Making the Most of Dark Nights
The main breeding station of the marine bird known as the swallow-tailed gull is the Galápagos Islands, which straddle the Equator to the west of continental South America. This is unusual, because very few gulls live in the tropics. One reason for this is that tropical waters are far less productive in terms of food than waters at higher latitudes, so it is harder to find food, especially if, like a gull, the searcher is unable to dive deep. This is particularly the case for the open, very deep waters far from land where the swallow-tailed gull mainly feeds. There is, however, one aspect of the oceanic cycle on tropical waters that is more reliable than most and that is known as the Diurnal Vertical Migration, or DVM. The term refers to the regular movement of organisms from deeper depths by day toward the surface at night. On the whole, the animals rise to shallower waters at dusk and plunge deeper at dawn, meaning that, in extreme cases, the density of food at the water’s surface may be 1,000 times greater at night than during the day. Animals likely do this to avoid being eaten by predators that are diurnal (active during the day).
For any predator on the oceans, it would make sense if they could somehow use DVM to their advantage. And it seems that the swallow-tailed gull manages to do just this. At any rate, it has evolved a lifestyle quite unlike any other member of its family-it has become nocturnal (active at night), coinciding with the enhanced abundance of food at the surface. At the colonies on cliffs on the Galápagos, the birds become excited and animated at dusk calling and milling about before they head out to sea in flocks as darkness falls.
A study carried out recently has added a most intriguing twist to the swallow-tailed gull’s nocturnal foraging plot. Conducted on 37 breeding pairs in Galápagos, the study, which used Global Location Sensors fitted with a wet/dry component so that the scientists would know when the birds were swimming on the sea, showed that the gulls did not forage every night, but only on some nights. There were occasions when the Global Location Sensors detected them at the breeding cliffs after dark, and other times when they would just be flying about at night, and not settled on the sea. This is in some ways a surprising result, because when birds were breeding, and would presumably have chicks to feed, it would be expected that they would take every opportunity to go out foraging. But on some nights they are feverish foragers, while on others they simply sit still.
It turned out, however, that the swallow-tailed gulls were being decidedly pragmatic. They tended to stay put when strong moonlight lit up the surface of the sea. Evidently, the costs of nocturnal foraging in moonlight were greater than the potential reward. The number of birds foraging, and the amount of time they spent on the sea during the night, followed closely the phases of the Moon, with increased foraging at new Moon as well as a general lethargy at and around the time of full Moon. It has long been known that daylight is not the only determining factor for DVM, but that it also follows the lunar cycle. Just as very small ocean organisms avoid the daylight and migrate to the depths for safety during the day, they stay put in deeper waters on strongly moonlit nights too. The traffic involved in the usual surface-oriented DVM greatly reduces, although it does not stop completely.
The favorite foods of swallow-tailed gulls are the purple-back flying squid, which is about 10 centimeters long, and small fish in the family Clupeidae. The bird catches them by a technique known as surface-plunging, which involves a forward lunge into the water from a swimming position. The hunter can therefore only catch food when it comes right toward the surface of the ocean, and both the squid and shoals of clupeid fish are known to show a strong tendency toward DVM. With its limited fishing technique, it might be said that the swallow-tailed gull is most adversely affected by DVM variation. It would seem that, unless there is significant nocturnal DVM. there is no benefit to foraging at all.
1
The main breeding station of the marine bird known as the swallow-tailed gull is the Galápagos Islands, which straddle the Equator to the west of continental South America. This is unusual, because very few gulls live in the tropics. One reason for this is that tropical waters are far less productive in terms of food than waters at higher latitudes, so it is harder to find food, especially if, like a gull, the searcher is unable to dive deep. This is particularly the case for the open, very deep waters far from land where the swallow-tailed gull mainly feeds. There is, however, one aspect of the oceanic cycle on tropical waters that is more reliable than most and that is known as the Diurnal Vertical Migration, or DVM. The term refers to the regular movement of organisms from deeper depths by day toward the surface at night. On the whole, the animals rise to shallower waters at dusk and plunge deeper at dawn, meaning that, in extreme cases, the density of food at the water’s surface may be 1,000 times greater at night than during the day. Animals likely do this to avoid being eaten by predators that are diurnal (active during the day).
According to paragraph 1, which of the following is NOT true of swallow-tailed gulls?
