Trends in the abundance of farmland birds: a quantitative comparison of smoothed Common Birds Census indices
Trends in the abundance of farmland birds: a quantitative comparison of smoothed Common Birds Census indices
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农田鸟类丰度趋势：平滑常见鸟类普查指数的定量比较
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
Jeremy D. Wilson
中科院分区：
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作者：
G. Siriwardena;S. Baillie;S. T. Buckland;R. Fewster;J. Marchant;Jeremy D. Wilson
[1]自20世纪70年代初以来，英国许多农田鸟类的数量普遍下降。 我们必须了解这些下降的原因，以便提出保护和农业管理的建议，这可以通过调查物种之间的关系，丰富和农业变化之间的关系来解决。我们描述了新的，定量的方法来解释丰度指数，从可靠的推断保护状况。
2.我们计算了42种农田常见鸟类普查指数，平滑序列以揭示潜在趋势，并估计了丰度变化的置信区间。
3.1968 ~ 1995年，有12种物种的丰度显著下降，14种物种的丰度上升。
4.专业化是丰度变化的唯一重要决定因素（针对物种特征的10项测试）：13个农田专业物种平均下降了30%，而29个更通用的物种平均增加了23%，证实了农田鸟类应该引起保护关注。
5.然后对平滑的丰度曲线进行量化比较，以确定各组物种是否有共同的趋势。
6.物种往往没有很强的分组性，但发现了具有共同趋势的小种群。 分组物种之间的生态相似性澄清了其人口趋势的可能环境原因，表明未来的研究重点。
7.已确定的类群包括：一个类群由三种画眉和云雀Alauda arvensis L组成。 其中一组包括三种撒哈拉以南迁徙莺（Sylvidae），其丰度在20世纪70年代初下降，后来增加;还有一组由六种平稳增加的物种组成。
8.转折点被确定为每个物种的种群趋势发生重大转变之处，揭示了种群可能受到环境变化影响的关键时期。
[9]发现了三个下降的转折点，包括20世纪70年代中期的一个转折点，当时许多农田鸟类开始减少。 其他四个时期都有许多好转。各组转折点应有助于查明具有广泛影响的环境变化。管理处方，然后可以设计扭转或反映这些关键的变化，从而有效地集中保护工作。
1. Widespread declines in the populations of many British farmland birds have occurred since the early 1970s. We must understand the causes of these declines tomake recommendations about conservation and agricultural management, andthis can be approached by investigating the relationships, across species, betweenabundance and agricultural change. We describe novel, quantitative approaches to the interpretation of abundance indices from which reliable inferences about conservation status can be made.
2. We calculated farmland Common Birds Census indices for 42 species, smoothed the series to reveal underlying trends and estimated confidence intervals for the changes in abundance.
3. Between 1968 and 1995, the abundance of 12 species declined significantly andthat of 14 species increased.
4. Specialization was the only significant determinant of changes in abundance (of 10 tests against species characteristics): 13 farmland specialists declined, on average, by 30%, whilst 29 more generalist species underwent an average increase of 23%, confirming that farmland birds should engender conservation concern.
5. Smoothed abundance curves, transformed to emphasize trend direction and timing, were then compared quantitatively to identify whether groups of species had shared common trends.
6. Species tended not to be strongly grouped, but small groups of species with common trends were identified. Similarities in ecology among grouped species clarify the possible environmental causes of their population trends, indicating future research priorities.
7. The groups identified included: one group consisting of three thrush species Turdus and the skylark Alauda arvensis L. which all declined from the mid-1970s after being stable previously; one group comprising three trans-Saharan migrant warblers (Sylvidae), whose abundance fell in the early 1970s and later increased; and a diverse group of six smoothly increasing species.
8. Turning points were identified as where each species’ population trend turned significantly, revealing critical periods during which populations are likely to have been affected by environmental change.
9. Three collections of downward turning points were found, including one in the mid-1970s when many farmland bird declines began. Four other periods each included many upturns. The groups of turning points should facilitate the identification of environmental changes which have had widespread effects. Management prescriptions can then be designed to reverse or to mirror such key changes and thereby focus conservation effort effectively.