Herons are among the more obvious and accessible of birds, and so, unlike many other species, they readily can be counted and monitored. We do this for two reasons: for the birds and for their environment. With the historical loss of wetlands throughout Europe, fewer and fewer locations have become more and more important to herons. By monitoring numbers and distribution of herons in these few special locations, such as the Camargue, we are able to assess how well the environment is supporting them and what might be done to improve their environmental situation. Also, since herons are top predators and depend on specific conditions of water, habitat, and prey, they are indicators of the quality of their environment. Many herons, in fact, thrive in environments that are human managed – such as rice fields, cane swamps, and impoundments. Thus numbers and trends of herons can tell managers how well they are doing in providing habitat for wildlife.
Excellent examples from Tour du Valat are Purple Herons and Great Bitterns, both highly sensitive to disturbance of their reed bed environment. Several generations of Tour du Valat scientists developed ways to monitor their numbers and determined their ecological requirements and so were able to make recommendations for the management of reed beds not only for biodiversity but for continued human use as well.
Monitoring and research go hand in hand. Scientific research is needed for setting up methods of standardized surveys allowing statistical analyses and the interpretation of the observed trends. Once monitoring is underway, the long term data bases become invaluable assets in asking scientific research questions. In fact as the years go by, questions can be asked of long term data bases that were never thought about when the monitoring began. For example, when monitoring of herons began in the Camargue, there was no thought given to questions of global climate change, because this had not yet been revealed to be an important process. But once such questions are discovered to be important, the long term data sets become the basis of sophisticated and broadly applicable analyses. It is a similar case with demographic questions. The complexity of these analyses increment exponentially as the field of inquiry becomes more developed. Long term data sets are what allow demographic questions to be addressed and models to be tested. A ten, twenty, thirty year run of monitoring information provides data for scientific questions that can be answered in no other way. The data sets maintained by tour du Valat are globally unique for herons.
Beyond the exploitation of monitoring data, research on herons has led consistently to better understanding of their ecological requirements and of possible conservation approaches. As begun by the late Dr. Heinz Hafner several decades ago, the heron research program at Tour du Valat stood head and shoulder above any other in the world for its accomplishments. Much of the basic understanding of heron feeding ecology, nesting, and survivorship was discovered or confirmed through the studies of Dr. Hafner and his several generations of student collaborators. In fact many of the questions were answered with such definitiveness that is there is no longer a need to pursue some of them. But the long term data bases that were developed in this program stand ready to be used by the next generation of biologists asking questions of current scientific interest such as demography, climate change, parasitology, and genetics.
What makes herons so valuable as a monitoring system and conservation tool is their adaptability. Despite the loss of naturally functioning habitat, many species persist and some thrive in the human dominated environment. A Grey Heron is among the more commonly encountered large wild bird as one wanders the European countryside. To many, herons have become a symbol of the residual wildness of the countryside. Of course some do not do so well in the human environment, and certain species, particularly in Asia, are critically endangered, some reduced to mere dozens or few hundreds of individuals. The little known White-eared Night Heron and the giant White-bellied Heron are two such species at great risk. The former is known to nest in only a few places in southern China and the latter is known to persist mostly in Bhutan, where its habitat is about to be unsustainably altered by hydroelectric projects. These species have been brought to the brink of extinction by habitat alteration, namely deforestation. Habitat alteration is the near universal major challenge to the wellbeing of heron populations. On the other extreme, habitat alteration has benefitted the Cattle Egret, which has followed the expansion of improved pastureland and spread around much of the globe in the past 1000 years. The impact of humans all depends on the species’ requirements. Many other species are in the middle of this spectrum, and benefit from the provision of wetland habitat for nesting and feeding, even if shared with human activities.
The global conservation situation for herons is led, monitored and facilitated by HeronConservation, the IUCN Heron Specialist Group. The Group was co-founded at Tour du Valat by Heinz Hafner and is in its third decade of providing such leadership for heron conservation. The scientific research, practical management studies, and syntheses supported over the years by Tour du Valat form an important part of the core of the European and North African information base of the Specialist Group. The Global Heron Action Plan, published by Tour du Valat provides the basic outline of activities for heron conservation globally. What began locally, as research and monitoring projects by a few far-thinking people has now informed and influenced heron conservation worldwide.