| Diffusion has recently become a new field of animal study, and the dispersal ecology research on birds has also become increasingly intensive. It is generally believed that there are four types of dispersal which include natal dispersal, breeding dispersal, non-breeding dispersal and post-fledging dispersal. To date, the study on post-fledging and natal dispersal of the reintroduced population of the Crested Ibis in Ningshan County has been conducted, but the knowledge on breeding dispersal of the population remains unclear. To accurately understand the dynamics of population and improve the study on population life-history characteristics, the paper reported the patterns and the effect factors of breeding dispersal accoding to the data on the reintroduced population. Our results may provide a theoretical basis for further protection of the reintroduced population.A total of 34 breeders including 26 breeding pairs were recorded from 2008 to 2015. The location, elevation of all nests and reproductive parameters of all breeders were recorded in details during 8 breeding seasons.The paper aimed to overview the dispersal ecology, and focused on breeding dispersal which included the concept, category, research history and actuality, influence factors and so on, and then described the basic information, the status of development and research progress of the reintroduced Crested Ibis in Ningshan County. The breeding dispersal pattern, influence factors and consequences of breeding dispersal of the reintroduced Crested Ibis were summarized, as well as some management suggestions during the breeding season.The main results have been listed as follows:(1) The frequencies of breeding dispersal for females (91.7%) (n= 12) were significantly larger than that of males (57.1%, n= 14) (Fisher's exact test, P= 0.02< 0.05). The dispersal distance for all individuals averaged at 0.62 ± 0.86 km (n= 38), in which the shortest and longest distance was 0.03 km and 4.38 km, respetvely. Females and males dispersed had non-significant dispersal distance (0.79 ±1.12 km for females, n= 20; and 0.41 ± 0.39 km for males, n= 18; Mann-Whitney U test:U = 167, P= 0.72). However, long-distance movements (>2 km) were performed only by females, which were three times than that of males. Therefore, all most of the breeders exhibited short-distance movments within same breeding territories. Females dispersed more frequently and farther than males, while males behaved strongly site fidelity.(2) Age of the dispersal individuals were significantly smaller than that of non-dispersal ones (Mann-Whitney U test:U= 25.5, P= 0.03< 0.05, n= 26), indicating that the dispersal probability decreased with age. Dispersal distance was negatively correlated with age of all individuals (Spearman, r=-0.391, P= 0.03< 0.05, n= 30), but the relationship between dispersal distance and age was significant only for females (Spearman, females:r=-0.519, P= 0.04< 0.05, n= 16; males:r=-0.219, P= 0.39,n=17).(3) The breeding failure had no significant influence on dispersal distance for both sexes (Mann-Whitney U test:females, U= 38.5, P= 0.60, n= 20; males, U= 37.5, P= 0.95, n= 18), as well as lower breeding success (Mann-Whitney U test:females, U= 47.5, P= 0.98, n= 20; males, U= 37.5, P= 0.95, n= 18). Of the successful breeders,32.4% of females (n= 37) and 30.6% of males (n= 36) changed their nest sites in the next breeding season. However, of the failed breeders,87.5% of females (n= 8) and 88.9% of males(n= 9) changed their nest sites in the following year. Therefore, we conclude that breeding failure will more easily result in breeding dispersal (Fisher's exact test, P= 0.006< 0.01 for females; P= 0.002< 0.01 for males).(4) There was no significant difference in breeding experience between dispersed and non-dispersed breeders for both sexes (Mann-Whitney U test:females, U= 20.0, P = 0.09, n= 18; males, U= 20.0, P= 0.22, n= 16).(5) After a nest predation, there were 42.9% for females (n= 7) and 66.7% for males(n 9) which dispersed. Therefore, nest predation was an important factor to cause breeding dispersal. However, nest predation had no significant influence on the reoccupation of the same nest in the next breeding season (Fisher's exact test, females:P= 1.000 vs. males:P= 0.637).(6) Age of previous mate (as an indicator of quality) had no effect on dispersal for both sexes (Mann-Whitney U test:females, U= 5.0, P= 0.47, n= 10; males, U=0.5, P= 0.10, n= 7). But, mate loss had a strong influence on dispersal (Fisher's exact test, P = 0.04< 0.05). Age of mate loss individuals that dispersed and non-dispersed had no significant difference (Mann-Whitney U test:U= 10.0, P= 0.07). Besides, dispersal due to breeding success or not in the previous year had extremely significant difference (Fisher's exact test, P= 0.00< 0.01). Thus, dispersal caused by mate loss had nothing to do with competitive capacity, but mainly due to previous poor breeding performance. |
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