“Birds usually used their bills to manipulate preys before eating them. The prey will usually be manipulated to prepare it for swallowing. It is usual to position the prey head first towards the bird’s throat. This is followed by tossing of the prey into the bird’s throat. Another technique observed is raising of the prey above to slide it into the throat by gravity.
“Attached are pictures of a Grey Heron (Ardea cinerea) stalking and eating a fish (below: top to bottom, left top right in sequence. Time at bottom right of images). Not very exciting – except that on this occasion, neither tossing nor raising of the prey was observed. The fish that was initially caught, at the tip of the bill, was “sucked?” by an invisible force upwards. Subtly, defying gravity, the fish was moved from the lower part to the upper part of the bill before being swallowed into the heron’s throat. Please note that the prey was not tossed and the bird’s bill remained slanting downwards below the horizontal plane.
“The images were taken continuously and the actual timings were superimposed onto the close-up images of the heron’s head to show the speed and continuity of the action. At 4:19:10, the fish was caught at the tip of the heron’s bill. Less than a second later, the fish was now closer to the middle of its bill. At 4:19:13, the fish was at the middle of the bill. At 4:19:14, the fish moved closer to the bird’s throat and its position was just below its nostril. At this point, there was a slight tilt of the heron’s head towards its left. Less than a second later, the bird’s mandibles were wider and its head was tilted slightly upwards but its bill still remained below the horizontal plane. At 4:19:16, the fish disappeared into the mouth with its mandibles fully shut. Finally, the bulge at the heron’s throat disappeared as the fish was gulped down its long neck.
“As seen from the images, the fish was clamped in the heron’s mandibles at all times and there was very little movement of the bird’s head. There was definitely no tossing action.
“This leads us to a question: Are birds able to suck? Did the Grey Heron suck the fish into its throat?”
Kwong Wai Chong
Singapore
6th April 2010
Note:
Our field ornithologist Wang Luan Keng believes that this heron may have manipulated the fish by minimum movements of its bill. Unless the tongue has barbs to pull fish down throat… but has the Grey Heron a barbed tongue?
Birds generally do not have the ability to suck. In drinking, a bird dips its bill into the water then tips its heads back to allow the water to run down its throat. However, pigeons and doves are able to suck water. In the Greater Flamingo (Phoenicopterus ruber), the “[P]umping action of the throat and rapid piston-like movements of the thick tongue suck a current of water into the mouth, forcing it…” (Evans & Heiser, 2004). Sunbirds “suck” nectar by capillary action of its laterally folded tongue that may resemble a tiny tube.
Reference:
Evans, H. E. & J. B. Heiser, 2004. What’s inside: Anatomy and physiology. In: Podulka, S., R. W. Rohrbaugh Jr & R. Bonney (eds.), Handbook of bird biology. The Cornell Lab of Ornithology, Ithaca, NY. Pp. 4.1-4.162.
3 Responses
Without knowing what happened seconds before what the images showed, this is pure speculation from me. The heron picked up the fish. Moved its head up and perhaps nearer to the body. With the upward momentum of the fish, it opened the bills slightly to guide the fish to slide along towards its throat. It then moved its head slightly forward from 4:19:14 to 4:19:15 and then upward at 4:19:16 to gulp down the fish. Those who know physics or play the Yo-yo will understand my reasoning.
Amazing – if the fish was indeed moved upwards by the minimum movement of the heron as its bill was consistently slanting downwards, even before the above images.
For a more complete idea before the above images, there were 3 images captured at 4:19:09 with the first frame showing the heron plunging its head into the water. The second frame had the heron’s head emerging out of the water with fish in its mandibles. Both mandibles and fish were on the surface of the water. The third frame showed the heron back in its normal posture with fish at the tip of its bill.
Total of 4 frames were captured at 4:19:10 with the first frame showing the heron swaying its head by about 60 degrees to its left, probably to subdue the fish. The next frame showed the heron resuming to its normal stance, identical to the first few images posted here. This was followed by the images posted.
Herons do have barbed tongues. Visit allaboutbirds.org for cornell u. bird cam on Great Blue Heron nest in Ithaca, NY. What I wonder is why the barbs do not prevent the fish from being regurgitated when they feed their chicks?