South West Trains services were delayed by the power failure near Feltham at about 07:30 GMT.
Commuters were later told at 09:30 that further delays were being caused by the "awkward" swan.
South West Trains apologised on Twitter and said the bird had been rather tricky to remove despite the train driver's "best efforts".
Network Rail has directed customers to its website, explaining how leaf mulch can cause problems with signalling.
Many commuters vented their frustrations on social media.
Phil Young tweeted: "After 2 hrs stuck on @SW_Trains outside Twickenham cos of power failure, now stuck at Staines cos of a swan on the bridge! #greatworkexcuses"
Geoffrey Ganda tweeted: "I waited 2 hours at Reading for a SW train in the cold. Are there any compensations? The prices go up each year but same problems."
Rail services between Berkshire and London have been disrupted by leaves, a power cut and a swan on the line.