An Unexpected Vistor: The Giant Palm Weevil

Occasionally our mist-nets capture unintended visitors. Over the past week we have caught two impressive Giant Palm Weevils (Rhynchophorus cruentatus), which thankfully stayed put long enough for a quick photograph.

These native weevils are restricted to the southeastern United States and are among the largest weevils in the world. Their native host is the Cabbage Palm (Sabal palmetto), which is abundant at our field site. As you can see in these two individuals, Giant Palm Weevils come in a variety of black and red color patterns. 

The similar Red Palm Weevil (Rhynchophorus ferrugineus), native to the Old World, is rapidly colonizing the globe and is considered a serious pest to a variety of palm species. Likely traveling with imported palms, this species has recently arrived in the Caribbean and seems poised for an invasion of the Americas. 

Larvae of the genus Rhynchophorus are considered a delicacy in Asia. They are said to taste creamy when raw, and like bacon when cooked.

Migrant Warblers

Boreal migrants such as the Blackpoll Warbler and Magnolia Warbler are under increasing pressure throughout their ranges. One of the principal goals of our work in Apalachicola is to find out how important the barrier islands are as en route stopover sites for these species. 

Blackpoll Warblers perform one of the most impressive migrations of all North American birds. Weighing just 12 grams, they breed in the boreal forests of Canada and spend the rest of the year in the rainforest of South America.

To fuel this journey, they must first double their body weight in fat stores. They then take off on a non-stop flight that will take them over 1,000 miles, crossing over vast sections of ocean. Like most migrating songbirds, they migrate at night, using celestial cues to orient themselves.

 The Magnolia Warbler has very specific habitat requirements during the breeding season, depending on young stands of conifers. During the winter, it is found in a variety of habitats in the West Indies and Central America. Very active and colorful, the Magnolia is one of the crown jewels of the wood-warbler family.

These two birds are both adult males that we have caught in the past week on St. George Island. Males arrive first in the Spring, so that they can establish their breeding territories before the arrival of the females.

Island Snakes

The barrier islands south of Apalachicola have their fair share of snakes, including four venomous species. Over the past week, we have seen a variety of species at our field site on St. George Island, ranging from small garter snakes to black racers and black rat snakes.

During the heat of the afternoon, many snakes can be found sunning themselves on the gravel back roads. A couple of days ago we spotted this water moccasin (Agkistrodon piscivorus). Also know at the cottonmouth, this semi-aquatic viper is relatively common in swampy country of the Southeast. When threatened, a moccasin flattens its short, fat body and opens its mouth, revealing the bright white lining.

Venomous snakes often get the short end of the stick, so we decided to give this one a free pass. With a long stick, we picked it up and moved it off the road.

Mist-nets and a molt-limit

One of the main components of our field research on St. George Island is mist-netting. These nets are designed to passively capture birds that are passing through an area, which we then extract, band, and examine in hand. The aluminum band is placed on the bird's leg and has a unique number on it which serves as a sort of social security number. Studying birds in the hand allows us to better age and sex the bird, as well as check their physical condition.

Below is a photograph of one of our net lanes on St. George Island.  If you look closely you can see a line of nets set up in the open path. We have ten nets set up, varying in length from 6 meters to 12 meters. The nets are designed to be invisible to birds.

Monitoring the nets every 10 minutes, we extract any birds and bring them back to our banding station, which is a portable table surrounded by lounge chairs. It typically takes us two to three minutes to process the bird before it is released back into the wild.

Below is a photograph of a male Summer Tanager that we caught on April 22nd. An adult male Summer Tanager is all red, but if you look carefully you will see that the flight feathers of this bird are still green. This tells us that it is a second-year bird, which means it was born last summer. The green feathers are retained juvenal feathers that the bird had when it first fledged. This contrast between old and new feathers is called a molt-limit, and is one of the vital clues we can look at to help age a bird.

Summer Tanagers are neotropical migrants that breed throughout the southern United States. They winter in forested areas of Central America, and on their Spring flight northward cross over the Gulf of Mexico. Close examination of this bird told us that it had burned most of its energy reserves during its crossing.

First Day Fallout!

Our research team from Delaware State University arrived in Apalachicola, Florida on April 19th. To the average person, the weather was rotten, with howling winds and intermittent downpours. To bird researchers like us, however, the weather was perfect.

After dropping off our gear at the trailer we'd be staying in, we took the car and crossed the bridge onto St. George Island to check out our field sites. As we scanned the pine forests and suburban streets, we could immediately tell that birds were everywhere. Mixed-species flocks of warblers, vireos, tanagers, orioles and grosbeaks were streaming through the island, filling peoples front yards and the surrounding shrubs.

What was going on??

During Spring migration, many songbirds that have wintered in the tropics must cross the Gulf of Mexico to return to their summer breeding grounds. Being a Gulf Coast barrier island, St. George is positioned as one of the first safe havens for these arriving trans-Gulf migranst.

The island experiences the highest volume of migrants when southwest winds push them east of their principal flight paths further to the west. If these conditions are followed by strong north winds (a head wind), then many of the recently arrived birds will be forced to stay on the island, creating a bird fanatic's dream: a fallout. As luck would have it, today was one of those days.

As we explored the island, we tallied over 90 species of birds, including 20 species of warbler. We saw birds in outlandish places: Dickcissels in pine trees, Gray-cheeked Thrushes on the roadside. We saw dozens upon dozens of Black-throated Green, Hooded, and Yellow Warblers, while flocks of Indigo Buntings rained down from the sky. Scrub oaks were packed with glimmering birds of all sorts, foraging feverishly on the arthropods that they could find. All the while, we could hear the soft chip notes of arriving migrants high the sky, slowly getting closer.

As dusk descended we reluctantly pulled ourselves away and drove the short commute back to Apalachicola. Arriving at our trailer, we feverishly ate some food and got ready for bed. Like the birds we had just observed, we too had traveled over 1,000 miles and were tired. Tired and excited about our next three weeks of work.