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1: Case of the Junin Grebe

I rma Franke




Junín Grebe, Podiceps taczanowskii

Population Junín Grebe

The Junín Grebe, Podiceps taczanowskii, is a critically endangered species of restricted distribution in Peru because confinement in Lake Junin and its inability to fly. The population size of the diver has received attention and controversy for decades and is one of the populations that have focused greater number of censuses.

Red List of IUCN Species Amernazadas 2010.1 indicates that the diver "was extremely abundant in 1938 and was a far larger number 1961.En 1000 individuals in the 80 there were 250 birds, which dropped to 100 in 1992 and 50 in 1993. Extrapolations made in 1995 using other methodologies estimated 205 individuals. The breeding seasons of 1995-1996 and 1996-1997 failed, but two nests were achieved in 1997-1998. In August 1998 counted more than 20 individuals in 4 km ² the lake. Censuses conducted in late 2001 suggest a population of approximately 300 individuals, although this extrapolation of transects may be too optimistic. It is considered that even if this estimate is correct, represents the number of individuals after an excellent breeding season and the number of mature individuals could be half. Currently it is considered that the population can be estimated between 100 and 300 individuals (BirdLife 2010).

In surveys conducted since the 80 draws attention to the increases and decreases in number of individuals in very short periods of time, it would not be expected in the case of a species because it has a long service life and reduced investment in each reproductive season (O'Donnell & Fjeldsa 1997). Because the latter feature, if the population declines sharply, one would not expect rapid growth even in good conditions for reproduction.

Census by direct counting in 2001

Some of the differences in numbers of individuals obtained may be due to methodology, the area sampled lake to extrapolate the results and the time of year when the census was conducted. This conclusion can be reached by analyzing the results of censuses conducted in 2001 under Project "Conservation Plan to save from extinction Junín Grebe (Peru SA Walsh 2002) that has had little circulation.

In this project three censuses were conducted in May, August and December 2001 was used

total count method of individuals on a sampling frame consisting of square

side a mile (148 km2) comprising entire body of water (Fig. 1). It swept through the mirror surface water simultaneous work with three boats each carrying a team of two observers, one equipped with a GPS navigator and the coordinates of the sampling units. This method allowed not only to have divers, but to know its location on the lake This allowed isoline maps to analyze their spatial distribution in the lake.

Fig 1. Location map of sampling units


Fig 2. Isolines of distribution map of Junin Grebe-May 2001


Fig 3. Isoline map of the distribution of Junín Grebe - August 2001.



Fig 4. Isoline map of the distribution of Junín Grebe - December 2001.

As you can see from the table, in the three censuses there was a growing number of individuals, from 113 in May to 304 in December. This increase in the number of individuals in the central water body of the lake is due to two factors. First, in May breeding pairs are still nesting in the reeds and are not spotted when crossing the lake. Secondly, it strongly influences the water level. In May, the lake's water level is high, allowing divers to use small lakes located among the reeds play as both protection and therefore were not recorded in the census. In December, at the end of the dry season, the lake's water level is at its minimum, which is why divers are forced to leave the reeds and remain in the central water surface, facilitating their sighting. Results


three Junín Grebe census made in 2001

May 2001, 113 individuals, four juveniles
August 2001, 160 individuals, 0 juveniles
December 2001, 304 individuals, six juveniles


is important highlight two other aspects. The low recruitment rate found for 2001 1.97% coincide with expectations of a species with the characteristics described above, increased longevity and low rate of annual recruitment. Another notable aspect is the concentration of divers in three high-density cores. One might wonder whether these nuclei remain in time as they had slight variations between the three censuses conducted. This seems to be the case for the existence of these nuclei had already been warned by Francisco Tueros, local fisherman who worked for a long time supporting studies J. Fjeldsa in the area and by R. Valdivia, head of the Paracas National Reserve in the period in which censuses were conducted (personal communication).

The described results raise several questions among which should be highlighted:

1 .- The various surveys reported by BirdLife (2009) were conducted in different years, so it is not possible to confirm the population dynamics of divers among the cattails, and the central water body based on a methodology. Only supported by verbal communication from local people familiar with the lake. If confirmed, this dynamic as an annual cycle, the number of divers counted vary markedly by the time the census is conducted. The variations in numbers reported for the three censuses of 2001 are similar to the increases and changes considered reducing the population through the years. Would be the "reductions and increases" reported for Junin Grebe real changes?

2 .- Several of the censuses carried out since the 80's were based on counts made from the edge of the lake or the edge of the cattails,. Given the difficulty of distinguishing the Junin Grebe Blanquillo Grebe, Podiceps occipitalis , if they are within a certain distance even for experienced people apply the values \u200b\u200bobtained by these methods?

