Some predators are attracted to the food in bird feeders, and end up targeting nestlings, too. Jason G. Goldman reports.

一些捕食者会被喂鸟器中的食物吸引，最终发现雏鸟。贾森·G·戈德曼（Jason G. Goldman）报道。

撰文\播音：贾森·G·戈德曼（Jason G. Goldman）

翻译：杨枭

审校：李轩

More than half of U.S. households provide food for birds. It's a billion dollar industry. Now a study asks whether the same feeders that attract birds also attract predators that eat the eggs and newly hatched nestlings of those birds.

一半以上的美国家庭会为鸟类提供食物。这是一个十亿美元的产业。近日，一项研究开始探究，喂鸟器在吸引鸟类前来觅食额同时，是否也同样会吸引以捕食这些鸟的蛋和雏鸟为生的猎食者。

“We imagined that the food resource on the landscape could have a couple different effects on relationships between nest predators and their prey.” Ohio State University researcher Jennifer Malpass.

俄亥俄州立大学研究员珍妮弗·马尔帕斯（Jennifer Malpass）说：“我们猜想，这种食物资源可能会对捕食者和它们猎物之间的关系产生一系列不同的影响。”

“On the one hand, you could see that the food might be attracting predators to certain areas, and that could increase nest predation risk. However, predators may be exploiting these food resources, and if you've got a good, predictable food resource on the landscape that's easy for predators to access, you could imagine that they could switch to those anthropogenic, or those human-provided foods, like bird feeders. And that could perhaps lessen nest predation risk.”

“一方面，你能看到食物会吸引捕食者到某些区域，这可能会增加鸟巢被发现的风险。另一方面，捕食者也可能会自己利用这些资源，如果人类提供的食物资源恰好是捕食者所需要的，可以想象，捕食者会转向这些食物。这样或许又会减少鸟巢被捕的风险。”

Which could also be a problem, because predators help control the population.

这种效应可能会造成问题，因为捕食者会影响鸟的数量。

Malpass and her team looked at the nests of American robins and Northern Cardinals in seven Ohio neighborhoods. They noted the presence or absence of feeders and recorded potential nest predators, like squirrels, domestic cats, and other birds. Over the four-year study, they observed more than 15,000 day-active predators across 19 species, but only brown-headed cowbirds and American crows were associated with bird feeders. The results were published in the journal The Condor. [Jennifer S. Malpass, Amanda D. Rodewald, and Stephen N. Matthews, Species-dependent effects of bird feeders on nest predators and nest survival of urban American Robins and Northern Cardinals]

马尔帕斯和她的团队在七个俄亥俄州周边地区观察了旅鸫和北美红雀的巢穴。它们记录下了这些地区是否存在喂鸟器，以及存在哪些潜在的巢穴捕食者，如松鼠，家猫和一些其他鸟类。在这四年的研究中，他们观察了超过15,000只白天活动的捕食者，涉及19个物种，但只有褐头牛鹂和短嘴鸦与喂鸟器有关。该结果发表在了期刊《秃鹰》上。

The survival of Northern Cardinal nestlings did not seem to be related to the presence of these nest predators or even to bird feeders. But the American robins tell a different story.

北美红雀雏鸟的种群数量似乎与这些巢捕食者以及喂鸟器都没有关系。但旅鸫的情况则不同。

“In areas that had both many crows and many bird feeders, American robin nest survival was the lowest.”

“在那些既有乌鸦又有许多喂鸟器的区域，旅鸫巢穴的幸存率是最低的。”

So the effect of bird feeders on urban wildlife communities differs from species to species, neighborhood to neighborhood.

由此可见，喂鸟器对城市野生动物群落的影响会因物种和区域的不同而不同。

“At least some predators seem to be attracted by bird feeders and the food resource they provide, and in some cases this can lead to increased nest predation risk for native backyard breeding birds.”

“至少一些捕食者会被喂鸟器和其中的食物资源吸引，在一些情况下，这可能增加了后院鸟巢被袭的风险。”

But that doesn't necessarily mean that we should get rid of all the bird feeders.

但那并不意味着我们不应再放置喂鸟器了。

“There are some great ecological and social benefits from this practice. We see them as nature's ambassadors. They're a point of connection to nature and the outside world and our native wildlife.”

“这种做法还是有很大生态和社会效益的。它们是自然的大使，是我们与自然、外部世界和本土野生动物的连接点。”

Homeowners have been feeding wild birds for a long time, but only now are scientists finally beginning to understand just how that affects urban ecosystems. And the upshot, of course, is: it's complicated.

房主们长期以来一直有饲养野生鸟类的习惯，但直到现在科学家才开始逐渐了解这种行为如何影响城市生态系统。当然，它们之间的联系是非常复杂的。