Rarities on the Cape and Islands

Oct 23, 2019

 

Yellow-green Vireo
Credit Nancy Ransom

As we head into the last days of October, change is evident in the bird world. Our backyard catbirds are mostly gone, headed for Central American forests. New ducks are arriving by the day on both pond and bay. Behaviors are also changing, as our resident woodpeckers, titmice, and chickadees are loading their winter larders by stashing sunflower seeds and acorns in holes and crevices. 

 


But one thing that does not change is that the Cape and Islands attracts more rare birds than probably anywhere in the northeast, and this month has been no different.

Western Kingbirds, yellow bellied cousins of our grayscale Eastern Kingbirds, breed west of the Mississippi, as you might expect. But this month they have turned up at Wellfleet Bay sanctuary, and in the last few days, South Chatham and Cuttyhunk Island. Others may yet to be found - look for these flycatchers in open areas where they like to perch atop anything from a flower head to a tall tree, changing perches every few minutes. Known wanderers in fall, a few can be expected every year, especially on the Cape. Check for their white outer tail feathers to rule out less likely lookalike species like Cassin’s, Couch’s, or Tropical Kingbirds, all of which have been seen in Massachusetts.

Last week, two wayward birds found on the Cape vied for rarest bird in New England. While the Black-throated Gray-Warbler found at Salt Pond in Falmouth last Tuesday was indeed rare, it was the second individual seen on the Cape in about a month, and one of over a dozen for the region all time. These warblers of West Coast mountains should be in their winter quarters in western Mexico by now, not Falmouth. But as I noted last week, this bird was only the second rarest bird on Cape Cod that day. A Yellow-green Vireo was banded at the South Monomoy banding station, an astounding second New England record of a mainly Central American species, and one of only five eastern records north of Florida.

This small insectivorous songbird closely resembles our very common Red-eyed Vireo, but the sharp-eyed banders led by station manager James Junda noticed the bright green back, yellowish flanks, and bigger bill that made this a Yellow-green, and snapped some confirming photos. That day, ornithologist Sean Williams happened to be conducting bird surveys on Monomoy and briefly saw a strange vireo in the lighthouse thickets, suspecting but then dismissing the absurd notion that it was Yellow-green Vireo. Later, a conversation with the banding team revealed the truth, distinguishing Sean as the only person to see a free-flying Yellow-Green Vireo in New England because the other two records were of birds caught in nets at banding stations.

Why is this bird so rare? The Yellow-green is unusual in that it completely vacates its breeding range in Mexico and Central America to winter in South America, meaning that an individual in Costa Rica or even Panama would be heading south at this time. Why a bird would need to leave Costa Rica for the winter is an open question, as is how it would end up in Chatham instead of the Peruvian Amazon. This is why birds are, in my humble opinion, inherently more exciting than, say, trees, which don’t tend to end up in strange places very often. The apple doesn’t fall very far from the tree, and all that.

Birds, with their potent combination of wings and wanderlust, can turn up just about anywhere. You just need to be in the right place at the right time with your eyes open and ready. Then, like Sean, you too can find a bird that makes the other birders yellow-green with envy.