INTRODUCTION
Natural monument 323-8, the common kestrel (Falco tinnunculus) is an opportunistic forager (Kű.bler, 2005); it is a species of urban predatory birds that effectively adapted to both rural and urban environments. Furthermore, it is the uppermost predator of the food chain within the natural ecosystem and preys on rodents and insects that damage crops in farms, so they control their numbers in a nature-friendly fashion (Demarchi and Bentley, 2005; Kang et al., 2012). In the breeding season, however, when they breed near homes, excrements from the nests and begging calls or breeding songs during breeding season can act as contamination and noise, resulting in discomfort for some residents (Kang et al., 2012). Furthermore, they also often appear in airports and act as threats to flight safety due to bird strikes (Kitowski, 2014), so it is necessary to have ecological data to establish management plans such as studies on the home range of the common kestrel. Studies on the home range of predatory birds include prior studies that examined the home range of Accipiter gentilis living in cities by dividing their occupancy ranges into data for breeding and non-breeding seasons (Rutz, 2006), and studies on the habitat and home range of Buteo lineatus around cities in the United States (Dykstra et al., 2001). These studies mainly used satellite tracking devices in which GIS software (Arcview GIS 3.2) was applied for collecting location information in order to calculate the home range with the MCP (Minimum Convex Polygon method) or FK (Fixed Kernel Method). For home range studies of the common kestrel using markings, Village (1982) has conducted a study on the change of home range area according to seasons by marking on the wings and setting free for observation in Scotland. Meanwhile, in Korea, previous studies on home range of animals included the home range evaluation for restoration within the field of the Asiatic black bear (Kang and Paek, 2005); it used the line density tool of ArcGIS 9.0 Spatial analyst to analyze the road domination rate and road density, while Choi et al. (2006) analyzed the home range of wild boars (Sus scrofa) in Jirisan using location information obtained from electronic signaling devices. In the case of birds, there is only a case in studying the home range of Platalea minor by tracking with a natural marking by Choi (2004), and there were almost no studies on the home range of the common kestrel. Therefore, through observation of not only the home range of the common kestrel living in the outskirts of city, but also of those inhibiting areas near airports, this study will create important base data for preventing bird strikes for airplanes and for providing management plans and protecting common kestrels breeding in urban areas.
MATERIALS AND METHODS
1.Study Site Overview
The mathematical location of the study site was east longitude 128° 53′ 69″ -128° 57′ 49″ and north latitude 34° 52′ 50″-35°23′ 36″, and for the administrative region, it was Eulsuk-do, Hadan-dong, Saha-gu (Area Ⅰ), Myeongji-dong (Area II), and Daejeo 2-dong and Gangdongdong (Area Ⅲ), of Gangseo-gu of Busan Metropolitan City. To its east is the urban area of Saha-gu between Nakdonggang (Area U) and to the north, it is near Gimhae International Airport (Figure 1). The total area of the survey site is approximately 3,483 ha (34.83 km2) and there is a high density distribution of Phragmites australisis on its riverside and internal waterway. There is also a Citizens' Park inside the study site, and most of the other areas are farming areas mainly consisting of crops such as Allium fistulosum and Oryza sativa. For the main facilities, to the southern coastline is an apartment complex, and inland along the road, there are small and mid-sized towns, schools, hospitals, government offices, factories, and other such facilities, while also having utility poles and street lights. When viewing from the level of urbanization, it is a typical 'suburban' sector (Hur, 2005).
2.Days of Appearance and Coordinate Records
The survey on the home range and number of days of appearance from December 2009 to May 2010 was carried out designating the location of appearance for each individual. It was carried out in 18 sub-area (Figure 1) locations in Areas I, II and III at least once a week for five times a month from 08:00 to 19:00, and the point of appearance was recorded for the coordinates and observation time using GPS. The coordinates were recorded whenever the point of appearance changed after the individual subject moved, and photos were also taken to identify the individual subjects. The method of transportation was by vehicle and walking, and surveys were taken at approximately every 30 minutes in each location. The GPS used for recording coordinates was Garmin GPSMAP 60CSx and the camera used for observation was Nikon D300, the magnifying lens was Nikon F2.8 AF-S 400 mm, and binoculars used was Nikon Action 7×35 9.3°.
3.Individual Identification
The age and gender of the common kestrel were determined using the categorization method using molting and feather patterns provided by Baker (1993) and Forsman (1999). Individual identification was divided into two groups through gender analysis using external formative differences, and each group was then once again divided into four different sub-groups by age. Identification of individuals within each group for males were made by the patterns of the scapulars, greater coverts and tertials, while that of females were identified by comparing the patterns of the tail feathers and the under tail covert (Figure 2). Also, patterns of all parts that could be used for judgment such as the patterns of head feathers and the wearing of feathers were also compared. The identified female individuals were marked in the order of Fa, Fb, Fc, etc. and males as Ma, Mb, Mc, etc. While individual identification using remote electronic signal devices may be a more scientific method, in this study, it was possible to identify individuals with natural identification, which in this case was the pattern of feathers, and it was judged to be a more effective method to obtain natural research results, while saving on expenses.
