Breeding

Nesting: As other members of its genus, Galapagos Flycatcher is a cavity nester. Few natural nest sites are known; these were in hollow trees or hollow cacti, especially Jasminocereus thouarsi, but also Opuntia spp. (Lanyon, 1978, Ervin 1994), or in used nests of Darwin's finch (Geospiza spp. or Camarhynchus spp.) (Harris 1992). In recent years, they have been seen nesting in the hollow concrete power-line poles, accessing the hollow from the opening at the top (personal observation; Ervin 1994). In Ervin's (1994) study, nest openings varied from 3-5 m above ground, although these nestes were in low-stature cacti. The entrances to the concrete power-line pole nest sites usually are 7–10 m above the ground.

Nest material is vegetable matter (Harris 1992), although the flycatchers have been seen collecting hair from cattle and goats for nest lining. Ervin (1994) reports that the birds used chicken (Gallus gallus) feathers and plant materials including sticks from saltbush (Cryptocarpus pyriformis). Saltbush, however, is only available within 100 m or so of the coast; therefore, further inland it is likely that the flycatchers use sticks and filaments from other plant sources. During the nesting season they will also attempt to harvest hair from unsuspecting tourists, by landing on the tourist's shoulder and pulling on long hair, as also noted by Lanyon (1978). Joseph (2004) includes the use of chicken feathers.

Nesting season: Although like other Galapagos birds they may breed year round, breeding activity appears to be concentrated in the hot humid season (January-March), with earlier nests from November and later ones to May.

Clutch size is 3-5 with one possible clutch of six eggs (Joseph 2004). Ervin's (1994) measurements of one 5-egg clutch gave averages of 18.5 x 15.0 mm (range of 18.8–18.3 x 15.2–15.0), with a mass of approximately 2 g.