Help us Survey Caribbean Martins!

By deweidemann September 1, 2014
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Get ready for the annual Caribbean Martin Survey coming up this September. Started by Anthony Levesque on Guadeloupe eight years ago as part of a long-term research project on the species, Anthony and eBird Caribbean expanded the survey to the entire Caribbean region in 2010. But we need your help! During the last couple of years participation has been low, severely limited how much we can learn about Caribbean Martin migration and populations. We need more volunteers to survey more areas.

What is the Caribbean Martin?

The Caribbean Martin (Progne dominicensis) is an important migratory species and Caribbean endemic. Larger than most other swallows, male Caribbean Martins are the only swallows with an all blue body and white belly. Females and immatures are brownish and more difficult to identify, but their shape and size are different from other common swallows in their range. For more identification information, take a look at the photos in this article and consult your field guide.

Caribbean Martin male (left) and female (right). Immature birds look similar to females. Photographs by Anthony Levesque.

Caribbean Martin male (left) and female (right). Immature birds look similar to females. Photographs by Anthony Levesque.

Caribbean Martins occur in most of the Caribbean except for Cuba, the Bahamas, and a few other areas (range map below). Despite their abundance, no ecological studies have been conducted on this species and we know nothing about their migration patterns. In fact, scientists aren’t even certain where the birds go when they leave the Caribbean!

Map of eBird Caribbean sightings for Caribbean Martin. Purple areas indicate areas where Caribbean Martin has been seen. The interactive map can be found here.

Map of eBird Caribbean sightings for Caribbean Martin. Purple areas indicate areas where Caribbean Martin has been seen. An interactive map can be found here.

Why survey Caribbean Martin roosts?

During the day, swallows travel widely, catching insects in mid-air and often circling above observers multiple times, making it difficult to count populations accurately. The Caribbean Martin is no exception. However, at night (especially during migration), martins gather in large flocks to roost (often on power lines or buildings), making it possible to obtain accurate counts of local populations quickly and easily. By surveying Caribbean Martin roosts across the entire Caribbean, we can begin to estimate the population size and trends of Caribbean Martins in the region.

Caribbean Martins in Guadeloupe

Anthony Levesque has surveyed Caribbean Martins at a roost in Pointe à Pitre’s town center (in Guadeloupe), counting bird at the roost every 10 days for the last 4 years! His data show that the peak of migration each year is around the 15th of September. Check out his survey results in the graph below.

Survey results from Pointe à Pitre, Guadeloupe. Figure by Anthony Levesque.

Survey results from Pointe à Pitre, Guadeloupe. Figure by Anthony Levesque.

How to Participate in the Survey

Step 1. Locate your local Caribbean Martin roost

Martins tend to roost on man-made structures, often in towns. Roosts are easiest to find during the early evening when birds are arriving. At sunset, arriving birds fly together in large circles above the roost site. Once it gets dark, the birds land on the roost for the night. If you don’t know where the martin roost in your area is, you will need to locate it beforehand. Try walking or driving around your neighborhood/town at sunset and watch the sky for flying martins. You may also want to visit the roost once or twice close to the survey date, to get a better idea of how you will do the count (what time to arrive, how visible the birds are, the best vantage point, etc.).

Step 2. Conduct a census (or more than one)

To participate in the survey, count martins at your local martin roost after the birds have arrived for the night. To coordinate your counts with other observers, please count birds on two days, September 5 and 15. However, any counts you can make of roosting Martins during September, and in fact during the whole year, will be very helpful and appreciated.

Do the count around sunset, when the birds fly in to the roost site to sleep for the night. Your count method will depend on the structure of the roost site and whether or not all the birds are visible from your observation point.

Method 1. If all the birds are visible at the roosting site and easy to count, then count them after they have all arrived to roost for the night (about one hour after sunset, or anytime during the night). It may be getting dark at this point, but if the roost site is in the city, you will probably have lights to help you see. You can count the birds 1 by 1 or 2 by 2. It takes Anthony about half an hour to count >2,000 sleeping birds. Be sure to record your start count time and duration of the count.

Method 2. If it is not possible to see all the birds at the roost site (e.g., if they are on a roof), then count them as they are flying in to the site. Arrive at the site about one half hour before sunset and count the birds as they fly in. If large numbers of birds are flying in rapidly, you will need to estimate how many are in flight by counting them 5 by 5 or 10 by 10. Do your best to estimate numbers and don’t worry if you are not absolutely sure of the exact count. Your results—whether you count 50–500 birds or 5,000 birds—will be very important in helping to estimate the population size and trends of Caribbean Martins in the region. Again, be sure to record your effort—that is, the amount of time that you spent counting the birds (start time and duration). If you are able, we encourage you to record all other birds observed at the site too.

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The Caribbean Martin roost in Pointe a Pitre, Guadeloupe. Caribbean Martin's often roost in urban areas like this where they perch on buildings and wires.

The Caribbean Martin roost in Pointe à Pitre, Guadeloupe. Caribbean Martin’s often roost in urban areas like this where they perch on buildings and wires. Photographs by Anthony Levesque.

Step 3. Submit your census results

To submit your roost survey data, enter your counts into eBird Caribbean using the “Caribbean Martin Survey” protocol option. Of course, you do not have to limit eBird Caribbean submissions to only roosting Caribbean Martins. Any sightings of Caribbean Martins are welcome, especially during migration. However, please select the martin survey protocol option only if you have followed the survey instructions. Other sightings can be submitted as normal checklists. If you have any questions, don’t hesitate to contact the persons listed on the instructions page.

If you have any questions about the protocol or how to enter your data, please don’t hesitate to contact Anthony Levesque (anthony.levesque@wanadoo.fr) or Jeff Gerbracht (jeffgerbracht@gmail.com).

Thank you and good luck!

Anthony Levesque, Jeff Gerbracht, Lisa Sorenson, and Doug Weidemann