評論
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Pro:Well, last time we talked about passive habitat selection,
教授:上一次，我們談到了消極棲息地的選擇，
like plants for example, they don't make active choices about where to grow.
比方說植物都不會對于它們生長地點做積極地選擇。
They are dispersed by some other agent, like the wind.
它們被一些風之類的原因分散。
And if the seeds land in a suitable habitat, they do well and reproduce.
而如果種子在一片合適的棲息地著陸，它們會生長的不錯，并且繁殖。
With active habitat's selection, an organism is able to physically select where to live and breed.
但是對于積極的棲息地選擇，生物就會在生理意義上選擇它們生長繁殖的地方。
And because the animal breeding habitat is so important, we expect animal species to develop preferences for particular types of habitats. Places where their offspring have the best chance for survival.
并且因為動物的棲息地是如此的重要，以至于我們認為動物物種傾向于選擇使它們的后代有最好生存幾率的地方。
So let's look at the effect the preference can have by looking at some examples,
那么，讓我們通過幾個例子來看一下這些偏好的影響，
but first let's recap.
但是首先我們復習一下。
What do we mean by habitat? Frank?
弗蘭克，棲息地是什么意思？
Stu:Well, it's basically the place or environment where an organism normally lives and grows.
學生:它是生物通常生長生活的地方或者環境。
Pro:Right, and as we discussed, there are some key elements that habitat must contain, food obviously, water, and is got have a right climate and basics for physical protection.
教授:是的，正如我們所討論的，一處棲息地必須包含有一些關鍵因素。顯然，食物、水，然后還有合適的氣候，以及自我保護的空間。
And we were sound how important habitat selection is when we look at the habitat were some of the factors are removed, perhaps through habitats' destruction.
我們可以看到當這些因素被移除的時候，這些棲息地的選擇是多么的重要。
I just read about a short bird, the plover.
我剛剛讀了一些關于一種叫珩科鳥的資料。
The plover lives by the ocean and feeds on small shellfish insects in plants.
珩科鳥生活在海邊，以小貝殼、昆蟲還有植物為食。
It blends in with the sand, so it well camouflage from predator birds above.
它們會躲在沙子里，與沙子混為一體，所以可以很好的躲避捕食鳥類。
But it lags eggs in shallow depressions in the sand with very little protection around them.
但是，它們總是在幾乎沒有遮護的低洼地里面產蛋。
So if there are people or dogs on the beach, the eggs and fledglings in the nest are really vulnerable.
所以如果有人或者狗在沙灘上，在巢中的蛋和幼鳥會非常脆弱，很容易受到傷害。
Outing California weather has been a lot of human development by the ocean.
而在加州的海灘有很多的人工建筑。
The plovers are now is threaten species.
所以現在珩科鳥已經是一個瀕危物種。
So conservation is tried to recreate a new habitat for them.
所以動物保護主義者們正在嘗試著為它們建立一個新的棲息地。
They made artificial beaches and sun bars in area inaccessible to people and dogs.
他們做了一個人工的海灘以及防止人類和狗進入的沙洲。
And the plover population is up quite a bit in those places.
而在這些地方，珩科鳥的數量增加了不少。
Ok. That is an incidence where a habitat is made less suitable.
好了，這就是一個關于棲息地變的不適于居住的例子。
But now, what about the case where animal exhibits a clear choice between two suitable habitats in cases like that.
但是現在，如果兩個棲息地都很合適，那么動物會表現出怎樣的選擇呢？
Dose the preference matter?
偏好會起到關鍵作用嗎？
Let's look at the blue warbler.
讓我們再來看看藍鶯。
The Blue warbler is a songbird that lives in the North America.
這是一種生活在北美的鳴鳥。
They clearly prefer hard wood forests with dense shrubs, bushes underneath the trees.
它們很顯然的偏好于有著稠密的灌木叢闊葉樹森林。
They actually nest in the shrubs, not the trees.
它們通常會在灌木叢中筑巢，而不是在樹上。
So they pretty close to the ground,
所以，它們傾向于接近地面，
but these warblers also nest in the forests that have low shrub density.
但是這些藍鶯也會在有著稀疏灌木叢的森林里面筑巢。
It is usually the younger warblers that next to the area because prefers spots where a lot of shrubs are taken by order more dominant birds.
通常，年輕的藍鶯將會在這些地方，因為更好的地方已經被成年藍鶯所占據。
And the choice of habitat seems to affect the reproductive success.
并且這些棲息地的選擇貌似將會影響繁殖的成功與否。
Because the order and more experienced birds who nest in the high density shrub areas have significantly more offspring than those in low density areas,
因為，更加成熟，更加有經驗的鳥將會在高度稠密的灌木叢中筑巢，相較至于在低密度灌木叢筑巢的鳥，它們明顯會繁育更多的后代。
which suggests that the choice of where to nest does have impact on the number of chicks they have.
這也就表明了在哪里筑巢對于下一代的數量有著很大的影響。
But preferred environment doesn't always seem to correlate with greater reproductive success.
但是，偏好的環境并不總是與高繁殖率有關。
For example, In Europe, study has been done of blackcap warblers.
比如歐洲對于黑頂鶯就曾進行過一些研究，
We just call them blackcaps.
我們把它們叫做黑頂。
Blackcaps can be found in two different environments.
這些黑頂被發現在兩種不同的環境里面，
Their preferred habitat is forest that near the edge of streams.
它們偏好的環境是在溪流附近的森林里面。
However, blackcaps also live in pine woods away from water.
但是，黑頂也住在遠離水源的松林中。
Study has been done on the reproductive success rate for birds in both areas,
在這兩種地區都做了有關于繁殖成功率的研究。
and the result showed surprisingly that the reproductive success was essentially the same in both areas-the preferred and the second choice habitat. Well. Why?
結果很令人驚異的表明在這兩種地方的繁殖率基本一致。為什么呢？
It turns out there were actually four times as many bird pairs or couples living in the stream edge habitat compared to the area away from the stream,
結果是，事實上，在溪流邊緣的森林里面住著比遠離溪流地區四倍多的鳥。
so this stream edge area had much denser population which meant more members of same species competing for the resources.
所以溪流附近的地區有著更加稠密的人口密度，也就意味著對于資源的競爭很激烈。
When into feed on same thing or build their nests in the same places, which lower the suitability of the prime habitat even though its their preferred habitat.
而競爭就降低了動物在這些主要棲息地的適應能力，盡管這是它們所偏好的地區。
So the results of the study suggests that when the number of the competitors in the prime habitat reaches a certain point, the second random habitat becomes just as successful as the prime habitat, just because there are fewer members of the same species living there.
所以研究結果顯示當在主棲息地的競爭者數量達到一定的量時，第二選擇的棲息地將會在和主棲息地一樣能夠的成功，僅僅是因為有相對較少的物種在那里生存。
So it looks like competition for resources is another important factor in determining if particular habitat is suitable.
所以相互爭奪資源也是判斷一個棲息地是否合適的重要影響因素。