Factual Information Questions事实信息题
AThey share their habitat with many other species of gulls
BThey breed on tropical islands at the Equator.
CThey are shallow divers
DThey find most of their food far from their main breeding station.
2
For any predator on the oceans, it would make sense if they could somehow use DVM to their advantage. And it seems that the swallow-tailed gull manages to do just this. At any rate, it has evolved a lifestyle quite unlike any other member of its family-it has become nocturnal (active at night), coinciding with the enhanced abundance of food at the surface. At the colonies on cliffs on the Galápagos, the birds become excited and animated at dusk calling and milling about before they head out to sea in flocks as darkness falls.
The word “animated” in the passage is closest in meaning to
Vocabulary Questions词汇题
Acrowded
Bhungry
Clively
Dawake
3
A study carried out recently has added a most intriguing twist to the swallow-tailed gull’s nocturnal foraging plot. Conducted on 37 breeding pairs in Galápagos, the study, which used Global Location Sensors fitted with a wet/dry component so that the scientists would know when the birds were swimming on the sea, showed that the gulls did not forage every night, but only on some nights. There were occasions when the Global Location Sensors detected them at the breeding cliffs after dark, and other times when they would just be flying about at night, and not settled on the sea. This is in some ways a surprising result, because when birds were breeding, and would presumably have chicks to feed, it would be expected that they would take every opportunity to go out foraging. But on some nights they are feverish foragers, while on others they simply sit still.
It can be inferred that the swallow-tailed gulls in a “study carried out recently”
Rhetorical Purpose Questions修辞目的题
Aobtained little or no food on nights when they were either flying around or sitting on the cliffs
Bspent more time swimming on the sea than they did sitting on land
Csometimes foraged during the day rather than at night
Dspent some nights finding food for themselves and other nights catching food to bring to the chicks
4
It turned out, however, that the swallow-tailed gulls were being decidedly pragmatic. They tended to stay put when strong moonlight lit up the surface of the sea. Evidently, the costs of nocturnal foraging in moonlight were greater than the potential reward. The number of birds foraging, and the amount of time they spent on the sea during the night, followed closely the phases of the Moon, with increased foraging at new Moon as well as a general lethargy at and around the time of full Moon. It has long been known that daylight is not the only determining factor for DVM, but that it also follows the lunar cycle. Just as very small ocean organisms avoid the daylight and migrate to the depths for safety during the day, they stay put in deeper waters on strongly moonlit nights too. The traffic involved in the usual surface-oriented DVM greatly reduces, although it does not stop completely.
The word “pragmatic” in the passage is closest in meaning to
Vocabulary Questions词汇题
Apractical
Bcareful
Cfocused
Dreluctant
5
Paragraph 4 suggests that the amount of time that swallow-tailed gulls spend on the sea changes with the phases of the moon for which of the following reasons?
Inference Questions推理题
AThe gulls are more efficient predators on brightly moonlit nights than on darker nights.
BThe gulls can safely rest on the water’s surface while foraging at full Moon but not at new Moon.
CThe gulls compete with greater numbers of ocean animals at full Moon than at new Moon.
DThe gulls respond to increasing food availability around new Moon by foraging more than they do at full Moon.
6
It turned out, however, that the swallow-tailed gulls were being decidedly pragmatic. They tended to stay put when strong moonlight lit up the surface of the sea. Evidently, the costs of nocturnal foraging in moonlight were greater than the potential reward. The number of birds foraging, and the amount of time they spent on the sea during the night, followed closely the phases of the Moon, with increased foraging at new Moon as well as a general lethargy at and around the time of full Moon. It has long been known that daylight is not the only determining factor for DVM, but that it also follows the lunar cycle. Just as very small ocean organisms avoid the daylight and migrate to the depths for safety during the day, they stay put in deeper waters on strongly moonlit nights too. The traffic involved in the usual surface-oriented DVM greatly reduces, although it does not stop completely.
According to paragraph 4, which of the following is likely to occur on strongly moonlit nights?
Factual Information Questions事实信息题
ASwallow-tailed gulls will spend most of the night foraging on the sea.
BMany marine animals that would normally go to the surface will stay in the deep.
CMany very small marine organisms will come to the surface to look for food.
