In this piece, I tend to chronicle the various migratory bird species that mark the changing seasons, especially now, when everyone is desperate for signs of spring. But even I will admit there are some signs of spring even more important than newly arriving birds, and I bore witness to one of them this weekend during a family hike in Harwich. Each year at this time, something primal and fundamental happens in certain of our ponds and streams. As we speak, river herring are fighting currents and a gauntlet of anthropogenic barriers in an epic annual struggle to make more of themselves. And many of our newly arriving birds are depending on them.
It’s hard to overstate the importance of our herring runs here on the Cape. The runs involve an inscrutable mix of blueback herring and alewives returning from the ocean to spawn in local ponds each spring. These fish bring the ocean’s riches well inland, at least by Cape standards, in bodies built with oceanic plankton. Ponds with herring runs are objectively better than those without – they have more fish, more birds, more otters, more turtles. They are more likely to have loons and Common Mergansers, Bald Eagles and Osprey. As their population has recovered in recent years, the ponds where the pioneer Bald Eagles have chosen to nest in southeastern MA are all herring run ponds, including the one nest here on the Cape.
Despite their importance, we don’t make it easy on the herring – culverts and dams slow them down, reducing their breeding success and making the herring easy pickings for snapping turtles, bass, and raccoons. Huge oceanic trawlers don’t differentiate river herring from the sea herring they target, further reducing stocks. Droughts are exacerbated by water draws for agriculture, and nutrient pollution depletes oxygen in the ponds – add all this up and we’re lucky we have any herring left. Fifteen years of harvest closures and culvert projects have not recovered the stock.
But the herring still run, and the birds are there to meet them. On Saturday, my family and I were lucky to see some of the drama that has increasingly been playing out at local herring runs – Ospreys and Bald Eagles in aerial dogfights. I guess “fish fights” is more like it, and the Osprey generally lose. Harwich hosts one of the biggest runs in the state, with over a million herring counted by electronic counters two years ago. Most other big runs are on the order of tens or low hundreds of thousands. As a result, the reservoir at West Harwich Conservation Area hosts more Ospreys, eagles, cormorants, and night-herons than just about anywhere else this time of year.
It was during one of the many snack breaks required with small children in tow that I saw an Osprey make a big splash and snag a big fish, which it took to a pondside branch to enjoy. While my eyes were elsewhere, a young Bald Eagle had apparently relieved this Osprey of its catch – we watched as it zig-zagged around the pond, once passing very close to us, with the Osprey in futile pursuit. Others have also been seeing these kinds of dramatic pursuits based on some photos going around on social media. It’s the kind of thing you expect to see on the Discovery Channel, not across town. There are quite a few herring runs on the Cape, and action is peaking now, so get yourself to your nearest one. If I had to create a marketing slogan for the local herring runs, it might be something like “Cape Cod herring runs: come for the fish, stay for the eagles pummeling Ospreys to steal their fish”. I probably need to tighten that up a bit, but you get the idea.