Swallows (migratory birds) usually return from Africa here in early April. Swifts are later, arriving here in early May. The return of swallows is something I look forward to.
I have heard a few reports of swallows that managed to survive long into winter on the insects near seaweed. There was a report of at least one hanging-on over the entire winter. The Daily Mail sometimes gets its facts wrong, so I have no idea if this report was correct or just journalistic hyperbola. It dates from 2009.
See http://www.dailymail.co.uk/sciencetech/article-1115442/Meet-Rambo--tough-little-swallow-forgot-fly-South-winter.html .