Question

Comprehend the passage and answer the given questions :
Here is a scientific experiment on the homing of birds, the facts
which are quite certain. A few years ago seven swallows were caught nea
their nests at Bremen in Germany. They were marked with a red dye
some of their white feathers, so that they could easily be seen. Then the
were taken by aeroplane to Croydon, near London; this is a distance of 400
miles (640 km).
flew back
The seven swallows were set free at Croydon. Five of them
to their nests at Bremen. How did the birds find their way on that long
journey, which they had never made before ? That is the great puzzle. It is
no good saying that swallows (or dogs) have a 'sense of direction,' or an
‘instinct to go home'. These are just words, and explain nothing. We want to
know exactly what senses the animals use to find their way, how they know
in which direction to go until they can see familiar landmarks. Unfortunately,
practically no scientific experiments have yet been made on this question.
Perhaps migrating birds are the greatest mystery of all. Swallows leave
England in August and September, and they fly to Africa, where they stay
during the winter period. The swallows return to England in the spring, to
nest. There are other birds too that leave England in the late summer for
the south. A lot has been found out about the journeys of migrating birds
by marking the birds with aluminium rings put on one leg. An address and
a number is put on the ring.
Questions :
Why were the swallows marked with a red dye ?
. What two methods of identifying birds have been mentioned in this passage
What facts about homing or migrating birds are difficult to explain​

Answer 1

1)the swallows were marked with a red dye to identify them easily.

2)The methods of identifying birds which were mentioned in this passage are of marking the birds with red and marking them with aluminium rings put on one leg which haf the address and number.

3) How do the birds find their way on that long

journey, which they had never made before , what senses do they use to find their way, how they know  in which direction to go until they can see familiar landmarks are the facts about homing or migrating birds are difficult to explain.