การเพิ่มประสิทธิภาพวิธิการสำรวจและประเมินประชากรนกป่า: กรณีศึกษาพื้นที่แปลงศึกษานิเวศวิทยาป่าไม้ระยะยาว มอสิงโต อุทยานแห่งชาติเขาใหญ่

บทคัดย่อ

ABST RACT.-Distance sampling is usually preferred over uncorrected point counts for surveys of forest birds, but rarely has its accuracy been assessed against known numbers, particularly in tropical forests. We compared density estimates of eight species of breeding bird-Black-naped Monarch (Fiypothynis azurea, Hill Blue Flycatcher (Cyornis banyusae, White-rumped Shama (Copsychus mala baricus), Puft-throated Bulbul (Alophoixus pallidus), Abbotts Babbler (Malacocincla abbotti). Puft-throated Babbler (Pellorneum mficeps), White-browed Scimitar Babbler (Pomatorhinus schisticeps), and White-bellied Yuhina (iuhina zantholeuca)-obtained through color-banding. nest finding, and territory mapping with those derived from distance methods in cvergreen forest in northcastern Thailand. IWe also assessed the availability of birc w be detected using a closed-capture model and incorporated this with point-transect distance sampling, Abundance estimates from territory mapping and distance sampling were highly correlated, but biased for two species using line transects and five species using point transects. Six of the seven biased estimates were biased low. Probabilities of detection were nut significantly different betwe een lives and points, and there was no significant difterence in the overall accuracy between methuds. Accuunting for observer difterences improved density estimates but reduced precision. The variance in accuracy was mostly related to the behavior of the different species. Adjusting for availability did not improve the overall accuracy of the estimates, because of the low singing rates of tropical birds. Nonetheless, distance sampling provided relatively robust estimates despite the near total dependence on aural cues. Violations of distance-sampling assumptions may be frequent in heavily forested habitats, where both availability for detection and probability of detection on the transect line (or point) are likely to be <l. Received 13 Alay 2008, accepted 9 January 2009.

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