This work compares the effect of the climate and some different protein diets on the activity of flesh and blow fly populations in one of the biggest mountains of Sarah region, south-westKingdom of Saudi Arabia. Trapping of adult flies revealed the presence of three populations, namely, Engelisca adhamae (Lehrer & AbouZied, 2008) and Liosarcophaga babiyari (Lehrer, 1995), in addition to a single calliphorid species Calliphora vicina (R−D, 1830). Adults of L. babiyari showed a year round activity, with the major peak during August. The species E. adhamae showed its major peak during May and June, while in addition, adults of C. vicina showed spring activity during the period from March to April.  Adult activity of L. babiyari showed a direct correlation with both of the temperature and the wind velocity, but it was inversely correlated with the relative humidity. Otherwise, adult C.vicina was directly correlated with rainfall. However, the studied climatic factors showed a very weak effect on the activity of adult E. adhamae. The trophic niches, was predicted to affect male L. babiyari which showed great affinity to be trapped with fish followed by liver then meat. In comparison, male E. adhamae preferred fish, followed by both, liver and beef. Meanwhile, female L.babiyari, showed higher tendency to both, fish and liver compared with both, beef and hash-hash. In contrast, female E.adhamae showed nearly the same tendency to fish, liver and beef. However, male and female C. vicina showed more attraction to liver compared with both fish and beef.