Bacterial diversity
Nestlings from fumigated nests had higher bacterial richness than nestlings from sham-fumigated nests (Figure 1A, χ2 = 4.04, P = 0.04). Shannon diversity index was not significantly affected by parasite treatment (Figure 1B, χ2 = 1.10,P = 0.29). Urbanization did not significantly affect observed richness (Figure 1C, χ2 = 2.30, P = 0.13), but did influence the Shannon index (Figure 1D, χ2 = 7.50,P = 0.006). Non-urban nestlings had higher Shannon diversity index values compared to urban nestlings. Observed richness and Shannon index were not affected by the interaction between parasite treatment and urbanization (Figure S1, Observed richness: χ2 = 0.28, P = 0.60, Shannon Index: χ2 = 0.21,P = 0.65). The year that samples were collected (2018, 2019) did not significantly affect the observed richness (Table S1, χ2 = 2.55, P = 0.11) or Shannon index (χ2 = 0.38, P = 0.54).