Saturday, December 1, 2012

Nutting's Flycatcher: a Big Year Birder's Dream

A Nutting's Flycatcher--Myiarchus nuttingi--recently made an appearance in the desert oasis of Bill Williams National Wildlife Refuge for the second time this year. This makes Arizona a pretty lucky state: Nutting's Flycatcher is a Code 5 (a.k.a. accidental) species in the ABA Area, meaning that the species has been recorded five or fewer times in the North American continent, and yet it has been recorded twice in the same spot in the same year! It even seems to have overwintered in this wildlife refuge, as it was first found in December of 2011, and was last found March 25th, this year. Basically, it's one of those really rare birds that make ANY Big Year that much better, including Sandy Komito's record setting Big Year of 1998 after which both the book and the movie titled "The Big Year" are based. Nutting's Flycatcher was the first rarity that Komito started with. Image that. January 1st; you start your year with a Code 5. That's good birding man.

But beyond the birding aspect of it, let's look into the biological aspects of this sighting. We'll start with a perennial birding favorite: the range map.
From this fine map--found on Cornell's Neotropical Birds--we can see that Nutting's Flycatchers are not migratory, but can infer that they probably disperse from their breeding territories when the season's brood is raised. We can also see that their range stretches up the western half of Mexico almost to Arizona, so it's not much of a stretch, one would think, for Nutting's Flycatchers to occur in Arizona. Their nonmigratory habits would account for their Code 5 status, though, because the birds just don't move around enough to make them common outside of their range. So what would draw the bird (if it is the same individual) to this wildlife refuge twiceBill Williams National Wildlife Refuge is described as a rare desert habitat with some of the last stands of native cottonwood-willow forest along the Colorado River. This creates a rich, even lush riparian habitat that would appear attractive to neotropical migrants, and even neotropical rarities. But why didn't the bird just stay where it was? Wouldn't the bird have plenty of habitat in its actual range? There's not an easy answer to these questions as we don't know much about this individual other than its occurrence north-of-range, but the answer may be yes. During the nonbreeding season, a hierarchy develops that dictates which songbirds get which qualities of habitats, with older adult males at the top, younger males and females just below, and young females at the bottom with the lowest quality habitat. As habitat destruction and degradation continues, this hierarchy is pressured for all sorts of species, and the birds at the bottom are getting it worse and worse. This could push some of the individuals on the bottom of the scale out-of-range just to survive, so it would be interesting to see if this individual is a young female. We'll see how long this bird sticks around--we might get some experts on the job.

With every rarity, there are always tons of questions, even beyond identification. IDing Nutting's Flycatchers is a challenge in of itself; they even used to be considered the same species as the more common Ash-throated Flycatcher. Luckily, they give their distinctive callnotes frequently. But beyond that, why the bird is occurring out of range raises all sorts of questions, such as how it behaves differently when in and out of range. Sadly, the likelihood that most of these questions will be answered is slim, but that's one of the best things about birds, and nature as a whole: it puts you in a constant state of inquiry, and that's a big reason why I'll never stop.

To read more about the bird, check here and here.

Internet Photo of the Nutting's Flycatcher. Found here.

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