Our Neotropical migrants go through much to come up to our northern regions for their summer breeding efforts, that we should know by now, they aren’t “our birds” but fly up here seasonally to gather insects that plague us and our vegetable gardens, as well as munching tree foliage every spring and summer.
It is a vigorous pursuit for their gathering needed protein for nestlings, because these numerous avian species have evolved since glacial times to see our “bug season” as opportune fodder — however its brief moment — before returning to Central and South America in late summer. Nearly half of the more than 800 species that breed in the United States and Canada temperate zone migrate south for the winter months.
Smithsonian Migratory Bird Center scientists have been most helpful in this regard. I smirk that just a few decades ago, any serious ornithological field researcher could have wound up as a “shrunken head” in that Amazonian basin. That did sort of get in the way of sticking around to monitor birds in the rainforest canopy.
Now that those Indians and that equatorial habitat are going by-the-bye, we can more safely cover any ground remaining down there and see what our barn swallows, purple martins, ospreys and warblers travel to.
However, successful coffee brands may have confiscated these over-wintering territories for ever increasing consummate tastes for that caffeine brew, with large scale plantations growing the coffee beans.
My Bluebird Society’s magazine tends to publish other’s research efforts and published essays (with permission) to look at the migration paths of those species we treasure.
The prothonotary warbler was featured in NABS’ issue of summer/2014 and this “golden warbler” of the southern swamps is profiled as an ecological example. It is a beautiful bird that I nor many others in the Northeast will ever get to see because of its reclusive habits; it is also a swamp cavity dweller.
Hence, NABS’ interest in such a bird that reproduces in this manner. My good friend of Louisiana’s bayou habitats, Bonnie Deere, mentions their coming during spring times. She calls them the “swamp warbler.”
The Audubon Society of New Hampshire took a photo of one in early November of 2016 in North Hampton, which was truly incredible, as there are only five previously accepted records in New Hampshire and all from spring or early summer.
Smithsonian’s research biologist and author Lisa Petit writes of its needs and life history. Although food is plentiful in our temperate zone, the breeding season is short with much to accomplish as a parent bird.
Petit states that the female prothonotary warbler must build the nest alone in a natural cavity, and build up energy stores quickly to lay five to six eggs, which represent up to 70 percent of her body mass, then incubate these eggs for 40 to 50 minutes of every hour for 12 to 13 days.
Then she has to find and bring food to those hungry youngsters every 15 minutes from dawn to dusk for another dozen days. She will continue to take care of their forage needs for 15 to 20 days after they leave the nest. Busy lady.
Her breeding season ends in late August, and then adults and new young begin moving off their territories, following river corridors toward the Gulf of Mexico as they gather energy for the migration journey ahead. Worries abound among birders that habitat patches they need to refuel are disappearing and becoming smaller due to human development on the coast.
Even mangrove forests’ dense tangles are being cleared for prime resort properties. These shoreline habitats are in the southern United States, Central America and South America in the Caribbean. If you have seen some the N.H. PBS-tv documentaries about the birds, these mangrove forests are being cleared faster even than the jungle rainforests we hear so much about.
Birds funnel down to gather in the little remaining habitat, even among the high-rise resort hotels and other development along the Gulf Coast of the US from Texas to Florida. The must forage daily to vigorously rebuild body fat, and once again at dusk they set off for their 10-hour flight across the Gulf to the Yucatan Peninsula.
Birders frequenting coastal migration routes know that one can walk along beaches during an early morning in spring or fall and find the sand littered with small birds too tired to move away very quickly. A thrill for us, but many will not survive to continue their arduous journey south.
These situations also exist on our offshore islands in Maine and New Hampshire, and in the Great Lakes where the migrants cross large bodies of water. Lisa states that most prothonotary warblers will follow the Atlantic coast of Central America down to Costa Rica, Panama and northern Columbia to reach their mangrove swamps’ wintering grounds by September or October.
Dave Eastman also broadcasts “Country Ecology” four times weekly over WMWV 93.5 FM. As vice president of the Lakes Region Chapter/ASNH, he welcomes you to monthly programs at the Loon Center in Moultonborough. He is available at: firstname.lastname@example.org (or) countryecology.com for consultation.