Parasitism by, species composition, morphometry, and parasitoidism of Protocalliphora bird blowflies (Diptera: Calliphoridae) in Quebec’s farmlands: a 16-year dataset

Bird blowflies, Protocalliphora spp. (Diptera: Calliphoridae), are prevalent ectoparasites of altricial bird nestlings across the Holarctic region. Yet, their spatial and temporal dynamics of infestations, species composition, and interactions with parasitoids remain poorly understood. We present a 16-year (2004–2019) multisite study of Protocalliphora infestations based on 2673 tree swallow (Passeriformes: Hirundinidae) nests collected across a 10 200-km 2 gradient of agricultural intensity in Quebec, Canada. Nest infestation prevalence and parasitic load varied markedly across space and time but recurred synchronously at approximately 75% of sites, suggesting regional and local process influences. Yearly rates of Nasonia wasp (Hymenoptera: Pteromalidae) parasitoidism of bird blowfly puparia were high but variable (48–90%), likely contributing to the temporal fluctuations in Protocalliphora prevalence and load. Substantial interannual shifts in relative abundance of P. bennetti , P. metallica , and P. sialia emphasise the importance of species-level identification in bird blowfly ecological studies. Large overlap in puparia size among species challenged the utility of traditional diagnostic traits for species identification. Dormancy or mortality of Nasonia occurred in 3–16% of Protocalliphora puparia, depending on year. These findings highlight the importance of long-term, multitrophic, and spatially explicit monitoring in unravelling the drivers of host–parasite–parasitoid dynamics.