Monday, February 2, 2009
Why aren't the Great Blue Herons Nesting along Rookery Road the way they did before the lake was being Drained?
Here we are in the first week of February and the duck season is over, so the shotguns are quite and legal hunting season in the rookery is finished until September when the teal season opens. The deck being constructed by The Nature Conservancy into the rookery on the southside is almost finished so the roar of skill saws should soon cease, but something is still causing the Great Blue Herons and Great Egrets who have normally been the first to nest there in the past to stay away.
My belief is that the lowered water levels are the cause of the birds departure from the area along the road where the photographers once had great opportunity to make the bird photos Lake Martin is famous for. The Great Blue Herons and the Great Egrets are staging the construction of this years first nests in another area about a mile away near the lake which was deep enough to hold water all during the autumn drawdown of water and courtship is presently in progress. I expect to see the first pair begin to set on eggs very soon. It seems that the first birds to begin nesting are the largest birds due to having a larger body mass and greater ability to withstand the cold of Louisiana's winter. A prime example of this is the Bald Eagle which begins to nest in the autumn and lay their eggs in the first week of December.
There are many factors which attracts wading birds into a nesting area. One is cypress trees in an area flooded year round. My belief which is based upon personal observations of wading birds in rookeries for the last 20 years of doing swamp tours, is that if it is not safe to roost there year round, the birds will not nest there in the springtime. The first birds to nest at Lake Martin do not migrate in from the south. They are fulltime residents who roost in the rookery all through the autumn and begin nesting in the first trimester of winter. This coincides with the end hunting season and based upon my observations in the past, the first nesters would start constructing nests in the last week or two of duck hunting. My point being that it appeared that duck hunting in the rookery never stopped the birds from selecting the south end of the rookery as a safe nesting site.
Another attraction of wading birds seeking a nesting site is the presence of other birds already nesting giving evidence to the arrival of migrating birds that it is a safe nesting site. This is similar to duck hunters using a plastic decoy to lure and fool ducks durting the hunting season.
What I have noticed is that the Great Blue Heron which are typically the first of the wading birds to nest, are now nesting in an area where it remains flooded during the autumn draw down of the water. The area where they once nested year after year prior to the draining of the water for as long as I have observed them at Lake Martin is presently not flooded with enough water depth nor has it been flooded since the man made drainage of the lake in September. This causes me to consider that the drainage of water and the lower water levels is influencing the birds choice of locating the nests.
Here is a grove of cypress where the herons nested years ago before the water was lowered every year. None are nesting there this year. The photo below shows what the area looked like a few weeks ago when the first phase of the nesting season began before the pump was turned on. Even though you can see water in the photo above, it is not deep enough to hold alligators and it was dry land a few weeks ago at the time the Great Blue Herons began to nest.
Unfortunately on Saturday January 31st I was in the rookery and observed a tour guide who was conducting a swamp tour, driving directly under the area where the Great Blue Herons are presently nesting. The result was that the birds left the nest and I must assume that the tour guide's activity was in violation of the warning posted on the sign at the landing leading into Lake Martin.
25 years ago I learned how to develop relationships with the nesting birds in the Atchafalaya Basin that allowed me to bring tourists into close range of the birds without disturbing the birds normal nesting behavior.
I discovered this during the course of my occupation as a commercial fisherman during crawfish season. One day while raising crawfish traps in the Gravemberg area of the Atchafalaya Basin, I looked up and saw a pair of Red Tailed Hawks standing on a nest with baby chicks less than 20 feet away from the tip of my nose. When I thought about it, I realized that the adult birds were accustomed to a regular passage of my boat and were not threatened by the fact that my boat was less than 10 feet away from the tree where they observed me coming and going every day causing no harm to anyone. Try getting close to a Red Tailed Hawk in any other scenario!
There were two things I observed that the birds would not tolerate. One was the use of a big bright light at night disturbing the roost, and the other was passing close enough to the nest to cause the bird to fly away prior to the laying of eggs during nest construction. Both of these activities often caused a permanent abandonement of the nest area, and the adults would then move to another location to attempt a new nest. The worst of the two was the night light in a well established nest area because it would cause adults to abandon eggs or chicks in the nest. I believe this was the cause of the great mysterious departure of nesting birds along Rookery Road in March of 2006. Most likely due to someone in a truck on the road shining a light into the rookery at night.
So when I got to Lake Martin in the late 1980's out of respect for what I knew the birds would not tolerate, I did not do night tours into the rookery during nesting season, and I would stay out of any area where the birds began to arrive and were constructing nests prior to the laying of their eggs.
Following that, once a bird was setting on eggs or had hatched chicks, I would then begin to develop a relationship of approaching a nesting bird right up to a point where I could get close enough to not cause the bird to fly away from the nest. Knowledge of when the bird was about to fly came from observing the birds body language. Over time I was able to develop the skill of creating a relationship with the wild inhabitants that would span several generations of nesting birds. It seemed that the birds that had hatched in the nests I visited everyday the year before were very accustomed to being in close procsimity to my boat. The following year the hatchlings would themselves return to begin to nest in the same area where they had hatched. I could approach these birds even closer than previous generations in that they had known me all their life and had observed me passing by the nest where they had hatched and knew that I was not a threat. Because of this, many tourists who I took into the rookery during nesting season would make exclamations to the effect that they felt like they were in a National Geographic program due to the close contact that my tour afforded, without disturbing the birds.
Unfortunately, most people who attempted to copy my style of swamp tour using a similar boat that allowed access to these sensitive areas where the birds nested, failed to understand the importance of developing a very gradual relationship of mutual respect between the birds and the tour guide. For this reason, I have observed a great deal of disturbance of nesting birds at Lake Martin by other tour operators.
For the first 12 years that I did tours into the rookery at Lake Martin, I watched it expand in area and population in spite of duck hunting and numerous tour operators in close range of nesting birds. Then in 2002, after The Nature Conservancy began to lower the water there, the bird population began to decrease. Initially I assumed that the decline of the bird population at Lake Martin was due to a tour guide who I discovered was doing night tours into the rookery during the restricted nesting season. Perhaps this was also a factor in the decline of the bird population, but I am beginning to wonder if maybe the lower watwer levels are the major influence in the departure of the birds from Lake Martin which was once the largest nesting area of wading birds in North America .
Here is a picture I took of the pump outlet on the northside on Saturday January 31st giving evidence that the water is still way below normal and nothing is being done to replenish what was lost during the drainage last fall. It appears that the water is about 2 feet below where it was when it was drained off.
Posted by Marcus de la Houssaye at 6:30 PM