การศึกษาการย้ายอาณาเขตของลูกนกปรอดโอ่งเมืองเหนือ (Alophoixus pallidus) โดยใช้วิทยุติดตามตัว (ระยะที่ 2)

บทคัดย่อ

While natal dispersal can have a significant impact on population dynamics particularly for cooperative breeders, it is typically difficult to quantify. We modelled probabilities of staying in the natal territory and timing of dispersal in juvenile under the effects of social factors including sex, group size, and presence of helpers. The best fitting model indicates that juvenile birds did not disperse until the second calendar year, at the beginning of and during the breeding season following the hatching year. Dispersal was strongly female-biased both in frequency and distance. Most females dispersed away from their natal territories (94.4%), median number of territories crossed (excluding philopatric birds) : interquartile was 3.9 + 1.9 territories. Half of the males re ained on the natal site as helpers in their second year, while 50% dispersed, 25% of which moved to neighbouring territories. Dispersing female offspring were not influenced by any of the social variables measured, while the presence/absence of helper(s) influenced both timing of dispersal and the probability of staying for males. Using radio telemetry to study natal dispersal of small passerines that exhibit delayed dispersal is not reco hended. This problem was due to the life span of the battery is relatively short while timing of natal dispersal is unpredictable. Furthermore, catching targeted juvenile for fixing the radio was extremely time consuming and difficult. However, radio telemetry maybe useful tool to study their movement prior to dispersal, which is more practical for small birds in dense vegetation. Our findings of natal philopatry in males and sex-biased dispersal contribute to a growing body of literatures that suggests a range of complex behaviours influence the dispersal patterns of cooperatively breeding birds.

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