3. For gregarious species that occupy very small areas, which remained relatively stable during show changes year, would be valid to extrapolate results from surveys of small areas to larger areas without clearly knowing the area they occupy? How to select sampling units appropriately? Extrapolating back to the area should be calculated? For the southern half of the lake? In a smaller area? How to set?



References BirdLife International 2010. Podiceps taczanowskii . In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.1. . Downloaded on 29 March 2010.

O'Donnel, C. & J. Fjeldsa. 1997. Grebes. Status survey and conservation action plan.
IUCN / SSC Grebe specialist group. Cambridge: IUCN Publications Services Unit
Walsh
Peru SA 2002. Conservation Plan to save from extinction the Junin Grebe. Tell PROFONANPE.

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What we know and what we need to know about Peruvian birds?

Irma Franke

What birds live in the Peruvian territory?

The answer to this question has been accumulating since the beginning of exploration by naturalists and ornithologists in Peru, both strangers in a first stage, as Peruvians then and now a large set of individuals, professionals and amateurs great preparation that constantly roam the Peruvian territory.

In this long period, which started in the Century XVIII, is known as the stage of historical exploration of biodiversity. The main results have resulted in new species descriptions and inventories of the species present in a significant number of locations.

As a result of these activities we know about 1800 species of birds that occur in Peru. This number of species varies according to different authors. These variations are mainly due to the constant revision of the systematics and classification of birds and acceptance or disqualification of records obtained in our territory by observation or not properly documented.

know all the birds of Peru? Certainly the answer is no. Peru is a country where the exploration of biodiversity can not be considered historical. There are still many areas that represent gaps. True, we can not think of devoting the resources and extensive efforts to explore these areas with unknown or known as shallow as in the past. However, as part of the work of ornithologists and serious amateurs, this knowledge that will increase to complete the national inventory of birds. Probably never be a totally complete, because the dynamic nature of nature, climate change and the quality and extent habitats due to both natural causes as human intervention, there will be new records of species and species disappear from our territory.


Where each species of bird live? What is their distribution in the Peruvian territory?

knowledge of the distribution of bird species in the Peruvian territory was accumulating in parallel with the progress of the exploration of biodiversity. In the beginning these skills were quite uncertain, mainly due to the low accuracy of the location of the locations of the records. In the specimens from the early expeditions, the indication of "Peru" the label of a specimen was a sufficiently clear indication that time. The accuracy of the location of the records was improving steadily over time until the present situation, in which each record can be very accurately georeferenced with the help of the expanded use of GPS.

However, the knowledge of their distribution within the Peruvian territory is still very incomplete books and consulted more widely used, field guides (Clements & Shany, 2001, Schulenberg et al., 2007), create the opposite impression, even if this is not his intention. The maps generally used are obtained plotting the locations where a species has been recorded, thus obtaining a map with a number of points in a geographic area of \u200b\u200bvariable size. By joining the boundary points, outline the contours based on the extent of habitat where the species is known or height above sea level curve, you get the general area of \u200b\u200bdistribution of the species. This area, usually represented without the points, it is widely assumed as a continuous range of the species. In reality, these areas include includes large areas where the presence of the species is alleged, unproven, and represent a major information gap. The number of points or locations used for the production of maps is very variable for different species. The density of points is usually also very variable according to areas that have been evaluated or which has reported a list of species. In fact, even for the most common species are numerous areas where its presence is assumed, with large areas without data within the continuous area of \u200b\u200bthe map.

Our knowledge of the distribution of our birds in the Peruvian territory is still quite incomplete.

have many individuals of each species in the Peruvian territory?

The information in relation to the size of the Peruvian bird populations is very low. The only population fully enumerated at the species level is the Junin Grebe. This has been possible due to the fact that it is a small town and found located in one lake. However, even though there have been several surveys in different years, controversy regarding the exact number of existing individuals. Estimates for all individuals of a species also exist for Guan, a species that also has a very limited distribution.

For other species the problem of knowing the population size is more complex due to their greater number and wider distribution. Major efforts have been made for species migration, thanks to international funding for this purpose. Second are non-migratory waterfowl. There is more easily to conduct censuses or estimates for localities as they are more visible and conspicuous. Estimates are primarily for major guano birds and among birds in freshwater environments, the Flemish is the working group. Get

estimates of terrestrial bird populations is more complex. Existing data generally refer to relative density in certain areas than the number of individuals in the population.

Some organizations give values \u200b\u200bthat are obtained by seeking the opinion of those people, professionals or not, who have greater expertise in the field. These values \u200b\u200bare subjective approaches, rough estimates, untested, which could be quite unrealistic. While it is the best thing is today for many species.

Other aspects

For other aspects such as behavior, reproduction, sensitivity to disturbación, etc., The knowledge we have are very basic. Even for important species being endangered and their populations are very accessible to be located on the coast, as is the case of the Peruvian Cortarrama not recently been found in a nest. This is only known by the description of him makes a naturalist For almost a century.