Black-naped Terns mobbing a Grey Heron

posted in: Heron-Egret-Bittern, Interspecific | 0

April 2008 is when the Black-naped Terns (Sterna sumatrana) on the rocky islets off northern Singapore are actively breeding. Many eggs have already been hatched and young chicks are everywhere (above). This is the time when the adult birds are most protective of their chicks. This is also the time when they are extremely aggressive with intruders.

Lee Tiah Khee was at the scene when an adult Grey Heron (Ardea cinerea) approached the colony. A large Grey Heron in the midst of their breeding colony poses much danger to eggs and chicks. Standing 90 cm or more tall, with a prominently long and pointed bill, it is a formidable intruder indeed. And although herons normally take fish mainly, they also take amphibians, crabs, mollusks, crustaceans, insects, snakes, rodents and birds – possible also bird eggs.

Black-crowned Night Heron (Nycticorax nycticorax) has actually been reported to consume the eggs and chicks of terns and other birds (Martinez-Vilalta & Motis, 1992).

The tern that first noticed the heron set off the alarm and immediately attacked the intruder (above). Naturally the heron tried to defend itself, opening its bill wide and taking a threatening stance. But reinforcement arrived and more terns began mobbing the heron (below).

Black-naped Terns may be a third the size of the heron, but they are extremely agile in flight. Besides, they out-number the lone heron. And they are extremely aggressive during this stage of breeding. They put up a spirited defense, mobbing the intruder from all sides, swooping low one after another. And there was the constant shrill cries of the defenders that was enough to scare away most intruders. Terns are generally noisy birds and a colony of disturbed breeding terns can be extremely vocal and agitated indeed.

All these were too much for the intruding heron. In the end it left the colony, flying off, followed by the noisy terns (above).

The above images were first posted in The account has now been published: Deng, S. H., T. K. Lee & Y. C. Wee, 2008. Black-naped terns (Sterna sumatrana Raffles, 1822) mobbing a grey heron (Ardea cinerea Linnaeus, 1758). Nature in Singapore 1: 117-127. A PDF copy can be downloaded from this LINK

Martinez-Vilalta, A. & Motis, A. (1992). [‘Family Ardeidae (Herons)]. Pp. 376-429 in del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the birds of the world. Vol. 1. Ostrich to ducks. Barcelona: Lynx Editions.
2. Podulka, S. (2004). Defense bahaviour. Pp. 6.52-6.56 in: Podulka, S., Rohrbaugh, R.W. Jr & Bonney, R. eds. Handbook of bird biology. Ithaca, NY: The Cornell Lab of Ornithology.

Comment by Shawn

Made Tuesday, 22 of April , 2008 at 4:39 pm

I am surprised that as a Bird Ecology Group that linked to NSS, there is no sensitivity in publishing active nesting images!!

Comment by YC

Made Tuesday, 22 of April , 2008 at 7:29 pm

The breeding area is an open secret, known to birders, photographers and fishermen. The breeding months are also well known. However, the area is rather isolated and there are police patrols and boats are not allowed to approach too near the islets.

Comment by Subaraj

Made Tuesday, 22 of April , 2008 at 9:42 pm

Considering the very clear and close images, I do hope that the photographer ensured that he was not too close to the colony, to himself create a disturbance.

While it is true that this breeding site is well known and that patrol boats are in the area, I have observed fishing boats right next to the islet and on one occasion, a photographer standing on the islet itself, with his camera and tripod, while the terns flew around agitated!

As a breeding resident, the Black-naped Tern is Locally Endangered, with just one active breeding site.

Comment by YC

Made Tuesday, 22 of April , 2008 at 9:49 pm

You need to see the equipment these photographers are armed with. The are bazookas, unlike the “toys” birders normally carry.

Comment by Shawn

Made Tuesday, 22 of April , 2008 at 10:10 pm

OK, now I get it. If it is well known to birders and photographers, it is ok to publish active nesting images without considering the welfare and well being of the birds. Particualtly as Subaraj mentioned Black-naped Tern is locally endangered and the place is the only known active breeding site.

