Yes, the warmer the ambient temps are outside but also consider that the bottom side of a hen, especially during nesting/egg laying time/down time is quite a bit warmer and VERY moist, facilitating a most desirable environment for hatching maggots.
Our chickens are free range and do an amazing job at keeping fly egg population down completely. This is the first year that I haven't had to hang the fly bait bags, sprinkle the fly predators out on the manure piles (which would also be feeding the chooks!) and fly population had radically...
Flystrike usually precedes maggot infestation. If there is any wound, pecked area, open tissues or dirty tissue from poopy butt/vent, flies will lay eggs near or in those areas that develop and migrate inward because tissue starts to deteriorate about the times maggots start to hatch. I had...