Where Have All the Cuckoos Gone?

cuckoo bird crtv commons

This is not a figurative or rhetorical question!  (Believe me, all of the figurative cuckoos are still with us, and any departure amongst their ranks is usually immediately corrected by a new arrival.  But, I digress. . .)

Our neighborhood cuckoo birds, who arrived around April and delighted us with their enthusiastic calls, seem to have fled.  Not a cuckoo within earshot for weeks now.  What gives?

I googled cuckoos, and it sounds as if they generally stick around this area until September, so this in an unusually early departure.

Anyone out there have any cuckoo bird experience and can shed light on this?