1. Does the pelican's pouch store fish, or work like a scoop net?
The Smithsonian’s National Zoo explains that the brown pelican uses its pouch like a "scoop net." The bird scoops up water and fish together, then holds the catch there while the water drains out. This means the pouch acts as a tool for scooping, not a place to store items [1]. The same source notes that the fish are not carried in the pouch but are moved into the esophagus (the throat tube). So, the pouch is a scooping device, not a storage bag [1].
2. How does the pelican drain the scooped water out of its pouch?
Before swallowing the fish, the pelican must remove the water. The Cornell Lab of Ornithology explains that the bird tilts its beak forward to let the water flow out [2]. Other sources suggest the bird might press the pouch against its chest to squeeze the water out. It is unclear if this difference depends on the species or the situation. The capacity of the pouch also varies by source. Japanese zoo materials state that the roseate pelican’s pouch holds 15 liters or over 10 liters [3][8]. In contrast, the Smithsonian’s National Zoo writes that for the brown pelican, the pouch holds about 1 gallon (about 3.8 liters) of water and fish combined, but it can drain up to 3 gallons (about 11 liters) of water [1]. There is no single number that fits all cases.
3. How far can the pelican's pouch skin stretch sideways?
A study on pouch tissue reports that the brown pelican’s pouch can stretch up to 200–300% in the horizontal direction. This is about 3 to 4 times its original length. The vertical stretch is about one-third of that amount [4]. Researchers think this stretchiness comes from wavy collagen fibers and a membrane shaped like wrinkles. It is not like stretching rubber fabric; it is more like unfolding something that was folded up [4]. As a net, stretching wide horizontally without stretching too much vertically might help catch water and fish. This is one theory about the meaning of this structure [4].
4. How does the brown pelican hunt by diving from high above the water?
The brown pelican dives into the water head-first from the air. It is one of the species that uses this plunge-diving method (the Peruvian pelican also dives) [5]. At the moment of hitting the water, it opens its beak and spreads the pouch to catch small fish. Then it floats on the surface to spit out the water and swallow the fish [5]. The net opens for just a brief moment during the dive. A paper in the Journal of Field Ornithology reports that observed dives started from heights over 4 m up to 19 m. The speed was about 18 m/s (about 65 km/h), lasting less than 1 second. The birds also rotate about 180 degrees in the air before entering the water [6]. After a successful dive, it can take up to 1 minute to process the water and fish [6].
5. How do pelicans that do not dive herd fish together?
The American white pelican does not dive; it hunts on the water surface. It swims in a line with others to herd schools of small fish into one place or drive them into shallow water. Then it scoops them up with its pouch when they cannot escape easily [7]. Japanese zoo materials also explain that pink-backed pelicans (a different species from the American white pelican) cooperate in groups of 5–10 birds to catch fish [3]. According to an introduction on AskNature, a 1991 study in western Nevada found that groups of 2–6 birds caught significantly more fish than solitary birds or larger groups [7]. This suggests there is an optimal number, not that "more is better." However, the original paper was not read directly for this article; the information comes via an introduction site.
6. How does the pelican's pouch help cool its body?
The pouch is said to help lower body temperature. The mechanism uses the heat movement of evaporation from a thin membrane with many blood vessels, allowing heat to escape. Japanese zoo materials also describe the pouch’s role in cooling the body by shaking it [8]. This explanation is mainly found in Japanese sources, and primary professional sources have not been verified. Pelicans may use the pouch not just as a tool for scooping fish, but also as a tool to handle heat [8].
7. How can you test a pelican's scooping at home?
If you want to investigate further, you can try this at home. Put water in a washbasin and add many large items like plastic bottle caps. Treat these as fish. Shape both hands into a bowl form and scoop up the water and items together. Gently tilt your hands, and the water will flow out while the caps remain in your hands. This lets you experience the pelican’s movement of draining water. Put a towel down because the floor will get wet. If there is a zoo with pelicans nearby, check the feeding time and go there. Watch which way the beak points before the bird swallows the fish. Can you see the "tilt and drain" movement described in the sources?