4.Home Range and Statistical Analysis
The survey period was divided to examine the differences of home range during wintering and breeding period. Of the six months total, December to February was set as the wintering period and March to May as the breeding period (Won et al., 2005; Kang et al., 2012). The normal period inclusive of the late breeding period is until June, but because it is difficult to identify the individuals due to effects of molting in the corresponding period, it was set to May in this study. The home range analysis excluded individuals that were observed irregularly during the study period and individuals that appeared less than five times. 14 individuals that were regularly observed five times or more were selected for overall analysis. Comparative analysis was made on the eleven individuals that were consistently observed throughout the entire survey period for observable changes by dividing into wintering and breeding periods. Also, in order to more clearly judge the changes of the two periods according to gender, home range analysis was conducted separately for three pairs (six individuals) that bred within the survey site. The total number of appearances for the fourteen individuals that were regularly observed at least five times was 158 times, and through observation, 640 location coordinates were obtained. For analysis, the location was calculated by applying GIS software (Arcview GIS 3.2; ESRI, 2000) to use 100% MCP (Minimum Convex Polygon method) that connects from the outermost point (Murphy and Dowding, 1995; Walton et al., 2001; Choi, 2004). In addition, FK (Fixed Kernel method) was used to calculate the home range according to the spatial use distribution (Worton, 1989; Seaman et al., 1998; Choi, 2004). The MCP method also includes areas that individuals do not use, so it is judged that the method using FK has higher accuracy (Worton, 1989; Kang and Paek, 2005; Choi et al., 2006). In this study, the locational coordinates forming each group for the 14 individuals were analyzed by dividing the home range according to analysis using 100 % MCP and FK methods by dividing into three main regions such as 50 %, 75 % and 95% fixed kernel home ranges (or the utilization distribution; UD). For statistical analysis, the groups' significance was checked through t-test, a SPSS statistical analysis software.
RESULTS AND DISCUSSION
1.Number of Individuals, Coordinates and Individual Identification
26 total individuals were observed during the study period in Eulsuk-do of Saha-gu and Myeongji-dong, Daejeo 2-dong and Gangdong-dong of Gangseo-gu. Among them, 14 were observed more than five times and first winter plumage was for three females and two males, while there were three females and six males among adult birds. Furthermore, the total number of appearances for the 14 birds was 158 times and 640 locational coordinates were obtained through observation (Table 1). Twelve (12) of the individuals that were observed appeared less than five times and were observe irregularly, with one female in first winter plumage and two females and eight males being adult birds, showing that more males were observed (Table 2).
For adult birds, in the case of head feather, females had black shaft streaks on a yellowish brown base, while males had narrow black shaft streaks on a gray base. In the case of tail feathers, females had regular complete or incomplete dark bars on a yellowish brown base, and males were uniformly grey with broad black subterminal band and whitish tip. For individuals in first winter plumage, in the case of upper tail covert and scapulars, molting had already been finished, so they showed features of adult feathers. In the case of upper tail covert, females had black bars on a brownish gray base, and males showed corresponding gray features. In the case of scapulars, females had black bars on a yellowish brown base, while males had black spots that look like water drops on a reddish-brown base.
A total of six females were examined. Three were in first winter plumage (Fa-Fc) and three had adult feathers (Fd-Ff), and each individual female was identified by the formative differences of the tail lines and under tail covert (Appendix 1). A total of eight males were examined. Two were in firs winter plumage (Ma, Mb) and were distinguished by their scapulars and back, and six birds with adult bird feathers (Mc-Mh) were identified by the formative differences of the greater coverts (Appendix 2).
Group 1: Fa-Fc were identified as females in first-time winter plumage. The angle of the tail feather and tail lines were in the shape of '-', while being thicker than adult feathers, and each individual was distinguished with this formative difference.
Group 2: Fd-Ff were adult female birds. Each individual was identified by the angle and thickness of the under tail coverts and tail feathers.
Group 3: Ma and Mb were found to be male individuals with first winter plumage. Each individual was identified by the size of the dot on the end feather of scapulars, and compared to Mb, Ma had slightly smaller and finer formative differences.
Group 4: Mc-Mh were all adult male birds. They were distinguished with the patterns of the greater coverts, and in the case of Me, there was no bars on the greater coverts. The other individuals could be distinguished by the size and shape of patterns. It was found that the patterns and shapes of the end feather spot of all coverts were different as well.
2.Home Range Estimation
The scope of the home range examined for six months from December 2009 to May 2010 was on average 34.49 ha when using 100 % MCP, with a range of 2.74-163.96 ha. However, when excluding the range of the two extremes, the average was 26.34ha with an activity range of 8.20-74.46ha. For home range estimates using 95 %, 75 % and 50 % of utilization distribution (UD) of the FK method, when using 95 % of UD, the average was 41.35 ha and the range was 3.54-99.02 ha, when 75 % of UD, the average was 14.33 ha and range was 0.20-31.57 ha, and when 50 % of UD, the average was 5.75 ha and the range was 0.52-14.74 ha (Table 3, Figure 3).
