Question

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During a wildlife survey of wintering locations for migratory birds, a large number of waterfowl have been found to have died due to a large dose of a toxic substance. During follow-up research of the birds’summering locations and migratory path, no sources of the toxic substance were found with concentrations sufficient to explain the body-burden measured in the dead birds.In fact, no sources were found that would have led to a fatal exposure at all (even for young birds) Describe what you consider to be the most-likely cause for the observations above.

Answer 1

Bird migration is very common term . At the winter time the birds are travelled a lot of distance for a warm place to keep their body worm and in summer they travelled same for maintining the temperature for better survive. But when they came to a poisoning or toxic place and take food from their they became ill and finally died.

Since there are very little regulations regarding pesticide use in the tropics, the farmers in South America use high quantities of highly toxic pesticides to protect their crops. For example, DDT is currently banned in North America because it killed millions of birds in the 1960s, but it is still heavily used in the tropics. Pesticides can kill birds both directly and indirectly. In the case of DDT, it can kill birds directly by poisoning their nervous system and indirectly by making the eggshells thinner and thus reducing reproductive success of birds.

Here we can see the western country was very developed and they were used for migration for bird. So when they travelled they became I'll and finally died.

But at the time of summer they came to the middle part of world where the countries are not well developed and not use too much pesticides . So that at the time of summer that effect was very low and negligible.

Thanking you. Hope you get help from the answer.