Several months ago there was a B-Aus post asking about Silver Gulls flying around the top of the Sydney Harbour Bridge at night. Some suggested that this behaviour was associated with feeding on insects attracted to the lights at the top of the bridge. I have just captured a shot from my balcony of a Silver Gull amongst a flock of 50-100 birds circling near my apartment at Homebush Bay. On a warm Sydney night they were snapping up tiny insects flying in the air. A photo of one of the protagonists is here:
http://www.flickr.com/photos/calidris-photos/5246339346/
Please excuse the crudity of the photo; I have enjoyed a few glasses of Pinot Gris which has obviously impacted on my photographic abilities. However, you can see that the gull is homing in on a very tiny object. It’s pleasing to see that these gulls, at least, expend some energy in catching live prey rather than cashing in on human left-overs.
Jon Irvine
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Comments
7 responses to “Silver Gull Aerial Predation”
G’day B’Aussers
Back in 1991 I published a short note on opportunistic nocturnal feeding by Silver Gulls in Melbourne. They were feeding on Black Field Crickets at one site, and Bogong Moths at two other sites. We ended up doing some filming for Burk’s Backyard on the Gulls taking Bogong Moths very high up over Melbourne.
If anyone wants a PDF of this note I would be happy to send it, off – list.
Sorry this is a delayed response but I have been out bush, chasing WTNT.
Cheers
Mike =================== Prof Michael Tarburton tarburton.m@optusnet.com.au ===================
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Michael,
I agree that the availability of rubbish leads to over abundance of many species, particularly at land fill sites. Although if the rubbish were to disappear over night (or even over a longer period as silver gulls can live ~30 years) it would probably result in prey switching by the scavengers. This may result in depleted insect and other prey taxa numbers while the scavenger numbers correct themselves. THe birds may also become aggressive as food resource become more limited. As some one else pointed out reducing silver gull numbers may also impact on other fauna (notably predators feeding on silver gull and other species competing for the same resources) now dependant on the over abundance species as a food resource.
It is an interesting problem, but not one with an easy answer!
Cheers, Ben
Hi Jon
No – it’s not good to see them catching live prey, especially at night.
German research has indicated, if not proved, that light pollution has serious effects on insect diversity and abundance. For instance, the “vacuum cleaner” impact sucks insects into the light and, for some species where one sex does not fly, this means the potential partners die in disproportionate numbers when they are killed by bats… and silver gulls….
And why are the gulls feeding on live prey? Because their vastly increased numbers, and now all-year round breeding, in urban areas as a result of trash means there are many more individuals short of day time food that need to hunt at night.
I guess we agree the trash is the issue to be tackled. Ian Temby’s work on silver gulls in Melbourne includes accounts of roof top nests surrounded by chicken bones. And estimates the damage caused by their excretions etc in the millions.
Michael Norris ===============================
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Thirty years ago I saw Silver Gulls in acrobatic aerial pursuit and predation over the Seaford foreshore (near Frankston,Vic.), where there was no artificial light at all. This was in late twilight after sunset. They were taking advantage of a big hatch of flying ants. Welcome Swallows were also catching the ants – quite large ones. The birds were hunting in the last of the evening light – I wondered how dark it would be before they couldn’t see their prey.
One site where I have seen Silver Gulls using artificial light was at Webb Dock in Melbourne, where containers are handled at all hours of day and night. Here Silver Gulls feed on small prey in the water – perhaps schools of very small fish attracted to the surface by the lights. Birds were flying close to the surface, dipping or skimming for prey, as well as swimming in their normal manner. They may also have been taking insects from just above the water.
Anthea Fleming ===============================
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It is not just Silver Gulls that do this. Most nights you can see Herring Gulls wheeling around over the old city in Istanbul. I guess it is just a Gull thing. Cheers,
Carl Clifford
Several months ago there was a B-Aus post asking about Silver Gulls flying around the top of the Sydney Harbour Bridge at night. Some suggested that this behaviour was associated with feeding on insects attracted to the lights at the top of the bridge. I have just captured a shot from my balcony of a Silver Gull amongst a flock of 50-100 birds circling near my apartment at Homebush Bay. On a warm Sydney night they were snapping up tiny insects flying in the air. A photo of one of the protagonists is here:
http://www.flickr.com/photos/calidris-photos/5246339346/
Please excuse the crudity of the photo; I have enjoyed a few glasses of Pinot Gris which has obviously impacted on my photographic abilities. However, you can see that the gull is homing in on a very tiny object. It’s pleasing to see that these gulls, at least, expend some energy in catching live prey rather than cashing in on human left-overs.
Jon Irvine
===============================
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Hi Michael,
It is interesting to note your take on this behaviour and whether it is “natural” or influenced by human activity. I agree that light pollution and gulls are a problem in our cities but last night’s activity was based over an area which is not affected by light pollution and the sun was only just setting. The insects seemed to be emerging from areas of mangroves and the gulls appeared en masse for approximately 10 minutes and then dispersed again, before it was dark. I’ve seen other mass feeding events like this by Silver Gulls during the day, for instance, when a very high tide flushes leaf debris down the creek, the gulls sit on the water and pick over the floating leaves for insects. This appears to be purely opportunistic behaviour in that a few gulls start off feeding and, by doing so, gain the attention of other gulls in the area that then come and join in.
complex one. Our pair of nesting sea-eagles certainly take advantage of the gulls nesting on the sunken barges in the bay. There is no doubt that if the barges and human food sources were not there, there would be far less Silver Gulls in the area, but, as we have witnessed over the past three years, when the eaglets are between 6 and 10 weeks old, Silver Gulls (adults and full-sized immatures) form a large and important part of their diet.
Jon Irvine
Hi Jon,
Same in Birchgrove tonight over the water – my guess is Xmas Beetles. Any other guesses?
Cheers,
Graham Buchan
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Hi Jon
No – it’s not good to see them catching live prey, especially at night.
German research has indicated, if not proved, that light pollution has serious effects on insect diversity and abundance. For instance, the “vacuum cleaner” impact sucks insects into the light and, for some species where one sex does not fly, this means the potential partners die in disproportionate numbers when they are killed by bats… and silver gulls….
And why are the gulls feeding on live prey? Because their vastly increased numbers, and now all-year round breeding, in urban areas as a result of trash means there are many more individuals short of day time food that need to hunt at night.
I guess we agree the trash is the issue to be tackled. Ian Temby’s work on silver gulls in Melbourne includes accounts of roof top nests surrounded by chicken bones. And estimates the damage caused by their excretions etc in the millions.
Michael Norris