1 . Chimney swift (烟囱雨燕) numbers have fallen by more than 70 percent since the 1960s, scientists believe, and by more than one-third over the past 16 years. That large drop have made the International Union for the Conversation of Nature regard chimney swifts as“vulnerable(脆弱的)”. That is the last step before they are considered “endangered”.
Chimney swift numbers are becoming smaller as the shape and design of the nation’s buildings change. People are tearing down old factory buildings and schools. Many of these buildings have chimneys. Today, most American homes do not have chimneys. And many homeowners who do have chimneys cover up the top to keep out.
People across the United States are putting up tall, narrow buildings to help chimney swifts. They hope they will use these buildings as nesting areas and resting places.
Bird lovers, Georgean and Paul Kyle, are often praised for starting the present interest in building towers. “It does give us hope that if we put them up, they will use them,” the Kyles said. They have put up more than 100 towers in Central Texas. Eighty percent of those buildings before the birds’ March arrival get nests in their first year. Hundreds of migrating swifts make use of the towers.
But the link between the drop in chimney swift numbers and chimney loss is not clear. The flying insects that swifts eat also appear to be dropping.
Professor Rubega thinks the cause of the birds’ drop could be in South America. “Chimney swifts are basically a South American bird that stays in North America for four months, ” she said. Rubega said a big problem is that scientists have only a few reports of small numbers of chimney swifts in the upper Amazon Basin. So, they do not really know where the little birds spend the winter, let alone what may be happening to them there.
1. Where are chimney swifts used to living?| A．In rooms with humans. | B．In useless old buildings. |
| C．In the woods near villages. | D．In chimneys of buildings. |
| A．Give them much food. | B．Build homes for them. |
| C．Add chimneys to new houses. | D．Open chimneys for them to get in. |
| A．Chimney swifts suffer a lot in South America. |
| B．It’s necessary to build homes for chimney swifts. |
| C．Scientists know only a little about chimney swifts. |
| D．Chimney loss has nothing to do with the birds. |
| A．Chimney Swifts Numbers Are Dropping |
| B．Chimney Swifts Will Change Their Lifestyle |
| C．Chimney Swifts Prefer Their New Homes |
| D．Chimney Swifts Live in Peace with Humans |
