Three for Three!

4th May 2013

Before I came to Las Cuevas I never questioned how scientists catch, analyze, and track birds. Today I learned their methods. Mist netting is a method all scientists use to capture birds for tagging in an ethical fashion. In the Chiquibul, most of the birds are caught wood marbles; they migrate from September to March through the forest. Boris explained the reason for tagging birds is to track their migration pattern as well as the population dynamics. Population dynamics are essential to know the health, age, and the environment the birds reside in. For animals, health and environment go hand and hand. Body composition is an indicator of an unsuitable environmental and improper health. To check the body composition, one will look at the bird’s neck bone depression to determined the amount of fat. A bird with a low body composition indicates that the environment is not suitable.

Boris untangling the yellow- green tryannulet

To determine the age of the bird, one would look at the skull. If the bird is young the skull is soft and has openings, similar to a human infant. If the bird is an adult it has a much firmer skull. The age categories for the birds are hatching, first year, and third year. The molting pattern also is an indicator if age as well as gender.

At 5:00am our group of six set two mist nets, 2m by 10m, in the forest close to the research station. The reason the nets have to be close is due to the fragile state of birds when they are caught. If the birds are forgotten in the mist net and stay too long, the probability of them dying is high. Every 20 minutes we checked the two mist nets. We were lucky enough to catch three birds! The first bird was a Yellow-Green Tyrannulet. We indicated it was in its hatching year because of the feathers and size. After one analyzes a bird, they have to release it and categorize how the bird flew. They have to send that data back to the organization that distributes the bird tags. Zero category is when the bird didn’t fly at all, two is the bird flew with injury, and three is the bird flew without injury. Of the three birds caught today, all three flew with the category of three. None were injured, three for three! Mist netting is a fascinating, ethical way scientists track birds and I was able to experience it!

Lindsey with releasing a bird

Boris with the last bird caught.

The super calm yellow-green Tyrannulet resting in Boris's hand

The other group went to the bird trail, hiking to the bird tower. Although I did not go, I can definitely share that the hike was strenuous one. All the trails we have been on so far have been rather flat, but apparently this one had a few steep hills. After the hour hike, they reached the bird tower. They thought the hike was hard, but they misspoke too soon. The ladder for the tower was put together with zip ties! They all traveled to the top except for Dr. Alegria. The other group didn’t see many birds, but they were able to see the sun rise above the tree line. On Tuesday our group will take the hike to the bird tower, and the other group will capture some birds in with some mist nets.

After breakfast, the whole study abroad crew headed into the forest to set up Sherman Traps. The Sherman traps are used for the same reason as the mist nets, to determine population dynamics. Rodents are indicator species because of their short life span. Therefore capturing and analyzing them is essential for knowing if the environment is suitable. The weather conditions have to be perfect to set traps for rodent survival and protection. If it is either too hot or cold, they may not survive.

First we had to set up a  10m by 100m transect. Every ten meters in the transect we would set a trap filled with peanut butter. The transect has to be an exact rectangle, with 90 degree angles at each corner. Both groups had great trouble setting this up right. We did not follow the directions correctly. Instead of following the North direction, we aligned the transect in accordance to the trail, leading to great error. The compass should not have been leading the group, rather behind the group directing everyone. It is true in the field error is expected, but not as much as our groups had. This was a learning experience; sometimes the basic skills are rather difficult when coupled with low visibility and group discrepancies. Fieldwork is all about practice, practice, practice!

Boris showing the ladies how to work the Sherman traps

Boris with the precious bait

Alex and Mike checking the traps for rodents!

We went back to the Sherman traps this afternoon and there were no rodents in anyone’s trap. We left them open for the night, so let us hope for success! I shall report back tomorrow, sweet dreams again.