Every year in the month of March, one of 【小题1】 world's greatest wildlife migrations (迁徙) stops in central Nebraska. For a short time, sandhill cranes (沙丘鹤) fill the state's wide, flat fields. The land provides the birds 【小题2】 the perfect place to rest and eat.

In recent years, more and more people 【小题3】 (discover) the migration. Visitors crowd into river blinds — special buildings that help keep the bird watchers 【小题4】(hide) themselves. They look through their cameras or telescopes in wonder.

The sandhill cranes are worth the trip. They are 【小题5】(general) a little over a metre tall. They have long legs and necks. Their wings stretch over two metres. Sandhill cranes have soft, grey feathers. They 【小题6】 (know) for having a bright red area on the top of their heads.

The birds stop in Nebraska as they make their way from their winter homes in Mexico and some 【小题7】(south) parts of the United States. The birds usually spend two or three 【小题8】 (week) at this place 【小题9】 they leave. They arrive in waves, at times as many as 400,000 in one day. They eat in the nearby fields and grass lands. Leftover grain, insects and small creatures give 【小题10】 (they) the energy they need as they continue their trip north, towards Canada and Siberia.

The number of Amur tigers, also known as Siberian tigers, moving from Russia into northeastern China, 【小题1】(increase) because of lower levels human activity, improvements in their habitat 【小题2】 a smoother transit corridor between countries. The area 【小题3】 tigers lived across the Sino-Russian border expanded by about 12 kilometers every three years from 2003-2016. In 2021 the Northeast China Tiger and Leopard National Park was established. 【小题4】 (cover) approximately 14,100 square kilometers, the park straddles the provinces of Heilongjiang and Jilin. By the end of 2021 the number of wild Amur tigers living there 【小题5】 (rise) to 50 from 27 in 2017. The conservation of tigers is recognized as a global challenge, due to 【小题6】 (they) expansive habitat requirements. A female needs 400 to 500 square kilometers while a male requires over 1, 000 square kilometers. The collaboration between these neighboring parks creates a 【小题7】 (share) home for the animals. The construction of the Sino-Russian cross-border environmental corridor is vital 【小题8】 several barriers hinder the movement of tigers between the two sides. Border fences and roads built in the area are among those obstacles. Efforts are required by both sides 【小题9】 (promote) the corridor. As the population of prey species including wild boar and deer rises, Amur tigers are travelling 【小题10】 (far) into China for food. The expansion of the tigers’ range is expected to continue.

In the last seven days I have seen the pressure that the NHS is under. I have seen the personal courage not just of the doctors and nurses but of everyone, the cleaners, the   【小题1】(cook), the health care workers of every description-physios, radiographers 【小题2】have kept coming to work, kept putting themselves in harm's way, kept 【小题3】(risk) this deadly virus. It is thanks to that courage, that devotion, that duty and that love that our NHS has been unbeatable.

The Arctic Ocean in summer will very likely be ice free before 2050, at least temporally. The research team 【小题4】   (analyze) recent results from 40 different climate models. Using these models, the researchers considered the future evolution of Arctic sea ice cover in a scenario with high future CO2 emissions and little climate protection. As 【小题5】(expect), Arctic sea ice disappeared quickly in summer in these simulations.

However, the new study finds that Arctic summer sea ice also disappears occasionally if CO2 emissions are   【小题6】(rapid) reduced.

In order to understand【小题7】 bird brains changed, a team of 37 scientists used CT scan data to create endocasts(内腔)of hundreds of birds and dinosaurs, which the【小题8】(combine)with a large existing database of brain measurements from modern birds.

They then analyzed brain-body allometry (体形变). “There is no clear line 【小题9】the brains of advanced dinosaurs and primitive birds,”【小题10】(note) co-author Dr. Amy Balanoff of Johns Hopkins University." Birds like pigeons have the same brains sizes you would expect for a dinosaur of the same body size, and in fact some species like moa(恐鸟) have smaller-than-expected brains.”