I will be really interested to find out what is the code of ethics in NSS and BESGroup towards breeding endangered birds?

BTW, looking at the chics photos, even the bazookas 0f 600mm need to be really close. Imagine if the present of Grey Heron is considered a threat, which all these inconsiderate visitors, how will the birds feel???

Comment by YC

Made Tuesday, 22 of April , 2008 at 11:54 pm

By the way, are you a photographer, Shawn? Can you let us know how near can a photographer go, using a 600mm lens plus a x2 tele-converter, before he is unable to focus on his subject. We can then have an idea of the relative distance involved.

Comment by Shawn

Made Wednesday, 23 of April , 2008 at 8:37 am

I hope you do not shift focus. My question was a ethical one and not technical. Since you want to discuss technical, Let talk technical. For a 600mm lens (be it Nikon or Canon), the minimum focusing distance is about 6m. Since you are a photographer, I am sure you know what is an Extension Tube, that can bring minimum focus distance to 3 or 4m. Even without the ET, and the photographer is standing 10m away, you don’t think there will be any disturbance? BTW, not all photographers are using 600mm, since you are associate with NaturePixel, someone managed to pull a couple of photos for me showing the lens that they were using shooting these poor birds, not too familiar with the lens, but some are 200mm or 300mm:

Enough of the technical, let’s come back to ethical issue,let me reiterate my concern and question, as a blog that linked to NSS, what is the code of ethic in active breeding site?

Have you thought of how many people, be it photographers, birders or just layman will be attracted to the active breeding site? Please pare a thought for the poor birds and their chicks.

Comment by Vanny P

Made Wednesday, 23 of April , 2008 at 11:41 am

To me there’s always a trade off between maintaining the welfare of the subject, vis a vis documenting their behaviour while nesting.

I supposed without knowing how the photographs were made by the photographer, we should probably offer him/her the benefit of the doubt and assumed it has been done in good faith and without detrimental effect to the birds.

To address specifically to the point raised by Shawn.” Imagine if the present of the grey heron is considered a threat, which all these inconsiderate visitors, how will the birds feel”

My take is if the terns find the photographers a threat, they will have similarly been dive-bombed. Terns and some other birds have been known to dive-bombed on what they perceived as intruders and threats. If they think the photographers are a threat to their offspring, they will not hesitate to attack.

This is what happens to a group of us when attempt to visit breeding colonies of terns and seabirds in the coast off UK.

As for how near the photographer is, Im not able to comment on that because I’m not well versed in photography and how the lenses function. Maybe Shawn can shed more light on this because he seems to be expert in this field?

to Subaraj, Oh dear, for photographer to stand on the rock at another occassion was a no no. I hope you have a chance to advise him/her not to repeat it again the next round.

and to YC, thanks for putting this up. I’ve enjoyed your site tremendously.


Comment by YC

Made Wednesday, 23 of April , 2008 at 2:49 pm

Thanks for your comments, Vanny. And for your support.

Comment by BESG

Made Wednesday, 23 of April , 2008 at 8:13 pm

For Shawn’s information, NSS has currently no code of ethics regarding active breeding sites, period.

I have communicated with the photographer who informed me that he used a 600mm lens with a tele-converter attached. His boat was about 18-20 metres away. And the images have been heavily cropped. And I believe that there was no disturbance to the colony.

How other photographers operate is outside my concern. How many other people will be attracted to the site as a result of this posting is a matter of speculation.

Comment by Subaraj

Made Wednesday, 23 of April , 2008 at 10:06 pm

Hi Vanny. With regards to the photographer standing on the tern islet, I set the marine police on him by stating that it was illegal to land there without permission (not sure if that is true)!

As for the debate, there are ethical photographers and there are non-ethical photographers! We have to be careful about the latter as they are out there….those that trim vegetation around an active nest to make for a better photo, those that stand for long hours under a nesting hole which causes the bird to abandon, those that put their interest above the interest of the animals that they photograph. These morons have to be disgraced somehow, if education fails.

