Purple Martin Roost at Lake Pontchartrain
The Purple Martin roost under the Causeway Bridge over Lake Pontchartrain was discovered by Carlyle Rogillio in the early 1980s. It is one of the largest martin roosts in the nation. During the most active period, you are likely to see at least 10,000 martins! Martins aggregate there in large numbers after the breeding season and before they migrate to South America. There are roosts at both the north and south ends of the Causeway. The north one is about 1 mile offshore. The larger, south roost is easily visible from land.
In June of 2015 OAS launched a Purple Martin roost monitoring project spearheaded by Dr. Peter Yaukey. Dr. Yaukey is conducting evening surveys of the Purple Martin roosts at the Causeway during June and July. Colleagues working at Oklahoma University will produce abundance estimates from Nexrad doppler radar images for the following mornings when birds are departing from the roosts. It will be exciting to see how closely the radar estimates correlate with the counts. We hope to develop a method of monitoring this and other populations of birds and bats remotely, using radar.
Causeway roosts may hold more than 260,000 martins!
Dr. Peter Yaukey writes:
On Thursday night (July 10) I kayaked out to the Purple Martin nocturnal roost at the north end of the Causeway bridge over Lake Pontchartrain, which starts over a mile from shore. In short, I covered 1.3 miles of the 2.6 mile long roost (this total length is based on the whitewash on the bridge under structure viewed from a motorboat in daylight the previous weekend), and estimated 125,000; thus, my best guess is 250,000 birds. I anticipate making additional forays to confirm that the other 1.3 miles has similar densities to the first, but the amount of whitewash suggested it does. Because the roost is farther offshore than anticipated, I have to be more careful in terms of going out on conditions when winds and chop are mild enough for a night kayaking that will (I hope) extend 3.5 miles out from shore.
I have been continuing to measure rates of birds leaving the Metairie roost most mornings, and have entered data from a few of these days into a spreadsheet that I have coded to calculate the total number departing based on the rates. It tentatively appears 10-15,000 birds are regularly using the south end, but I need to error check my coding.
Phillip Chilson, Professor, School of Meteorology & Advanced Radar Research Center, University of Oklahoma
Jeff Kelly, Associate Professor of Biology, Heritage Zoologist, Oklahoma Biological Survey, University of Oklahoma
Kyle Broadfoot, Master’s student in Dr. Jeff Kelly’s lab
Eli S. Bridge, Assistant Professor, Oklahoma Biological Survey, University of Oklahoma
Visiting the roost: The roost is most active between June 15 and July 15, usually peaking around July 3. Visit the area at dusk when the martins are flying into the roost or at dawn when they are leaving.
Directions: Access the roost on the east side of Causeway Blvd. from the north end of Ridgelake Dr. in Metairie. Park and follow the jogging path under the bridge. Walk along the bridge’s west side out to the waterfront.