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Grasshopper sparrows produce unusually high-pitched vocalizations for birds, with fundamental frequencies of species typical songs in the range of 7-9 kHz. The characteristics of vocalizations produced early in life, however, are relatively understudied in this and related species. In this study, the development of vocal signal structure and vocal behavior in grasshopper sparrows was investigated in the field immediately after birds hatched. Acoustic characteristics of nestling begging calls were measured throughout the course of the 8-9-day nestling period. Starting at day 6 post-hatch, nestling calls changed qualitatively, incorporating frequency-modulated elements that resembled some parts of the adult vocalizations....
The traditional method of identifying wildlife habitat distribution over large regions consists of pixel-based classification of satellite images into a suite of habitat classes used to select suitable habitat patches. Object-based classification is a new method that can achieve the same objective based on the segmentation of spectral bands of the image creating homogeneous polygons with regard to spatial or spectral characteristics. The segmentation algorithm does not solely rely on the single pixel value, but also on shape, texture, and pixel spatial continuity. The object-based classification is a knowledge base process where an interpretation key is developed using ground control points and objects are assigned...
    map background search result map search result map Fledging times of grassland birds in North Dakota and Minnesota Fledging times of grassland birds in North Dakota and Minnesota