by Alison Mitchell, Co-Executive Director, New Jersey Conservation Foundation
This time of year brings fireplace mantles, dinner tables, and storefronts donned with boughs of American Holly. The bright red berries and dark green, waxy leaves are symbols of holiday cheer and the wintery season upon us. We are not the only species that rejoices at the sight of holly trees; enter the American Robin!
Robins – with their familiar reddish-brown breasts and abundant “cheer-ee-oh” songs in springtime – are a prevalent species of the thrush family. Contrary to popular belief, many robins do not leave New Jersey during winter. They simply go into hiding, congregating in the state’s coastal swamp forests where abundant native fruits make up their winter diet.
With the onset of cold weather around Thanksgiving, holly berries start to ripen, and fruit-eating robins begin flocking to this nutritious food source. Over tens of thousands of years, the timely ripening of the holly tree fruit and the existence of hungry robins changed the course of evolution for both species.
And so, robins and holly trees coevolved: holly trees feeding famished flocks of robins, and robins spreading the seeds of the trees. Coevolution is when two species head down an evolutionary pathway together. In most cases, the pathway is built on reciprocity.
Robins are uniquely equipped to assist holly trees with the spreading of seeds. Fruit-eating birds have no teeth or gizzards, so seeds pass quickly through their guts unharmed. In fact, their digestive juices vastly improve seed germination by providing an initial breakdown of the seed coating!
Holly and many other shrubs and vines have coevolved with fruit-eating birds that winter in New Jersey. Many plants, especially those with large seeds, have developed chemicals to discourage seed-destroying mammals from gnawing or chomping their fruit. Holly trees, for example, have big seeds and fruit pulp that taste bitter, discouraging humans and other mammals from consuming them. Birds, however, love them. And the vibrant red berries of the holly tree do not just liven up our holiday décor. The bright colors attract fruit-eating birds that will carry their seeds.
The few remaining forests that once covered the entire stretch of the Garden State’s Atlantic coastline are dominated by trees, shrubs, and vines whose seeds are dispersed by fruit-eating birds. From holly and hackberry, to black cherry and red cedar, to poison ivy and Virginia creeper, almost every woody plant that we find on a barrier island forest germinated from a fresh bird dropping. No better way exists for seeds to pioneer into ever-moving sand dunes after a nor’easter than to be dropped by a winged seed-pooper.
Interdependence and coevolution is everywhere in the natural world, and understanding it can teach us how to live in a more harmonious relationship with the natural world. As humans continue to ravage natural resources with no end in sight, we must recognize that our consumptive behaviors not only lack benefit to virtually any other species, they actively cause harm to nature. If we slow down amidst the hustle and bustle of the season and look around, we will see relationships flourishing all around us in nature – like our relationships with loved ones, friends, neighbors, and community members when we are at our best. Beyond our human relationships, we need to extend the idea of reciprocity with the natural world into our everyday lives. After all, the earth gives us everything. Shouldn’t we be giving something back if we want to thrive and survive?
This winter, visit New Jersey’s barrier island forests at Sandy Hook or Island Beach on a nice day and witness hundreds of thousands of years of coevolution: the interdependence between birds and woody plants. A magnificent 300-acre holly forest at Sandy Hook in the Gateway National Recreation Area is a magical place to witness robins devouring holly berries. The Evert Nature Trail on Buddtown-Ong’s Hat Road in Pemberton Township is another ancient swamp forest that is filled with towering holly trees. Visit this boardwalk trail on a balmy December day to discover the robins hiding in the woods: https://www.njconservation.org/preserve/evert-trail-preserve/
Come spring – when robins begin to lay their bright blue eggs to create the next flock of seed-spreaders – know that they spent the winter in New Jersey, feasting on native holly tree berries and carrying baby trees in seed form around the ecosystem – literally spreading the seeds of holiday cheer throughout the year and flourishing in community. If we embrace the idea of reciprocity with the natural world, we too can flourish.
For information about preserving New Jersey’s land and natural resources, visit the New Jersey Conservation Foundation website at www.njconservation.org or contact me at info@njconservation.org.
