This feeding statistic is a bit suspiscous. Concidered that average mosquito weights 2 mg, one bolus weights 600 mg (0,6 g). So, 3000 boluses per day per nest is 1,8 kg. That's a lot :) Deliver of food per chick is around 4-9 g per day, according to this article - Brood Reduction in Response to Manipulated Brood Sizes in the Common Swift (Apus apus), Thaís L. F. Martins and Jonathan Wright Behavioral Ecology and Sociobiology , Vol. 32, No. 1 (1993) , pp. 61-70.