This summer I interned at the Wells National Estuarine Research Reserve in Wells, Maine and one of my favorite projects was the bird survey. Every day at high tide I went to five different locations on the Webhannet Marsh and recorded the number and location of 4 different species of predatory wading birds: Snowy Egrets, Great Egrets, Great Blue Heron and Glossy Ibis. I quickly became enthralled by these graceful, stealthy hunters. Through out the summer I noticed different hunting strategies exhibited by the snowy egret and the great blue heron.
The Snowy Egret is a small bird (20-27 inches) identified by its black legs with yellow "slippers" and its black beak. I observed Snowy Egrets hunting with a wide range of techniques. Some of the "snowies" were very slow and consistent in with their strikes. They struck the water often but did not consistently catch fish and when they did the fish were usually very small. Snowy Egrets often shake their feet in the water to stir up the muck and scare the fish. During July and August, the peak season for wading birds, I noticed a change in Snowy Egret hunting behavior. Many of the snowies were running around in a comical way, frantically striking the water and hopping around. My partner and I wondered if these were juvenile snowies that had migrated for the first time and were still perfecting their hunting skills. We also observed that Snowy Egrets often fished in groups ranging in size from 3-15. I am interested in returning to the marsh to see if these two hunting strategies produce similar results or if one is more successful than the other. I would also like to find a way to better identify the age of Snowy Egrets so I could better identify which age group used which strategy.
Great Blue Heron were also very common on the marsh. The Great Blue Heron is a tall (45-54 inches) majestic, and solitary bird. We observed that unlike Snowy Egrets, Great Blue Herons hunted alone or only with Snowy Egrets. Perhaps this is because they did not feel competition with the smaller egrets. Great Blue Heron were much more consistent with their feeding behavior and were very slow and stealthy. Often I sat and watched a Great Blue hold itself in a striking position for 5 minutes a time. Great Blue Heron definitely struck the water fewer times than the Snowy Egrets; however, they made catches more often and their catch was often bigger. A couple of time I observed a Great Blue Heron eat a snake and a baby turtle.
I found these two bird species extremely fascinating and I would love to return and be able to observe them in greater detail. Below are two links where you can observe the feeding behaviors of the two birds:
Snowy Egret (you can fast forward to about a min)
Great Blue Heron
Posted By Suzanne Birdman Sullivan
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It is very interesting that the two different birds had such different hunting strategies- I wonder if it has anything to do with their body size or some other aspect of their body structure? Also, this differentiation in hunting technique seems to closely parallel reproduction techniques. There are some species that produce many young and don't nurture them very much; these young tend to have low survival rates but because there is a large number of them the amount that survives is adequate. On the other hand, some species (typically mammals or larger species) produce far fewer young, but also nurture their young for quite a while; as a result, their young have a high survival rate. These strategies seem similar to the hunting strategies of the Snowy Egrets and Great Blue Herons, respectively.
ReplyDeletePosted by Johanna Brophy
Very interesting article, and you're lucky to have had such a great research experience. I like how the hunting beahaviors of these two birds was near polar opposites, and I think it probably has to do with their needs. Perhaps their size plays into how much food they need versus how much energy they can afford to spend on hunting. Maybe the smaller birds, having less mass, require less food and therefore can afford to have a more clumsy hunting style. This allows multiple strikes with less success rates. On the other side is the much larger Great Blue Heron, who must consume more food to survive. Therefore, it patiently waits until it see opportune moments to strike, using less energy by striking less but having more success when it does attack. I hope you get to return there to continue doing research.
ReplyDeletePosted by Austin Gray
I have noticed a great blue heron in the Brandywine pond and also a larger one in Puffer's Pond down the road. Have you ever seen these birds or observed their feeding strategies? It would be interesting to see how their feeding habits differ because one is much larger and hunts in a larger pond. Also, the large one is much less skittish than the small one (it lets you approach it much closer). It is probably more mature and successful as a hunter. I have not seen either one hunt although perhaps now I will observe them closer and add to your findings. Good stuff Birdman Sullivan!
ReplyDeletePosted by Patrick Holmes
Indeed I have witnessed the Great Blue in Brandywine and agree that its very calm around people and not frightened at all. Its definitely been around awhile and I wonder if the same bird comes back every year. It would be interesting to compare the feeding habits of great blues who hunt in marshes to great blues who hunt in fresh water. Pans in marshes are virtually fast food because of how many minnows get caught in such a small bed of water. I would think hunting in streams and other bodies of moving water would be harder. keep observing pat and keep me updated!
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