However, there are a few who go out of their way to minimise any disturbance and still obtain wonderful documentation. To these few, I say well done and keep it up. The data obtained is crucial in improving our knowledge of the species needs and this will allow us to find ways to improve management of our fragile and shrinking eco-systems, so that the biodiversity larger remains.

At the end of the day, there is always a need for balance. However, nature’s welfare should never be compromised. Blogging sensitive nesting sites must be done carefully. The photos and text should never reveal the exact location of the site and the contributors ought to be screened so that they do not attain fame, if it is at the expense of nature.

Just my “two cents”.

Comment by Vanny P

Made Thursday, 24 of April , 2008 at 12:36 am


Although I do not necessarily agree with what you’ve expressed, I respect your point of view. Specifically to the black-naped terns issue on hand here, I feel one should not be too swift to pass moral judgment as to whether a photographer is ethical, or one that is less so before we know him/her well enough. Unfortunately Shawn appeared to have formed his conclusion despite less than conclusive evidence, but have you Mr. Subaraj? I hold the view we have to give the benefit of the doubt unless the evidence shows otherwise.

As to sending the marine officer to the photographer that planted his camera equipment on the nesting rocks of the black-naped terns , I find it was a rather, how should I put it, futile effort. Firstly, it may not be illegal in Singapore to do so. Secondly the marine officer may not be able to educate the person on the right way to approach nesting birds and thirdly, it is a waste of state’s resources when there are more important tasks at hand for them to do.

I re-read the article on the black-naped terns again, and I do not see mention of the precise location of the terns as you seems to suggest so. Perhaps I overlooked, I beg your pardon. However, in this internet era and through the ease of googling for information, I came across many sites and information that seems to lead me straight to the location of the terns in Singapore. One such location even includes the detail map of the place. I believe It was quite dated and talked about possible conservation efforts of the black-naped terns in Louyang Rock. And I was pleasantly surprised to find one champion of the cause bearing the same name-sake as you Mr Subaraj. Only Subaraj was his first name, and yours is the surname I supposed 🙂

I copy the link here: YC please feel free to remove or edit if this is not appropriate.

My point really is with the information widely available across the web, pin pointing the exact location of the nesting rocks is as easy as finding direction to the Harrods. What additional harm, if any, can this article possibly bring?

I think I have raised enough here, and I probably should stop and go back to my quiet reading.

If any of my view above offends anyone, my sincere apology.


Comment by Subaraj

Made Thursday, 24 of April , 2008 at 10:18 pm

Hi Vanny,

Thanks for your views. No, I certainly do not judge wildlife photographers without foundation. However, after 27 years in the field, I have known my fair share of both the ethical and non-ethical variety….so I am naturally cautious. All the comments regarding bad practices are based on personal encounters and actual events. There are a few photographers, that I know, who I would trust. They will simply not want to take any photos if there was a risk to the animal concerned and when they do, they are very careful.

With regards to the photographer on the islet, there was no way to reach the chap without a boat and the marine police are supposed to patrol the area. Additionally, this islet has a beacon on it and, to the best of my knowledge, you cannot land there without written permission from the authorities. Hence, setting the police on him was the right thing to do and immediately removed the disturbance to the tern colony.

Actually, my first name is Subaraj (surname is Rajathurai). I did write that article and it was posted by the chap on his website. This was done at a time when they were planning the 2 kilometre coastal boardwalk and had plans to have it go out to the rock, where the terns were nesting. This would have spelled the end of the nesting site and our collective feedback made them change their minds.

Finally, when it comes to more sensitive situations such as birds nesting, I would still prefer a proven trustworthy photographer, as it is simply not worth taking any risk with such situations. Wildlife in Singapore have enough to contend with….development, over-management, sanitisation, large weekend crowds! They do not need wildlife lovers adding to the disturbance factor.

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