幽居的画眉唱着甜美的歌
The wood thrush’s song is one of the most beautiful among eastern birds, and its flute-like warble is one of the reasons Vitek Jirinec picked this species to study.
“It’s a charismatic species,” he said. “Even the lay public knows about wood thrushes because of their beautiful song. 它的歌声通常被描述为美国东部人口即将到来的春天的象征。 Unfortunately it’s been declining over the last 50 years.”
Jirinec is a master’s student in William & Mary’s Department of Biology. 他关于画眉和它们的微栖息地的工作在3月20日至21日举行的艺术与科学学院研究生研究研讨会上得到了认可，该研讨会既展示了威廉与玛丽学院研究生的卓越研究成果，也为他们提供了荣誉。 他对画眉鸟微栖息地和人类改造景观对该物种健康的影响的调查获得了诺斯鲁普·格鲁曼公司奖，这是研讨会颁奖午宴上颁发的几项荣誉之一。
In mid-March Jirinec was finishing up his master’s thesis on wood thrush microhabitat, the culmination of several years of studying the birds with his advisor, 马提亚低浓缩铀, associate professor of 生物学. Jirinec said the “eee-oh-wee” trill of the wood thrush is familiar to many people who wouldn’t be able to identify the species either by song or by sight.
“It sounds like a soloist playing the flute off in the woods. 画眉以能够同时唱出至少两个不同的音符而闻名。 It’s this eerie, flute-like song. You can hear it usually early in the morning, but also right before it gets dark,” Jirinec said. 有时到了晚上，他补充说，除了虫子，你在森林里听到的只有画眉鸟的叫声。
There’s more to this bird than a pretty song, though. Jirinec说，画眉鸟喜欢生活在落叶林中，所以它可以作为环境健康的指示物种。 It’s related to the robin, but you aren’t likely to find a wood thrush in the middle of a grassy space. Jirinec说，画眉喜欢在森林地面上觅食，这种习惯往往会让它远离人类的视线，就像另一种亲戚——隐士画眉一样。
“The Latin name really describes these birds. It’s Hylocichla mustelina. It means woodland thrush-weasel,” Jirinec explained. “It describes just how elusive these birds are, mostly because of their shyness and coloration.”
Jirinec开始研究单个鸟类与它们的栖息地之间的关系。 他说，画眉鸟将在4月中旬从中美洲迁徙到美国。 它们是来这里繁殖后代的，雄性会在几英亩宽的领地上安家落户。 Jirinec is interested in finding out what landscape features draw—and hold—wood thrushes. 传统的鸟类学观点认为，画眉鸟需要大面积、成熟的森林区域，但这种鸟似乎在弗吉尼亚半岛零星的林地中生存得很好。
“They’re associated with the forest, but people have been seeing them in their back yards,” he explained. “We want to figure out what they need in the environment.”
位置，位置，位置：Jirinec说，当谈到房地产时，林地画眉鼬喜欢一个漂亮，纠结的地方，脚下有很多枯叶。 They scratch around, kicking up the leaves for food, dining on “ticks, worms, insects, any sort of invertebrate,” he added. Presence of snags—upright dead trees—is a bonus in wood thrush real estate, and Jirinec said that the birds seem to have preference for certain tree species.
Jirinec在半岛上总共追踪了47只画眉鸟。 他的样本包括37名男性和10名女性。 他说，要捕获雌性要困难得多。 To collect his birds, he set up mist nets—imagine volleyball nets with very fine mesh—in likely wood thrush habitat. 他用这种方法抓了很多鸟，但都是雄性。
“The males are very territorial,” he explained. “I can go out to the woods and set up a mist net, then I have a speaker and I play the wood thrush song. A male thinks another male is moving into his territory, and he comes out to deal with the intruder and, boom, he gets caught in my net.”
The female wood thrushes lack the territorial instinct, and so are immune to Jirinec’s aural lure. 为了捕捉雌画眉，他不得不使用大约六米高，十几米宽的树冠网，在雄性巢穴附近或多或少地随机捕捉雌性。 He banded all the birds, but the usual ornithologist’s color-code scheme was only of limited use for tracking the reclusive wood thrushes.
“To be able to follow individual birds we have to attach a little transmitter on each bird. 这些发射器很小； it’s like a little backpack sitting on the rump of the bird,” he said. “The whole thing weighs maybe three percent of the body weight of the birds, so it’s really tiny. 它们持续大约60天； that’s how long we have to track these birds.”
