Friday, March 22, 2013

Panama -- Mist Netting Birds

By mid-March in 1983, I was well ensconced in the lowland forest of central Panama. After two and a half months mist netting birds, I could quickly identify the birds in hand. I recognized the pre-dawn owl-like call of the rufous motmot, "ho-hoo-hoo" and the nasal "cwahnk" of its cousin the broad-billed motmot. After more than two months in the tropics I was used to seeing armadillos and anteaters root around in the leaf litter. I was acclimated to the humidity and the steady 80 degree days. Yet, I was still thrilled to watch the ungainly flight of the locally common keel-billed toucan.

On December 31, 1983--the first full day living in Gamboa and only two days after we arrived in Panama--three keel-billed toucans flew by us as we walked around the small town. I exclaimed with delight at seeing my first toucan, and one with such a huge, colorful bill. Jim, who had been studying birds here for many years, barely gave it a look, calling it a "dirt bird." Birders use that term for birds that are so common, they don't give them a second look.

Toucans live in the tree tops and since we were studying birds in the understory, we never caught them in our nets. I never tired of seeing them fly across the road from one tree top to another. Check out this link to toucan photos if you want to gasp at their physical beauty. We caught plenty of other common and not so common birds in our nets. Here is how we did it.

Our main study site was located along Pipeline Road, an old discontinued road that leads deep into Soberania National Park. We drove 5 miles from town to reach our main study plots -- each about 5 acres in size and encompassing different habitats. The four sites had different moisture/humidity conditions ranging from dry to moist to humid to wet. These were slight differences, but apparently enough to affect the movements of resident birds. Our goal was to study whether birds were moving among these different habitat conditions, within a given season, from season to season, or year to year. In other words, did they migrate locally to take advantage of more food or higher humidity, or some other local condition.

The trees in mature lowland tropical forest in central Panama reach more than 120 feet tall. Most are deciduous, dropping their leaves at the beginning of the dry season. The understory of these forests is relatively open, although we still carried machetes to clear back the encroaching jungle so we could erect our mist nets.

Mature lowland tropical forest along Pipeline Road, Panama (1983)
At each plot we put up 15 mist nets, spaced 150 feet apart. Mist netting is a black nylon 36 mm mesh, measuring 12 meters (36 feet) long by 3 (9 feet) meters high. We suspended the net between two PVC plastic poles that were then tied to trees. Birds had a hard time seeing the mesh net as they flew through the forest. When they hit the net they bounced into a little pocket, staying caught until we came around to check the net and release them from their entanglement.

The plastic PVC poles with rolled up mist nests,
at our main study site along Pipeline Road
My co-worker Hanni, sets up a mist net with a volunteer
(photo by Larry Kolczak)
I untangle an orange-billed sparrow from the lower tier of the mist net
(photo by Larry Kolczak)
We monitored each set of 15 nets from 6 am to about 6 pm. Sometimes we closed the nets earlier if we reached our goal of 100 captures per plot. In between net runs, we often had down time, to relax in a small clearing, read a book, or watch birds, butterflies, or other tropical creatures. This was a time before GPS, laptops, cell phones, iPads, and other forms of distraction. It was us and the jungle and I'm glad for it. On the last net run each day we furled each net so that birds and bats would not get caught.
If we opened the nets too early in the morning, when it was just a bit too dark, we caught bats. And oh boy are they hard to remove from a mist net. Still, in the forest it was always a little dark on the opening round at about 6 am. We had to carry a flashlight, although sometimes we got lazy or thought we could manage with just our eyes. That is until Jim reinforced the real reason for the flashlight -- to avoid stepping on a poisonous snake. Like a fur-de-lance......a deadly pit viper.

Jim with a fer-de-lance, which he released after reminding us of their potential,
and hence the need to carry a flashlight in the morning
When mist netting birds we wore a small bag with banding tools -- pillowcase, weighing scale, pliers, metal leg bands. When possible we banded birds at the site of their capture. Sometimes we brought them back to a clearing - our headquarters in the forest -- to process and to show others. Then we'd take them back to the point of capture and release them. The birds were weighed and measured and banded. For some of the bigger hawks we had to measure their leg size to get the right size band. We blew on their wing feathers to see if the birds were molting.

Measuring and banding birds along Pipeline Road
(photos by Larry Kolczak)
Panama is home to more than 900 species of birds - an incredible number for such a small country. About 125 of the 900+ are migrant birds, including species that spend the breeding season in New England. While I was in Panama I saw 340 different species of birds. We captured about 40 different species in our mist nets. Some of my favorites....

The male and female royal flycatcher. These birds raise their crest and turn their head from side to side only when handled. Likely it is a threatening defense mechanism. We were happy to release them and allow them to lower their crests and their stress levels.

A male royal flycatcher has a red crest with black spots and deep purple tips,
while the female has a yellow crest with black spots and blue tips.
Some birds required special handling for other reasons. The hawks had huge, dangerous talons. Woodpeckers had huge beaks. The tanagers had short, stout but strong beaks that could really take hold  of a finger, or worse, a pinch of skin between fingers. Ouch.

A semiplumbeous kite

Tomorrow I will share more photos and stories of the birds and other wildlife along Pipeline Road and other sites that we studied thirty years ago in central Panama.

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