There are a number of birds that have returned to New England from their southern wintering grounds and are working hard to find enough to sustain themselves until food is more plentiful. Eastern Bluebirds, Hermit Thrushes, Northern Mockingbirds, Eastern Phoebes and Yellow-bellied Sapsuckers adapt their diets to whatever is available at this time of year, which can mean going from eating insects to consuming fruit. Fruits that persist through the winter are few and far between, but one of the plants that provides the most sustenance to birds in early spring is Poison Ivy. The off-white, berry-like fruits are extremely popular with at least 60 species of birds, including the early returning migrants previously mentioned, as well as Gray Catbirds, Yellow-shafted Flickers, Wild Turkeys, and Downy, Hairy, Red-bellied and Pileated Woodpeckers. The popularity of Poison Ivy fruit with birds explains why this plant is common along fencerows and other areas where birds roost (and pass the seeds). (Caution – irritating urushiol, an oily resin found in the sap of Poison Ivy, is present in the leaves, stems, flowers, roots and fruit of this plant.)
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Several recent studies demonstrate that wild birds are actively transporting ticks and their associated diseases during migration. In addition, a number of bird species are able to contract Borrelia burgdorferi (the bacterial causal agent of Lyme Disease infection) and transmit it to uninfected ticks that parasitize the birds for a blood meal. Since ground-feeding species such as Northern Cardinals, Gray Catbirds, Song Sparrows (pictured) and American Robins spend a significant amount of time foraging for food at the optimal height for ticks, they are excellent hosts and have all demonstrated the ability to infect larval ticks with Borrelia burgdorferi upon their first blood meal. (Look carefully at the Song Sparrow’s neck and you will find a tick.)
Now that the leaves are off the deciduous trees, it is much easier to see where songbirds nested this past summer. Just as every songbird species has a specific song unlike that of other species, each species also constructs nests that are very similar to each other, but not to other species’ nests. Thus, one American robin nest looks a lot like any other American robin nest – nests of one species are usually found in roughly the same kind of habitat, with the same dimensions and similar building materials. Sometimes there are key characteristics that help with identification – grape vines and a lining of rootlets told me a gray catbird built the nest in the photograph. (Plastic told me humans weren’t far away.) Most songbirds only use their nest once; after the young have fledged, they abandon their nests. Before the weather and/or critters recycle this year’s nests, take advantage of the opportunity to examine these gems of avian architecture up close. (A federal permit is needed in order to collect bird nests.) A good book for nest identification is Peterson’s Field Guide to Bird Nests.