Habitat Evaluation for Crested Ibis X

Blackwell Science, LtdOxford, UK ERE Ecological Research 0912-38142002 Ecological Society of Japan 175September 2002 515 Habitat evaluation for crested ibis X. Li et al. 10.1046/j.0912-3814.2002.00515.x Original Article565573BEES SGML Ecological Research (2002) 17, 565–573 Habitat evaluation for crested ibis: A GIS-based approach XINHAI LI,1* DIANMO LI,1 YIMING LI,1 ZHIJUN MA2 AND TIANQING ZHAI3 1Institute of Zoology, Chinese Academy of Sciences, 19 Zhongguancun Lu, Beijing 100080, China, 2Institute of Biodiversity Science, Fudan University, Shanghai 200433, China and 3The Conservation and Observation Station of Crested Ibis, Yang County 723300, China We evaluated habitat quality for crested ibis (Nipponia nippon) using a geographic information system (GIS). First, we digitized the topography map, vegetation map, river map, road map and villages/ towns map by ArcInfo, and gave each map layer a suitability index based on our perceptions of the needs of crested ibis. Second, we overlayed these maps to obtain an integrated map of habitat quality. Finally, we compared the calculated habitat quality with the actual distribution of crested ibis. We found that the birds were almost always located at the site of high quality (habitat suitability index [HSI] > 0.6), which indicated that the factors we selected were important for crested ibis. We also found that crested ibis were never located at some sites of high quality, thus, we assume that other factors not considered in this study limit the distribution of crested ibis. Regression analysis indicated that crested ibis preferred lower elevation habitats and tolerated higher levels of human disturbance in recent years than previously reported. These results reflected a 20-year protection program for this species. Key words: geographic information system; habitat quality; habitat suitability index; Nipponia nippon. INTRODUCTION erences and use. Shi et al. (1991a) reviewed the extinction process of crested ibis at many of its The crested ibis (Nipponia nippon) became one of original habitats and discussed how habitat loss the most endangered birds in the world in the late played a role in its decline. Zhai and Lu (1991) 20th century. Its population size has fluctuated at described the current distribution and abundance a very low level since its rediscovery in 1981 (Li of crested ibis at different habitats in different & Li 1998), but recently increased to 155 individ- stages of its annual life cycle. Wang et al. (1985), uals (including 31 pairs) in the summer of 2001 Wang (1993) and Shi et al. (1991b) evaluated sev- (T. Zhai, pers. comm., 2001). Among the reasons eral features of the landscape that were important for declining numbers of ibis, habitat destruction for crested ibis. Shi et al. (1991c) and Wang et al. is the most important (Lu 1989; Shi et al. 1991a; (1994, 1995) examined the relationship between Cao & Lu 1994). After rediscovering crested ibis population dynamics and habitat quality. Li et al. in remote mountains in Yang County, Shaanxi (1998) discussed key factors for the survival of province, China in 1981 (Liu 1981), researchers crested ibis and evaluated the carrying capacity of have completed several studies on its habitat pref- its current habitat. Ma et al. (2000) analyzed nest site alternation and its influence on population dynamics. Li et al. (2001) weighted the birds’ pref- erences for different habitat factors. However, no reserchers have evaluated habitat quality by *Author to whom correspondence should be considering numerous habitat features simulta- addressed. Email: [email protected] neously. We used a geographic information system Received 27 September 2001. (GIS) to record detailed information on the habitat Accepted 25 February 2002. of crested ibis and we used these data to assess 566 X. Li et al. habitat quality. Our study provides an important METHODS base for determining potential habitats of crested ibis and provides information on how to rehabili- Selection of key habitat features tate other habitats to support large populations of Habitat use by crested ibis has been documented ibis, including potential areas for the reintroduc- from 19 years of monitoring (Wang et al. 1985; Li tion of captive ibis into the wild. et al. 1998). The crested ibis is a mid-sized wading Crested ibis live in Hanzhong Basin and on the bird that roosts in tall trees, and feeds in shallow southern slopes of Qinling Mountain in central water. In addition to being found at different alti- China (33°08–35′ N, 107°17–44′ E), mainly in tudes in different seasons, these birds are timid Yang County, Shaanxi Province (Fig. 1). The and are, therefore, easily disturbed by humans. We crested ibis’ habitat consists of breeding, post- analyzed nest site selection of this species using breeding and intermediary prebreeding regions. logistic regression, and the results indicated that From February to June, crested ibis breed in forest vegetation, elevation, wetland and human distur- patches in remote, high (680–1300 m) mountains bance have larger selection coefficients than six