|Results from radio telemetric tracking of farm Pheasant (Phasianus colchicus) released in the Pazardjik region
The aim of the study is to determine the losses after farm pheasants are released in nature.
In the spring of 2011 20 Pheasants (Phasianus colchicus) were tagged with radio telemetry transmitters. A total of 20% of the birds survived until the end of the study. The main reason for the losses is the carnivorous mammals. The human factor significantly affects the survival rate of pheasants. The dispersion of the birds from the place of release increases with time. Direct displacement of farm pheasants in nature is not an appropriate method of recovery of the population in Bulgaria.
Keywords: pheasant, survival, loss, dispersion, radio telemetry, release.
The Common Pheasant (Phasianus colchucus colchicus, Linnaeus) used to be the primary species of the Bulgarian fauna. At the end of the XIX century the Pheasant inhabited areas from the middle streams of the Maritsa River to the Black Sea Coast (Simeonov et al. 1990). The Common Pheasant had a natural population until 1895. After that the wild Ring-necked Pheasant (Phasianus colchicus torquatus, Gmelin), Japanese Green Pheasant (Phasianus colchicus mongolicus, Brandt) and Korean Ring-necked Pheasant (Phasianus colchicus karpowi, Buturlin) were introduced into the Bulgarian fauna. The hybridization that followed subsequently led to the disappearance of the local subspecies (Boev et al. 2007). Today about 20,000 pheasants (data of National Hunting and Fishing Association) with morphological features of the Common pheasant subspecies are released in Southern Bulgaria annually (?).
The displacement of farm birds is widespread in Bulgaria. They are bred in specialized farms and released into the wild in their typical habitats. The purpose of placing farm birds in the wild is to achieve an increase in their growth in nature and thus an increase in the birds available for hunting purposes. The low level of control over the quality of poultry in the farms can lead to disease or impoverishment of the genetic diversity in wild populations (Viggers et al. 1993; Hodder, Bullock 1997).
The aim of this study is to determine the losses and dispersion of farm produced pheasants that are released into the wild.
Materials and methods
The study was carried out within the territory of the Hunting and Fishing Association of Pazardjik, in the land boundaries of the village of Govedare (42º 09’N; 24º 29’E). Radio telemetry transmitters weighing 10 grams RI–2BM (12) (Holohil Systems Ltd) were placed on 20 pheasants (10 males and 10 females). All birds that were marked carried the morphological features of the Common pheasant subspecies. The birds were 120 days old and were dispersed by a method of direct release into the environment (this is the most popular method of settling practiced by the Bulgarian hunters).
The study area is characterized by a wealth of farmlands, divided by a network of irrigation canals, around which there is dense Reed vegetation (Phragmites austrialis, (Cav.) Trin. Ex Steud), Blackberry (Rubus sp.), Willows (Salix) and Poplar (Populus). The surrounding farmlands are planted primarily with Alfalfa (Medicago), cereals and maize. There are small orchards of peaches scattered in a mosaic pattern over the whole territory along with abandoned vineyards, with an area that accounts for less than 10% of the study area.
The pheasants were observed during the period 18.03-28.05.2011. A total of 11site visits were performed, each bird is located between 3 and 5 times in an average of 3 days. There have been 78 localized displaced pheasants. All distances are measured using the Garmin eTrex Legend Global Positioning System and the program MapSource, Version 6.11.6 (Garmin Ltd.).
The causes of death were determined by the traces on the dead animals and the tracks around them. The causes are divided into 4 categories: birds of prey, predatory mammals, humans and unspecified reasons. The index of survival is determined by Kaplan - Meier (Kaplan, Meier 1958).
The resources selection for the birds was determined by dividing the area of the habitat into different categories (Table 1) and by calculating the number of birds in each category.
After that a χ² test is used to determine whether the number of birds in a localized area is significantly higher than the number of birds in the other (Fowler, Cohen 1995). To avoid distortion of the results by the impact of external factors, the only observations taken into account are those carried out in the same time period of the day and under the same weather conditions.
Sixteen (80%) birds died during the study period (Table 2). A total of 4 birds survived until the batteries of their transmitters were depleted (Fig. 1).
