmental assessment: a conceptual framework

Direct biological monitoring is essential for effective assessment efforts. Past approaches to biomonitoring are too simplistic (for example, toxicity testing, indicator species) or conceptually invalid (diversity indexes). Assessments that use ecological guilds use ecological principles in a more integrative fashion. The best long-term approach is development of suites of metrics, like those used in the index of biotic integrity (IBI), to reflect individual, population, community, and ecosystem attributes in an integrative framework. Efforts to use the conceptual content of IBI in a wider diversity of habitats should be encouraged and followed up with effective control actions.     

Culture and the environment on the Cape Verde Islands

The Cape Verde Islands originally supported a limited island ecology which, since the arrival of settlers 500 years ago, has been steadily altered or destroyed. Today, deforestation and overfarming, combined with the natural conditions of aridity and strong winds, have rendered the islands barren and eroded. The current government of the Republic of Cape Verde is attempting to alter traditional attitudes and customs of environmental neglect and mismanagement, while at the same time striving to restore or create self-sustaining ecosystems. The introduction of plants, animals, and physical structures enhancing soil and water conservation may create a more viable total ecosystem than existed before humans arrived.     

Vocal signals,isolation and hybridization in the vinaceous dove (<Emphasis Type="Italic">Streptopelia vinacea</Emphasis>) and the ring-necked dove (<Emphasis Type="Italic">S. capicola</Emphasis>)

Two closely related dove species, Streptopelia vinacea and S. capicola, show clear interspecific divergence in one acoustic signal (perch-coo), but much less so in another (bow-coo). Both signals play a role in territorial defense and mate attraction and may thus convey information used for species recognition. In Uganda, there is a small zone of overlap where the two species most probably hybridize. With playback experiments in allopatric populations of each species we tested the potential of the two signal types for species isolation. Allopatric populations showed a stronger response to conspecific than to heterospecific perch-coos, but an equal response to bow-coos of either species. However, S. vinacea responded relatively stronger to S. capicola perch-coos than vice versa. The hybrid population showed an equal response to bow-coos of either species, but a marginally stronger response to perch-coos of S. capicola compared to perch-coos of S. vinacea. Hybrids have a variable and intermediate vocal structure compared to both parental species, which allowed for testing of behavioral coupling between production and perception of these signals. Hybrids showed no relationship between their coo structure and that of the species to which they respond most strongly, indicating a lack of behavioral coupling. Although perch-coos may differ sufficiently to allow species isolation, the similarity in bow-coos may allow interspecific interactions. We suggest that the similarity in bow-coos and the higher salience of S. capicola perch-coos may have allowed S. capicola to extend its range into that of S. vinacea, resulting in hybridization. Electronic Publication     

Orientation in captive migratory and sedentary Australian silvereyes <Emphasis Type="Italic">Zosterops lateralis</Emphasis> (Zosteropidae)

The orientation of two closely related subspecies of Australian silvereye Zosterops lateralis was studied in captivity over 14 months. Migratory silvereyes Z. lateralis lateralis showed significant directional preferences during the spring and autumn migration periods and also displayed orientated behaviour during the breeding period. In contrast, the non-migratory subspecies Z. lateralis familiaris did not display any significant directional preferences at any time. This is the first time that the orientation behaviour of a migratory and non-migratory subspecies has been compared over the duration of an annual cycle, both during and outside the migratory periods. The results suggest that migratory silvereyes possess an endogenous program determining the timing and direction of autumn and spring migration and that this program is unique to the migratory subspecies. This is also the first comparison of this nature on southern hemisphere birds and demonstrates that the migratory behaviour of southern hemisphere migrants may be more similar to that of northern hemisphere migrants than previously thought.Submitted to Behavioral Ecology and Sociobiology: 23 Jan 2006.     

Soft song in song sparrows: response of males and females to an enigmatic signal

Low-amplitude “soft song” is used by a variety of songbirds; in some species during aggressive encounters, in others during courtship, and yet others in both these contexts. In song sparrows (Melospiza melodia), soft song has thus far been observed only in aggressive encounters, where its production is a more reliable predictor of attack than any other signaling behavior. We used song playback to test the response of both male and female song sparrows to soft song. The design of the playback experiments took into account the existence of two classes of soft song: crystallized soft song, which consists of song types also found in the broadcast repertoire, and warbled soft song, which consists of less-structured song types not found in the broadcast repertoire. Female song sparrows responded with significantly less courtship display to the playback of crystallized soft song than to that of normal broadcast song, and response to warbled soft song was if anything lower than to that of crystallized soft song. Male song sparrows responded equally aggressively to normal broadcast song as to crystallized soft song, and equally aggressively to warbled soft song as to crystallized soft song. The female results support the conclusion that neither form of soft song functions in courtship. The male results suggest that the reliability of soft song as a signal of aggressive intent is not maintained by a receiver retaliation rule.     

