As DDT fades, eagles recover but face new threats

Research continues to show that the reproduction rate of bald eagles is recovering after the US ban on DDT a decade ago. However, the latest study reported also warns that reproduction is not synonymous with survival. It still is too early for more than restrained cheering.

Last March, the Department of the Interior reported that a number of DDT-endangered bird species, including the bald eagle, appeared to be recovering. The National Wildlife Federation reported that its annual winter eagle census showed a substantial increase in the number of bald eagles counted since the 1960s.

Now James W. Grier of North Dakota State University says a 16-year study of eagles that breed in northwestern Ontario shows a breeding recovery that he calls ''highly significant'' and ''striking.'' Yet he also finds it ''puzzling.''

He points out in a research paper in Science that the main pesticide culprit has been the chemical DDE, which forms from DDT in the environment. DDE is highly persistent. Once eagles have ingested it when eating contaminated fish or other prey, it should persist for a long time and continue to show up in eggs. Yet his data show it is rapidly disappearing from the breeding population he studies.

He speculates that there may be a higher turnover among breeding birds than has been realized, with young, relatively uncontaminated females replacing older birds. This could indicate trouble.

He explains: ''. . . Reproduction is only one dimension of eagle population dynamics. . . . Changes in survival rates, in fact, may be even more important. . . . If a high turnover among breeding birds is responsible for flushing DDE contamination out of the population, it also may signal lower survival rates than expected.''

Grier's research differs from the bird counts of the National Wildlife Federation or the general population data gathering of the Interior Department. He has been studying, in detail, the reproduction of eagles in a specific breeding range in northwestern Ontario. These eagles migrate to the United States during the winter. It is there that they pick up pesticide residues while feeding. Their Ontario breeding ground has little contamination.

Grier notes that DDE is not the eagles' only poison problem. PCBs (polychlorinated biphenyls) remain a continuing threat, as do residues of dieldrin, another banned pesticide. This reinforces warnings of some environmentalists at the time of the Interior Department announcement. They noted, among other things, that new poison threats could arise as in the case of Compound 1080, which is used on coyote bait. President Reagan lifted the ban on this poison, which also kills eagles feeding on the bait.

Grier points out that, while research on reproduction is important, there are virtually no good data on bald eagle survival rates. Bird counts are helpful, but of limited scientific value. What is needed is the kind of detailed research into eagle survival that Grier has provided on reproduction.

Nuclear 'gold'

Spent fuel elements from nuclear power plants may one day help meet US needs for certain strategic minerals.

These are the so-called platinum group metals - palladium, rhodium, and ruthenium. The US imports almost 99 percent of its supply of these metals, which have critical industrial and military applications.

The metals are present in reactor fuel. It should be possible to recover economically useful amounts of them from spent fuel or from the waste from military plutonium-producing reactors, according to Battelle Pacific Northwest Laboratories.

Such a process is well along in development at the Department of Energy's Pacific Northwest Laboratory, which Battelle manages. It would be used along with the process for turning reactor wastes into a glassy solid for burial. Lead oxide added in this process produces molten lead as a by-product. This lead contains the valuable metals, which then can be recovered.

Battelle estimates the US has over $180 million worth of the metals in its 9, 000-ton spent-fuel inventory. The process now can recover 80 percent of the palladium, 60 percent of the rhodium, and 14 percent of the ruthenium in spent fuel. Research chemists are aiming at a goal of 80 to 90 percent recovery for all three metals.

Bees dance for profit

Bees use dance to tell hive mates where to find food. Now it seems they can also tell how worthwhile it is to harvest the resource. In modern economic jargon, they convey cost-benefit information.

This may resolve a puzzle Nobelist Karl von Frisch encountered when he deciphered the dance language several decades ago.

Using a so-called ''waggle dance,'' a bee tells other foragers the direction and distance of a food source more than about 100 meters from the hive. For closer food, she does a round dance with no specific directional meaning.

Von Frisch suspected that the round dance also tells foragers how profitable such searching would be in terms of food energy gained over energy spent in exertion. But he was unable to show this. University of Miami ethologist Keith Waddington now has some proof.

He used artificial flowers and a sugar solution. By varying both the food value of the solution and the distance between the flowers, he changed the profitability of visiting the flowers in terms of energy spent flying between flowers versus food gained. This appears to be reflected in the frequency with which a bee changed direction in the round dance. Conclusion - the more worthwhile it is to exploit the food source, the livelier is the dance.