Interannual Changes in the Habitat Area of the Black-Necked Swan, Cygnus melancoryphus , in the Carlos Anwandter Sanctua
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ARTICLE
Interannual Changes in the Habitat Area of the Black-Necked Swan, Cygnus melancoryphus, in the Carlos Anwandter Sanctuary, Southern Chile: A Remote Sensing Approach Luisa E. Delgado & Víctor H. Marín
Received: 5 September 2012 / Accepted: 7 November 2012 / Published online: 13 November 2012 # Society of Wetland Scientists 2012
Abstract Bird monitoring is frequent in wetlands; however, in the absence of information on other variables, trends in bird numbers are difficult to interpret. In this article we describe a methodology for bird’s habitat area assessment based on remote sensing. We calibrated the methodology to study the changes in the habitat area of Cygnus melancoryphus, the black-necked swan, at the Carlos Anwandter Sanctuary, a wetland located in Valdivia, Southern Chile. Swan habitat area was estimated by means of the Normalized Difference Vegetation Index (NDVI) based on Landsat images and calibrated through spectral photography by means of a portable Tetracam ADC Camera. Results show that calibrated NDVI values from Landsat images can be used to estimate habitat area but not to separate individual species of vegetation. We also show that the joint analysis of habitat area and swan count can indeed be used to separate some of the scales of variability of bird counts: those with “local-influence” associated with changes in habitat area from those of larger scales not related with habitat area. Keywords Wetland monitoring . Landsat images . GIS . Habitat area
L. E. Delgado Fundación CTF, Avenida Suecia 84, Oficina #93, Providencia, Santiago, Chile V. H. Marín (*) Laboratorio de Modelación Ecológica, Depto. Cs. Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Ñuñoa, Santiago, Chile e-mail: [email protected]
Introduction Wetlands are considered havens for wildlife and sources of many ecosystem services; yet they are also under increasing threat (Fernández-Prieto and Finlayson 2009; Brinson and Eckles 2011; Fariña and Camaño 2012). Main threats are watershed modifications by agriculture, forestry and climate change (Marín et al. 2009; De Steven and Lowrance 2011; Marquet et al. 2012). In the year 2003 the European Space Agency and the Ramsar Convention Secretariat launched the GlobWetland project (http://www.globwet land.org) with the purpose of developing and demonstrating remote sensing technology to support wetland management. The project is currently in its second phase (GlobWetland II) aiming to the set up of a Global Wetlands Observing System. Indeed, remote sensing is likely to play an increasingly important role in wetland monitoring (Euliss Jr. et al. 2011). Although medium-resolution sensors, such as Landsat TM (pixel size030×30 m) has historically being the most used platform for the remote sensing of the biosphere, small wetlands require higher resolutions (Klemas 2011). However, for large wetlands (e.g. 45 km2 and larger) Landsat images are still a good working solution, especially given its nearly 30 years of temporal coverage (http://glovis.usgs.gov). T
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