Vocalization

Bird banding was just one of the activities the crew worked on at the Cary Institute Dr. Kara Belinsky, Ethan Duke and Cara Krieg (from NSF’s program: Research Experience for Undergraduates) were members of the crew who specifically worked on avian communication -. Birds can produce a great variety of sounds - with so much diversity, it helps to characterize individual birds.

Communication refers to the songs and calls of a bird. It is generally accepted that songs are loud vocalizations, often delivered from an exposed perch, with the intention of attracting a mate or to ward off intruders. My last post about banding explains the technique used to start the identification of a bird. Once an individual is identified, it complements the goals of studying communication because recording of vocalizations can now be attributed with known individual.

After Ethan, the sound recordist, has recorded all the calls and songs, he then converts them into sonagrams. A sonogram is useful by converting what we hear into a visual diagram of the frequency or pitch of a vocalization over time. This helps to visualize and characterize the complexity and anatomy of the song. By converting sound into something physical that we can observe and quantify, it allows researchers to study the communication of birds in detail

The song of the veery is distinctive, with complex harmonics – and sound produced from the dual ‘vocal cords’ of the bird - people find the song very beautiful. There are many questions that remain unanswered at this point. One is how does the male’s song affect female mate choice? Unpaired birds of most species typically sing all day long, and paired males sing less often. But not all calls are meant for females – there are calls that defend a territory from another intruder. Experimenting on which acoustic elements may signal the likelihood of attacking in male-male competition, Ken Schmidt discovered veeries make a soft “whisper call” when engaged in counter-singing with another males. Wondering if this functions to warn or ward off rivals. Cara Krieg and Dr. Kara Belinsky found that veeries that act more aggressively towards a mounted model (i.e., simulating an intruder) give the “whisper call” more frequently than males that act less aggressively toward the mount.

See if you can hear the “whisper call” that can be heard if you listen carefully to the recordings, and more easily when you study it on a sonagram.

Veeries have another challenge - researchers suspect that owls eavesdrop on bird songs to help them hunt. Dr. Schmidt and others have noticed that veery songs are hard to locate or judge distance to the singing bird. Have the veeries developed their complex harmonics to make it more difficult for them to be localized – its not quite jamming owls ‘radar’, but it does create difficulty. If Ken and Kara are correct, then you can thank the owls for supplying the evolutionary selective pressure that makes veeries sound so beautiful and unique! When the researchers study the complexity of the veery song and the effects that the environment has on it, they are trying to learn more about the total repertoire and vocabulary for this species. This first field season the biologist worked hard on establishing a control. With two more field seasons to come we can anticipate for the research to move along further.

For more song recordings and spectographs click here.

Banding, part 2

Banding is one step in the research that has many purposes; it’s about information in ecology. Banding birds helps to reduce the uncertainty, making the world of birds more predictable for researchers. We gather information to individualize a bird. By doing so, it allows researchers to study dispersal and migration, if mates stay together, reproductive success and population growth, life span and survival rate, social and behavior structure, and previous success. It helps in how to tell birds apart from one another and gather information about an individual’s history and its decision-making, such as whether to return to a site it previously occupied, which nest is it attending, or even what sex is it. Since male and female veeries are monomorphic, there are no visible means to distinguish the sexes from a distance. Biologists solve this by putting unique color bands on their legs to identify individuals (and sexes by putting an aluminum Fish and Wildlife Service band on either the left (F) or right (M) leg). Thanks to identifying individual birds through banding, researchers have gained information that is useful for understanding this otherwise cryptic behavior.

Banding birds also helps with toxicology and disease research. As we know that birds can be vectors for disease, sampling wild birds for serious disease can help determine the prevalence in a population. The banding of birds in the U.S. is protected under the Migratory Bird Treaty Act, banding in the U.S. requires a federal banding permit. The data researchers can acquire from banding is useful in research and management projects.

Going out with the banders for the day was always an adventure. We would meet up before the sunrise, everyone with dark coffee in hand - it was not a pretty sight when people did not have their java. Some were morning people and some were not. You would either hear a sprightly “morning!” or a “grramgsh.” The lead banders for the team were Jason and Dana. As experienced banders they make it seem effortless, which is not the case because banding requires a lot of work. Jason has experience working on Block Island and Dana has been banding every field season for the past several years. One of the most important tools needed for banding is the net. It’s a lightly woven net that is very susceptible to damage if the bander who is setting up or disentangling a bird is not careful. It is made of very light and sensitive fibers that will not damage any part of the bird.

There were days when we were doing “target banding” which is a rather difficult task. It means trying to catch a specific bird in the mist net by going to its pre-determined territory and luring it in with playbacks of the male’s (usually) song. This works because it simulates a territorial intrusion and no self-respecting male is going to tolerate that! When we target a female, we need to flush her off the nest into the 1 or 2 nets surrounding her nest. When target banding we have to set up the mist net quietly and discretely, trying to avoid the wind, poison ivy and flecks of sunlight. When there is wind, there is trouble. We had to make sure that the placement of the net was perfect so it would not sway in the breeze or catch sunlight - the birds will be discouraged of anything that seems out of the ordinary. Dawn is prime time for banding and it’s surprising how quickly that time will fly by. Most of the time we were trying band veeries and ovenbirds, but on one occasion, Ken took us all out into a part of the research territory to band all kinds of birds. The area is called the “Lowlands” and is a riparian habitat that surrounds Wappinger’s Creek – full of warblers, veeries, sparrows, and many more. When we banded in the "Lowlands," my favorite area, this is what we got.

Yellow Warblers-

Dana & Jason holding Yellow Warblers-

Janice holding an American Robin-

Jeff holding a Common Yellowthroat-

It was a beautiful day.

Ecology of Information

Ecology of information is the study of how organisms acquire and use information in decision-making to manage their lives of, e.g., finding food, selecting habitats, allocating time to vigilance and foraging, and trading off current and future reproductive success, and its significance for populations, communities, landscapes and ecosystems. 


- Ken Schmidt

Veery

The first veery sighting of the day is always different from the second or third. It seems to me that when you spot your first veery of the day, their song is the loudest and their indistinct reddish-brown spots seem ever more ginger.

This veery was banded this morning, Ken is holding the

veery in a position called "the photographers hold."

On Banding...

Banding is essential to the research effort here. Mist netting and banding helps to identify and characterize each individual bird to better gather personalized information.

Map of Cary Institute

Below is a map of Cary Institute. I will often refer to

plots of land by their names and this can be used to

get a better sense of direction.

The Veery

The research I am interpreting is primarily focused on the

Veery (Catharus fuscescens). The Veery is a North American

woodland thrush with a brown back and speckled breast. The

Veery resides in the forest where it is more often heard than

seen. The Veery has a beautiful distinctive song.

Recording and sonogram provided by Ethan Duke.

A sonagram, or more descriptively called a sound spectrogram,

plots the sounds frequency against time and it makes a visual

representation of the sound. Frequency is measured in hertz or

kilohertz. Investigators have found that a particular bird has

specific songs for specific events. To the human ear, we may not

catch the subtle differences, but with a sonagram, this problem

is diminished. Researchers and sound recordist typically use a

computer software program called Raven to make sonagrams.

Veeries inhabit deciduous forests in North America

where they nest on the ground or low in shrubs.

Veeries are ground foragers eating primarily

insects.