Tracking the Bird Spring Migration
It's a busy time in the birding world. The spring migration is underway. Mark Faherty tells us more in this week's Bird Report.
The first few scouts have arrived, the trickle hinting at the neotropical migratory flood behind them. A Northern Parula here, a Black-and-white Warbler there. Most of their brethren are still making their way north from far-flung wintering grounds from South and Central America to the Caribbean and southeastern US. Many are gathering in places like the northern tip of Mexico’s Yucatan Peninsula. Brightly breeding-plumaged and bursting with migratory restlessness, they wait for the right conditions to launch out over the Gulf of Mexico. Hopefully they found enough to eat in their tropical winter digs to sustain them on their marathon flights north. Texas and Florida already have their full complement of spring migratory warblers, and we will too in a couple of weeks. But it’s already time to start checking the Beech Forest or Aquinnah or Steve’s Woods or Gooseberry Neck, or whatever your local migrant trap is. We’ll get our share of warblers and tanagers out here, but it won’t be quite the torrent of migrants they see on the mainland. The Cape and Islands tend to be a stopover of last resort for these travelers, who prefer a more inland route. Think of us as primarily a fly-over state. Why? I probably don’t have to tell you that spring comes reluctantly to Cape Cod. The winter’s cold lingers in the ocean that surrounds us, which keeps our trees a few weeks behind the mainland in leafing out, which in turn delays the insects.
Interested in tracking the migration? On my list of “cool things that didn’t exist ten years ago” is the Cornell Lab of Ornithology’s BirdCast website. It’s like the Weather Channel for birders. The forecasts analyze broad-scale weather patterns like fronts and regional wind directions and combine them with expected migration dates and on-the-ground bird observations from the eBird database. You get a forecast along the lines of “in the northeast, today will be cloudy with a 90% chance of warblers”. The weekly forecasts are broken down by region and species. The last week in April is a transition period, and this week’s report for the northeast clearly shows the expected decrease in April migrants like ducks and sparrows, and a sharp increase in the May migrants like warblers and vireos. I also like the animated wind maps that show predicted wind directions for the next week, and the Doppler radar images showing masses of migrating birds taking off a definitely worth checking out. But even with all these tools, fallouts of migrants are notoriously difficult to predict, especially on this broken archipelago we call home. Ultimately, you just need to push away from the computer, wrest your gaze from your smartphone, and get out there to try your luck.
While you’re waiting for the warblers, buntings, flycatchers, tanagers, thrushes, and orioles to all get here, maybe you’ll catch a look at the pair of adult Bald Eagles that have been seen several places between Dennis and Eastham over the last few weeks. This is almost certainly the same pair that took over an Osprey nest back in January, only to have the Ospreys return in March and forcefully evict them. I suspect this was the eagles’ first nesting attempt, and I know I’ll be on pins and needles to see if they try again next year. We are overdue for the first Bald Eagle nest on Cape Cod in modern times. It’s not a question of “if”, it’s a question of when and where. But there’s another question and that’s “who?” Will you be the one to discover it?
Mark Faherty is Science Coordinator with Mass Audubon’s Wellfleet Bay Wildlife Sanctuary.