Abstract Interactions and dependence between species can transmit the effects of species declines within and between trophic levels, resulting in secondary endangerments and, in some cases, extinctions. Many mixed-species avian breeding aggregations commonly have a protector species whose aggressive nest defense is used by other species to defend their nests. Disappearance of the protector species may have population demographic consequences on the dependent species. Aggressive nest defense behavior of small colonial gulls, such as the black-headed gull (Chroicocephalus ridibundus), is used by many waterbird species to gain protection against predators. We used data from 15 local waterbird communities in Finland to study long-term changes and dynamics of breeding numbers of other waterbirds as a response to long-term changes and dynamics of black-headed gull colonies. We found that breeding numbers of many species tracked long-term changes in the size of black-headed gull colonies. This was true even after controlling for a common trend in the size of the black-headed gull colony and the breeding numbers of the other species. The trend-controlled positive temporal association with black-headed gull was relatively stronger in species that nest in similar habitats of a lake as the black-headed gull, and in species that have a more critical conservation status due to drastic population decline. Our results suggest that the overall decline of black-headed gull colonies has resulted in secondary endangerment of many other species in waterbird communities.

中文翻译：

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保护物种的崩溃导致水鸟群落的二次濒危

摘要 物种之间的相互作用和依赖可以在营养级内和营养级之间传递物种衰退的影响，导致次生危害，在某些情况下甚至灭绝。许多混种鸟类繁殖群通常有一个保护物种，其他物种使用其侵略性的巢穴防御来保护它们的巢穴。保护物种的消失可能会对依赖物种的人口统计产生影响。许多水鸟物种利用小型殖民地海鸥（例如黑头海鸥 (Chroicocephalusridibundus)）的侵略性筑巢防御行为来抵御捕食者。我们使用来自芬兰 15 个当地水鸟社区的数据来研究其他水鸟繁殖数量的长期变化和动态，作为对黑头鸥群落长期变化和动态的响应。我们发现许多物种的繁殖数量跟踪了黑头鸥群落大小的长期变化。即使在控制了黑头鸥群体规模和其他物种繁殖数量的共同趋势之后，情况也是如此。在与黑头鸥类似的湖泊栖息地中筑巢的物种以及由于种群急剧下降而具有更关键保护状态的物种中，与黑头鸥的趋势控制的正时间关联相对较强。