Last weekend’s veritable fiesta of warbler goodness was not, of course, the first event of its kind. The September 2005 Kingbird has an interesting article about an even more intense (and earlier!) pulse of Prothonotarys, Yellow-throated Warblers, and similar goodies that took place in the spring of that year, and discusses some of the evidence that can be used to weigh different causes for notable southern incursions (generally favorable migration conditions vs. expanding populations vs. discrete, disruptive weather events). It’s an interesting read, if you’re into scientific papers, or if you need to induce sudden and vertiginous jealousy towards those who were birding in NYC in March 05 for some reason.
h/t Shaibal Mitra on the NYS Birds mailing list.