Marra Peter P, Francis Charles M, Mulvihill Robert S, Moore Frank R
Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, MD 21037, USA.
Oecologia. 2005 Jan;142(2):307-15. doi: 10.1007/s00442-004-1725-x. Epub 2004 Oct 5.
Ecological processes are changing in response to climatic warming. Birds, in particular, have been documented to arrive and breed earlier in spring and this has been attributed to elevated spring temperatures. It is not clear, however, how long-distance migratory birds that overwinter thousands of kilometers to the south in the tropics cue into changes in temperature or plant phenology on northern breeding areas. We explored the relationships between the timing and rate of spring migration of long-distance migratory birds, and variables such as temperature, the North Atlantic Oscillation (NAO) and plant phenology, using mist net capture data from three ringing stations in North America over a 40-year period. Mean April/May temperatures in eastern North America varied over a 5 degrees C range, but with no significant trend during this period. Similarly, we found few significant trends toward earlier median capture dates of birds. Median capture dates were not related to the NAO, but were inversely correlated to spring temperatures for almost all species. For every 1 degrees C increase in spring temperature, median capture dates of migratory birds averaged, across species, one day earlier. Lilac (Syringa vulgaris) budburst, however, averaged 3 days earlier for every 1 degrees C increase in spring temperature, suggesting that the impact of temperature on plant phenology is three times greater than on bird phenology. To address whether migratory birds adjust their rate of northward migration to changes in temperature, we compared median capture dates for 15 species between a ringing station on the Gulf Coast of Louisiana in the southern USA with two stations approximately 2,500 km to the north. The interval between median capture dates in Louisiana and at the other two ringing stations was inversely correlated with temperature, with an average interval of 22 days, that decreased by 0.8 days per 1 degrees C increase in temperature. Our results suggest that, although the onset of migration may be determined endogenously, the timing of migration is flexible and can be adjusted in response to variation in weather and/or phenology along migration routes.
生态过程正随着气候变暖而发生变化。尤其是鸟类，有记录表明它们在春季到达和繁殖的时间提前了，这被归因于春季气温升高。然而，尚不清楚那些在热带地区越冬数千公里的长途候鸟是如何感知北方繁殖地温度或植物物候变化的。我们利用40年间北美三个环志站的雾网捕获数据，探究了长途候鸟春季迁徙的时间和速度与温度、北大西洋涛动（NAO）和植物物候等变量之间的关系。北美东部4月/5月的平均气温在5摄氏度范围内变化，但在此期间没有显著趋势。同样，我们发现鸟类中位捕获日期提前的显著趋势很少。中位捕获日期与北大西洋涛动无关，但几乎所有物种的中位捕获日期都与春季温度呈负相关。春季温度每升高1摄氏度，候鸟的中位捕获日期平均提前一天。然而，紫丁香（Syringa vulgaris）的芽萌动在春季温度每升高1摄氏度时平均提前3天，这表明温度对植物物候的影响比对鸟类物候的影响大三倍。为了探究候鸟是否会根据温度变化调整向北迁徙的速度，我们比较了美国南部路易斯安那州湾岸一个环志站与向北约2500公里的另外两个环志站之间15个物种的中位捕获日期。路易斯安那州与其他两个环志站的中位捕获日期间隔与温度呈负相关，平均间隔为22天，温度每升高1摄氏度，间隔减少0.8天。我们的结果表明，尽管迁徙的开始可能由内在因素决定，但迁徙的时间是灵活的，可以根据迁徙路线上天气和/或物候的变化进行调整。