DThe usual surface-oriented DVM will occur much earlier in the night than usual
7
The favorite foods of swallow-tailed gulls are the purple-back flying squid, which is about 10 centimeters long, and small fish in the family Clupeidae. The bird catches them by a technique known as surface-plunging, which involves a forward lunge into the water from a swimming position. The hunter can therefore only catch food when it comes right toward the surface of the ocean, and both the squid and shoals of clupeid fish are known to show a strong tendency toward DVM. With its limited fishing technique, it might be said that the swallow-tailed gull is most adversely affected by DVM variation. It would seem that, unless there is significant nocturnal DVM. there is no benefit to foraging at all.
Why does the author discuss the swallow-tailed gull’s use of “a technique known as surface-plunging”?
Rhetorical Purpose Questions修辞目的题
ATo suggest that the gull’s foraging technique is most successful in shallower waters close to shore
BTo explain why the purple-back flying squid and clupeid fish show a strong tendency toward DVM
CTo provide evidence that swallow-tailed gulls’ hunting success is dependent on DVM
DTo cast doubt on the idea that the DVM behavior of the purple-back flying squid and clupeid fish is an attempt to avoid predation
8
The favorite foods of swallow-tailed gulls are the purple-back flying squid, which is about 10 centimeters long, and small fish in the family Clupeidae. The bird catches them by a technique known as surface-plunging, which involves a forward lunge into the water from a swimming position. The hunter can therefore only catch food when it comes right toward the surface of the ocean, and both the squid and shoals of clupeid fish are known to show a strong tendency toward DVM. With its limited fishing technique, it might be said that the swallow-tailed gull is most adversely affected by DVM variation. It would seem that, unless there is significant nocturnal DVM. there is no benefit to foraging at all.
According to paragraph 5, which TWO of the following are true about the fishing technique of the swallow-tailed gull? To receive credit, you must select TWO answers.
Factual Information Questions事实信息题
Select 2 answers
AIt is not effective against prey that is less than 10 centimeters long
BIt requires the gull to be swimming before dipping into the water to catch prey
CIt attracts prey to the surface with a plunging motion.
DIt is only helpful when a large number of prey come to the surface.
9
The main breeding station of the marine bird known as the swallow-tailed gull is the Galápagos Islands, which straddle the Equator to the west of continental South America. This is unusual, because very few gulls live in the tropics. One reason for this is that tropical waters are far less productive in terms of food than waters at higher latitudes, so it is harder to find food, especially if, like a gull, the searcher is unable to dive deep. This is particularly the case for the open, very deep waters far from land where the swallow-tailed gull mainly feeds. [■] There is, however, one aspect of the oceanic cycle on tropical waters that is more reliable than most and that is known as the Diurnal Vertical Migration, or DVM. [■] The term refers to the regular movement of organisms from deeper depths by day toward the surface at night. [■] On the whole, the animals rise to shallower waters at dusk and plunge deeper at dawn, meaning that, in extreme cases, the density of food at the water’s surface may be 1,000 times greater at night than during the day. [■] Animals likely do this to avoid being eaten by predators that are diurnal (active during the day).
Look at the four squares [■] that indicate where the following sentence could be added to the passage
Compared to temperate waters at higher latitudes, these waters have a less predictable food distribution, as well as less structured food supplies.Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
Swallow-tailed gulls are unlike other gulls in several respects.
Prose Summary Questions概要小结题
Select 3 answers
AAlthough gulls are not deep divers, swallow-tailed gulls have their breeding ground in the tropics and hunt for food in the open water where food near the surface is relatively scarce.
BA study conducted on breeding swallow-tailed gulls in the Galápagos found that these gulls spend more time in the air than other types of gulls do when they are out foraging.
CWhile most gulls use a fishing technique known as surface-plunging the preferred prey of swallow-tailed gulls are unsuitable to be caught by this technique.
DSwallow-tailed gulls are nocturnal, taking advantage of the Diurnal Vertical Migration which brings many small sea creatures, particularly the purple-back flying squid and clupeid fish, to the surface.
EThe gulls often do not bother to forage when the Moon is full and bright, because the DVM is much more limited on such nights and the gulls’ surface foraging technique would make success unlikely.
FThe swallow-tailed gull is more attracted to the abundant variety of foods in tropical waters than to the less-varied food in waters at higher latitudes, where the lunar cycle has little effect.