Modelling asymmetrically distributed circular data using the wrapped skew-normal distribution

We consider problems of inference for the wrapped skew-normal distribution on the circle. A centered parametrization of the distribution is introduced, and simulation used to compare the performance of method of moments and maximum likelihood estimation for its parameters. Maximum likelihood estimation is shown, in general, to be superior. The operating characteristics of two moment based tests, for wrapped normal and wrapped half-normal parent populations, respectively, are also explored. The former test is easy to apply, maintains the nominal significance level well and is generally highly powerful. The latter test does not hold the nominal significance level so well, although it is very powerful against negatively skew alternatives. Likelihood based tests for the two distributions are also discussed. A real data set from the ornithological literature is used to illustrate the application of the developed methodology and its extension to finite mixture modelling. Received: September 2003/ Revised: April 2005     

Bird song as a signal of aggressive intent

A central question in animal communication research concerns the reliability of animal signals. The question is particularly relevant to aggressive communication, where there often may be advantages to signaling an exaggerated likelihood of attack. We tested whether aggressive signals are indeed reliable signals of attack in song sparrows (Melospiza melodia). We elicited aggressive signaling using a 1-min playback on a male’s territory, recorded the behavior of the male for 5 min, and then gave him the opportunity to attack a taxidermic mount of a song sparrow associated with further playback. Twenty subjects attacked the mount and 75 did not. Distance to the speaker was a significant predictor of attack for both the initial recording period and the 1 min before attack. For the initial recording period, none of the measures of singing behavior that we made was a significant predictor of attack, including song-type matching, type-switching frequency, and song rate. For the 1-min period immediately before attack, only the number of low amplitude “soft songs” was a significant predictor of attack. Although most aggressive signals contained little information on attack likelihood, as some models suggest should be the case, the unreliability of these signals was not caused by convergence of individuals on a single signaling strategy, as those models argue should occur.     

Genetic Identification of Spotted Owls, Barred Owls, and Their Hybrids: Legal Implications of Hybrid Identity

Abstract:  Recent population expansion of Barred Owls (  Strix varia ) into western North America has led to concern that they may compete with and further harm the Northern Spotted Owl (  S. occidentalis caurina ), which is already listed as threatened under the U.S. Endangered Species Act (ESA). Because they hybridize, there is a legal need under the ESA for forensic identification of both species and their hybrids. We used mitochondrial control-region DNA and amplified fragment-length polymorphism (AFLP) analyses to assess maternal and biparental gene flow in this hybridization process. Mitochondrial DNA sequences (524 base pairs) indicated large divergence between Barred and Spotted Owls (13.9%). Further, the species formed two distinct clades with no signs of previous introgression. Fourteen diagnostic AFLP bands also indicated extensive divergence between the species, including markers differentiating them. Principal coordinate analyses and assignment tests clearly supported this differentiation. We found that hybrids had unique genetic combinations, including AFLP markers from both parental species, and identified known hybrids as well as potential hybrids with unclear taxonomic status. Our analyses corroborated the findings of extensive field studies that most hybrids genetically sampled resulted from crosses between female Barred Owls and male Spotted Owls. These genetic markers make it possible to clearly identify these species as well as hybrids and can now be used for research, conservation, and law enforcement. Several legal avenues may facilitate future conservation of Spotted Owls and other ESA-listed species that hybridize, including the ESA similarity-of-appearance clause (section 4[e]) and the Migratory Bird Treaty Act. The Migratory Bird Treaty Act appears to be the most useful route at this time.     

Bird song and parasites

Bird song is a typical sexual trait that may have evolved at least partly to reflect health and vigor. However, the role of pathogens in modulating acoustic communication systems in birds is still less than clear as studies testing the relationship between parasites and song have provided inconsistent results both within and among species. It is often neglected that avian song is complex trait consisting of numerous and variable features with potentially different biological backgrounds. By using meta-analytic approaches to the available intraspecific evidence I demonstrate that different roles are applicable to song traits with different signal design, which could explain, to some extent, the inconsistency of results. I found that condition-dependent, performance-related traits are more closely related to immediate health status, whereas condition-independent features are more likely to be associated with intrinsically determined parasite resistance. Hence, parasitism may mediate the evolution of different acoustic features. Considering the signal function of songs, a communication system depends on the reaction of the receivers, but little is known about how mate choice and male–male competition are affected by parasite-mediated song production. This review of the literature thus suggests that receivers of songs may benefit by responding to these acoustic signals of health through the acquisition of resistance genes, paternal care of superior assistance, success in territory disputes, and the avoidance of directly transmitted parasites.