The Present Status of Lake Istokpogaís Water Birds

By Dr. Paul Gray, National Audubon Society

Several people have expressed concern about low numbers of water birds on Lake Istokpoga this year, and about low numbers of wading bird nests the past several years. Whether bird numbers are lower than before is a rather hard thing to "prove," partly because we donít have many detailed bird surveys. Keeping track of bird numbers might sound like something of importance only for bird watchers, but birds are an important indicator of the health of the Lake itself.

Like the proverbial canary in a coal mine, when birds disappear, it often is one of our first clues that things are not well in the ecosystem. When I first visited Everglades National Park, I read their brochures about how the Everglades needed to be "restored." Yet, I drove down the road through the Park and the Everglades "were there"Ö .water, sawgrass, tree islandsÖ. what needed to be restored? As I learned more, it turns out that I should have seen a million wading birds out there (somewhere), but now there are one-tenth that number. Research into why much of the Everglades are "still there" but the birds arenít, has revealed that the water cycles arenít normal (too dry, or too wet, too much of the time). Unnatural water cycles means that many of the plants and bugs canít grow or establish normally, which in turn means many of the fish canít get food (or die from frequent dry-outs), and wading birds are not able to find enough fish (or frogs, crawfish, grass shrimp, or other foods) to feed nestlings. This description is simplified, but you can get the idea that subtle changes in the ecosystem affected many things. Is something like this happening with Lake Istokpoga?

Scientist Mike McMillian of Archbold Biological Station has been doing studies on Ospreys around the Lake for years. He reports that autumn populations usually drop to about 50 birds, and around January, depending on the weather, the Ospreys start returning from their migratory wanderings (often in Central America) to start nesting. Last yearís total of about 250 nests around Istokpoga was very high and Mike expects a fairly good return this spring. Dr. Glen Woolfendon, also from Archbold, reports that they recorded about 14,000 lesser scaup (the white-backed diving ducks out in the middle of the Lake) on this yearís Christmas bird count. During the drawdown, FWC biologists report endangered Snail Kites nested on Lake Istokpoga in what appear to be the highest numbers on record. These numbers sound pretty good.

But many people note that there seem to be fewer coots, moorhens, inshore (dabbling) ducks, and wading birds than normal. Unfortunately, we donít have a scientist following each of these birds and it is hard to tell whatís going on. My guess is that most of the changes probably are short-term effects related to the drawdown and hydrilla control. Plants help create habitat. Wetland plants drop seeds that wait until conditions are just right, sometimes waiting for decades, before they germinate. If you watch a shallow water area in consecutive years, this remarkable ability to wait allows "drier" condition plants to grow during drought years, and "wetter" condition plants to grow during wet years; the same spot will grow completely different plants in different years. During the drawdown and tussock removal project, heavy equipment removed material to help restore the natural sandy bottom. Along with the tussocks, seeds were removed as well. Rather than a diverse plant community, the first plant to grow in many areas was pickerelweed ("flag"). FWC subsequently sprayed this "weedy" species to allow time for more desirable plants to return. Hydrilla was controlled as well, and as vexing as hydrilla is for boating, many ducks and other birds like it. When more plants return, birds should too. Aquatic plant seeds are good at floating around and re-colonizing areas. My guess is by the end of 2002, many of our old friends: coots, moorhens, purple gallinules, ducks, wading birds, and others should be back in normal numbers.

As spring approaches, we wonder how wading bird nesting will be. Big Island and Bumblebee Islands have had large wading bird nesting colonies for years, and have made Lake Istokpoga one of the "Top 100 Wading Bird Colony" sites in Florida. When looking at the numbers of wading birds over the years, you will notice they are quite variable. Part of the variability arises because these breeding estimates are the records of only 1 to 3 counts per year. If the nesting season is earlier or later than average, the count day may not catch the rookery at its peak. Probably the largest source of variability is the climate itself. During extreme drought or flood years (El Nino winters can be very wet), wading birds may not find suitable conditions and either will forego nesting entirely, or move to another region to nest.

As mentioned above, wading birds were one of the most dramatic indicators of Everglade's problems. Similarly, wading bird declines were one of the important parameters that motivated Kissimmee River restoration, and their return is one of the restorationís criterion for success. This group of birds are good environmental indicators because they tend to feed at the "top of the food chain." A proper chain of events is required to make fish abundant, or to make healthy snail, crawfish, worm,

tadpole, worm, or shrimp populations, and if that chain is not working, then wading bird populations often show the effects long before some biologist sifting through the mud will detect it.

Another thing you can see from Table 1 is the counts have been sporadic over the years, which hurts our chance to determine trends. Our agencies have not placed a high priority on funding counting activity. To obtain more counts, Audubon has a program called Project ColonyWatch where we recruit volunteers to monitor wading bird rookeries. We have a booklet that helps train people how and when to count birds, lists of species, and data sheets. People report their counts annually and we compile and publish all the numbers. Over time, these numbers give scientists data to analyze birds across Florida, and give people numbers to study trends on their own lake. I would like to start a ColonyWatch program on Lake Istokpoga. If anyone is interested in participating, please contact me at 863-467-8497. ColonyWatch is new to me, so weíll learn how to do it together, but I think it will be fun, and we will obtain information valuable to protecting this wonderful Lake that we (the birds and us) call ours. All youíll need is access to a boat, binoculars, a bird book, and a few days a year.

My conclusion about birds on Lake Istokpoga right now is that they are doing fine. Of course we canít be sure "how fine" they are, without long-term data sets. By next year we will be able to see in general if plants and most birds come back. For one set of "indicator" birds, wading birds, we can start a project to monitor their numbers. In the future, we can know their trends. Please call me if you are interested.

Table 1

Year

 Bumblebee Island

Big Island

1970ís

200-300

(Great Egrets)

1000

 (White Ibis)

1988

 Vacant

 (one count)

250 - 500

(Large Waders)

1993

132

(Great Egrets)

  200

(Mixed Species)

1996

222

(Great Egrets, Anhinga)

705

 (White Ibis)

1997

 21

(Great Egrets)

Vacant

(one count)

1998

 152

(Great Egrets)

 5000

 (White Ibis, Great Egrets)

Table 1. Approximate number of nesting pairs of wading birds in Lake Istokpoga (not including Cattle Egrets) a determined by 1-3 annual counts. Most abundant species are in parentheses.