In the case of 10 (62.5%, n=16) pheasants the cause of death is a predatory mammal, five birds (31.25%, n=16) were killed as a result of human intervention, one (6.25%, n=16) pheasant remains with an unknown cause of death. In three cases a Red Fox (Vulpes vulpes, (Linnaeus 1758)) was determined as the cause of death. In one case a Golden Jackal (Canis aureus, Linnaeus 1758) was seen next to the body of male pheasant (04/05/2011). During the fieldwork, there were no observed cases in which the cause of the loss was a bird of prey. There is no significant difference between the number of dead male and female pheasants where the cause of loss was a predatory mammal (H=0.004, p>0.05). There is no statistically significant difference between the loss of male and female birds, regardless of the cause of death (H=0.08, p>0.05). We cannot state that losses are greater for a certain sex of birds.
There is no significant difference between the pheasant losses during the first two days after the release and 4 days-later (H=0.79, p>0.05). However, losses up to and including the 15th day after the release are significantly higher - than those between the 30th day after the release and the end of the study period (F=5.0081, p<0.01).
Only 2 females built nests. One of them was successfully observed with 12 chicks on 28.05.2011. The nest of the other female was found ruined by predatory mammal on 05.04.2011 (Fig. 2). The bird did not breed again and the reasons for this remain unknown. Both females built nests close to irrigation canals.
The average distances of dispersal of the pheasants from the site of release are shown in Table 3.
There is no statistically significant difference between the dispersal of male and female pheasants (H=0.918, p>0.05). Distances increase as the period after the release increases.
During the light part of the twenty-four-hour period between 10.a.m and 4.p.m when there are no clouds and no wind, areas occupied by irrigation canals adjacent to vegetation are preferred by the dispersed Pheasants significantly more than other areas (χ²=236.4; p<0.01).
After that, in our case, the most preferred areas remain the bushes and farm lands along with pastures and meadows. The roads are avoided by the birds, but there the birds that had been observed were mainly male.
This study shows that the dispersal losses of pheasants in Bulgaria are at their highest during the first 15 days after the release. Similar results have been established by other authors in similar studies (Robertson 1988). The results for the survival of other farm birds are also similar (Britas et al. 1992, Leif 1994, Petrini et al. 1995, Sage et al. 2001 2003, Venturato et al. 2001).
We found that the highest percentage of losses is caused by predatory mammals. Similar results are presented by Sage et al. (2001). During the study there are no registered losses caused by birds of prey, unlike other similar studies. We explain this finding with the low number of birds of prey in the research area. The losses caused people are 31.25%. Other authors also establish increased losses after the start of the hunting season (Bagliacca et al. 2008). However, in this case, the losses are outside of the hunting season. We think the losses are caused by unscrupulous people, most often with low social status and culture and due to lack of control by the authorities. One should not underestimate the fact that in many cases the farm pheasants are not afraid of humans. Perhaps this is due to the production practices in the farms. Some authors explain the higher losses in Grey Partridges (Perdix perdix, Linnaeus) with ethological, physiological and anatomical limitations that reduce their fitness compared to the wild birds (Csermely et al. 1984, Paganin, Meneguz 1992, Putaala, Hissa 1995). Other authors find low mortality rate and statistically insignificant difference in the mortality of farm and wild pheasants. They attribute this result to the change in the rules of production in farms and dispersal in nature (Bagliacca et al. 2008). In Bulgaria, one of the most popular practices is to release the pheasants directly into the wild without taking care to improve the quality of habitats. Often the birds are settling in unsuitable areas. This calls for the creation of new rules for breeding and dispersal of the farm birds in nature and improving the qualifications of people who engage in this activity.
The results for the dispersal of the pheasants after the release show that the distance from the release site increases with the length of stay of the birds in nature. Only a few birds reach further than 1 km away from the release site, indicating that generally the pheasants remain in the region of dispersal. Similar results are presented by Bagliacca et al. (2008). We assume that the dispersal increases until the density of dispersed pheasants reaches a defined value within the survey area and then this density remains relatively constant. Nevertheless, in order to prove this hypothesis additional studies are required.
In this study the preferred habitat areas are irrigation channels with adjacent vegetation. There the pheasants find refuge and peace. The birds use agricultural land mainly as a source of food. Due to large scale agriculture in the studied region, the wetlands near the farmlands remain the preferred areas. Similar birds’ preferences but in the winter period are indicated by the Homan et al. (2000).
The obtained results show that pheasants must be dispersed in wetland areas with reliable and constant water sources. The birds remain in the area of release, but mortality is high, which makes the dispersal inefficient. The current production practices and dispersal methods of the pheasants in Bulgaria cannot be used to restore or maintain populations of this species. Changes in farm production technologies and methods of dispersal are needed, in order to improve the efficiency of the release of pheasants in the wild.