科研之友
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摘要
Changes in the timing of arrival and departure of migrant bird species to and from breeding and wintering grounds in response to rising temperature have often been reported. A recent study from Ireland found earlier indications of spring departure for some waterbirds but not for all. In order to examine if it is possible to determine any change in the length of time these birds spend at their wintering grounds, we examined indicators of the timing of autumn arrival and the subsequent duration of stay. We used the earliest reporter dates in autumn from BirdWatch Ireland's East Coast Bird reports (1980-2003) as an indicator of the timing of arrival and determined the duration of stay as the number of days between arrival and departure for each species. Although these reports did not specifically document earliest and latest dates and therefore make it difficult to conclusively determine duration of stay the data extracted may still provide some useful indications of changes in the 'tails' of a distribution. Of the nineteen species examined, two arrived earlier and one later, whereas none extended their duration of stay. In addition we analysed average autumn (August October) and average annual (July-June) temperature from within the study area and correlated these with autumn arrival and duration of stay, respectively. In response to average autumn temperature, two waterfowl (Brent Goose (P = 0.023) and Eurasian Teal (P = 0.037)) delayed arrival by approximately 10 and 11d/degrees C respectively whereas one wader (Bar-tailed Godwit (P = 0.008)) advanced its arrival by roughly 22d/degrees C. Even though the majority (six out of eight) of the birds examined revealed a reduction in their duration of stay with increasing annual temperature, none were statistically significant. Due to the highly variable nature of these data, the limitations associated with dealing with the 'tails' of a distribution and difficulties with extracting specific earliest and latest records, we recommend using more robust data from dedicated bird observatories where possible. Overall, this analysis revealed the difficulty in finding suitable data by which to examine the influence of climate change on bird migration and highlighted the value of systematically tracking the timing of arrival and departure of a range of bird species as an indication of what may be expected in a wanner future in relation to Ireland's bird diversity.
- 出版日期2016
