In spite of his deep communist persuasion, Souček arguably remains the most popular and most widely known author of Czech Science fiction.
His books of "Portents" (Tušení souvislosti, 1974, Tušení stínu, 1978) are collections of Däniken-styled non-fiction essays on striking, surprising, obscured, or otherwise "not-yet" explained facts from the history of mankind, which are indeed hard to impossible to explain either given the present day scientific knowledge or our assumptions on the scientific knowledge or technology level of ancient civilizations.
Similarly to his forerunner Däniken, Souček hinted that cultural and architecture phenomena (such as megaliths of Baalbek) some natural catastrophes (such as Tunguska event), mythologies and biblical histories (such as the destruction of Sodom and Gomorrah) can be best explained through an alien, extraterrestrial intervention.
Souček's "Blind Birds" actually mimic the method and composition of "War with the Newts, 1937" (translation of Válka s mloky, 1936) by Karel Čapek.
Both Čapek and Souček develop the fantastic element only very slowly, starting with the very sober 1st book, accelerating in the 2nd, and culminating in the 3rd book as hard SF par excellence: The victory of Newts and near extinction of human race, Čapek; International (both western and communist powers collaborate) discovery and rescue mission to Mars, Souček.