A quick look at the listserves of the Northeast shows that rarity season is off to a relatively slow start. A few Cave Swallows in Connecticut, a continuing Green-tailed Towhee in Massachusetts, and a great find in a Gray Flycatcher, also in Mass. However, aside from the rare-but-regular stuff, northern New England’s rarity season has been rather slow. In fact, so far this month, only one “one-asterisk” bird has been found in Maine (1-3 asterisks are the somewhat arbitrary designation that I use to denote rarities on our Southcoastal Maine Rare Bird Alert.) By this time date last year, 1 triple-asterisk, one double-asterisk, and two single-asterisk species were discovered.

So, what’s the difference? Well, we don’t really know. But, weather is likely playing a large role. If you peruse the archives of the Southcoastal Maine Rare Bird Alert on our website, you can check back for transcripts from the two previous years. Since you can also reread the week’s weather summary, you can see what factors may have influenced the occurrence (or lack there of) of various species.

“Strong west winds on Monday followed an overnight cold front and associated rain. Northwest winds increased on Tuesday, following a weak disturbance. Overnight lows dipped down into the 20’s throughout the area. Mixed precipitation turned to all rain overnight on Wednesday, as a strong cold front pushed through the area. Cloudy skies, and cool northwest winds followed for Thursday and Friday. This continued dynamic weather pattern has helped to produce exciting rarities again this week,” read the November 11, 2006 SCMRBA. This time last year, we had already seen a number of very strong cold fronts sweep through the area. This year, we have had mostly weaker cold fronts, with high pressure dominating - none of those massive fronts that stretched from Canada to the Gulf sweeping birds to the coast (and none on the horizon).

While weather is often given more credit than it deserves for causing vagrancy, it certainly plays a large role in producing vagrants for birders. To extremely oversimplify things, if a lost bird (lost in a broad sense of being in the “wrong” place) is wandering around the East do to a reverse-migration, mirror-migration, or just plain making a wrong turn at Albuquerque – to quote Bugs Bunny), a big, sweeping cold front is a great way to push them to the coast, concentrate them, or at the very least put them where there are lots of birders looking for them (hence the concept of the Rarity Roundup). Without those massive storm systems – like this fall so far – a vagrant may not end up in a place where it is more likely to be found.

Of course, this is just part of the puzzle, and I have made no attempts at including all of the theories of vagrancy – both the proximal and ultimate causes. However, if this topic interests you, I once again highly recommend subscribing to North American Birds. The “Changing Seasons” article that begins each issues take all of the season’s sightings and puts them into a big-picture perspective. Weather, population changes, Global Warming, birder coverage, and so on, all play a role. This stuff, by the way, is why I love seeing rare birds – the addition to a respective list pales in comparison to the intrigue – for me anyway – as to the how’s and why’s.

This morning in the cold rain, vagrants were not on my mind as much as getting the dog’s walk in before heavier rain moved through – unfortunately not from a strong cold front however. But, despite the rather unpleasant conditions, I found myself unusually cheerful. Hmmm, what could have happened yesterday that did that? . . .I wonder . . . Yes, Jeannette and I did enjoy a Northern Shrike at Pineland Farms, and a Nashville Warbler in Portland – while trying to relocate my Chat from Sunday – was nice, but there was something else. Yes, Rutgers football is one tomorrow night, but that wasn’t it (yet). Hmmmm…