Current Nature: Nest Building 101

Around the island, it is hard to miss the birds that are hard at work building nests and getting ready to raise their young. Recently, I’ve spotted birds in my neighborhood whizzing by with a bill full of grass and seen osprey clutching sticks in their talons. When you think of a bird’s nest, you probably imagine a small cup of woven sticks on a tree branch- usually made by songbirds. While many birds build nests like this, nests vary widely in shape, construction, materials, and placement. Birds are like nature’s little architects and real estate agents and have a diverse array of homes that do not need to go through HDC permitting.

Some of the most surprising nests come from beach-nesting birds on island, such as the piping plover, least terns, and American oystercatchers. These birds prefer to nest on our shorelines by making a small “nest cup” in the sand. If you throw a tennis ball into the sand, the depression left behind would be about the size of the piping plover or a tern nest, whereas an American oystercatcher would be slightly bigger. Shorebirds have some of the simplest, no-fuss nests, just a bit of a scrape in the sand decorated with shells and bits of beach debris they find nearby. Their sand-colored eggs camouflage perfectly with their surroundings. These species face many threats and are federally protected. For these species with dwindling populations, human intervention, like fencing and beach closures, is necessary to protect the birds and their nesting habitat from extinction. By respecting closures and allowing the birds to nest and fledge their young, the beaches will reopen sooner. If their nesting is disrupted, these birds will nest again and lay up to two more clutches of eggs, restarting the process and beach closures.

Nantucket is a sanctuary for other ground-nesting birds because there are few ground predators. Nantucket does not have skunks, foxes, or coyotes, which is great news for birds like northern harriers, American woodcock, and eastern towhees, who thrive here. Northern harriers prefer shrubland and sandplain grassland for ground nesting; typically, the denser the thicket, the better. American woodcocks love to nest in the understory of the woods and shrublands under leaves and debris. Eastern towhees will also nest on the ground under leaves in a range of habitats, from the woods to a simple brush pile in a yard or garden.

Many birds have become adapted to human assistance, especially those that depend on old dead trees. Dead trees are hard to come by, especially on Nantucket, and are often removed for safety or aesthetic reasons. Ospreys are large birds that nest on top of old dead trees, especially near water. Without tall, dead trees, Ospreys moved on to the next best thing; active telephone poles. Since active telephone poles are very dangerous to nest on, electrical companies started putting up “osprey poles” near active nests to get the birds to use a much safer option. Over time, Ospreys learned to look for these tall structures with a wide, flat platform and know they are the perfect nesting spot. Tree wwallows are another species of bird adapted to artificial nests. Being cavity nesters, tree swallows love using natural dead tree cavities or abandoned woodpecker cavities- again, quite scarce, especially here. Humans have helped fill that gap in housing for tree swallows, who have learned to use nest boxes. At the Linda Loring Nature Foundation, we have been monitoring our active tree swallow boxes for many years, and right now is an excellent time to come and watch their nest building display as they bring pine needles, leaves, and grass into the boxes.

This time of year, it’s not uncommon to find a bird’s nest around your home or yard. Depending on the size and color of the eggs, it could be an American robin, northern cardinal, a mourning dove, or possibly a Carolina wren taking up residence in your outdoor shower (a favorite spot of theirs). Some other songbirds, like the red-eyed vireo and Baltimore oriole, will weave a hanging basket from a branch. A great way to figure out the nest owner is to carefully observe who is coming and going from the nest location from a distance. An average songbird or backyard bird requires 12-16 days of incubation and another 10-16 days for the chicks to grow big and strong enough to fly. You may come across baby birds on the ground; the best practice is just to leave them. If you can hear their parents around, that is one of the best signs that the baby bird is attending flight school and is trying to figure out their wings. A great way to be sure the baby bird doesn’t need help is to consult this chart created by Mass Audubon.

On your next outdoor adventure, whether hiking, gardening, or sitting outside enjoying the sunshine, keep an eye out for bird’s nests! They offer a sweet peek into the lifecycle of the everyday birds around us and are as diverse and unique as the birds themselves.

Starting May 3rd, the Linda Loring Nature Foundation's popular Birding Field Trips are back for the season. These trips are held every Wednesday morning until the late fall. Participants will get to explore Nantucket’s birding hotspots and observe a variety of species in many different natural habitats. All experience levels are welcome, and all the birding essentials are available to borrow. To register and view all upcoming trips and programming, please visit LLNF's event page at: https://llnf.org/events

Stay tuned for more editions of Current Nature, a bi-weekly column featuring seasonal topics, natural history information, and advice on the outdoors from the staff at the Linda Loring Nature Foundation.