within Yang County. After reproduction, crested other factors (density of trees, average height of ibis congregate and fly to the postbreeding region, trees, slope [where the nest tree was located] direc- south of the breeding region. Low hills (450– tion, slope gradient, nest orientation in the tree 840 m) and plains are the main landscape features and coverage above the nest) (Li et al. 2001). of these areas. In the postbreeding season, ibis Consequently, we selected vegetation, elevation, occasionally fly to neighboring counties. In wetland and human disturbance as key habitat November, flocks of crested ibis divide into small features to evaluate for habitat quality. groups and fly to a separate area/habitat between the breeding and postbreeding regions to spend the winter. GIS analysis Vegetation type, topography, rivers, reservoirs, roads, villages and towns were digitized from 1996 to 1998 using ArcInfo (PC Version 3.4.2) on the basis of topography maps (1:100 000) (China National Mapping Bureau 1990) purchased from China National Mapping Bureau, and vegetation maps from the Department of Forestry, Yang County in 1995. The GIS database was modified by ground investigation from 1997 to 2000. Dig- Shaanxi Province itized maps were edited to four different ‘coverage’ layers in ArcInfo (Workstation Version 7.0): the Yang County vegetation layer contained 12 different vegetation types, the topographic layer included contours ranging from 200 m to 2600 m by 200 m inter- vals, the river and reservoir layer contained 1756 main and branch rivers and 72 lakes or reservoirs, and the human disturbance layer included a 482 km highway, 20 km railway and 47 villages N and towns. The map covers the whole Yang County, which includes most crested ibis’ activity ranges. Within each layer, different habitats were assigned different suitability values based on the Fig. 1. The location of crested ibis’ habitat, Yang opinion of six experts (Y. Zhang & B. Lu, Crested County, Shaanxi Province, China. Ibis Conservation Station; Y. Cao & X. Lu, Shaanxi Habitat evaluation for crested ibis 567 Department of Forestry; Y. Liu & Y. Tan, Institute cell was assigned a habitat suitability index (HSI) of Zoology, Chinese Academy of Sciences) on this value according to the following rules. species (Tables 1,2). After overlaying the four layers with different weights, we obtained the average Vegetation value of the suitability index for each layer, which is the integrated suitability of the complicated Vegetation types differ in habitat suitability in landscape for crested ibis. different seasons (Fig. 2). Rice paddies are the For ease of calculation, we transformed vector major feeding sites of crested ibis during the late images to raster images by using the grid module prebreeding and breeding season. During the post- of ArcInfo. Each raster layer contains 13 192 cells breeding season, however, rice paddies are not suit- measuring 500 m2. In each layer, every individual able for feeding because the rice grows too dense and high. Near the end of the postbreeding season and at the beginning of the prebreeding season, Table 1 The suitability of different vegetation types cropland is usually rotated to rape, which is sel- to crested ibis dom used by crested ibis. Masson pine forests and oak or birch forests are often selected for roosting Vegetation type Seasons HSI and these forests are considered to be highly suit- Masson pine forest 1 able habitats for ibis. Fuel forest and economic Oak or birch forest 1 forest are designed for the farmers’ daily use, they Conifer-broadleaf forest 0.75 are frequently disturbed by humans; wasteland is Cypress forest 0.5 unused mine or idle crop field with rare vegetation Chinese pine forest 0.5 cover. Such areas are seldom visited by crested ibis Cropland Breeding season 1 and were assigned low suitability (Table 1). Postbreeding season 0.25 Prebreeding season 0.5 Wasteland 0.1 Altitude Fuel forest 0.25 Crested ibis move annually between their breeding Shrubland 0.1 and postbreeding regions. The breeding region is Sand 0.1 centered on the middle slope of Qinling Mountain Economic forest 0.25 Fir forest 0.25 at approximately 1000 m a.s.l. The postbreeding region is near the bottom of Hanzhong Basin at (HSI), habitat suitability index. an altitude of 500 m. We believe that crested ibis prefer different altitudes in different seasons. Based on the experience and knowledge of experts, Table 2 The suitability of different altitudes to we assigned a suitability value to the different crested ibis altitudes in the different seasons (Table 2) (Fig. 3). HSI Altitude Breeding Postbreeding Prebreeding Rivers, reservoirs, roads and towns (m) season season season Rivers, reservoirs and their adjacent habitats are 200–400 0.25 0.5 0.15 foraging sites for crested ibis. Thus, areas within 400–600 0.5 1 0.5 250 m of water bodies were assigned a suitability 600–800 0.75 1 1 of 1.0, areas within the next 250 m from rivers 800–1000 1 0.75 1 were assigned 0.75, whereas all other areas had a 1000–1200 1 0.5 1 suitability of 0.5.

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