The Urban Heronries - Woe or Blessing?

Text by Chinmoy Swargiary & Himakshi Borah


Cattle Egret nesting in one of the urban heronries of Guwahati

Photo: Chinmoy Swargiary


The Herons and their heronries


Being one of the major contributors of the environment for the role they play in the food chain, birds and their habitats are of vital importance for the ecosystem. Birds commonly called as Herons come from the family Ardeidae and are characterized by long legs and necks. There are in total 66 species of birds in this family, being referred as Egrets, Bitterns and Herons. These birds are commonly found in wetlands and mainly feed on a variety of aquatic prey. They hunt standing motionless on the edge of the shallow water and wait until prey comes within the range. Some species of Heron like Little Egret and Grey Heron have even been found using bait to lure prey within striking distance. Herons are mainly colonial when it comes to breeding.


A Little Egret, one of the several urban heronry species

Photo: Udayan Borthakur


The abundance and availability in nature has included heronry species like Cattle Egrets and Pond Herons as “Least Concerned” on IUCN Red list. Though concern for the survival of such common species is yet to be developed, importance of these species in the ecosystem are undeniable.


An Indian Pond Heron, one of the common urban heronry species

Photo: Udayan Borthakur


Most of the Herons are referred as generalist species because of their occurrence in a wide range of habitats. Since many of the Herons are found in urban areas, therefore they also have a direct connection with human beings. However, the relationship between the human and Heron is not something that we generally witness with that of other animals and birds. As colonial nesting birds, they are inherently more vulnerable to disturbance than many other bird species as large numbers of breeding individuals gather in a small area. The Egrets are fishers, and they feed their young one by regurgitating partially digested fish and frogs. And during this process of feeding, the pungent liquid and parts of their food often dribble through the nests to the ground and generate foul smell. Therefore, besides being noisy, they are also disliked for making places dirty and unhygienic. Many a times, the species are feared to be the carrier of diseases, for e.g., Egrets and Herons are known to be reservoirs of Japanese Encephalitis.


The most common Heron!

The Cattle Egret, one of the most common of all the heronry species, is scattered in different parts of African, European, South American and Asian continents. The Cattle Egret has greatly expanded from Africa and is now found in Europe and America, while the Asian subspecies can be located in area between India, Japan, Australia and New Zealand. The figure below shows the expansion of the distribution range of Cattle Egrets in the Americas within a specific period of time.


According to a study on Cattle Egrets made around Laxmangarh city of Rajasthan covering 400 sq. km, it was found that among 30 root sites identified in the study area, 16 were located in urban areas and 14 were located in rural areas. The habitats of the Cattle Egret are changing with times and they are more attracted towards urban areas rather than rural areas.


A Cattle Egret in breeding plumage

Photo: Udayan Borthakur


Herons of the urban world


The urban human population of developing countries is growing at the rate of 5 million people per month. Approximately 70% of global population is expected to be urbanized by the year 2050 and it is expected to be triple by the year 2030. Thus the threat to urban biodiversity and need for their conservation has become a pertinent issue in the current context.


Dr. Parimal Chandra Bhattacharjee, renowned wildlife expert and retired Professor, Guwahati University speaking on urban biodiversity.

Video: ecoNE


The Urban biodiversity is a very strong indicator of the types of culture the people are going to adopt or whatever the culture was there that it can be maintained. If any township can have a heronry, it expresses a great thing for the culture of the city. So, city planning must accommodate these species in their thought process” – says Dr. Parimal Chandra Bhattacharjee, renowned wildlife expert and retired Professor, Guwahati University.

The increasing number of human population migrating to urban areas has converted forests, grasslands and wetlands of the city to manmade structures. As a result birds like Cattle Egrets, Pond Herons etc. which are commonly found in large numbers in various are facing various threats such as -

  • Due to presence of heavy metal pollutants in the air, the heronry species are adversely affected leading to oxidative stress.

  • Intense urbanization has resulted in loss of their heronry sites.

  • Abundance of food in form of garbage in the urban areas had been a main factor of attracting the birds to those areas. But this is also diminishing day by day due to modern waste disposal system.

  • In urban areas there is a chance of rapid transmission of disease due to higher density of birds and large gathering of birds at small feeding grounds.

  • Predators like feral cats and dogs put a constant pressure on these birds and eat their eggs or fallen chicks during breading time.

  • The fear-factor of their presence near human habitation due to being possible reservoirs of Japanese Encephalitis.


