Martin Julien, Kitchens Wiley M, Hines James E
Florida Cooperative Fish and Wildlife Research Unit, University of Florida, Building 810, Gainesville, FL 32611-0485, USA.
Oecologia. 2007 Aug;153(2):291-301. doi: 10.1007/s00442-007-0729-8. Epub 2007 May 26.
Despite the accepted importance of the need to better understand how natal location affects movement decisions and survival of animals, robust estimates of movement and survival in relation to the natal location are lacking. Our study focuses on movement and survival related to the natal location of snail kites in Florida and shows that kites, in addition to exhibiting a high level of site tenacity to breeding regions, also exhibit particular attraction to their natal region. More specifically, we found that estimates of movement from post-dispersal regions were greater toward natal regions than toward non-natal regions (differences were significant for three of four regions). We also found that estimates of natal philopatry were greater than estimates of philopatry to non-natal regions (differences were statistically significant for two of four regions). A previous study indicated an effect of natal region on juvenile survival; in this study, we show an effect of natal region on adult survival. Estimates of adult survival varied among kites that were hatched in different regions. Adults experienced mortality rates characteristic of the region occupied at the time when survival was measured, but because there is a greater probability that kites will return to their natal region than to any other regions, their survival was ultimately influenced by their natal region. In most years, kites hatched in southern regions had greater survival probabilities than did kites hatched in northern regions. However, during a multiregional drought, one of the northern regions served as a refuge from drought, and during this perturbation, survival was greater for birds hatched in the north. Our study shows that natal location may be important in influencing the ecological dynamics of kites but also highlights the importance of considering temporal variation in habitat conditions of spatially structured systems when attempting to evaluate the conservation value of habitats.
尽管人们普遍认为有必要更好地了解出生地如何影响动物的移动决策和生存，但目前仍缺乏与出生地相关的移动和生存的可靠估计。我们的研究聚焦于佛罗里达州蜗牛鸢出生地相关的移动和生存情况，结果表明，鸢类除了对繁殖区域表现出高度的地点忠诚度外，还对其出生地表现出特别的吸引力。更具体地说，我们发现从扩散后区域向出生地的移动估计值大于向非出生地的移动估计值（四个区域中的三个区域差异显著）。我们还发现，出生地留居性的估计值大于对非出生地的留居性估计值（四个区域中的两个区域差异具有统计学意义）。此前的一项研究表明出生地对幼鸟生存有影响；在本研究中，我们表明出生地对成年鸟生存也有影响。在不同区域孵化的鸢类成年鸟的生存估计值各不相同。成年鸟经历的死亡率具有测量生存时所在区域的特征，但由于鸢类返回其出生地的可能性大于返回其他任何区域，它们的生存最终受出生地影响。在大多数年份，在南部地区孵化的鸢类比在北部地区孵化的鸢类有更高的生存概率。然而，在一次多区域干旱期间，北部的一个区域成为干旱避难所，在此干扰期间，在北部孵化的鸟类生存状况更好。我们的研究表明，出生地可能对影响鸢类的生态动态很重要，但也凸显了在试图评估栖息地的保护价值时，考虑空间结构系统栖息地条件的时间变化的重要性。
