Aquatic foraging techniques of the Little Egret

posted in: birds, Feeding strategy | 0

The Little Egret (Egretta garzetta garzetta) is diverse in its foraging techniques for catching aquatic prey (mainly fish but also insects). This has been extensively documented by a variety of authors. The Little Egret is an ‘active feeder’ and success rates are said to be relatively high compared to many other heron species (my observations as well). Little Egrets use techniques that vary to some extent with the habitat. The foraging techniques that have been described by various authors include lean and wait, stand and wait, walking slowly, walking quickly, running, open wing feeding, double wing feeding, aggressive behaviour, bill vibrating (or tongue flicking), using rafts/perches, wing flick, foot stirring (or foot shuffling or foot raking), kleptoparasitism, hovering, dipping, foot dragging, jumping and hopping (the last few in deeper waters). There are many variation and descriptions for these and Kushlan (2011) offers definitions.

The methods I have observed include:

  1. A common technique is to wait patiently (stand motionlessand leaning forward) by the shallow end of a pond to pick out smaller fish. This often can be seen at fish farming ponds. They often have a fairly high success rate and I wonder if the shadow cast by the body encouraged fish to swim nearer enabling capture?
  2. When opportunity offers itself, the bird will perch on overhanging wires or metal/wooden protrusions in the water as a perch to feed from. This often can be seen at sewage oxidation ponds.
  3. Opportunistic feeding occurs when large fish ponds are drained and there is fish in shallow waters or mud to take at ease.
  4. When fish farming ponds are not well tended, toxins can develop (an anaerobic layer at the bottom) or leech into the water (after heavy rain); when this happens fish tend to swim at the surface. These are occasions of high food availability and the Little Egrets feed by joining other birds to form mixed species aggregations; usually a variety of herons and egrets species. They hover or skim over the surface of the pond, with legs trailing in the water (foot dragging) to catch prey. Many successful dive in to obtain prey. Occasionally some will float on the surface to get prey.
  5. I have also seen some Little Egrets using Water Buffalos (Bubalus bubalis) who are soaking in the water as a platform to fish in deeper waters. The Little Egrets would perch on their back and fish from there with a good success rate. The Water Buffalos do not appear distressed in being used in this way.
  6. I have observed a prolonged episode of kleptoparasitism by a Little Egret of a Little Cormorant (Phalacrocorax niger). The Little Cormorant was foraging in the shallower section of a pond. The Little Egret would follow it and attempt to take the fish whenever the Little Cormorant surface with prey.

On this occasion I saw the foot stirring (foot shuffling or foot raking) technique employed successfully by the Little Egret. Five birds, of different species, were feeding in a small shallow pond without any competition or conflict. They included an Asian Openbill (Anastomus oscitans), a Great Egret (Casmerodius albus modestus), a Purple Heron (Ardea purpurea manilensis), a Pond Heron and this Little Egret. Each bird was using a different foraging technique with the Purple Heron standing and waiting, while the Great Egret was walking slowly as well as standing and waiting, and the Asian Openbill was walking and probing for snails. The shallow pond was covered extensively by an edible creeping plant, Ipomoea aquatica (Water Spinach or locally called Kangkong).

The Little Egret was the most active feeder, walking about quickly, frequently stopping to do a foot stirring action to flushing fish. Kushlan (2011) states “Herons also make special use of their feet in feeding. Foot movement behaviors include Foot Stirring in which the foot and leg are vibrated, Foot Raking in which the toes are scratched across the substrate, Foot Probing in which the toes are inserted into the substrate, and Foot Paddling in which the feet are moved up and down on the substrate.” I observed this activity for quite some time (a short video is here, keep your eye on the Little Egret especially 2nd half: (https://youtu.be/ZD1bsaAJUVM) and it is predominantly ‘foot stirring’ with occasional ‘foot probing’. A local paper examining the foraging behaviour of five egret species, documented foot stirring (authors call it foot shuffling) as 16% of feeding techniques used by Little Egrets; note that the habitats for that paper wetlands but were varied.

References:

Kushlan, J. A. 2011. The terminology of courtship, nesting, feeding and maintenance in herons. [online] www.HeronConservation.org (available here: https://www.heronconservation.org/wp-content/uploads/resources/Heron-Behavior-Terminology.pdf)

Aboushiba, Ramli and Azirun (2013). Foraging Behaviour of Five Egret Species in POME Pond Area at Carey Island, Peninsular Malaysia. The Journal of Animal & Plant Sciences, 23(1), Page: 129-135. (available here: https://www.researchgate.net/publication/236843795_

Foraging_Behaviour_of_Five_Egret_Species_in_POME_Area_At_Carey_Island_Peninsular_Malaysia)

 

Amar-Singh HSS (Dato’ Dr)                                                                                                                                                                    Ipoh, Perak, Malaysia

Location: Wetlands, Perak, Malaysia                                                                                                                                                                                                                                                                                                                                      Habitat: Extensive ex-tin mining area with pond/lakes, wetlands                                                                                                             Date: 24th February 2020                                                                                                                                                                   Equipment: Nikon D500 SLR with Nikon AF-S Nikkor 500mm f/5.6E PF ED VR, handheld with Rode VideoMic Pro Plus Shotgun Microphone.

 

 

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