The heronries of Guwahati

Intermediate Egrets in an urban heronry of Guwahati

Photo: Chinmoy Swargiary


Guwahati, the capital of Assam, is the largest city in the entire Northeastern region. The city lies within the Indo-Burma Biodiversity Hotspot, situated between the southern bank of the river Brahmaputra and the foothills of the Meghalaya. It is spreading over 216.79 sq km area with a population of over a million people. Guwahati is surrounded by exceptional greenery with hillocks and forested areas and total eight reserve forests and two wildlife sanctuaries occur nearby Guwahati. A recent study shows that in the hills of Guwahati Municipal Area, there are 65,894 households out of which 10,208 falls under the reserve forest area. It clearly shows the pressure on the ecosystem and bio diversity resulting from deforestation and finally polluting the wetlands and having severe effects on biodiversity of the city.


Bar diagram showing the increase in built area of Guwahati within a time period of 1911 to 2015 (Rachna Y and Anamika B, 2016)



In several parts of Guwahati metro such as Panbazar, Fancy Bazar, Dispur etc., heronries exist amidst human habitation, even in the busiest commercial areas, with species such as Cattle Egret, Indian Pond Heron, Black-crowned Night Heron etc. While being a fast growing city, these heronries of Guwahati too faces several threats mentioned above. However, there is a positive attitude amongst the local residents of these places who are tolerant to the presence of these birds around them.



A local resident of Guwahati on urban heronries.

Video: ecoNE


The fear-factor of being hosts of Japanese Encephalitis, which is prevalent in many parts of Assam, often play a negative role while tolerating heronries in urban areas. Regarding this, Dr Sashanka Sekhar Dutta, Veterinarian & Social entrepreneur says, “We human are spreading more diseases than anyone else. Yes there is a role of Herons in spreading Japanese encephalitis as maintenance host of such diseases. However, pigs are amplifying host of the disease and thus pigs are more responsible than the Herons. So there is no point of blaming Herons who are already very few in numbers, rather we should take preventive measures at our end”.




Dr Sashanka Sekhar Dutta, Veterinarian & Social entrepreneur from Guwahati speaking on the role of heron species as reservoir of diseases.

Video: ecoNE


There are so many theories regarding Japanese encephalitis and there is no clear picture of it spreading from birds. In depth study is required before blaming any species for spreading diseases. We need to be careful and aware but it doesn’t mean we will cut down their habitats. Destruction can't be a solution”, says Dr. Parimal Chandra Bhattacharjee.



Dr. Parimal Chandra Bhattacharjee, expressing his opinion on the role of birds in spreading diseases such as Japanese encephalitis.

Video: ecoNE


Conservation of Herons demands proactive measures


The most critical conservation issue of Herons is the identification, protection and management of important nesting sites and associated feeding grounds along with the identification of important stopover and non-breeding feeding areas. Few herons required direct species-specific conservation initiatives whereas most of the herons required their habitat and landscape conservation action. Colony site or habitat conservation includes protection, control of disturbance and vegetation management whereas conservation of feeding areas includes management of hydrology, salt intrusion, contaminants and disturbance. Under species- specific conservation action, attention to some of these species through research and especially dedicated species specialist groups such as IUCN SSC Heron specialist group formed in 1981 is increasing understanding and leading to initiatives of conservation actions.


A Black-crowned Night Heron in one of the urban heronries of Guwahati.

Photo: Udayan Borthakur


We have already witnessed various examples where species once abundant and labeled as Least Concerned, whose drastic population decline or extinction has created an unbalanced situation in our ecosystem. We do not need to look back too far to understand that. The catastrophic decline of Gyps species of vultures is a recent example of how once highly abundant species is on the verge of extinction within a period of one to two decades. And we have not yet realized that species like the Cattle Egrets playing a vital role in ecosystem can also be threatened to extinction.


Unfortunately, due to the abundance in number, contributions of common Herons in sustaining the ecosystem remain unnoticed. The kind of critical outcome that the absence of these common species can bring is still a less concerned matter for us. The current scenario of global climate change has already given a hint on why maintaining ecosystem balance is so important for its productivity and human survival. Thus there is a need that every conscious citizen should play an active role before it’s too late to safeguard them. We generally think about conservation only when a species is threatened with extinction! Rather than becoming conscious when a species is endangered, we should think of keeping once abundant as always abundant.


At the last, no conservation action can be successful unless the people develop compassion and tolerance towards presence of these species living around us. In the words of an elderly lady resident of Guwahati who has been living next to an urban heronry for her entire life, “Now we have birds in the mango tree, Bael tree, etc., especially Crows and Egrets. So we need to be careful of bird droppings on clothes while crossing under those trees near the street. But for that only reason if we start killing the birds or cut the tree, where will the birds live?”


A local resident of Guwahati expressing her views on living with neighbourhood birds.

Video: ecoNE


About the Authors:

Chinmoy Swargiary and Himakshi Borah have worked as Interns in Media Production & Communications Division of Aaranyak, with support from Internews' Earth Journalism Network (EJN).




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