Uncategorized

cactus wren

4

Bling with a Purpose

Bands used on cactus wrens and burrowing owls, far left is aluminum wren band, middle are wren color bands, far right is alphanumeric band for owls.

Bands used on cactus wrens and burrowing owls, far left is aluminum wren band, middle are wren color bands, far right is alphanumeric band for owls.

Bird banding is an important tool for researching wild birds, allowing them to be individually identifiable in the hand or by sight. This can be especially important for birds that are too small to carry tracking devices such as radio collars or GPS tags. Both conservation research projects that I work on involve understanding some aspect of the population dynamics of birds that are too small to put transmitters on: coastal cactus wrens and western burrowing owls. An alternative method of distinguishing individual birds is to mark them with color or alphanumeric bands, in addition to standard aluminum bands from the US government, which are required for all banded birds and have a unique ID number.

This cactus wren sports a unique color band combination.

This cactus wren sports a unique color band combination.

To mark cactus wrens, we use plastic bands that come in several different colors and also have our US government aluminum bands dyed green so as to distinguish them from bands used by other organizations also conducting research on cactus wrens in southern California. Each wren gets two bands on each leg (two plastic on one leg, one plastic and one aluminum on the other), giving us lots of combinations to work with so that each wren has a unique color combination. In the field, we use binoculars, spotting scopes, and photographs to identify individual birds. Because we know where and when each bird was banded, we can get a sense of how long the birds live, how far they move, and how they interact with each other.

Federal and state governments both require researchers to have a permit to band birds, and obtaining one can be a lengthy process because it involves gaining a lot of experience with bird handling and capture techniques. Throughout my academic and professional career, I have been involved with capturing and banding many different species of birds, but only at a trainee/apprentice level. Recently, I took a class in bird banding through University of California, Riverside, Extension to gain additional experience with mist netting and banding of small passerines (songbirds).

A Gambel’s white-crowned sparrow is caught in a mist net.

A Gambel’s white-crowned sparrow is caught in a mist net.

Mist netting is a commonly used technique for capturing songbirds; mist nets are made of very fine material that is difficult to see when set up properly. They are usually set up in high flight traffic areas (e.g. between trees or shrubs), and when the birds fly into them, they are caught in a pocket and become slightly tangled. The nets must be checked often or watched from an inconspicuous location so birds can be removed in a timely manner. Although we already use mist nests to capture cactus wrens, taking the class allowed me to gain a lot of additional practice in extracting birds from the nets. We also had the opportunity to work with many different bird species that we don’t usually catch.

After a bird was captured, we identified its species, banded it, determined its age and sex, and took standard morphometric measurements. Determining the age of birds can be very difficult, and in many cases you can only say that a bird is a juvenile of that year (a hatch-year bird) or an adult (an after-hatch-year bird). We learned how different feather wear and molt patterns can be used to determine the ages of the birds we caught. We also assessed body condition by looking at fat deposits on the breast and hips (birds have very thin skin, so it is easy to see the fat layer just below the skin). Over the course of the weekend, we captured and banded almost 300 birds! We also recaptured birds that were banded in the past and recorded their band numbers. All of the data collected will be given to the Federal Bird Banding Lab (part of the US Geological Survey) and used to look at trends in bird populations across the country.

Steve Myers (instructor) bands and takes body metrics of lesser goldfinches.

Steve Myers (instructor) bands and takes body metrics of lesser goldfinches.

This experience will help me in the permitting process and proved to be an invaluable opportunity to learn new skills and get lots of practice with banding and mist netting. I can’t wait to get out and put my new skills to use. Watch out, cactus wrens, here I come!

Colleen Wisinski is a senior research technician in the Applied Animal Ecology Division at the San Diego Zoo Institute for Conservation Research. Read her previous post, A Sense of Wonder for Wildlife.

4

Counting Mosquitoes

Summer interns Kathleen Connolly, left, and Christina Mangan pose with some of their finds.

Since October 2011, we have been monitoring disease vectors in the Safari Park Biodiversity Preserve (aka The Back 900). Here, the valuable coastal sage scrub habitat has been undergoing cactus restoration as well as monitoring of one of its important inhabitants, the cactus wren (see post Cactus Wrens Rise from the Ashes). Our goals are to monitor the presence and activity of mosquitoes and midges, two important disease vectors, and test them for West Nile virus and blood parasites, including plasmodium, the cause of avian malaria, in and around this reserve. From this data, we will be able to look at the occurrence of these disease agents in insects within the cactus wren habitat and which mosquito or midge species act as likely vectors.

Another interesting aspect of this study is analyzing what hosts these insects have been feeding on by evaluating their blood meals. Only females feed on blood; the male mosquitoes and midges feed on nectar. So for this study we are only concerned with the female insects. DNA is extracted from the blood meal, and a barcoding PCR is performed. The PCR product sequences are then compared to published sequences in the Barcode of Life database, which contains DNA sequence information for a large number of animals. Finding a match between the DNA sequence extracted from the blood meal and a known DNA sequence will enable us to determine which animals these insects have been feeding on. Mosquitoes and midges within the Safari Park have been found to feed upon various local creatures, including mallards, desert cottontail rabbits, mule deer, humans, and an occasional collection animal.

So, how do we convince the insects to be tested? Once every other week, our summer interns and I go out into the field, setting up UV traps and CO2 traps to attract and capture mosquitoes and midges. While out in the field, it can be quite an adventure, from the bumpy roads and rolling hills to the occasional visit from a resident mule deer or a speeding roadrunner. It is often enjoyable to get out of the laboratory and into the field and observe virtually undisturbed habitat right in our own Park’s backyard.

The UV traps attract the mosquitoes by emitting a UV light of about 350 to 400 nanometers; this acts as a visual stimuli for the mosquitoes and midges. The CO2 trap contains dry ice that emits CO2 to mimic the respiration of an animal and works as a chemical attractant for the insects. After anesthetizing the insects back at our Wildlife Diseases Laboratory, the students then have the arduous task of tediously counting and identifying the various species of mosquitoes and midges. Later, they extract the DNA and RNA from these insects and utilize it for the PCR testings.

This project has given our interns the opportunity to gain experience in the laboratory and in the field!

Jennifer Burchell is a research coordinator for the San Diego Zoo Institute for Conservation Research. Read her previous post, Invisible Clues.