It’s officially the fall seabird season, one of my top 27 favorite times of year in the Cape Cod birding calendar. My visits to various ocean and bay viewpoints from Provincetown to Dennis in the last week or so have produced big clouds migrating sea ducks known as scoters, the first flocks of wintering Long-tailed Ducks, hundreds of Red-breasted Mergansers, dozens of Bonaparte’s Gulls, flocks of football-shaped Razorbills, flotillas of Common Loons, squadrons of gannets, and a handful of Black-legged Kittiwakes, all signs that winter is nigh on the ocean.
But not all the seabirds out there portend of winter. On Halloween, local bird expert and author Peter Trull was sorting through one of those squadrons of gannets diving on baitfish off Corporation Beach in Dennis, when he found one that was a little off – smaller, browner, and diving at a shallower angle. He knew this was not a gannet in a Halloween costume, this was a rare visitor, a tropical relative of gannets called a Brown Booby.
Like a lot of warm water seabirds, Brown Boobies have a sprawling breeding range across multiple oceans, but the closest breeding colonies to here are in the Caribbean. As recently as 2011, here in Mass the Brown Booby was considered a “mega” rarity in birder parlance, but now we get multiple annual records. No one is sure why – they have been driven out of many of their former breeding islands around the Caribbean but are greatly expanding their non-breeding range. Maybe they are searching for new breeding islands.
It was back in 2011, right there at Corporation Beach, that the Brown Booby era began here in Massachusetts. Before then, there were maybe four or five records going all the way back to 1878, then suddenly they were annual visitors, with sometimes multiple birds per year. That 2011 bird showed up on the Corporation Beach breakwater in mid-August, then later moved to Provincetown. Shockingly, it remained on the outer Cape until mid-December, long after we all expected it to get chilly and head south – they mainly winter in places with water temps in the 70s and 80s.
Brown Boobies look a lot like young gannets, which are various shades of brown, but unlike gannets, they will sit on rocks close to shore for long periods – gannets essentially never come ashore around here unless they’re sick. I managed to get down and see this booby on Monday morning, when I eventually found it sitting on a rock a little west of Sesuit Harbor, trying hard to blend in with the cormorants. It was probably well fed on menhaden and other bait fish, which were obviously in abundance given the hundreds of fish-eating birds I saw there, including over 60 Common Loons, smaller numbers of Red-throated Loons, hundreds of Red-breasted Mergansers, Forster’s Terns, and hundreds of Bonaparte’s and other gulls.
There are other birds around worth chasing, including two really nice ones found just yesterday – a Tufted Duck and a Gray Kingbird, both in different parts of Eastham – but I recommend heading to Dennis for the Brown Booby if you can manage it. It’s worth going just for the sheer diversity and abundance of other seabirds there right now, even if you don’t get the ultimate booby prize.
