If Giselle had 20 doves that laid 3 eggs each, the total number of eggs in the birdhouse is 20*3 = <<20*3=60>>60 eggs.
If 3/4 of the eggs hatched into birds, their total number is 3/4*60 = <<3/4*60=45>>45
In the birdhouse, there are 20 initial doves + 45 new squabs = <<20+45=65>>65 birds
#### 65