The owls will have completed their breeding cycle by the time the neotropical birds begin theirs. There are overriding concepts that clarify why different species time their breeding cycles in different ways. Energy Demands From an ecological point of view, on both the individual and species level, energy demands largely determine the ability to survive and reproduce. The ability to obtain food, retain the energy, and pass energy on to the next generation is the foundation of survival. The following quoted passages are taken from The Birder's Handbook by Erlich, Dobkin and Wheye.
Evolution generally adjusts the timing of avian breeding seasons to produce the most young.
Nebraska is in the temperate region. From this region to the subarctic and arctic regions, the main factor is availability of food. Abundant nourishment is needed, not only by nestlings and juveniles, but by the increased energy demands on breeding adults. For females it's the energetic demand of producing eggs. For males it's the increased energy demands of vigorous displays and defending territories.