If Jirinec were studying eagles or other large birds, he would have fit his specimens with solar-powered, satellite-linked transmitters that could track each bird’s progress in real time and map it on a web site. The little fanny packs on his wood thrushes aren’t nearly that powerful, so Jirinec uses radio telemetry.
“Each bird gets its own frequency,” he explained. “So we can dial in that frequency to a receiver and use a directional antenna to find out where that signal is coming from.”
画眉鸟的无线电遥测定位意味着用面包盒大小的接收器和GPS装置在树林里工作，并将天线穿过树林。
It’s a work-intensive method, and Jirinec got assistance from 16 undergraduate students, notably Akshay Deverakonda ’15 who was conducting his senior honors research in 生物学 on home range overlap of wood thrush pairs.
Jirinec said he assumed that the shy wood thrushes would be homebodies, rarely straying from the patch they’ve claimed. 在树林里呆了几天使他改变了想法。
“I thought they did not move. I said, I’m gonna go out in the forest and catch that bird and it’s gonna stay right there for the rest of the summer,” Jirinec explained. “But what we found out is that 56 percent of the birds actually move their territory, usually after something eats their nest.”
在一些大学生志愿者的帮助下，Jirinec能够为大多数鸟类找到新家，但搬迁给他带来了一些新的和意想不到的挑战。
“I have a permit to work in New Quarter Park,” he explained. “So I catch a bird in New Quarter Park and my bird decides to fly to Camp Peary.”
新季度公园距离皮尔里营地不到一分钟的路程，但皮尔里营地是中央情报局的设施。 对于一个打算带着一个大天线和一个嗡嗡作响的蓝盒子到处漫游的人来说，接入是不太可能的。
在约克镇海军武器站（Naval Weapons Station Yorktown）， Jirinec在追逐飞到地面上的鸟类时运气要好一些，那里的工作人员已经习惯了威廉和玛丽公司的研究人员在地面上工作。
“I talked them into letting me work there. 他们对我做了背景调查。 They gave me a ‘restricted area’ badge,” Jirinec said. “I was surprised. I had a harder time getting permission to work in Waller Mill Park than the Naval Weapons Station.”
其中一名与Jirinec一起工作的本科生在威廉斯堡一户人家的后院追赶一只鸟。 房主发现一个年轻人在房子里踱来踱去，慢慢地挥舞着天线。 从后窗向外看的那个人是斯科特·纳尔逊，威廉玛丽学院的勒格姆历史学教授，他以前是一名IT人员。 纳尔逊记得自己从后门出去调查。
“I asked him if he was wardriving,” Nelson said, using a hacker’s term for hunting a vulnerable wifi connection. “He didn’t know what I was talking about.”
The thrush in Nelson’s yard added to a set of data that documents how much time each bird spent in each section of its home range, Jirinec explained.
“We then go back to each habitat and take samples, measuring various aspects of the trees, such as diameter,” he said. “We evaluate what’s on the ground—leaf litter or needle cover? And we take food samples.”
Jirinec picked up and processed 370 items from the wood thrush menu—ticks, earthworms, spiders—their location pinpointed by GPS. He’s using the bird location surveys, habitat evaluations and food samples to put together an understanding of how the wood thrush population is faring in various landscapes.
He said it’s too early to talk about final results of his work, but doesn’t mind discussing preliminary findings. 画眉鸟似乎被吸引到无脊椎动物生物量最高的地区，换句话说，那里的食物最丰富。 这听起来很简单，但Jirinec说，仅仅通过观察景观来确定一个食物特别丰富的地区是没有好的方法的，所以这些数据可能表明画眉花了相当多的时间来寻找潜在的家园。
When it comes to real estate choice, the wood thrush wants a wooded area, but Jirinec’s data doesn’t entirely support earlier concepts that indicate that the species will only live in deep woods, and like to be away from humans. For the thrushes in Jirinec’s study, the quality of their woody home patches seems to be at least as important as the quantity, the size of available territory. 例如，Jirinec发现他的鸟类喜欢更成熟的森林和更高的树冠层，他指出，即使在远离森林深处的发达地区，也经常可以发现这些特征。
“It’s too simplistic to say: fragmented landscape, bad for the birds,” Jirinec said. “Let’s see exactly what they need in there, and then if those features are missing from the fragmented landscape, then we can say that’s it’s bad for the birds.”