Another is that they rely on their sense of magnetism.

而其它则认为候鸟依赖的是自身对磁场的感知。

And I am the Unalaska Visitor's Bureau executive director.

我是乌纳拉斯卡候鸟办公室的事。

And migratory birds that extend their visits may provide competition for some avian natives.

同时，逗留时间更长的候鸟也可能对一些本土鸟产生竞争。

Soon he'll be a " Freebird" . This winter, he'll be a " snowbird" .

很快它就能恢复自由了。今年冬天，它就是候鸟了。

In 1917, the Canadian Parliament passed the Migratory Bird Convention Act.

1917年，加拿大会通过了《候鸟协定法案》。

In 1918, the U.S. Congress followed suit, passing the Migratory Bird Treaty Act.

1918年，美国跟风效仿，也通过了《候鸟协定法案》。

Snowbirds flee northern states in the winter for the South or Southwest.

雪候鸟冬天从北部各州逃往南部或西南地区。

The warm weather sees the arrival of migrant birds.

候鸟也随着温暖的天气回巢。

Temperatures begin to cool and migratory birds set off on their southward journeys.

气温渐凉，候鸟踏上南迁的旅程。

The birds that we find are typically neo-tropical migrants.

我们发现的鸟类是典型的新热带候鸟。

Crows, she says, are what's known as partial migrants.

她说，乌鸦被认为是“部分候鸟”。

They even had an affectionate nickname, " uccelli di passaggio, " birds of passage.

候鸟。

On top of this, many migrating birds are land-lubbers at heart.

最重要的是，许多候鸟本质上是陆鸟。

Every spring, migratory birds flood back to where they breed.

每年春天，候鸟都会涌回它们繁殖的地方。

Migrating birds need to store calories to prepare for their end-of-season trips.

候鸟需要储存卡路里，为季末飞做准备。

It also provides nutrients to millions of migrating birds that can show up on radar.

同时也为数以百万计的候鸟提供营养，这些候鸟可以在雷达上显示。

People liked eating the migratory birds, and they disappeared from Europe.

人们喜欢吃候鸟，于是它们就从欧洲消失了。

Most migratory species travel at night, when lights near buildings can distract or disorient them.

大多数候鸟在夜间飞，那时建筑物附近的灯光会分散它们的注意力或使它们迷失方向。

Cryptochrome has been found in the eyes of several migratory birds.

人们在一些候鸟的眼睛里发现了隐色体。

The Nordic countries provide a home to millions of migratory birds.

北欧地区是数百万候鸟的容身之地。