For the difference of home range area of males and females, in the case of MCP, females showed an average of 11.80ha (2.74-24.48 ha) and males had an average of 51.50 ha (15.04-163.96 ha), showing that the home range area was larger for males than females. Even when not including Md, which had the highest home range area, it was 35.43 ha (15.04-74.46 ha), showing that the range was larger for males than females. In the FK method, when the UD area with the highest activity was 50 %, females had 2.72 ha (0.52ha-4.28 ha) and males had 8.02 ha (2.38-14.74 ha), showing an average of within 10ha, and males had larger areas of home range than females.
3.Home Range Estimation between Wintering and Breeding Season
For the home range difference in wintering season and breeding season using FK, there were no significant differences at 95 %, 75 % and 50 % of UD. However, when examining the average of groups, in the case of 95 % of UD, it was 38.36 ha in wintering season and 59.54 ha in breeding season. In the case of 75 % of UD, it was 13.65 ha in wintering season and 20.10 ha in breeding season, and at 50 % of UD, it was 5.28 ha in wintering season and 8.17 ha in breeding season, showing that the birds had higher home range in breeding season than in wintering season (Table 4, Figure 4).
While calculating the difference of home range in wintering and breeding season using MCP as well, no significant difference was found. The home range size for MCP was 26.68 ha for the wintering season and the range was 1.23-67 ha, and it was 55.80 ha in the breeding season with a range of 3.79-264.23 ha. Like FK, MCP also showed differences among individuals, but it was found that the area of home range was larger in the breeding season than in the wintering season (Table 4, Figure 5).
The home range of the common kestrel studied in areas surrounding the pastures of Scotland changed by seasons, such as 10-20 ha in the fall (October to November), 20-50 ha in the winter (December to February), and 30-60 ha in the summer (April to July). In the fall, the number of common kestrels increased with the rise in the number of rodents that are used as food, while the home range tended to narrow. Meanwhile, due to the decrease of rodents in the winter, the number of common kestrels also decreased while their home range increased, and in the breeding season, the outer areas of home ranges were shared to increase the area compared to the wintering season (Village, 1982). As shown in this study as well, there was a tendency for the home range to increase during the breeding season compared to the wintering season, but there was no significant difference due to the large difference among individuals. When comparing this data with other predatory birds, it was found that in the case of Accipiter gentilis in the urban areas of Germany, the home range (100 % MCP) was 863ha (Rutz, 2006). The breeding season home range (95 % MCP) was 65 ha and the non-breeding season (95 % MCP) was 138ha for the Buteo lineatus near cities in the United States (Dykstra et al., 2001). The common kestrel is judged to have similar home ranges with Buteo lineatus that hunt insects or small animals rather than Accipiter gentilis that hunt prey with high activity (birds).
4.Breeding Season Home Range of Breeding Groups
The results for the change of home range from wintering season to breeding season of breeding groups were as follows. In FK home range when it is a female, the wintering season home range area when using 95 % of UD was an average of 36.71 ha, but dropped to 10.54 ha during breeding season, and at 75 % and 50%, it dropped from 12.54 ha to 5.32 ha and 4.88 ha to 1.65 ha, showing similar tendencies. Meanwhile, in the case of males, at 95 % of UD, the home range area in the wintering season was 55.88 ha, but increased to 80.02 ha during breeding season, while at 75 % and 50 %, it rose from 20.04 ha to 20.07 ha and 6.84 ha to 8.27 ha. For change of home range according to MCP analysis, in the case of females, it dropped greatly from an average of 23.18 ha to 4.58 ha, but in the case of males, it increased greatly from 39.41 ha to 124.77 ha. However, in the breeding pair of the female Fb and male Mc that failed to breed, the male Mc was not observed after May, so when comparing with wintering season in the home range analysis, no large difference was observed. Meanwhile, male Md displayed behavior of expanding its home range to that of Mc's home range after Mc, which failed to breed, disappeared (Table 5, Figure 4, 5).
While the home range of females drop in breeding seasons, males tended to broaden their home range. The reason why females displayed opposite tendencies from males was because females stayed near the nest to lay and hatch eggs, and to supply food to their newborns and guard the nest, thus limiting their area of activity. The males fly to far away places to provide for their family. In the case of most predatory birds, 'parental role division', the roles of males and females are different and the females are in charge of laying and incubating eggs and feeding their newborns, while the males are in charge of providing for the family (Newton, 1979). Some individuals (Fb and Mc), however, showed opposite tendencies than that which is normal, and the reason for this is that after failing to breed in the early spawning period, they disappeared and did not adhere sufficiently to the home range features of breeding seasons.
The common kestrel is an opportunistic predator and it is a species of urban predatory birds that effectively adapted to both rural and urban environments. Furthermore, it preys on rodents and harmful insects that damage crops in farms, so they control their numbers in a nature-friendly fashion (Demarchi and Bentley, 2005; Kang et al., 2012). However, due to their nesting habits, they often appear near airport runways, which is a major cause of bird strikes for airplanes (Kitowski, 2014). This study will be an important reference for not only the inhabiting ecosystem of the common kestrel in suburban areas of the city, but also for the management of common kestrels in or near airports.
