The Magic of Fall Migration Along the Haw River

In late September many interesting changes in natural history are underway signaling the end to summer and the upcoming fall and winter. The fancy word for such changes with plants is “phenology,” the seasonal variation in flower and fruit production. If you look at a view of my backyard you can observe such changes underway. The non-native butterfly bushes and lantana are still blooming after almost three months, but many plants such as coneflowers, bee balms, iron and Joe Pye weeds have finished blooming. The bonesets are in full bloom as are the mist flowers which are attracting many insects. But there are few butterflies left compared to the middle of summer. There are many carpenter bees still working the flowers and some wasps including this bizarre thread waisted wasp (Ammophila). One of the very few swallowtail butterflies still in evidence was this pipevine swallowtail, famous as the toxic model for the “black and blue” mimicry complex. The inner hind wings are an iridescent blue that shines brightly only in a certain bright light, and the outer hind wings have a circle of large orange spots. There are also some large cloudless sulphur butterflies on the remaining flowers.

One of my few herpetological sightings recently other than river turtles has been an astonishing keeled green snake spotted in a sumac bush along my driveway. Its camouflage is so amazing that it is rarely seen in its arboreal habitat. It is so confident in its camouflage that it does not flee from humans until it is touched or closely approached.

The big news in nature in late September is the massive migration of birds from the northern to the southern hemisphere. These neotropical migrants have moved in their millions to northern climates to breed where they could not possibly survive the winter. So they undergo a very dangerous long distance migration to the tropics. As a backyard birder I am mainly excited to see the grosbeaks and thrushes that are attracted to my sunflower feeder and dogwood trees that are loaded with red fruit.

The rose breasted grosbeak is an impressive bird- the females are drab brown but the males are an extraordinary blend of white, black and red. They breed as close as the higher elevations in the NC mountains and more generally in the NE and central US and Canada. They have an extraordinary song if you are lucky enough to hear them in the breeding season which is sometimes described as like a “robin who took voice lessons.” They love sunflower seeds and can be attracted to a well stocked feeder. In our yard they co-exist for the most part amicably with the local cardinals who also have a huge bill for cracking seeds. Cardinals and grosbeaks share the circumstance of brilliant male colors generally called the “pretty boy male” phenomenon. It is thought that the bright colors of the male advertise their fitness to females as they chose their mates. Since these are year long colors they must pose some danger in increasing predation but apparently the evolutionary advantages outweigh the disadvantages.

This time of year I am very excited to watch two very similar sibling species of northern thrushes migrate through our yard. The more southerly breeder, the Swainson’s thrush, is found occasionally in the northern Appalachians, but primarily in the far western US and southern Canada. The more northerly species, the gray cheeked thrush, breeds in northern Canada (https://www.allaboutbirds.org/guide/Gray-cheeked_Thrush/overview ). Since they do not sing during migration but only emit call notes they can only be easily distinguished by the presence or absence of an eye ring and some other subtle differences in coloration. The sexes are identical. I jealously and somewhat unsuccessfully try to protect the fruit on my dogwood trees from squirrels so the thrushes will have a surplus. Fortunately this land we purchased several years ago has many old dogwood trees which are usually rich in fruit.

There are also avian competitors for the dogwood fruit including scarlet tanagers which breed locally and are also migrating through from the north. This male has already molted from its brilliant breeding season “pretty boy” red plumage into the drab winter plumage. Surprisingly the related summer tanager males do not lose their bright red color. Indeed it is somewhat surprising how difficult it is to spot the male summer tanagers in dense foliage when they move slowly around foraging.

As I write this in late September we still have some ruby throated hummingbirds feeding on the last flowers. They will have to leave soon as the flowers die and their long flight to S America must be undertaken. They are famous for flying across the Gulf of Mexico in a single flight. I do not get to see many warblers in our backyard and they are very hard to spot in the woods since they do not sing. I did photograph two warblers that were attracted to our dripping water bath. A female chestnut sided warbler might have bred in the nearby Appalachian mountains or much further north. A female red start could have been a local breeder or from further north.

Our local bird with the biggest mouth is surely the Carolina wren which breeds in our garage. It continues to sing even now in late September perhaps proclaiming its territorial ambitions that will continue all year.

There is perhaps no time of the year other than Spring in which the miraculous migration of birds is so interesting and astounding. This is happening all around us and it only requires you to make some minimal effort to observe these events. So take a moment and really watch what is happening outside with seasonal changes in plants and birds especially. You cannot fail to be amazed by the remarkable natural events accompanying the changes in the seasons.