The Mysterious Radar Echoes are No Longer Mysterious!

Earlier today the radar showed strange echoes across the Connecticut shoreline from North Branford to Salem. It was clear it wasn’t rain being picked up by the radar. How do we know that? For one, it wasn’t cloudy. Secondly, dual polarization radar products indicated (with correlation coefficient values near 0.65) these radar echoes were likely biological targets – NOT meteorological targets.

0.5º OKX Base Reflectivity and 0.5º Correlation Coefficient. Echoes are approximately 2000-3000 ft AGL.

We frequently see birds on radar around sunrise when they take off. We even see insects when they get caught up in various wind shifts. Today’s echoes were unusual in their persistence and the huge area they took up across the shoreline. Toward sunset it was clear these were indeed biological targets. The birds were flocking to the Connecticut River just before dusk.

OKX 0.5º Base Reflectivity 2145 UTC
OKX 0.5º Base Reflectity 2214 UTC
OKX 0.5º Base Reflectivity 2224 UTC. Red X marks Goose Island in Old Lyme on Connecticut River

How cool is that? On my Facebook page Paul Shipman thought the birds may be Tree Swallows that visit the lower Connecticut River this time of year. As it turns out Paul was right and tree swallows were the culprit behind the mysterious bird on radar.

According to the Hartford Courant as many as 500,000 Tree Swallows land shortly before sunset on Goose Island in Old Lyme on the Connecticut River this time of year. The radar shows the echoes disappearing  right over Goose Island. This means the Tree Swallows that had been flying near 2500 feet AGL during the day (that’s where the radar beam is) were diving under the radar beam. Here’s a close up look at where the Tree Swallows were landing in Old Lyme.

OKX 0.5º Base Reflectivity 2236 UTC.
1 – Coult Lane
2 – Route 156
3 – Tantummaheag Rad
4 – Pilgrim Landing Road
X – Goose Island (Radar sampling approximately 2700 feet AGL)

Apparently CT River Quest out of Haddam offers cruises to see the Tree Swallows landing on Goose Island around sunset. Based on what I’ve seen here on radar it must be an incredible site!

I’m excited to see if our 500,000 avian friends return tomorrow!

2 thoughts on “The Mysterious Radar Echoes are No Longer Mysterious!”

  1. Thanks for sharing the radar images! Aboard RiverQuest, we have been having fantastic Tree Swallow Cruises EVERY evening. Lots of birds, unbelievable sunsets and groups of very HAPPY passengers. We have seen all three pairs of our local mature Bald Eagles on one trip. This has certainly been the BEST Tree Swallow season thus far. We are pretty much sold out, a few more spots on October 2 at 4:30pm and we added September 27 at 5:00pm. Let’s hope the weather continues to hold out so everyone can enjoy this cruise.

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