The case against ddt was that it made the shells bird eggs very thin which cause the little birdies to die prematurally. But 30 years later along comes West Nile virus, which is spead by those pesky misquitoes. The misquetoes kill the birds before they even get a chance to lay the eggs. Since birds eat insects incuding miquitoes and there aren't many birds now, the population of the miquitoes continue to grow as the bird population dwindles.
what is happening to the bird population then?