Fates of orchard oriole, coral bean tree intertwined
The coral bean tree of Mexico and South America (Erythrina fusca) is often found near old coffee plantations where it was planted as a shade tree. It is related to the showy coral bean bushes that are marketed in the United States as part of the residential horticulture trade. The cultivated version is relatively compact and extremely profuse. The native version from Mexico is a bit straggly in comparison, but looks can be deceiving. It is the native tree that is much more important to the birds that are migrating though my back yard right now.
A pair of birds has found our choice of native trees and bushes a safe place to stop after battling last night’s thunderstorms.
Each bird of the colorful pair is about 7 inches long. The female is lemony olive on top and a rich yellow below. The male has a black hood, back and tail. The wings are also black, but they have a white wing bar and white edges on the flight feathers. The wings display chestnut-colored shoulder patches. That chestnut pattern is repeated on the bird’s rump and entire breast and belly.
The male orchard oriole (Icterus spurious) looks a lot like a Baltimore oriole. The color pattern is the same for both species. The only difference is that the male orchard is a dark, burnt orange rather that the yellow-orange of baseball mascot fame.
Both male and female orchard orioles have relatively short, pointed bills. The species has a lovely warbled song that changes pitch effortlessly. Because of their showy colors, diminutive size and voice, they are often mistaken for warblers.
First year males are colored like the females with the addition of a black bib that extends from the bill down to the top of the breast.
Every winter, orchard orioles spend months in the fields and woods of Mexico and South America. The orchard oriole feeds heavily on the nectar of the native coral bean tree, E. fusca. In fact, only the orchard oriole appears capable of properly opening the tree’s flower. Once open, the flowers yield the rich nectar available within. Also revealed within is the same dark chestnut color that matches the male orchard oriole’s body.
Orchard orioles travel in large flocks during the winter. A coral bean tree can be mobbed by dozens of male orchard orioles during these months. All of those opened flower pods with their brick red interiors mix with the birds to form an illusion that the tree is overrun with birds. The orioles themselves seem to be startled by the profusion of chestnut color and the flock will depart en masse for another coral bean tree, where the process will repeat itself.
The male orchard orioles carry pollen from plant to plant, providing the cross fertilization that we typically associate with bees and insects. Without the orchard oriole, the E. fusca would be robbed of this evolutionary requirement and the species would die out. Scientists have speculated that the bird and the plant co-evolved, to the benefit of each species. The tree gets all of the genetic strength of cross pollination and the oriole gets a rich food source reserved just for its use.
There are nine oriole species in North America, but only the Baltimore and orchard orioles are likely to be seen in the eastern United States. Orchard orioles are late migrants into the Chesapeake region, often not arriving until May. They may leave as early as mid-July. While here, the birds build their open-cup nests far out on the end of branches.
These orioles like to be near water, so most nests can be found along streams, rivers or lakes. We see them regularly on Maryland’s Eastern Shore along the Nanticoke River.
The orchard orioles in our backyard are probably looking for a park or open woodland near water. Once they find that spot, they will settle down to build their nests and get on with their own breeding.
Here in the Chesapeake region, orchard orioles eat insects and spiders as well as the nectar from many tree flowers and fruit. Often, they perch on the foliage and glean bugs as well as flowers.
Because they are here for a relatively short stay, orchard orioles produce a single brood annually. Nevertheless, the birds appear to be in stable condition and they are ranked among the birds of “least concern” by organizations that track avian population trends.
The orioles are dashing from tree to tree, keeping me busy with the binoculars. Here are beautiful creatures with lovely voices that play a critical role in the health of the planet — or at least a corner of it. They are invaluable to a certain Central American tree. They are also a bird of compelling beauty.
That’s an unbeatable combination…and certainly worth another look.
- Category: Wildlife + Habitat
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