Here is an interesting chart from a WFP study in 2008. It is hard to draw a definite conclusion from this chart. Overall, in-migration is high during cropping months. Out-migration is high towards the end of cropping months. If migrants don’t return, mainly from India, during the start from cropping season, then agriculture production goes down and food insecurity will heighten. The study found that lack of employment and food shortages were the two most important reasons for migration.
For more on food insecurity in Nepal, see this article. More on food security here and here. Here is a short paper on food security and aid in Nepal.
