Best Tv For Motorhomes

Bird Populations 1. Delimiting the area occupied by a population. The importance of the zeros. Issues to census birds

Irma Franke

Cauquenes Huallata, Chloephaga melanoptera

The ranges of various species of birds that indicate many publications, such as field guides for example, create the impression that most species occupy very large continuous areas. For many species indicates their preferred habitat and consequently tend to think that these species occupy or could occupy the entire length of preferred habitat. However, this is not correct in many cases. Often a population of some species to occupy only part of the preferred habitat, where local conditions are appropriate for your requirements.

Define the area occupied by a population is of great importance to various aspects of the study of birds, including the conservation and management of natural areas and areas of investment projects. Other types of studies can be derived from a precise knowledge of the area occupied by a population, such as a detailed analysis of habitat characteristics that favor their presence, population displacement, etc..

Delimiting the range with "positive points"

Information usually obtained and recorded on birds is mainly to places where individuals of some species are spotted. These points are georeferenced and are currently represented on a map as points. The "points" that represent the presence of a species, or "positive points" are the most commonly used to analyze the distribution of a bird and are the basis for determining the distribution of a species at macro scales.

An example of this use of "positive points", those where there has been the species, range maps found in a species over large areas such as Peru. These maps are the basis for of the maps in field guides. Figure 1 shows the locations where it is known Cauquén Huallata, Chloephaga melanoptera (Schulenberg et al. 2006), and Figure 2 shows the locations where it is known the Peruvian Cortarrama , Phytotoma raimondii (Flanagan et al. 2009) . Importantly, given their scale and level of detail is low for each locality.

Figure 1 Distribution of Cauquén Huallata, Chloephaga melanoptera in Peruvian territory (Schulenberg et al. 2006)

Figure 2. Distribution Map of the Peruvian Cortarrama, Phytotoma raimondii , in northwestern Peru (Flanagan et al. 2009).

Delimiting the range with "positive points" and "zero points"

When you need to study the location of a population of a species within a smaller geographic area as a protected area or natural area to be managed, the level of detail and accuracy required is higher. In these cases it is necessary not only to think of registering the "positive points" which are individuals of the species under study, but also the "zero point", where those having carried out an inspection, there has been the species. At these points the record for the species is 0 individuals.

Often the registration of "zero point" is not considered in a study. However, only providing an adequate number of "point zero", in addition to "positive points" can be define with greater certainty and precision the occupancy of a species in a given time.
Examples:

Junin Grebe.

In surveys conducted in May, August and December 2001, Lake Junin was divided into 148 sampling units (Figure 3), all of which were surveyed (Peru SA Walsh 2002). For each information was available on the number of divers present. The vast majority of the units were set to 0 and only registered fewer divers. This information allowed to be secure in their presence limited to the south of the lake forming three nuclei in it (Figure 4).

Figure 3. Location map of sampling units surveyed Lake Junín in May, August and December 2001

Figure 4. Isolines Map Distribution of Junín Grebe May 2001

Cortarrama Peruvian in Illescas Peninsula .

In some studies is not possible to divide the area sampling units or observations by dividing the area in such detail as the study of Junín Grebe, but an adequate number of locations where individuals are recorded 0 to define the area quite clearly and be sure of the location of the population and the area occupied by it.

In the case of the Peruvian Cortarrama in Illescas Peninsula, enumerated in 2006 and 2007, included observations of dry forest patches distributed throughout the Illescas Peninsula (Figure 5) and there was only the Peruvian Cortarrama in those located on the slopes of Cerro Illescas forming a belt on the basis of its eastern side (Figure 6). In all other points were recorded 0 Cortarramas.

Figure 5. Distribution map of sampling points in patches of dry forest in Illescas Peninsula.

Figure 6. Distribution map of the Peruvian Cortarrama the Illescas Peninsula.

only considering an adequate number of sites with 0 individuals of a species, in addition to "positive points" you can determine its distribution in an area. not rule out the zeros, represent important information.

References

Flanagan, JNM, Engblom, G., Franke, I., Valqui, T. & Angulo, F. 2009. Distribution of the Peruvian Plantcutter Phytotoma raimondii (Passeriformes: Cotingidae). Rev. peru. biol. 16 (2): 175-182

Golder Associates Peru SA 2007. Environmental Impact Study, Bayóvar Phosphate Project, Piura, Peru. Prepared for Compania Minera SAC May Miski

Schulenberg, TS, DF Stotz, and L. Rico. 2006. Distribution maps of the birds of Peru, version 1.0. Environmental and Conservation Programs, The Field Museum. Walsh

Peru SA 2002. Conservation Plan to save from extinction the Junin Grebe. Tell PROFONANPE.