Olaf Jahn

Audio parameterization with robust frame selection for improved bird identification

Audio parameterization method with robust frame selection.Automated acoustic recognition of 40 bird species.HMM-based bird identification. A major challenge in the automated acoustic recognition of bird species is the audio segmentation, which aims to select portions of audio that contain meaningful sound events and eliminates segments that contain predominantly background noise or sound events of other origin. Here we report on the development of an audio parameterization method with integrated robust frame selection that makes use of morphological filtering applied on the spectrogram seen as an image. The morphological filtering allows to exclude from further processing certain audio events, which otherwise could cause misclassification errors. The Mel Frequency Cepstral Coefficients (MFCCs) computed for the selected audio frames offer a good representation of the spectral information for dominant vocalizations because the morphological filtering eliminates short bursts of noise and suppresses weak competing signals. Experimental validation of the proposed method on the identification of 40 bird species from Brazil demonstrated superior accuracy and faster operation than three traditional and recent approaches. This is expressed as reduction of the relative error rate by 3.4% and the overall operational time by 7.5% when compared to the second best result. The improved frame selection robustness, precision, and operational speed facilitate applications like multi-species identification of real-field recordings.

Automated Acoustic Classification of Bird Species from Real -Field Recordings

We report on a recent progress with the development of an automated bioacoustic bird recognizer, which is part of a long-term project, aiming at the establishment of an automated biodiversity monitoring system at the Hymettus Mountain near Athens. In particular, employing a classical audio processing strategy, which has been proved quite successful in various audio recognition applications, we evaluate the appropriateness of six classifiers on the bird species recognition task. In the experimental evaluation of the acoustic bird recognizer, we made use of real-field audio recordings for seven bird species, which are common for the Hymettus Mountain. Encouraging recognition accuracy was obtained on the real-field data, and further experiments with additive noise demonstrated significant noise robustness in low SNR conditions.

Automated Sound Recognition Provides Insights into the Behavioral Ecology of a Tropical Bird

Computer-assisted species recognition facilitates the analysis of relevant biological information in continuous audio recordings. In the present study, we assess the suitability of this approach for determining distinct life-cycle phases of the Southern Lapwing Vanellus chilensis lampronotus based on adult vocal activity. For this purpose we use passive 14-min and 30-min soundscape recordings (n = 33 201) collected in 24/7 mode between November 2012 and October 2013 in Brazil’s Pantanal wetlands. Time-stamped detections of V. chilensis call events (n = 62 292) were obtained with a species-specific sound recognizer. We demonstrate that the breeding season fell in a three-month period from mid-May to early August 2013, between the end of the flood cycle and the height of the dry season. Several phases of the lapwing’s life history were identified with presumed error margins of a few days: pre-breeding, territory establishment and egg-laying, incubation, hatching, parental defense of chicks, and post-breeding. Diurnal time budgets confirm high acoustic activity levels during midday hours in June and July, indicative of adults defending young. By August, activity patterns had reverted to nonbreeding mode, with peaks around dawn and dusk and low call frequency during midday heat. We assess the current technological limitations of the V. chilensis recognizer through a comprehensive performance assessment and scrutinize the usefulness of automated acoustic recognizers in studies on the distribution pattern, ecology, life history, and conservation status of sound-producing animal species.

Acoustic bird activity detection on real-field data

We report on a research effort aiming at the development of an acoustic bird activity detector (ABAD), which plays an important role for automating traditional biodiversity assessment studies --- presently performed by human experts. The proposed on-line ABAD is considered an integral part of an automated system for acoustic identification of bird species, which is currently under development. In particular, taking advantage of real-field audio recordings collected in the Hymettus Mountains east of Athens, we investigate the applicability of various machine learning techniques for the needs of our ABAD, which is intended to run on a mobile device. Performance is reported in terms of recognition accuracy on audio-frame level, due to the restrictions imposed by the requirement of run-time decision making with limited memory and energy resources. We report recognition accuracy of approximately 86% on a frame level, which is quite promising and encourages further research efforts in that direction.

Lerneca inalata beripocone subsp. nov. (Orthoptera: Phalangopsidae; Luzarinae): a new taxon for the northern Pantanal of Brazil

The first record of the Orthoptera species Lerneca inalata for Brazil is presented here. The taxon is represented by a new subspecies Lerneca inalata beripocone subsp. nov. (Phalangopsidae, Luzarinae), collected in the Pantanal of Poconé, Mato Grosso, Brazil. This work includes morphological and morphometric data as well as descriptions of female genitalia and calling song. The new subspecies has as diagnostic features the male genitalia with six ventral spines on the B sclerite, the first spine having a subtle bifurcation; the mid-region of the strongly sclerotized pseudepiphallus; inclination of C sclerite with slightly concave curvature; tegmina-length ratio and the speculum (syn. mirror) width approximately three times the length of the apical area. The description of the female genitalia and the calling song is presented for the first time for the species Lerneca inalata. A distribution map covers the local occurrence of its subspecies.

The life history of the Long-wattled Umbrellabird Cephalopterus penduliger in the Andean foothills of north-west Ecuador: leks, behaviour, ecology and conservation

Summary The rare and threatened Long-wattled Umbrellabird Cephalopterus penduliger inhabits the canopy and mid-storey level of humid to wet foothill and montane forests (150-1,800 m) of the Andean slopes of south-west Colombia and western Ecuador. Here we report on male activity pattern and display behaviour observed at one of two leks recently discovered in the vicinity of Playa de Oro, Rio Santiago, Esmeraldas Province, north-west Ecuador. Courtship behaviour of C. penduliger is compared with the Central American and Amazonian congeners (Bare-necked Umbrellabird C. glabricollis and Amazonian Umbrellabird C. ornatus). The lek of C. penduliger was active during the whole study period (February 1997 to January 1998), but both lek structure and daytime activity pattern changed markedly within the observation period.

Tegmina-size variation in a Neotropical cricket with implications on spectral song properties

This study evaluates the relationship between shape and size of tegmen, harp, mirror, and spectral range of calling song frequency of a Neotropical cricket subpopulation (Lerneca inalata beripocone. In addition, we compare intraspecific morphological divergence and calling song properties between individuals from different sites of the Pantanal of Poconé, Mato Grosso, Brazil. Regression analysis showed that the dominant and maximum calling song frequencies were negatively correlated with tegmen size, i.e. frequencies are either lower or higher depending on the corresponding size variation in resonance structures of the forewings. Canonical variable analysis demonstrated marked intraspecific differences in morphometric characters between localities of a L. inalata subpopulation c. 35 km apart (SESC-Pantanal Advanced Research Base and Pouso Alegre Farm, Mato Grosso, Brazil). Lerneca inalata beripocone at SESC had larger forewings than conspecifics from Pouso Alegre Farm. These morphological variations of wing properties related to reproductive behaviours were interpreted as fitness parameters, likely shaped by restricted gene flow during temporal habitat isolation episodes. Such isolation patterns occur in the Pantanal wetlands for several months during the annual hydrological cycle.