Barn Swallow (Hirundo rustica) Science Article 8
Barn Swallow Hirundo rustica roosting time was studied at a south-coast Irish reedbed during 2003 to 2006. Roosting time varied between 11 and 35 minutes after sunset. There was no significant difference in roosting time after sunset across years. Roosting time (relative to sunset) was later in July than in August and September. The time interval between roosting of the earliest and latest birds usually spanned a period of about 10 to 15 minutes, but could be as long as 30 minutes. The light intensity at the time of roosting varied between 41 and 6 lux.
Patrick Smiddy, Chris Cullen and John O’Halloran, Ringing & Migration (2007) 23, 228-230